pistons and cams

MRHP · Post by **MRHP** » Tue Feb 03, 2004 6:32 pm

I am building a 354 and am planning to use PAW 392 pistons. I have heard conflicting reports on using those pistons. Could someone respond who has used PAW 392 pistons in a 354. I am also going to use Pontiac connecting rods. The rotating assy wil also be balanced. Any recommendations on cam and head choices would be greatly appreciated. I am trying not to make any mistakes on this motor as it is quite expensive. Thank you in advance!

hemirodder · Post by **hemirodder** » Wed Feb 04, 2004 2:24 pm

For the same money (about) you can get a set of Keith Black Hyeutetic pistons> I just got a set for mine and at a really good price. My feelings are that they will make a better piston than what PAW sells (which I was told were EGGE pistons)

392heminut · Post by **392heminut** » Wed Feb 04, 2004 6:50 pm

I built my 392 with Egge pistons, and got PAW 392 pistons for my son's 354. They were distinctly different pistons, and in my opinion did not come from the same source. The PAW pistons were about $100 less, and actually looked better than Egge's. The KB Hypereutectic pistons are better, but also cost more. Unless you're planning on really hammering your hemi at the dragstrip a lot, I'd go with the PAW pistons, you can't beat them for the price. I've put close to 100 passes on my 392 with cast pistons with no problems at all.
Larry

dodgedifferent2 · Post by **dodgedifferent2** » Wed Feb 04, 2004 11:01 pm

what if it was supercharged??

dodgedifferent2 · Post by **dodgedifferent2** » Wed Feb 04, 2004 11:01 pm

but only used for low boost!!! and hardly see track time just very rarely!

MRHP · Post by **MRHP** » Thu Feb 05, 2004 7:03 am

Hey 392heminut, what heads are you using? Casting number. Do you know the final compression of the engine? I just want to make sure I am doing it right. Have you got your sons engine running.

392heminut · Post by **392heminut** » Thu Feb 05, 2004 8:38 am

dd2;
Way too much compression with these pistons to run any kind of boost at all. I wouldn't run anything but forged pistons with a turbo, supercharger or nitrous.

MRHP;
My son's engine isn't running yet. We assembled the shortblock last summer and he took it up to Laramie where he lives. He just got the heads done, so I don't know the exact C/R, but going by the factory cc rating on the heads it should be in the neighborhood of 10.5 to 1. I'm not sure what heads he has, as I don't have my notes with me right now. 10.5 C/R is about the limit for pump premium. Bob Walker at Hot Heads will tell you that you can run one compression point higher with the hemi heads than you can with the wedge heads due to the more efficient combustion chambers.

Bailiesdad · Post by **Bailiesdad** » Thu Feb 05, 2004 6:44 pm

392 pistons compression height 1.955 in most cast pistons/hyper
354 pistons compression height 1.931 in most cast pistons?hyper
VALVE RELIEF POCKETS CUT FOR MAX 465 LIFT CAM
rod on 392 6.956
ros on 331-34 6.625

Put a 392 piston on a 331-354 rod and it sits .031 higher in the bore plus it is displacing more air .0625 overbore. It cuts the cam lift to below 430.

Do the math, the compresion is raised over that of the advertised 392 compression ratio. (This is if you have stock deck and heads.) Change heads or cut any and you raise the compression and stress them more plus reduce the cam lift available.......... 10 off heads 10 off block 31 for pistons being higher you cut the factory clearance on piston to valve clearance by HOW MUCH??? (These motors breather better and like bigger cams, do this and you go backwards.)

Egge/PAW CHEAP pistons are the same. CAST carbs 5000-5500RPM
KB hyper are hybred Carbs,( blowers blow them up) 5500RPM
Forged pistons you build to your specs 6500 plus RPM any appliction much much stronger and durable. (CHEAP INSURANCE)

Bottom line spend 300 bucks for Cast and gamble or spend 600-700 on forged and be sure. (When the cast pistons fail the bearings and gaskets alone will cost more than the difference.)

