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  #16 (permalink)  
Old 11-13-2012, 06:16 PM
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:/ ill check block decking prices tmrw.. Your right and I should just leave the stupid thing alone. I am just upset about the quality of piston and worried about quench/compression. Ill just leave it alone though.

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  #17 (permalink)  
Old 11-13-2012, 06:33 PM
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Originally Posted by 0trbo4myCHEVUICK View Post
???? I am under the impression that the pistons in my short block are around -33cc maybe more becuse they sit lower in the hole "rebuilder piston"
What? No i bet 3.3 cc is closer to the correct number. Full dish pistons are 12cc. I dont even think you can buy 33 cc pistons? Somebody correct me if im wrong. The calculater link has the deck hight seperate so you can use the piston cc number and your measured deck height. It will gwt you close even without full measure of the pistons cc. Figure 5 cc and .045 as your bad deck height. It should be .025 i think stock and .045 with rebuilder pistons.

Should be right at 9.2 to one. But your are right those pistons will make good power but will not hold up to n20 or blower. You do got the right stuff to make 350-400 hp with the right heads and cam.
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Old 11-13-2012, 06:49 PM
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well I was only hoping for 350hp at best so that makes me feel better.
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Old 11-13-2012, 08:16 PM
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Originally Posted by 0trbo4myCHEVUICK View Post
well I was only hoping for 350hp at best so that makes me feel better.
If your only looking for 350 reliable HP, and are on a beer budget.....find some 416 heads, spend some time, not money,time, porting them at home.....add 1094 felpro headgaskets, a used performer rpm or knock off equivilant, Holley 750, small 268 cam, long tube headers.....and a recurved Hei. This can be easily accomplished with the current short block you have. And likely for under 750$ on top of what you have already invested. It will be dead reliable, make the number your looking for, and give you a great feeling of accomplishment. And its fun when your buddies laugh at your budget build until they ride in it......there.,,,,,,I waited as long as I could.....sorry.
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Old 11-13-2012, 08:34 PM
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ive been looking for vortec heads and a roller cam but are the heads you are suggesting 58cc? Still worried about compression figuring i should get the smallest chamber possible. I like vortecs flow numbers though..

Last edited by 0trbo4myCHEVUICK; 11-13-2012 at 08:40 PM.
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Old 11-13-2012, 08:56 PM
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ive been looking for vortec heads and a roller cam but are the heads you are suggesting 58cc? Still worried about compression figuring i should get the smallest chamber possible. I like vortecs flow numbers though..
The cost of roller cam be alot more than flat hyd. If you want to spend 2g's on the engine just buy a complete kit. Add a 750 carb and you know you will hit the 350-400 mark with the block you have. But you do pay a little extra for the power packages over buying the same style parts as cheap as possible.
Edelbrock 2098 SB Chevy Power Package 410 HP Head Kit | eBay

Sorry about the ebay link the price seemed ok but im sure you could buy it cheaper somewhere else. This way you know it will run the numbers and dont have to sort thro a mountain of crappy vortech heads to find a set of performance heads. Not all the truck heads were big power. You may be better off buying new vortech performance heads from gm performance. If you buy used heads make sure they are ready to go. Heads that need to be rebuit can be a crap shoot. Better to spend a little extra to get parts that work the first time you buy them. Just make sure you get 64cc heads no matter what heads you get.
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Old 11-13-2012, 09:12 PM
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specs im reading sais 8:1 compression with these pistons under a 64cc. Im sure thats without a head gasket and a zero deck too lol. Im willing to spit out the 200-250 for a roller camshaft. I might just try and sell this block though. I need to sleep on it.
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Old 11-13-2012, 09:35 PM
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The 423np pistons are Speed Pro cast dished pistons. According to the Speed Pro electronic catalog they are 1.54 compression height "rebuilder pistons", with a .100" dish, 10cc dish/valve reliefs.

I don't see a H345CP piston listed.

The H345ACP is a hypereutectic flat top 4 valve relief piston with 1.548" compression height, so it's still .012" shorter compression height than the standard 1.560", but not as bad as most of the rebuilder pistons. The piston dome volume is 6.88cc, and the weight is 545 grams.

The H345NCP is a hypereutectic flat top 4 valve relief piston, full 1.56" compression height, 5cc dome volume, weight 546 grams.

