pistons and cams
Moderators: scottm, TrWaters, 392heminut
pistons and cams
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!
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Pistons
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)
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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
Larry
Owner of the Poor Man's Hemi Cuda
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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.
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.
Owner of the Poor Man's Hemi Cuda
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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.
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.
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SORRY!
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.
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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.
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.
Owner of the Poor Man's Hemi Cuda
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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
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
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