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Discussion Starter · #1 · (Edited)
I'm at the point to get the block to bore and hone.
From Gibtec the recommended piston to wall clearance is 0.0045.
I know that the piston ring gaps have to be set depending of application.
Will the piston to wall clearance also depend?
I will use a turbo and up to 30 psi in a Tecksid block.
 

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For a supercharged application at that boost level you would not want to go tighter than 0.025" ring end gap on an AP steel top ring or a tool steel top ring. the combustion pressures and more importantly the combustion heat at 30 psi will quickly close smaller ring gaps butting the rings and destroying the pistons and of course the engine.

Do not bore your engine until you have your Gibtec's in your possession. On a primarily street driven car you can close up the piston to wall to 0.0035" at that boost level. If the car is primarily a race car or a race car masquerading as a street car and living at the 30 psi boost threshold then you ought to give careful consideration to setting the piston to wall clearance at 0.0045". If the car is a street car that frequently is operated as a race car (but on the street) you ought to default to the 0.004" recommendation for piston to wall — just to let discretion be the better part of valor (and your engine repair bill).

Ed
 

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For the less experienced (me); What is the main downside to street driving a car with more PTW clearance?
 

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Predominately piston slap. Additionally the more the piston can rock about the wrist pin in the bore the more you barrel face a piston ring. The ring face upshot is reduced ring seal quality and increased blowby. In general you can make things work even if they are put together wrong. For the most part the issue is not so much does it work but more does it work properly and provide a good service life. The work properly part and the good service life part are what should be uppermost in the pecking order.


Ed
 

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Ed's specs are right on and will be reflected accordingly on the card that Gibtec will provide. With my Aluminator/Nemak block, we settled on 0.0040 PTW and it has been perfect. Then again, I'm only running a mild 9:1 CR. And of course by "we", I mean with plenty of input from Ed and some back-and-forth with the shop that handled the machining to settle on that figure:)

I will also add that the first start was a but scary (in more ways than one with such an expensive project), and as much as I though I adequately pre-lubed, apparently I could have gone further. What I thought was some piston slap - that smoothed out within a short period - was just the valvetrain getting the rest of the oil through the passages - perfectly smooth after. Hard to believe I started my project (and thread) almost five years ago, but the engine is still running incredibly well.
 

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Discussion Starter · #6 ·
Thank's Ed for the explaination.
This is a race engine and I will go for 0.0045.
This is my second engine I'm building for this car.
The first one blew up this spring..
This happen after all was tested out with 15 psi during tuning.
This was done in a hub dyno, made really good numbers and really safe.
Then we took a coffee break.
After the coffee break hell went loose.
Found that the Bosch fuel injectors 2200 cc, some went bad. At least changed the totally with the flow.
We tested each injector at least 3 times and the result was all over the place for each injector.
E85 mandate some better injectors what I have heard afterwards.
Probably due to heat.
All of them was new and then tested and turned out good before installation.

Then the sad story.
The company that do my machine work is (was) owned by 3 people.
2 brothers and another fellow.
One of the brothers that usually do the boring and honing of the blocks died for a week ago.
Therefore these questions.
 

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You can buy the Bosch 2200cc injectors flowed or not flowed. Buy them from a reputable shop that matches and flows them. You will be happier overall and spend less money in the end.

Ed


p.s. Do not try to run electric pumps. Use a mechanical pump with a flexible cable drive. Both you and the engine will be much happier. Waterman Racing pumps has both pieces available. you will spend about 2K (US$) before shipping, VAT and any import duties but your engine will be much happier. Put the pump in the rear of the car behind and just below the fuel tank. Run the pump drive cable to the front of the car where the drive gizmo is located. BTW at 30 psi you will need two 2200 cc injectors per cylinder.
 

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You should proceed with a fairly high level of caution when modifying main bearing oil clearances on any engine but in particular OHC engines, Kirk. The lubrication system is essentially a controlled leak that was engineered to deliver a specific volume of oil with the clearance specs published by the manufacturer, in this case Ford. The Modmotor oiling system oils the cams last which means increasing clearances anywhere without making proportional increases elsewhere increases oil flow at that point to the detriment of oil flows elsewhere in the engine.

Because the cams are the last to be lubricated you risk seizing a cam in its cam saddle killing both the cam, the head and potentially other pieces. Proper pan volume, baffling and oil viscosity will be more than adequate to protect engine internals without modifying crank oil clearances.


