302 Hypereutectic vs. Forged pistons? 5.0 HO w/ GT40P

[smoked77]

I'm trying to what rebuild kit to purchase for a 5.0. The block, etc cam from a 1990 5.0 HO and I am going to install GT40P heads and intake (1997 Mountaineer). Is it worth the money to install forged pistons? Is there anywhere cheaper to buy rebuild kits than Summit?

Merry Christmas!!!

 

[bax]

IMO. Forged is the only way to go. But I am rich as hell. L.O.L.

Bax

 

[JWMcCrary]

I used the Keith Black hypereutectic pistons in my 393, which are 302 pistons. You can't go wrong by using forged but I was told it wasn't necessary for my engine, especially if you don't plan on using nitrous, plus you should be able to get a little longer engine life.

Good luck with your choice.

 

[needabronco]

IMO... Unless you are going to use nitrous or supercharge it, hyperuectic pistons should be fine. Forged pistons have different expansion properties and need more clearence between the piston and firewall, and can be noisy, beside very expensive. I have used the Summit kits before and they seem to be pretty good quality. The bearings and rings are good quality, and the pistons were very close when I had them balanced. I'm sure you could go cheaper, but it is a complete package. Add a good quality timing chain and water pump and you should be on your way. I believe that a good machine shop is more important than the build kit, and sometimes there build kits are cheaper also... The guy I use fits the pistons to the cylinder bores to ensure they are machined right, and I know alot of them don't do that... Good luck.

 

[357Bronco]

I've used hyper pistons with no problems( street, trail truck). It's worth the time and money to balance the rotating asembly. Forged pistons are pretty rugged and can withstand power adders ( nitrous, blowers ), but some are heavy. If your a trail truck, hyper is fine. Want big compression or power adder go forged. Depends on your budget and application. I run forged ,light weight, high compression pistons but they are not cheap. Do your research and you'll be fine.

 

[scsm76]

My last two engines that have gone south on me were from failed pistons, one KB and the other speed pro hypereutectic pistons that dropped skirts and destroyed the block. Both were very mild naturally aspirated and less than 300HP. For the cost difference, I only use forged pistons. If you are going bigger HP (>450hp) then look into forged rods and crank. Ford used forged pistons in the first few years of the 5.0 HO.

 

[Doyle]

If budget permits go forged. I've lost two blocks to cracked piston skirts on Hypereutectic pistons. One was a 300-6 that never saw over 4500 RPM, failed at 32,000 miles.

 

[BUCKETOBOLTS]

I run hyperuetectics in my engine also. You need to follow the manufacturers directions for clearancing the pistons to the bore. That is the only reason I've ever seen one fail, with the exception to an OD on NOS.

 

[smoked77]

I thought 5.0 HO's used forged up to the early 90's. I'm planning on using the A9L mustang computer.....so.....with the GT40 heads/intake and headers, I think I should see 30-40hp??? gain over the stock HO output of 225hp. Not sure, though. I also assume I will need the BC Broncos headers.....unless anyone knows of headers that will fit the GT40 head in a bronco.

Back to the pistons......I need to do some research and see what the stock compression ratio was and then see if it changes w/ the GT40 heads.

Also, any suggestions on which cam to use - the mustang cam or the explorer cam?

Any good websites that you know of for general info like comp. ratio, cam profiles, head chamber volume, etc???

Man! I'm just full of questions..........

 

[slcpunk]

I have no idea but I bet you could see atleast 260hp...I would think atleast, but I really dont know

 

[broncnaz]

I believe Ford used the Hypertecnic pistons in 5.0's in the 90's of couse I'm not asure about the HO's. I would go with Hyper's over forged even standard cast pistons are fine. Forged are great but with the clearances need to run them you really have to let the engine warm up before driving. Ever hear a cold engine with forged pistons during startup? doesnt sound good. Hyper and cast pistons are a little more forgiving when the engine is cold. I know there were problems with the early Hyper pistons but the name brand companies should have it all fixed I've heard vert few failures lately and most of them that do were during races.
Id keep the comp ratio at 9.5 to 9.0 run the exploder cam and dont worry about actual HP numbers you may be disappointed with the results. If you call a cam company they will setup up with a cam that is based on your vehicle and needs if they give you the spec's you can compare it to the explorer or mustang cam to see if they are close enough for your needs or you need a aftermarket one. Basically match the cam to your vehicle then build the engine around the cam you'll get a better responding engine than most of us can suggest.

 

[jeepbus]

The Mustangs used forged pistons until 1992,then in the 93 model year got the Hyper pistons.I belive they started in 87 with the forged.;D

 

[OX1]

The Mustangs used forged pistons until 1992,then in the 93 model year got the Hyper pistons.I belive they started in 87 with the forged.;D

My 86 HO had forged. Been nitroused and turbod to death. No problems with cold slap that I've ever heard (I bought it new in 87), even after sitting for a long time. If the factory forged pistons are still avail, I would run them in a heartbeat.

 

[smoked77]

I think I'll tear it apart and figure out how the mountaineer engine looks (1997). Since it has 160000 miles on it, I assume it needs bored......so, I'll check with the shop and ask if they can size the pistons correctly for hypereutectic. Thanks for all the input..I'll welcome more if you have any.

 

[bmc69]

The typical skirt clearance spec for a hypereutectic piston is .0015 to .002". We typically set them up a little looser than that at .0025". For forged pistons, .004-.005" is typical..toward the larger number for a 'performance' engine'. The warm-engine running clearances are roughly the same for both..the forged piston expands much more than the hypereutectics.

In my experience, audible 'cold piston' slap does not apear on a stable* piston untill you see skirt clearances of .008" or more.

*by stable, I mean not a 'shorty' with low length-bore ratio..like a stroker piston for a 427W for example.