IF you are rebuilding for more power than stock, you need stronger pistons and rods with tollerances built in for bigger cam and higher rpms..... If you are rebuilding a stock motor, for stock power in the stock rpm range, EGGE is the very best stock replacement piston made today for the money. Then FORGED for more performance.

392heminut · Post by **392heminut** » Thu Feb 05, 2004 7:58 pm

Bailiesdad wrote:VALVE RELIEF POCKETS CUT FOR MAX 465 LIFT CAM
.

Hmmm...........that's strange, I'm running a .480 lift cam with no problems. Come to think of it, I had plenty of room for a .510 lift cam, and that was after doing a .010 cleanup cut on the heads!

Bailiesdad · Post by **Bailiesdad** » Thu Feb 05, 2004 8:14 pm

Factory tollerances are sometimes understated because people push the window, you can do the same thing with thicker headgaskets, what about the pistons got any comments on the subject?

392heminut · Post by **392heminut** » Fri Feb 06, 2004 8:32 am

Bailiesdad, as you can see, your last post was deleted. Any post you make which has derogatory remarks towards another member of this board will be deleted. If the practice continues you could be removed from the forum.

Bailiesdad · Post by **Bailiesdad** » Fri Feb 06, 2004 9:54 am

Apply the same rules to everyone.

MRHP · Post by **MRHP** » Fri Feb 06, 2004 11:38 am

I did not mean to cause any trouble! I just needed some info on building my 354. If anyone is running the 354 with PAW 392 pistons I want to hear from you. Please include head and cam choices. You do not have to tell me your secret recipe but I need to know so I can order these parts. It will be a street driven motor 375 horse 5500 max. I am going to put in a early 60's truck for a shop truck for my business. I appreciate all of your help and support.

392heminut · Post by **392heminut** » Fri Feb 06, 2004 8:40 pm

MRHP, you haven't caused any problems here, and you have some very valid questions. Fact of the matter is, anytime you build an engine with a cam or pistons that aren't factory stock the valve to piston clearance should be checked. A lot of people have gotten away without doing it, but there is always that chance that things could go wrong if you don't know for sure. I posted my findings with my motor with the parts I used, results may vary! There are a lot of variables, and no two engines are alike even if built with the same identical parts.

My son called today, and is hoping to be able to check his valve clearances this weekend. If he gets back to me with some numbers I'll post them. I still don't have the casting numbers on his heads yet, but they are 354 heads.

MRHP · Post by **MRHP** » Fri Feb 06, 2004 8:55 pm

Thank you very much.I called hotheads and Bob said I should have no problems. I would still like to hear a sucess story firsthand.

392heminut · Post by **392heminut** » Sat Feb 07, 2004 10:51 am

Bob Walker is very knowledgable about the early hemis, as he has been working with them for a long time, and he doesn't mind sharing what he knows with you. I got a lot of good info and advice from him when I built my first 392.

TrWaters · Post by **TrWaters** » Sat Feb 07, 2004 11:21 am

Ok..I did the math.
1st..... we are talking stock 354 motor bored to use 4.0" 392 piston.

1: rod length is not a factor. (in this case)
2: the compression will be affected by stroke, not rod length (in this case)
3: given that the 392 piston designed for 10:1 compression using a stroke of 3.90 inches is now moving only 3.63 inches, it is impossible that it will be moving, or compressing more air.

With that being said, the stock 58 392 piston is approx .080 taller than a 56 354 piston. This will raise the ratio over the stock 354, but not to the 10:1 advertised ration of the 392.

But then again, I could be wrong

panic · Post by **panic** » Sat Feb 07, 2004 8:02 pm

Bailiesdad · Post by **Bailiesdad** » Mon Feb 09, 2004 6:23 pm

dome volume pushed into a 92-102 cc head vrs the 112 cc of the 392 will make a difference. The early 331-354 heads have smaller combustion chambers than the 392 heads.

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