Ed
 

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Good insight, Ed and thanks for letting me know about priority oiling.

Yes it is an extremely difficult quandary. Issues I am dealing with are oil dilution in a 100% methanol environment, extremely long WFO pulls of 1 to 3 minutes and considerations of nitro percentages at a later date. I have zero answers and experience with the mod motor. In addition, I have a friend that uses a high quality dry sump and is experiencing loss of oil pressure in the middle of a run. I think that is attributed to the expansion of the aluminum block. All of the above has me looking at oil blends, viscosity, volume, and bearing clearances. Obviously, I need a reasonable solution before the crank is ground. The only thing I know at this point is that preheating is mandatory, everything else is TBD.

Any advice, help, comments, experiences, pearls of wisdom, or referrals are more than appreciated and will be read with the sincerest interest.
 

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I've built and raced blown alcohol (methanol) engines for almost 50 years. In the beginning we ran blown fuel engines and just defaulted to the same 70 wt oil we ran in the nitro engines. Inside the first year we dropped back to 60 wt and by year 2 we had come down to 50 wt. There was a brief dallience with 40 wt and we went back to 50 wt. The main bearing clearance we ran was between 0.0015" and 0.002" with the rod clearance run at 0.002". There was what Clevite used to call an H-Series performance bearing with an additional 0.0005" clearance per side for a 0.001" increase in oil clearance to 0.003". It was available for rods and mains.

I experimented with the larger oil clearance inserts at first using both upper and lower inserts with no visible imporovement. So I tried using just one increased clearance insert and one standard insert for a clearance of 0.0025". In the end the best bearing life performance came with the standard 0.002" oil clearance. I am assembling a ModMotor right now with a standard 0.002" oil clearance but narrowed inserts to clear the journal radius on the billet crank. The rods came in at exactly 0.002" and the mains came in at 0.0018". This is the normal clearance I see on rods and mains with King bearings - which I highly recommend. Use the soft King bearings do not use the hard bearing. For a supercharged engine you want the soft bearing, the motor likes it much better.

With respect to fuel dilution of the oil, we used the methanol to both fuel the engine and cool the engine so there was a fair amount of fuel dilution in the oil at the end of a weekend. The dilution was largely attributable to the rich idle we would use. Once under power we would lean the engine out to about a 0.63 lambda and there would be very little methanol that ever got into the pan.

The engines I built used a massive race oil pump and they would idle hot at about 85/90 psi oil pressure. You always needed to warm the engine before racing with either 60 or 70 weight oils. I once blipped the throttle a little too soon before the engine was up to temp and the oil pressure needle swung around and bent itself on the zero peg on the gauge. Once warmed up they would only get to about 150 psi or so at wide open throttle but they still idled at 80/85 psi.

On my modmotor I use a belt driven external oil pump made by RaceLine Pumps <= clickable. It is a large single stage dry sump style pressure pump without a pressure relief. I use a remote pressure relief regulator <= clickable, that allows me to set my oil pressure blow off at whatever pressure I want. I set the blow off at 130 psi and the engine idles at about 80 psi warm with a 15W 40 racing oil. Be sure to use a non synthetic break in oil for the first outing and then switch to the full synthetic.

For the external wet sump pump be sure to use a -16AN feed from the pan. Use a -16AN bulkhead fitting to go through the side of the pan and place you pickup in the middle of a diamond shaped, four sided, trap door equipped reservoir style well to trap oil during acceleration and deceleration. Milodon makes a swinging pickup, part # 21330 that looks like this:

Constr.jpg

This was my oil pan during the construction phase. The horizontal wall you see in the pan has two swinging trap doors that let oil back to the pickup and slam shut when you apply the brakes to trap the oil back by the pickup. The pickup itself pivots in its mount on the side of the pan to follow the oil backwards and forwards in the pan.

This is the finished pan with the windage tray installed;

Pan Side.jpg

You can see the two #12 AN bulkhead fittings that mount the pickup internally and exit through the side of the pan. To get to your -16 AN feed line for the pump you use a -12 AN to -16AN "Y" fitting which is never easy to find but out there if you persist.