You already have the short block with basically the factory piston style except for the shorter compression height. Either use it as is, or as suggested, disassemble it and have the block decked. Figuring you now have about .045" "in the hole", use a Fel Pro #1094 shim head gasket .015" thick, that will give you a .060" quench. With vortec 64cc heads you will still be about 9.4:1 static compression ratio, the same as the '96 thru 2000 vortec truck engines, and the same as the GM Performance Parts 350HO 350 cubic inch 330 HP crate engine and the CT350 350 cubic inch 350 HP circle track crate engine. These engines both use a very mild hydraulic flat tappet cam with .435"/.460" lift, 212*/222* duration at .050" lift, 112* lobe spacing angle. Even a very mild roller cam will improve these figures so you can reach your 350 HP goal.
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Old 11-13-2012, 10:05 PM
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Quote:
Originally Posted by 0trbo4myCHEVUICK View Post
ive been looking for vortec heads and a roller cam but are the heads you are suggesting 58cc? Still worried about compression figuring i should get the smallest chamber possible. I like vortecs flow numbers though..
Yep, before you get to stressed out about your pistons, search 416 heads, try and wade through the garbage from people who hate them, and have yet never used them, or used them wrong.....the more time you put in, the more you will get out. Find F-bird 88 posts, he knows what he is talking about.....yes, they are 58cc, yes, they CAN flow more then enough to meet your goals....and then some.....and people almost give them away.....mine were given to me free, my neighbour has a set for sale, 40$.....they are out there...with 1094 shim style gasket your compression will be there. I have a stone stock short block, my pistons look just like yours, I have a porting kit I bought, a small compressor, and a die grinder....assorted length carbide cutters.....and about 40hrs into them. Small lunati barebones cam, under 100$, I had a perfomre Intake, and a stock qjet card....it pulls....hard...very....on a gtech dashboard dyno it traps 112mph, factor in 5mph optimism....and I'm still around 107mph in the quarter......the math says 367hp......yah yah, its not a track.......I get that.....trust me...the math is close.....the motor works.....800$, from top to bottom....sees 6000rpm daily....gets decent mileage, sounds good, and has been reliable as hell.....look into it.......you will enjoy it.
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Old 11-13-2012, 11:43 PM
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350///357 build

Here is a website with the pistons that you have in your block. Federal Mogul Pistons 423NP - SummitRacing.com. Like was said the compression height is 1.540. 9.025-1.740-5.700-1.540=8.960. The piston would be .065 down in the block if the deck height is 9.025". Here is a website with the pistons H345CP that you want to buy. Sealed Power Hypereutectic Flat Top 4 Valve Reliefs Piston Std Size | Northern Auto Parts. The comp ht. is 1.548. 9.025-1.740-5.700-1.548=8.988 The piston would be .037 down in the block. With the new pistons in the block and a .015 compressed thickness head gasket with 64cc heads would have a static compression ratio of 9.669 and a quench of .052. If I had to make a decision like this I would get my measurement from the center line of the crank to the top of the deck. Then you can figure what comp. ht pistons you need. You can figure the compressed head gasket thickness and quench.

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Old 11-14-2012, 04:14 AM
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cdminter59, with the 1.54" CH pistons + 5.70" rods + 1.74" (half of stroke) I get 8.98", which would leave the pistons .045" in the hole with a nominal 9.025" deck height instead of .065" in the hole.

The GMPP 350HO and CT350 both use a .028" thick head gasket, with a "standard" .025" deck height would give a .053" quench distance. With .045" piston deck height with a .015" shim gasket would give a .060" quench distance, not ideal, but workable. It would make your CR just slightly lower than the stock spec of 9.4:1.
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Old 11-14-2012, 10:44 AM
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If my rods have been "resized" are they still considered a 5.7 rod?
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Old 11-14-2012, 11:13 AM
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350///357 build

Quote:
Originally Posted by BigEd36 View Post
cdminter59, with the 1.54" CH pistons + 5.70" rods + 1.74" (half of stroke) I get 8.98", which would leave the pistons .045" in the hole with a nominal 9.025" deck height instead of .065" in the hole.

