On the NHRA site they list several pistons for a stock 340 mopar. Can you use any of them when putting together a stock motor? or is only the TRW used. Seems one would have advantage from using say a JE, or a Diamond piston over the TRW because of the weight differences. Thanks Mark
I'm very interested to hear an answer. Where on the NHRA site did you see pistons listed? I found the NHRA limits for comp. ratio, etc.. What other info is on there? Matt
I used Keith Black ones in my Challenger T/A in a panic last minute redo. They were the only ones with an NHRA piston in stock at the moment back a few years ago. Love the small block Mopar but with correct pistons you can not get any compression. When I was done and we cert'd the motor for the race I had something like 10.13 to 1. And that was pushing the pistons as close to the head as we dared possible. We could not even meet the factory compression ratio on the car. It is a shame as it keeps them from being as competitive as they should be. I believe you just go to the replacement parts section listed near the blueprint specs on the NHRA site. Mark
It sounds like decking the block is in order then to acheive the compresion ratio or is that a no no? The piston list I seen was here http://www.nhra.com/tech_specs/engine/index.html this was a short cut from the pure stock certified page. The way I understand it they require certain parts to be in a stock motor to give it a certified stock motor. Is it safe to assume that what is on the NHRA site is ok? It does state no NHRA tricks to the block does that ax the decking of the block to acheive the compersion ratio needed.
From the list of NHRA accepted pistons for a 340 340 68-71 275-290hp TRW L2316F SEALED POWER 2332P CHILDS & ALBERT P1610 VENOLIA 275-340 BADGER B284 JE 136627 ROSS 55328 CP PISTONS M8-CP DIAMOND 68-71 340 340 72-73 240hp TRW L3062F SEALED POWER 2369P BADGER P296 TRW L2385F VENOLIA 240-340 JE 148623 ROSS 99588 CP PISTONS M5-CP DIAMOND 72-73 340 Looks like they are allowed to stick out of the top of the block by .045" .
i can not confirm it , but the NHRA i am sure has a minimum piston weight and for the piston to be legal i assume it must be at least that minimum weight ? i'm doing a 383 , stock is a cast piston which i am sure is lighter than the trw/sealed power forged i bought , 1003 grams piston and pin . the piston for my stroker is around 670 grams piston and pin .
That is correct. All the listed pistons by whatever manufacturer have to be accepted......weight and face configuration being primary.
pistons I just got off the phone with CP pistons. They are listed as a replacement piston for Olds. They could not give me the comp ratio of the piston but did say the min. wt could be 681 grams. Matt
You can deck the block to NHRA blueprint specs. The problem is that the odd shape of the small block Mopar piston does not allow you to get anywhere close to the maximum specs without the piston hitting the head. It is a tough motor to maximize. Take the NHRA specs with a grian of salt in this case as they are just wishful thinking. Mark
Well I guess I will just plan on using the TRW`s which I would say that is a safe bet to be excepted an see what I come up with on the compresion side of things.
IMO it was a sad day when we started using the NHRA specs. When Dan and Bob decided to go this route years ago, I called Dan the night I heard it and tried to talk him out of it. It is a great tool for specs and part #'s, but I have always strongly felt it should be held to ADVERTISED compression ratio. Dans concern for not wanting to stop this was that there was about three people that were doing it, and could not pass certifiaction if advertised compression ratio's were the rule. Some years have passed and more and more have gone this route. You can't change it back now, but still I feel advertised compression should be strongly urged and supported. Peter
Here, here! Now we have certified cars running faster than the cheaters! IMHO, the same can be said of x-pipes. Also, I was never a fan of allowing hidden electronic ignition. One of the initial attractions of P/S was the simplicity of the rules. But I also understand that there are tough decisions to be made when trying to grow an event. It's too late to go back... maybe? Regardless, P/S racing is still the best fun you can have with your musclecar.
I've got .060" off my heads! Too late. I also argued advertised compression when that happened, and no X pipes when that happened. It happened anyway, so now you can't have folks change engines and exhaust for a fun race where you win nothing! :laugh: I just think originally the thought was to be "competative" folks had to be in the top ten, so why not allow the NHRA stuff? Not a lot of folks are going to do it. That was an under estimation of just what "competative" means to everyone not in the top ten.
I like the idea of nhra rules being the guidelines.Most advertized compression ratios are really optimistic anyways. I am getting ready to build another RA 4 motor.Anybody heard anything about achieving nhra compression ratio,without cutting the crap out of high dollar parts,and still being able to certify ,if one so desires????
John Glasgo: John I sent you a pm that does not appear to have gotten to you. Please send me an e-mail when you have a moment to: rdl
John I was 6+ tenths of a point below the NHRA limit with the Judge motor and I felt I had cut to much already. It really makes me sick to hack up a pair of very expensive heads. I just could not go all the way and cut them anymore. As you and I know finding a good set of pure stock legal heads for a RA IV is very difficult and carries a very large price tag. I just paid 25% as much for a set of '70 heads as I did the entire Judge! The original Judge motor was a straight up +.030 rebuild and did not carry much compression and it still went 12's all day long. I would support a factory rating system. It would save a bunch of hard to find parts and money. In the short term we could grandfather in all the cars that were built and running at this current date. This would not short change the people who were playing by the current rules and not outlaw them. Mark
I think you'll run into more trouble with grandfathered cars and what not. Hey.....If a guy doesn't want to cut his heads or anything they don't have too. Same with gears....you want a 3.55 for street cruising....have at it. Once the genie is out of the bottle though....best too leave it alone.
Your right Brian the genie is out. Heck I have motors that would need "grandfathering"... I simply love this racing and would be open to either way. Both ways would not stop me from coming. Mark