The pan holds 12 quarts but I run it between 10 and 11 about another 1.5 quarts are in the lines and oil filter. Plan on a quart or a whisker more to wet the inside of the engine the first time, so your first fill should be about 13 quarts and a bottle of Prolong. Prolong is simply magic. In my opinion it is malpractice to not run it in your engine. Don't buy the 12 oz bottles at the auto parts store for $19. Instead buy the gallon jug off amazon for $63 or so and be way ahead of the cost power curve. Here is the Amazon link => Prolong. .Do not put the Prolong in until the rings seat or the process will be much more difficult.

Ed

p.s. The nitro experiment should not be performed on a Modmotor. The block casting is insufficient to withstand any detonation at all from nitro without massive failure. Additionally the power comes on so fast and so hard with nitro you complicate your already marginal traction problem that the salt presents when attempting to accelerate the car. A properly built, methanol fueled, engine will be capable of 3000 relatively reliable (I say that cautiously) detonation free horsepower which should be more than adequate to make you competitive in class.
 

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Ed that is some wonderful information and a great help. The bearing clearances are a big thing for me and kind of difficult to get a handle on because I have never run an aluminum motor. The mod motor will grow at least 0.002 on the main diameter with only a 100 degree delta. (80 degrees in the shop setting clearances and then 180 degrees in the middle of a run). In a few second drag race it won't matter because there is not enough time for any change to set in. Bonneville is a different story. So I want to (or have to) set tight clearances but when you add Kendall 70wt ridiculously big clearances are needed. I have to resolve this oil vs clearance issue soon. As you indicated thinking on heavy weight oil is changing. I have got to get up to speed on this!!

I plan to run King bearings and talked to someone at King that mentioned they were coming out with a "special" but nothing for the Mod motor at that time. Are you narrowing the bearings yourself or are they coming from king that way? I also talked to both King and Crower about using the Honda 1.888 bearing and they both indicated why bother? "Going with the ubiquitous 2" SBC rod journal gives you unlimited choice of bearings and for what penalty? The increased diameter is so slight there is little surface speed penalty". I'm undecided but interested in your thoughts.

I have heard these incredible numbers for Mod motors from 1,200-3,00 HP for years! I am just incredulous when I hear such numbers but purportedly MMR, Highland, and many others have been doing it for years. While I have to bow to reality; when I look at the block I just shake my head! The thing is full of windows and I have miced the walls (red circle) to find them as thin as 0.180" in many places. The side wall near the cross-bolt mains is as thin as 0.200"! I'm not sure of the casting alloy but it ain't 7075. I have never seen, or heard, what is done on the inside of these monster motors to make them live but it can't be non-trivial! Also, I can't find any source for aftermarket steel main caps. Am I to assume that everybody is running STOCK cast caps! I just can't see how the webs can hold all of it. Yeah, the Coyote is a better design.

I checked out the Raceline link (thanks) and there is not too much info on the internals of their dry sump pump. Are your suction stages gears or Roots? I am running a dry sump but haven't selected it yet. I have been considering Bailey and Aviad but completely open to suggestions at this point. I will be contacting Raceline also. I have a Moroso 5 stage gerotor laying around but do not know its flow numbers. I may send it back to Moroso for a refresh and talk to them. I make all my brackets and stuff.

Your comment about cam oiling has me thinking about a separate system for them but haven't even looked at where the supply would come from. Anybody you know doing such a thing? All the best.
 

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Ed that is some wonderful information and a great help. The bearing clearances are a big thing for me and kind of difficult to get a handle on because I have never run an aluminum motor. The mod motor will grow at least 0.002 on the main diameter with only a 100 degree delta. (80 degrees in the shop setting clearances and then 180 degrees in the middle of a run). In a few second drag race it won't matter because there is not enough time for any change to set in. Bonneville is a different story. So I want to (or have to) set tight clearances but when you add Kendall 70wt ridiculously big clearances are needed. I have to resolve this oil vs clearance issue soon. As you indicated thinking on heavy weight oil is changing. I have got to get up to speed on this!!.
The coefficient of thermal expansion for aluminum is 13 x 10[SUP]-6[/SUP] thousandths per ˚F. That means the expansion attributable to a 100˚F rise in engine temp over ambient machining operations temps will approximate a half thousandth of an inch!

