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Discussion Starter · #1 ·
Hi,
I am having some problems with my new motor. I have a 96 cobra with 01 heads and intake and a V7 YSI blower. I got the car running and took it to the dyno a couple of mounths ago and the car ran good. I started getting alot of blow by out of the filters on the valve covers. Over the weekand I lost compression on all cylinders. So I dropped some oil into the cylinders and did a compression test and got compression back up to 150-180 lbs per cylinder.

Has anyone had this happen to them. I have been thinking about some reasons why I would loose compression.
1: Rings didn't seat properly. I ran the car on the dyno to break it in. I didn't have any blow by at the beginning. The blow started to gradually get worse over the weekand after I took it for a 45 minute drive.

2. Not pulling enough vacuum out of the crankcase which cause the boost to blow the fuel past the rings causing the washed cylinders. This seems like a problem because I only have filters ontop of the valve covers and I am not using my crankcase vacuum pump to pull vacuum. So I am thinking about installing new pumps.

3. Cam timing is off and leaving the valves open. This could be I am looking into this a little more still. I did degree the crower stage 3 cams. I believe I degreed the intake to 110 and the exhaust to 118 and 118.5.

If anyone could give some input that would be great.
Thanks,
Mark
 

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I can't imagine it is 3 since the oil in the cylinders brought the compression back up. I can't see how no vacuum in the crankcase would cause this, so I don't think it is 2.

It seems to me that your rings did not properly seat. I have heard that using synthetic oil as your break-in oil can cause this. I have also heard that running the motor for a long time at one RPM during break-in can also cause this. However, I have never had a new engine where the rings did not properly seat, so this is all hearsay.

Sorry to hear about the troubles, BTW. It's frustrating after all that work.
 

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Discussion Starter · #3 ·
Thanks for the input and yes it is very frustrating. I used non sysnthetic oil for the break in and still currently have non synthetic oil in the motor. For the break in I took it to the tuner and he ran it on the dyno turning it up to 7000rpm. And he did some drivablility tuning on the dyno also. I took it twice to him and had about 6-8 pulls each time. I had some alternator problems which caused it not to be ran more.

I have heard to seat the rings you need to run the motor hard like your going to drive it.

What should I do to seat the rings properly if? Also what type of rings should I be running for a blower application?

Thanks for the help
Mark
 

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I was taught by my dad (who built SCCA race motors when I was growing up) to keep the rpms down under 3-4K RPMs, and never drive it for long periods of time at a steady RPM for at least 600 miles.

I have built a number of engines over the years and have never had any set of rings not seat using this method. In fact, a couple of weeks ago we just finished the break-in of a 96 Acura Integra GSR block with 84mm Darton MID sleeves, a stroker crank, Manley rods and CP pistons/rings. No change in compression before to after break-in.

I can't say that my dad was an expert in engine building, but what he taught me has worked well for me so far. But then again, maybe I've just been lucky. They say it is better to be lucky than smart. :)
 

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Well, it always depend. Read that great post from eschaider

http://www.modularfords.com/f17/aluminator-block-info-165485/#post1624218

If you use stainless as your top ring material you should not break the engine in like it had moly rings.

To seat properly, a stainless ring needs to be loaded heavily. The break in procedure is to go out with some sticky tires on, bring the engine up to 4000/4500 and launch the car from a dead standstill a few times and you are done! If you do the drive around town for 500 miles sort of breakin the chrome face on the stainless ring will burnish your cylinder walls and your rings will have to be replaced along with re-honing the block.
What I want to know, is if I should go gapless or not....
 

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Ed knows his stuff. I use the same machine shop he does.

Speaking of machine shops, did they perform the final cylinder hone per the ring manufacturer's recommendations? I am pretty sure different types of rings require a different surface finish. It may not have been your break-in procedure.

I hope you will share the photos after the tear down.
 

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I was always taught that high compression or boosted engines need a "hard and fast" break-in period and just be sure the engine is at operating temps. The "500 mile" break-in at low rpm and light load is for 'stock' setups.
 

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Discussion Starter · #8 ·
Ed knows his stuff. I use the same machine shop he does.

Speaking of machine shops, did they perform the final cylinder hone per the ring manufacturer's recommendations? I am pretty sure different types of rings require a different surface finish. It may not have been your break-in procedure.

I hope you will share the photos after the tear down.
Im not sure what the machinest did for the cylinder. I had him bore it over .020, but I can't remember about the ring gap or the cylinder finish.

Also I used moly rings so maybe I should have driven it easier. I will have to look into the rings and probably tear down the motor and start over.

Also is there a specific type of ring that I should use for a boosted application.

I appreciate all the help.
Mark
 

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Interesting thread. We ordered the Honda pistons and rings from CP. They asked if the engine would NA or FI, so we told them it would be supercharged (the blower arrives later this week). I know the machinest called them to get the proper finish spec. So they sent us the appropriate rings and told us the gaps they recommended for the application, but I never thought to ask them about their recommended break-in process. Thinking back, the top rings did look like stainless. Like I said, it is better to be lucky than smart.

