question about cast pistons
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From: Bristol TN.
question about cast pistons
I have a 71 302 engine on a stand in my garage. It has been rebuilt once before I know this becuase the cylinders have been bored (from my dads mic reading 30 over) The inside of the engine looks good as if when i have it rebuilt I might only have the have the crank polished and new bearing and rings. But what I was wandering was I was wanting to convert to a very mild roller cam(stock) with some nice aftermarket heads. I'm willing to bet that the pistons a 30 over CAST Stock pistons. I'm sure you guys have seen the article on CAR CRAFT about how they got 400 horsepower out of a stock 302 with 165's AFR heads but the stock pistons for that model 302 were factory forged. Well I am seriously thinking about going that route but It doesn't realy have to be 400 but with everything I have researched says that a stOck or very mild roller cam and AFR 165's will give a 302 over 350 horsepower at th flywheel. WILL STOCK CAST PISTON HOLD UP TO THIS WITH NO MORE THAN 9.5 COMPRESSION (i'D LIKE TO KEEP IT AS CLOSE TO STOCK COMPRESSTION AS POSSIBLE LIKE 9 TO 1 OR SOMETHING). I would be driving it often if not everyday maybe have some fun at a redlite or 2 but no drag racing high RPM at the strip.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Cast pistons are no problem for this application, they won't really be under any additional stress because the extra power comes mainly from the additional airflow of the heads. Forged pistons are really only necesary for boosted or nitros applications or extreme high rpm motors. BTW, you'll notice from the article that you'll need at least an HO roller cam and 1.7 rockers to get anywhere near 350HP(crank) with the AFR heads, as well as an intake and exhaust system that will support that amount of airflow. None of the stock Ford intakes qualify here.
Cargo Master
Joined: May 2007
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From: British Columbia
I assume there are good and not so good brands of cast pistons. Some of the oversized ones used to be "destroked" a small amount to prevent an increase in compression ratio. I don't know if this is still the case.
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Hotshot
Joined: May 2003
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From: south louisiana
Originally Posted by Beanscoot
I assume there are good and not so good brands of cast pistons. Some of the oversized ones used to be "destroked" a small amount to prevent an increase in compression ratio. I don't know if this is still the case.
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Postmaster
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Originally Posted by baddad457
The same is true for all 289/302/5.0 pistons, be they cast, hypers or forged, and applys to dished & flatops. Pin heights vary from 1.585" to 1.615" It pays to check this dimension before buying any piston.
Hotshot
Joined: May 2003
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From: south louisiana
The 1.585's usually come up to about .020 down the hole at TDC. That -.020 to -.035 plus the blocks with the 8.226 deck, subtracts about 1 full point in the compression ratio. I'll be there are lots of guys who think that 9 to 1 comp ratio is really closer to 8.
Cargo Master
Joined: May 2007
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From: British Columbia
As I understand it the real problem with the piston below deck makes too deep a "squish" area, which I have read leads to increased octane requirement. If so, the "cure" that the manufacturers use creates the disease.
Is this "squish" area story true? And are there other advantages/disadvantages to having the pistons below stock or below deck height?
Is this "squish" area story true? And are there other advantages/disadvantages to having the pistons below stock or below deck height?
Postmaster
Joined: Dec 2006
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From: Rockford, Il
do yourself a favor, replace the cast pistons that are in it now. nothing wrong with a cast piston in your application. they like all engine parts have a finite lifespan, unfortuneatly we cannot quantify that span. it would be a real shame to lose a motor, because you didnt replace a 17 dollar piston in your freshly rebuilt motor. Dan
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From: Bristol TN.
thanks guys I appreciate the info, I think I will definitely go with some new pistons and rings when i rebuild it. But I have mentioned before in other posts that I have a 87 302 truck shortblock out behind my garage under the shed. It was a hydraulic cam but is "roller ready" from what I have read on this site where all I have to do is drive and tap two holes in the valley of the engine and drop in some stock roller lifters and everything will work. I think I might have to go with this engine since I really want a roller cam. I have recently bought a stock mustang roller cam off ebay for 35 bucks and am awaiting it arival. I hope the lobes arn't messed up or anything and it is a good cam (the description says it is in good usable condition but you never know).