I plan to run King bearings and talked to someone at King that mentioned they were coming out with a "special" but nothing for the Mod motor at that time. Are you narrowing the bearings yourself or are they coming from king that way? I also talked to both King and Crower about using the Honda 1.888 bearing and they both indicated why bother? "Going with the ubiquitous 2" SBC rod journal gives you unlimited choice of bearings and for what penalty? The increased diameter is so slight there is little surface speed penalty". I'm undecided but interested in your thoughts.
That is excellent advice and the rods are an off the shelf item with Manley. FWIW that is the rod (Manley 5.850 center to center and 2.000" SBC bearing) I use in my personal engine. If you build for 3000 HP however that rod is not up to the job at those power levels. The only Manley rod using the SBC rod bearing and the strength to handle that power level is the Pro Series Manley I-Beam rods. When you run the SBC journal size you will require a crank with SBC rod journals. Not a big deal if you are ordering a billet. If you are not then the Wiseco Boostline rods would be a smarter choice. Equally as strong but only available in std Ford journal sizes however ½ the cost of the Manley Pro Series rods.

I have heard these incredible numbers for Mod motors from 1,200-3,00 HP for years! I am just incredulous when I hear such numbers but purportedly MMR, Highland, and many others have been doing it for years. While I have to bow to reality; when I look at the block I just shake my head! The thing is full of windows and I have miced the walls (red circle) to find them as thin as 0.180" in many places. The side wall near the cross-bolt mains is as thin as 0.200"! I'm not sure of the casting alloy but it ain't 7075. I have never seen, or heard, what is done on the inside of these monster motors to make them live but it can't be non-trivial! Also, I can't find any source for aftermarket steel main caps. Am I to assume that everybody is running STOCK cast caps! I just can't see how the webs can hold all of it. Yeah, the Coyote is a better design.
Actually the Coyote is not the better design. The Modmotor is the better design.

You can get billet steel caps from Cobra Engineering with my 10MM side bolt upgrade already done for you.

It takes 10 lbs of air per minute to produce 100 HP. These 3000 HP engines get their power at 10,500 rpm. That means they require 300 lbs of air per minute at 10,500 rpm. To do that you will need to be in the neighborhood of 60 psi or so of manifold pressure and importantly (if you don't want to destroy the block) no detonation. Even without detonation the block is going to require regular inspections at that power level and replacement when you see any signs of incipient failure.

I checked out the Raceline link (thanks) and there is not too much info on the internals of their dry sump pump. Are your suction stages gears or Roots? I am running a dry sump but haven't selected it yet. I have been considering Bailey and Aviad but completely open to suggestions at this point. I will be contacting Raceline also. I have a Moroso 5 stage gerotor laying around but do not know its flow numbers. I may send it back to Moroso for a refresh and talk to them. I make all my brackets and stuff.
Raceline only uses gear pumps and I only use a pressure pump. I do not use any scavenge pumps. My oil system is not a dry sump it is an external wet sump. I am unfamiliar with Bailey. If you mean Dailey Engineering then that is the right dry sump system to use. It is the Rolls Royce of dry sumps.

Your comment about cam oiling has me thinking about a separate system for them but haven't even looked at where the supply would come from. Anybody you know doing such a thing? All the best.
You could if you were really determined however it is not necessary if you run a good wet sump or dry sump system. FWIW Dailey likes to run 10 psi of oil pressure per 1000 engine rpm. There are a lot of people who subscribe to this oiling model and have good results. At 10K rpm he would have 100 psi of oil pressure. I would be a little higher at 130 psi because of my higher pressure relief. The difference in my low speed oil pressure would be decidedly higher than his. At 1000 rpm his 10 psi per 1000 rpm model would provide 10 psi of oil pressure. I like to provide 80 psi at idle. Personal preferences. You have to decide what you want to do. If you want high idle oil pressure Dailey does not make a pump that will do this. You will need to use his scavenge stages only and then deploy a separate pressure only pump to achieve the high idle pressure.

Ed
 

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Quoting a quote gets messy so I'll parse your post here.

CTE of aluminum:

Agree 13ppm is the best number to use. But Aluminum is kind of all over the map and I have done a lot with castings (in a former life) so I generally use 12ppm for aluminum. Me thinks you used an extra zero for your CTE. Check your calcs.