I will have to ask them about their recommendations for my Teksid Terminator build...
 

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Discussion Starter · #10 ·
I can't imagine it is 3 since the oil in the cylinders brought the compression back up. I can't see how no vacuum in the crankcase would cause this, so I don't think it is 2.

It seems to me that your rings did not properly seat. I have heard that using synthetic oil as your break-in oil can cause this. I have also heard that running the motor for a long time at one RPM during break-in can also cause this. However, I have never had a new engine where the rings did not properly seat, so this is all hearsay.

Sorry to hear about the troubles, BTW. It's frustrating after all that work.
Do you know have any thoughts on the vacuum in the crankcase. I quess I am trying to fiqure out if I should have the vacuum pump hooked up and pulling vacuum out of the crankcase when I get ready to run the motor again. I was doing some research and some people run vacuums on boosted motors but I haven't got a good understanding on why they do yet.

Thanks for you help
 

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The more air you have in the crankcase, the more mass the pistons need to move when they go up and down. The movement of that mass takes away a little horsepower and adds a little heat. That is why a relative vacuum is better than ambient pressure in the crankcase. There may be other benefits, but I am not aware of them.

If you run a stock PCV system, at idle you will have a little vacuum on the drivers side due to the vacuum in the intake manifold. But at the passenger side, the PCV pipe to the intake pipe will get the crankcase back to ambient pressure pretty fast. In fact probably quite a bit of the idle air goes through this system. At WOT, everything will go close to ambient pressure as you have no vacuum. The pressure may go above ambient if you have any significant blowby. It would be interesting to see data on this.

If you vent your valve covers to air, you will always have ambient pressure in your crankcase, unless blowby at WOT creates positive pressure. This system does not burn the hydrocarbons from the crankcase.

If you put in a vacuum pump, you will always have a vacuum in your crankcase. This is the best case for vacuum, although the pump adds a little weight to the car, and a little load on the engine from having to power the pump. This system does not burn the hydrocarbons from the crankcase.

In my opinion, an exhaust scavenging system is best over all. It uses the gas flow in the exhaust pipes to create a constant vacuum that goes up with increasing exhaust flow. It also does not burn the hydrocarbons coming from the crankcase. But those hydrocarbons, tend to lower the octane of your fuel slightly, so you are better off from a performance perspective without them. I'd put them after the cats, though. I suspect those unburned hydrocarbons would not be good for the cats.

This is the thing I would put in if I didn't live in California where the smog Nazis are in control: Moroso 97810 Moroso Crankcase Evacuation System
 

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I've built a couple of sbc engines & actually used atf (not type F) in the cylinders for break in. Also i've heard of putting something like baking soda in cylinders to help rings seat but would do more research on this because not 100 percent sure of this.
 

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To the OP: Any luck on figuring this out?
About the rings: Today they are made a bit different then back in the day. The whole ring seating happens a lot faster then it did before. Usually by the time you drive your car from your house to the tuner, the rings will be seated. At least that was the case with me. In any case, I dont see it being this complicated with the ring selection, etc. I used the manly chromemoly rings that came with the pistons (I am pretty sure they were not anything too special). I think ether the bores were not honed or the timing got jacked up somewhere.
 

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Discussion Starter · #14 ·
I am finishing the tear down of the motor. I havent pulled the pistons out yet but I got the rest of the motor taken apart. I have one problem I found 1 of the cylinder walls is scored so now I am looking into sleeving the block or buying a new block.

Thanks
 

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Discussion Starter · #17 ·
Well I got the pistons out. It was not good. There were 3 good pistons and the rest were pretty scored. Im not sure what caused it yet. On the pistons that were bad the rings were also stuck to the pistons and I am not able to get them to come loose. The only thing that i can come up with was the cylinders got washed when I added E85 winter blend mixture because the motor ran really rich.

I noticed when i was running it on the dyno there was some blow by coming out if the valve cover and toward the end there was puddles of oil on the valve cover that was coming out of the valve cover filter to vent to crankcase.

The motor running rich is what I think caused it because I was never able to get the car not to run rich because I had problems with m alternator and could never finish the tune.

How soon should the rings seat?

I am also going to put some pictures up this weekand of the pistons.
 

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Discussion Starter · #18 ·
Now for the rebuild could I get some help what I should do to make sure this dosent happen again. I am looking for new pistons. Does anyone have any advice on a good set of pistons. I had probe pistons before but since im doing it over i thought I would look to see if there is anything better.

Also any advice on what I should do about the block. One of the cylinders is scored and will need to be sleeved. Does anyone have any informations on if it is good idea to sleeve the block or should I just try to find another block.

I did find a 03-04 cobra block but it will have to be bored .030 over because it is also scored. Would this be better option sense I have to buy new pistons anyway?

Any input is greatly appreciated
Thanks,
Mark
 
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