The GMPP 350HO and CT350 both use a .028" thick head gasket, with a "standard" .025" deck height would give a .053" quench distance. With .045" piston deck height with a .015" shim gasket would give a .060" quench distance, not ideal, but workable. It would make your CR just slightly lower than the stock spec of 9.4:1.
Thanks for the correction BigEd36. I calculated it again this morning and came up with the .045" for the piston height. This would have a static compression ratio of 9.499 and .060 quench like you said. Sorry about the botched numbers.
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Old 11-14-2012, 12:15 PM
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If my rods have been "resized" are they still considered a 5.7 rod?
yes they resize the big end bearing hole. basicly make it round again. so its does not effect the length of the rods its just to make sure the hole for the crank pin is dead straight. Sounds like you had all the right work done. i think you will be happy. 9:1 will do the trick anything more is cake. Use the thin gasket and some good 64cc heads and let it rip it will run good. I actually think after running the numbers a few times that for iron heads 58cc might not be a good choice since you are so close to pump gas range. I also dont know your area so not sure if the car will need to run smooth in 110 degree days. 58cc you will want to run a normal or thick gasket just to be safe.

I think you have gotten some bad advice from the net it happens. I did a google search for your pistons and came up with silly numbers that didnt make since and every body had a different guess. Summit/jegs didnt even list the cc. One guy on ebay said they were 8:1 with 64 cc heads. If so every turbo and blower guy would no about these pistons. Usally you need full dish pistons to reach 8:1 or below with 64cc heads and those pistons cost twice as much unless you want the stock style and they are over 8:1 when 0 deck is used. Usally only forged/hyp. pistons will give you that low a compression. Simply because they will give a 6:1 compression on 87 cc heads and the engine might not even run right like that it would certainly be slow. You got to figure they make these thing to run with any head so you have to be able to get at least 7:1 with 87 cc heads most will produce more. You can buy forged/hyp. dished with large cc but they are purpose built for boosted motors. Its a good thing to check all the issues before it goes together now if the engine is soft and will not tune to the hp you are looking for you know exactly what needs to be done and can plan the job out. Much better than just going to pull the motor and try to find out whats wrong. Here it should run pretty good if you need more you know exactly where to go to get it. Rarely will you find yourself in such a good postion.

Hope all this helps... sorry for the long post.
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  #30 (permalink)  
Old 11-14-2012, 12:58 PM
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yes they resize the big end bearing hole. basicly make it round again. so its does not effect the length of the rods its just to make sure the hole for the crank pin is dead straight. Sounds like you had all the right work done. i think you will be happy. 9:1 will do the trick anything more is cake. Use the thin gasket and some good 64cc heads and let it rip it will run good. I actually think after running the numbers a few times that for iron heads 58cc might not be a good choice since you are so close to pump gas range. I also dont know your area so not sure if the car will need to run smooth in 110 degree days. 58cc you will want to run a normal or thick gasket just to be safe.

I think you have gotten some bad advice from the net it happens. I did a google search for your pistons and came up with silly numbers that didnt make since and every body had a different guess. Summit/jegs didnt even list the cc. One guy on ebay said they were 8:1 with 64 cc heads. If so every turbo and blower guy would no about these pistons. Usally you need full dish pistons to reach 8:1 or below with 64cc heads and those pistons cost twice as much unless you want the stock style and they are over 8:1 when 0 deck is used. Usally only forged/hyp. pistons will give you that low a compression. Simply because they will give a 6:1 compression on 87 cc heads and the engine might not even run right like that it would certainly be slow. You got to figure they make these thing to run with any head so you have to be able to get at least 7:1 with 87 cc heads most will produce more. You can buy forged/hyp. dished with large cc but they are purpose built for boosted motors. Its a good thing to check all the issues before it goes together now if the engine is soft and will not tune to the hp you are looking for you know exactly what needs to be done and can plan the job out. Much better than just going to pull the motor and try to find out whats wrong. Here it should run pretty good if you need more you know exactly where to go to get it. Rarely willmj you find yourself in such a good postion.

Hope all this helps... sorry for the long post.
Good quench makes a huge difference as well tho. I run a stock 4 valve relief dish, stock block, so .025 in the hole, with a shim gasket, and appr 60cc chambers after deshrouding.........I prefer to run 94 as it gets hot as hell here in the summer. But many times have used 91 with no issue at all.
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