Modular Design:
I am new to the Modular culture and constantly learning. I notice the Coyote has removed the windows and the main bearing bulkheads are thicker and machined much nicer. I assumed Ford learned from the Teksid and then improved the Coyote. What gives the Teksid more strength than the Coyote?

Billet caps and HP:
Many thanks for the Cobra Engineering reference. I have been looking all over and was confused about what appeared to be no aftermarket for the caps. And thanks for the air consumption numbers. Do you use or recommend an engine software analysis tool? I have heard about Performance Trends and Dynomation for years. Maybe it's about time to bite the bullet. Any recommendations?

Dry Sump:
Opps, sorry I meant Dailey Engineering. I have talked to Bill and am very impressed. Kind of pricey but I agree he has the most comprehensive system and I like how he treats the oil aeration problem. I didn't know about the idle low oil pressure. That may or may not be an issue for me. Don't know at this point. I'll have to talk to King bearing about it. I don't even know the oil path through the motor at this point. I kind of looked for it in Hyland's book but don't remember seeing anything on it or illustrations put out by Ford. Please indicate a source If you have seen an oil diagram for the Teksid.

THANK YOU for your time . . . all the best.
 

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Quoting a quote gets messy so I'll parse your post here.

CTE of aluminum:
Agree 13ppm is the best number to use. But Aluminum is kind of all over the map and I have done a lot with castings (in a former life) so I generally use 12ppm for aluminum. Me thinks you used an extra zero for your CTE. Check your calcs.
I just did the math from memory so I could easily have made an advanced years mistake. For the numbers below I was more deliberate and used used MATWeb data and let Excel do the math calculations. This is what the Excel calculated numbers look like;

Screen Shot 2020-08-30 at 5.32.03 PM.jpg

The crank is not actually 4340 steel it is a MicroAlloy that approximates 4340 so I attempted to mimic the MicroAlloy by using an oil hardened and tempered version of 4340 with a 1.9% nickel content for the toughness the crank version of the 4340 alloy is used for.

The reason for reducing the block and cap calculated expansion by a factor of 2, is that the bearing housing is half aluminum main web and half steel main cap. BTW your 12 x 10[SUP]-6[/SUP] CTE for the aluminum casting was closer to the mark than my 13 x 10[SUP]-6[/SUP] although in the bigger picture the difference does not contribute significantly. For the steel caps I used 1040 mild steel normalized at 900˚C although I suspect the normalizing temp had little if any impact on the numbers.

The 100˚F rise in block temperature appears to account for a 0.0002" clearance over my original half thousandth (0.0005") increase in oil clearance, which intuitively feels correct. Although at first glance the use of aluminum as the casting material would seem to set the stage for a significant bore size increase, in practice it is fairly small. The crankshaft that rides in the mains also grows in size, mitigating the main bore size increases and maintaining a somewhat normal oil clearance. I included it in the overall calculations because it was necessary in determining the change in oil clearance.

Although small at only 0.0007" it is noteworthy to remember that a 0.001" (rounded up) increase in oil clearance is essentially a 50 % increase over stock. If you subscribe to the low oil pressure at idle lubrication model the cams and cam saddles in the head will suffer. Other than a slight premium you pay in lost power to drive the oil pump for the high pressure low speed oiling, the reassurance and comfort In knowing everything, especially the tender pieces at the end of the oil supply food chain are all being adequately lubricated is priceless.

Modular Design:
I am new to the Modular culture and constantly learning. I notice the Coyote has removed the windows and the main bearing bulkheads are thicker and machined much nicer. I assumed Ford learned from the Teksid and then improved the Coyote. What gives the Teksid more strength than the Coyote?
The best block Ford produced in the Modmotor product line was the Aluminator block. According to an internal Ford engineering document,

"The foundation of these engines is the 4.6L engine block used in the '05-to-present Mustang GT. Thanks to a technology partnership with Cosworth, this new block features strength unmatched by any previous production 4.6L aluminum block. The employment of zircon sand for the casting molds, a chilled bulkhead cooling process, as well as a proprietary method of pouring the aluminum results in a denser block with better alignment in the aluminum's grain.

The casting also features increased main web thickness and round main cap windows to alleviate stress cracks often found with rectangular windows. The main caps are standard six-bolt but are now ball-burnished for greater strength. In production testing, the new block more than doubled the duty cycles of other aluminum 4.6L blocks."
.

