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Discussion Starter · #1 ·
The engine in our 1999 GT is being rebuilt, the work being mostly finished, will be assembled this next week. I have been doing searches and poring over all of the previous posting regarding stroking a 4.6L 2 valve and I am concerned about the likely results. Any suggestions for things we can still change and experience on the performance results we are likely to get?

Things being changed in the engine rebuild include forged rods, pistons, 5.0 stroker crankshaft, ARP head and bottom end bolts, BBK aluminum underdrive pulley kit, 03-04 Cobra aluminum flywheel (rebuilt by McLeod) and McLeod 11” Super Street Pro Clutch Kit, BBK 78mm throttle body & intake plenum (part #1780), ported PI heads, and shorty headers noted below.

Exhaust includes JBA ceramic coated shorty headers, Magnaflow Tru-X with cats and Magnaflow cat-back system modified for the panhard bar.

Things remaining stock for now includes valve train and cams, PI intake, 19 lb injectors, air intake, and mass airflow meter.

Suspension include MM strut tower brace and castor plates, 14” disk brakes, Eibach springs, subframe connectors, panhard bar, and larger wheels and tires.

This is my first post on this forum. We have several Mustangs including this 1999 GT (a 35th commemorative edition), a 1999 Cobra (got hit last Friday & may be totaled), and a 1967 GT convertible.
 

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Strokers have been widely debated on boards like this. Some swear the tq curve is better and others flat out say you wont see a increase in power. The problem I see with all the debate is nobody (that I know of) has bothered to take a stockish 4.6 dyno it, build a 5.0 stroker throw the exact same parts back on it and dyno it again. However from the looks of your combo you might be the first. My only problem with strokers if the increased side loading of the pistons which in my eyes will more then likely shorten the life of the engine. By how much I am not sure of.

If I were in your shoes I would lower the compression to around 9.5 for a good centri supercharger like a paxton novi 2000 or a vortech HD T-trim and make some real power.
 

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I disagree.

Closer to 10:1 or a little more with a centri is the sweet spot. You just have to use low timing. Which is fine because with the extra squeeze you won't need it.

The stroker crank is worth a bit more torque down low. I don't think it makes much difference on the big end when it comes to power. Maybe a little. But the car does feel a bit stronger down low.

Draw back to the stroker is the piston comes nearly out of the bore up the oil rings when it changes direction(If you use a piston with a fully banded skirt it's not as bad). Which leaves a wear or skuff. But even in the stock stroke you get this wear mark just futher down the skirt. So is it a issue. Yeah probably if your talking longevetiy. But how many miles do you think your going to get pounding the rings and bearings with boost?

I'm going to disagree with the above blower choices as well. I like the Novi2K but the T trim is too peaky on a small engine. I would use a YSI or F1A/C. You'll make much more averagre power.

If your only looking for around 600rwhp I'd go with the S trim or P1SC-2, maybe a D-1SC or T trim if you have a decent converter so you won't see the peaky ness of the 2 blowers.
 

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Well i just recently had a stock engine with a turbo. blew it. now rebuilding with just a stroker bottom end and changing nothing else, stock heads and cams so i will be able to see if it makes a power difference
 

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doing it with a 2v..
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one thing about strokers that some of the guys with cobras and twin screws have proven is that a stroker might make the same power with a given pulley combo, but it will be at a lower boost level...

which might come in handy if you are trying to get alot out of pump gas.....

if you are just gonna run around on c16 or something similar all the time booost wont matter though.
 

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one thing about strokers that some of the guys with cobras and twin screws have proven is that a stroker might make the same power with a given pulley combo, but it will be at a lower boost level...

which might come in handy if you are trying to get alot out of pump gas.....

if you are just gonna run around on c16 or something similar all the time booost wont matter though.
I think it would make a difference in a turbo car. Moves more air which means should spool the turbo's quicker.
 

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i just put my stroker in and i notice a big difference but thats also with heads and cams. the main thing i notice is the power gain at 3500+rpm not much change in the bottom end pull but around 3500-4000+ it really feels good!
i would say get some bigger injectors. the 19lbs. wont support the stroker,u might skimp by on some 24's but i'd go for some 30's if i were u. your tuner will just de-tune the injector to put the right amount of fuel in. better to have fuel on tap then have everything maxed out and working hard. i'd say the mass air because when i had mine tuned it was hard to get my stock mass air to work with the bigger injectors but i believe u have the 80MM mass air factory.if so u wont need one.

GL and enjoy!
 

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I have a Turbo automatic car. So i figured a stroker would spool the turbo quicker and stall the convertor faster. Im not after total power. I want the long flat torque curve and power band. peak power is for dyno racers.
 

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Discussion Starter · #11 ·
This has been a long time coming. The DynoJet rear wheels results:
278 HP @4,900 rpm
321 Ft Lbs @ 4,000 rpm
 

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Discussion Starter · #14 ·
A correction on my original post. The 99 GT has 13" Brembo brakes (not 14").

The 99 Cobra was replaced with a low mileage 07 GT500. I am very happy with this car.

The 99 GT has become more of a real pleasure to drive on the street. There is a lot of low end grunt and seems much faster that my 99 Cobra, though it is now impossible to do a side by side comparison. The new engine has a noticeably deeper exhaust growl.

The computer was tuned a few days before the dyno runs. I am told there is a couple degrees to much spark advance at higher RPM's. Our tuner thinks a F4.6 XE270AH-13 Comp cam would flatten the torque curve and maybe add another 30 to 40 HP.

We are interested in any comments, suggestions, thumbs-up or down, etc. Thanks.
 

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Discussion Starter · #15 ·
Sorry, I only managed to upload the before dyno sheet from 2001. The system won't accept the after dyno sheet.
 

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so can you type in the before and after so i can get a idea
 

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A correction on my original post. The 99 GT has 13" Brembo brakes (not 14").

The 99 Cobra was replaced with a low mileage 07 GT500. I am very happy with this car.

The 99 GT has become more of a real pleasure to drive on the street. There is a lot of low end grunt and seems much faster that my 99 Cobra, though it is now impossible to do a side by side comparison. The new engine has a noticeably deeper exhaust growl.

The computer was tuned a few days before the dyno runs. I am told there is a couple degrees to much spark advance at higher RPM's. Our tuner thinks a F4.6 XE270AH-13 Comp cam would flatten the torque curve and maybe add another 30 to 40 HP.

We are interested in any comments, suggestions, thumbs-up or down, etc. Thanks.
I have those exact same cams with my stroker kit. I have stock ported heads and those comp cams. have 491hp and 481tq on a mustang dyno. With a Vortech pushing 14psi.

I noticed my tq being right near my hp with my centri which is very un usual, The hp is always noticeably higher than the tq. The stroker has definitly helped wiht the torqe.

I cant say what my power would be like without the cams, but the engine definitly sounds deeper than a stock gt, and sounds just like a 5.0 mustang side by side. The cams give it a nice rumblesound, and a mussle car feel.
 
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