Stock Piston Questions.

Venom351R · Jun 7, 2009

Did the pistons in the 94/95 GT or Cobra come forged? I'm reading on another site that posters are saying the pistons are forged from the factory and that's why guys can run 500 RWHP safely. I thought the 94/95 had hypertunic positions which were not exactly boost friendly?

BlownFiveLiter · Jun 7, 2009

They're hypereutectic since 93 in the 302. The 95 R may have been forged though and I can't find anything that says one thing, or another.

blksn955.o · Jun 7, 2009

I would go with hyper across the board. The cobra shortblock is the same as the gt with a different cam. The R is the same as the gen1 lightning only with a roller cam/lifters. Hypers can take a good amount of abuse you just have to watch the tune.

Venom351R · Jun 7, 2009

Thats the same thing I thought guys. I also asked this question on SVTP in the "R" section and the R pistons were just cast nothing special.

This all started over on Turbomustangs.com. Guys were saying if I wanted to run boost I should have different piston's and rod bolts. I dont disagree w/ that but I made the point that there are plenty of 5.0 Mustangs running around w/ close to or at 500 at the wheels and they are all fine so I dont see why I could not do it w/ my 351 considering that it is an even stronger block (minus the fact it has cast pistons) and a few guys stated that they reason the 5.0's have been able to run near 500 and not blow the internals apart is b/c the pistons were forged. That is the first I ever heard of that I always thought the 93-95 Mustangs were hypertunic pistons.

I dont see Ford doing the consumers any favors and producing a run of the mill Mustang w/ Forged pistons. The only Mustang that I know of they did this with was the 2000 R, that has forged aluminum pistons.

revhead347 · Jun 7, 2009

Yeah, the Hyper's in the stangs are actually pretty good. The Hyper pistons in the 93' and up stangs are generally stronger than the forged pistons prior to that. They were a weak forging.

Kurt

Venom351R · Jun 7, 2009

I found an old stangnet thread from 07 that says 87-92 (last two months of 92 production) were Ford Forged pistons and 93-95 are hypertunic pistons.

http://forums.stangnet.com/708236-stock-5-0-pistons-forged.html

Venom351R · Jun 7, 2009

revhead347 said:
Yeah, the Hyper's in the stangs are actually pretty good. The Hyper pistons in the 93' and up stangs are generally stronger than the forged pistons prior to that. They were a weak forging.

Kurt

So in other words I could run around 10PSI and 500 at the wheels with a good tune and be "safe"

HGFireHazard · Jun 7, 2009

In a 302 or a 351?

Don't expect a 302 block to last long under that power level, a 351 should fare better.

Venom351R · Jun 7, 2009

351

I know the 351 is much stronger then the 302 but my main concern is if I can still run that power level w/ the stock pistons. Does not matter how strong the block is if the internals will give out on you long before then.

I did some digging and found out that I have Hypereutectic pistons. From what Ive read these are good for about 10PSI correct?

blksn955.o · Jun 7, 2009

You should be fine with a good tune. I would be shocked if they were cast...if I had to bet I would bet hyper for the simple fact Fords production blocks all used hyper it would probably cost more to run cast than the off the shelf hyper pistons they ran in everything else. Plus hypers had a better smog number as they did not expand at the rate or amount of forged pistons.

FWIW - buddy of mine is running a 150 shot on a B.O.P 400 with cast pistons not forged or hypers. Granted he knows he is playing with fire but he has run several bottles in it. I know its comparing apples and guitars but they are just stock rebuild cast pistons taking 150hp of abuse. This motor pulled the studs out of a billet trq. converter and the pistons are still good. He is just over fueling and running very little timing.

Venom351R · Jun 7, 2009

blksn955.o said:
You should be fine with a good tune. I would be shocked if they were cast...if I had to bet I would bet hyper for the simple fact Fords production blocks all used hyper it would probably cost more to run cast than the off the shelf hyper pistons they ran in everything else. Plus hypers had a better smog number as they did not expand at the rate or amount of forged pistons.

FWIW - buddy of mine is running a 150 shot on a B.O.P 400 with cast pistons not forged or hypers. Granted he knows he is playing with fire but he has run several bottles in it. I know its comparing apples and guitars but they are just stock rebuild cast pistons taking 150hp of abuse. This motor pulled the studs out of a billet trq. converter and the pistons are still good. He is just over fueling and running very little timing.