There is an excellent website you may want to consider adding to your favorites. It is authored by one of the members on this site and is devoted exclusively to the Modular engine. It is easily the most comprehensive Modmotor information website I have run across in 20 years. Here is the link => Terminator Cobra

The Terminator Cobra Website has a wealth of information. Here is a link to the blocks page. You'll find the cylinder block and head castings information and identification about half way down the page. Click here =>. Blocks

The main webbing in the Coyote is attractive as are the larger fasteners but the real issue is not the webbing or the fasteners it Is the bore centers and the bore size. Both blocks use a 100 mm bore center. Modmotors use a 90.2mm bore size. That leaves 9.8mm or 0.386" between bores for gasket sealing. A Coyote alternately uses a 92.18 or a 94 mm bore. Depending on which one you choose you only have 6 or 7.8mm between bores. That means the gasket sealing surface between cylinders has dropped to either 0.236" (less than a quarter inch) or 0.307" (less than 5/16 of an inch). Either one is very difficult to seal up in a supercharged engine. When you have a head gasket failure in a supercharged engine the flame of combustion is hotter than a cutting torch and literally torches out the block, the gasket and the head. While you can do a weld repair on the block and head, you can not reheat treat the aluminum. With aluminum it's a one and done - no mulligans. Upshot, new block and new heads (that you have to port again).

Coyote was a front office and finance department bandaid to get around the cost of a new engine platform to fit smaller engine compartments and compete with the LS engines out of GM for sales of daily driver performance cars. It was an abortion from a serviceable performance product point of view. If you needed to pull a head the head bolts / studs are directly below the cams which means removing the cams to remove a head. The block is currently on its fifth generation (possibly more by now) driven in large part by warranty failures that themselves were driven by poor engine design. The highly vaunted heads that supposedly out flowed the Modmotor head in modified form turned out to be about the same to whisper behind the power curve. Check out this thread => Comparative Head Flows

Modmotors already had a tenuous relationship with pulling pistons out the bottom of the bore because of the block height / stroke / rod length geometry. The Coyote stretched the stroke to get 5 liters and aggravated an already tender spot in the engine design making it worse that it already was. This means a rocking piston at the bottom of the stroke, premature skirt wear and barrel collapse in the skirt along with rounding the face on the compression rings and increasing blowby while decreasing combustion sealing. If you are a member of the social networking street race crowd this engine was made in heaven for you. Otherwise maybe not so much ...

Billet caps and HP:
Many thanks for the Cobra Engineering reference. I have been looking all over and was confused about what appeared to be no aftermarket for the caps. And thanks for the air consumption numbers. Do you use or recommend an engine software analysis tool? I have heard about Performance Trends and Dynomation for years. Maybe it's about time to bite the bullet. Any recommendations?
The best combination of price and capabilities I have found is in the DynoSim 5 (DS5) software package.This has been updated by the author(s) as DynoSym 6 (DS6) and lost fidelity in terms of accurately predicting likely power outputs. Additionally while some of the capability additions provided in the DS6 package are welcome expansions of the capabilities of the DS5 package there are also al lot of ICE engineer inside baseball type stuff that is well over the heads of the average enthusiast. The DS5 package is out of distribution now and only the DS6 package is available. If you want a DS5 package you are going to need to find someone with a DS5 package that is willing to sell it to you.

In the FWIW bucket, the Dynomation and DynoSim s/w products are written by the same guys. The Dynomation s/w has a number of nice tools the DynoSim s/w did not have in release 5. By release 6 the DynoSyn s/w had begin to offer more of the Dynomation type capabilities but not all and also not at the elevated pricing and need to use a hardware dongle to run the application. Dynomation is approximately 3X the price of DynoSym.

Dry Sump:
Opps, sorry I meant Dailey Engineering. I have talked to Bill and am very impressed. Kind of pricey but I agree he has the most comprehensive system and I like how he treats the oil aeration problem. I didn't know about the idle low oil pressure. That may or may not be an issue for me. Don't know at this point. I'll have to talk to King bearing about it. I don't even know the oil path through the motor at this point. I kind of looked for it in Hyland's book but don't remember seeing anything on it or illustrations put out by Ford. Please indicate a source If you have seen an oil diagram for the Teksid.

THANK YOU for your time . . . all the best.
Low idle oil pressure is not rocket science. Your mains and rods will very likely survive even in a hot engine. In a pushrod engine there are no OHC components only pushrods and rocker arms. In a DOHC engine there is a boat load of precision componentry riding in bearing journals with less than 0.001" oil clearance that do not use inserts. When the oil supply fails, and it can and does, with low idle oil pressures the carnage is massive and virtually instantaneous. Timing chans break, cams seize in the heads, valves get bent and broken, the broken valve and valve stems fall into the cylinders and get punched through pistons, cylinder heads and cylinder walls. When the show is over, all you need is a whisk broom to sweep up the broken parts and throw away the remains of your high dollar race motor. Why play Russian roulette with more than one bullet, especially when you don't have to and it is easy not to. BTW the failures never occur at idle only WOT above 7000 rpm!

Ed
 

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I have been so interested in the thread I completely forgot about forum etiquette! My apologies Tbird, I had no intention of creating any hint of thread drift! I think this might be related but I don't know if it should continue here or in a new thread. If a new thread is suggested, you or Ed start it and let me know the the title. Thank you all for your patience! :)

I am reviewing Ed's latest post now and will reply back here later unless a suggestion is to move elsewhere.
 

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I have been so interested in the thread I completely forgot about forum etiquette! My apologies Tbird, I had no intention of creating any hint of thread drift! I think this might be related but I don't know if it should continue here or in a new thread. If a new thread is suggested, you or Ed start it and let me know the the title. Thank you all for your patience! :)

I am reviewing Ed's latest post now and will reply back here later unless a suggestion is to move elsewhere.
I wouldn't worry too much, Kirk. Your digression was a more or less natural expansion of the topic as you dug into related engine building considerations. Tbird is pretty good about those things and so am I. We just try to avoid threads spiraling into the ether on unrelated topics. Your stuff is right in the thick of the engine building experience and valuable to anyone that is building or preparing to begin their build.

All good, no harm and no foul - actually a lot of good.

Ed
 

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Ed, I'm about to buy some of the 9mm pins from Cobra Engineering. But in a past post I think you referred to the pins as "my" pins. Are both you and Cobra selling them or do you just collaborate with him? I want to support our vendors and this site but need a little direction. Same deal with the pistons. Deal direct with Gibtec or . . . ??
 

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The reason I selected the 4.6 was primarily the smaller bore size to get a DOHC V-8 motor to fit a specific class size. The old 262 (not 265) SBC has a smallish bore too but of course 2 valve Neanderthal pushrod technology. So the issue is the 0.093” thick Modular integral cylinder liner for a blown alcohol application. It doesn’t help that all the Teksid blocks have many miles on them and need a clean-up bore. Thanks to this forum I have learned that Gibtec pistons are not restricted to the traditional .020 or .030 overbore but can be ordered in any size 0.001” at a time. That is great because I can now size only what is necessary for cleanup and no more.

However, the .093” wall bothers me a lot. I was going to sleeve the whole block and put in stock bore, 0.125” thick sleeves. In talking to a machine shop he advised that it was a bad idea and boring out the liners as well as additional aluminum (due to the increased wall thickness of the sleeve) would drastically weaken the whole block. He had seen a cut up 4.6 and said something about how much material was left down there near the mains. I was left with the impression that thicker, stronger sleeves would be useless due to drastically weakened the block.

Your wisdom and comments are valued.
 

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There is some truth to the reduction in liner support aluminum when you go to the replaceable liners. The small loss of material turns out to be inconsequential. there are a number of guys who have gone to the replaceable liners on the Modmotor and a huge number who have gone that route on the Coyote, even with its larger bores. The 0.125" wall liner is where you want to be for maximum effort engines.

In my Forum Article Why You Want to Use Standard Bore Sizes you will see a block that has been modified to accept the replaceable liners and you will also see the liners from the bottom (crankcase side) and the top (block deck) side. The flanges on top have been cut to provide receiver grooves for stainless wire o-rings and dead soft copper head gaskets like the nitro engines use. At about 30 psi of boost an MLS gasket is pretty much done. Above 30 psi of boost you are foolish to run MLS gaskets. You need dead soft copper and stainless wire o-rings.

BTW those pistons in the pics are the ùber high compression Gibtec's I spoke of. We had to make a combustion chamber mold for Gibtec to scan, that I commented to you about, to create them.

Ed
 
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