Wonder how long those will hold up lol

Another testament look at all the 5.0's on here running those hyper pistons and are at the 500 HP power levels and they are fine. Im not going to worry about it. The cost of putting in forged pistons is not cheap and I dont have the available tools needed to do so as far as pulling the engine out exc exc... so that's why I wanted to get away with what I had. Goes to show that you cant believe everything you read on the Internet b/c other people were saying I had cast pistons, according to the official SVT Cobra book I dont.

final5-0 · Jun 7, 2009

Redline_351R said:
So in other words I could run around 10PSI and 500 at the wheels with a good tune and be "safe"

Well Travis

Lets kick around a thing or two about this

The first thing would be the value of ... 10 psi

It goes without saying ........
10 psi on a stocker is not the same as 10 psi with all aftermarket parts

The whole psi thing can be so misleading

To get 500 you might only need 8 psi
then again
You might need to spin it enough to make 12 psi

I'd think the value of power output would be more of an indication
about how close you are to being in danger of splitting the block

I've always heard 450 to the wheels is about the limit
then again
When I got back in the Stang game ... SAE was the most used reference

I've seen STD values of 5% - 10% higher than SAE
so
I guess 450 SAE is about the same as 500 STD

I've seen many things written about what makes a ... "Safe" ... Blown Combo

It seems like most of those peeps boil it down to ....
the tune
AND
the quality of gasoline

anyhow ... just a random thought or two

Grady

revhead347 · Jun 7, 2009

Well, 500hp is kind of risky, but it will probably hold up.

Hypereutectic pistons are a type of casting. All pistons are either forged or cast. The cast pistons are broken down into three categories, hypo-eutectic (low silicone content), eutectic (medium silicone content), and hyper-eutectic(high silicone content). The more silicone you use, the stronger the piston becomes, but at the same time, they become more brittle. Forged pistons are heavier, but they flex more with heat. Hyper-eutectics can be physically just as strong as forged pistons, but once the heat gets too high, they shatter before they melt. Some of you might remember Keith Black pistons. Keith Black was an engine builder who specialized in selling his own brand of hyper-eutectic pistons. He was of the opinion that a hyper-eutectic piston made a better performance piston than a forged one.

When you use the term BOP, you have to be more specific. All the BOP transmissions are identical, but when you are referring to the engine, you have to brand specific, because the engines are totally different for different manufacturers.

Kurt

Venom351R · Jun 7, 2009

final5-0 said:
Well Travis

Lets kick around a thing or two about this

The first thing would be the value of ... 10 psi

It goes without saying ........
10 psi on a stocker is not the same as 10 psi with all aftermarket parts

The whole psi thing can be so misleading

To get 500 you might only need 8 psi
then again
You might need to spin it enough to make 12 psi

I always seemed to assoicate 10PSI w/ around 500 b/c thats what most people run for boost and the typical H/C/I 302 at 10 PSI (run of the norm stuff) puts them in the ball park of 500. Im not shooting for 500 and Im fine w/ 8 PSI I just want to know what my limit is before hand. I would be fine w/ 450..exc exc

revhead347 said:
Well, 500hp is kind of risky, but it will probably hold up.

Hypereutectic pistons are a type of casting. All pistons are either forged or cast. The cast pistons are broken down into three categories, hypo-eutectic (low silicone content), eutectic (medium silicone content), and hyper-eutectic(high silicone content). The more silicone you use, the stronger the piston becomes, but at the same time, they become more brittle. Forged pistons are heavier, but they flex more with heat. Hyper-eutectics can be physically just as strong as forged pistons, but once the heat gets too high, they shatter before they melt. Some of you might remember Keith Black pistons. Keith Black was an engine builder who specialized in selling his own brand of hyper-eutectic pistons. He was of the opinion that a hyper-eutectic piston made a better performance piston than a forged one.

When you use the term BOP, you have to be more specific. All the BOP transmissions are identical, but when you are referring to the engine, you have to brand specific, because the engines are totally different for different manufacturers.

Kurt

Great information thanks!

So in other words the heat is what will get to them and more timing causes more heat so keep the timing at a safe level and they should be alright?

blksn955.o · Jun 7, 2009

B.O.P 400-455 engines are what I am talking about. A 400 from a late 60s catalina put into an 80 f-body. The 400-455 engines across the B.O.P lines are very similar IIRC. I dont think the shortblock is totally different in the 400-455 family of B.O.P. engines make to make. However, I am not an expert...don't claim to be either. Is there a difference in the shortblock that is standout-ish?

Venom351R · Jun 7, 2009

What are you referring to as far as B.O.P engines?

revhead347 · Jun 7, 2009

The term BOP is an abbreviation for Buick Oldsmobile Pontiac. Back in the old days, each manufacturer of GM had their own engines, but they all started going to Chevrolet transmissions very early on. When you bought a GM transmission, it would either have a Chevrolet bolt pattern or a BOP bolt pattern. The BOP engines all had the same bolt configuration for the transmission, but the Chevrolet was different. So, if you ordered a Turbo 400 Automatic from Summit or something like that, you would have to specify that you wanted a BOP transmission if you were installing it on an old Pontiac 400 or something like that. And just to clarify, old Buick, Pontiac, and Oldsmobile engines are completely different, even though they bolt up to the same transmission, and they have a lot of similar displacements. There are virtually no interchangeable parts between any of those short blocks. For example, there is basically no such thing as a Pontiac small block. Pontiac only made a big block. The Pontiac 350 is the same physical dimensions, and actually weighed more than a Pontiac 455.

Kurt

Stock Piston Questions.

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