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#21
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I've also been curious how the Voodoo 702 would run in an engine like this. Something I may try in the future.
For the OP, I think anyway you slice it, you'll need to deck the block anyway if you're going for a proper rebuild and want things square. I guarantee it's going to be off on one end or the other. How much you want to deck it though is going to determine the route you take. I personally wouldn't start with a piston .040 in the hole though. Which means new pistons requires a rebalance of the assembly. And before decking the line bore needs to be checked and honed. Kind of got backed into a corner with pistons in the hole that far. One way or the other, even if just replacing pistons and getting them closer to deck, then a rebalance and call it good enough, it's going to be a spendy fix, and the block still won't be square. |
#22
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#23
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"He wants it to remain basically numbers matching and stock as far as block and heads go, but stated he would like maybe a bit of a camshaft upgrade to get a little more out of it, but nothing too radical."
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#24
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Close as it's going to get for a better compression ratio to use pump gas. He can keep his numbers matching heads on the shelf. |
#25
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#26
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Right. Just an example. They are still out there. 70 GTO heads.
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#27
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#28
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Options. More is better.
What would you do to get the compression down into the 9's? |
#29
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I'm building an engine very similar to this. I have decided to go with the factory 068 cam. It should be very easy on the valve train and should allow me to run pump gas with the stock 10:1 compression ratio. I am running a 744 cam in a 421 engine with 10:1 compression and 670's. I think the 068 cam would have probably been just as quick though. It does run good with the 744 but I think there would be more power to be had with a summit 2802 cam or something similar.
However, I don't think you could go wrong with that Crower 60916 cam either. Just use some big block Chevy rocker arm studs and nuts to change the valve train to an adjustable valve train. It should be a good runner. |
#30
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I would take a degree wheel and dial indicator and get some idea of what the present cam has for max lobe lift and 0.050" duration. No way to know what is an upgrade without knowing what you have now.
Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#31
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I do not see anything wrong with the proposed upgrade plans. Only comment I would mention is there is a good chance the engine has the original balancing yet on the crank. Most shops that use those 8vr cast pistons would not balance something. So if you can not talking him into the forged rods, use the originals, run arp bolts and get some 2vr pistons should be fine with out rebalancing. Does not sound like the owner is wanting a finicky pump gas engine. The smaller aggressive cams like the 702 voodoo or something similar do fine with less compression. The 60916 though would like a little more compression than where it currently sits. I would only use the 60916 if they go for the upgrades. |
#32
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I've been using Icon pistons in most builds, but there may be other varieties out there for 400's that don't end up so far down in the holes at TDC.
Lowering compression is always an option, but even with lower compression the cam choice is still critical to make sure it makes optimum power and still manages pump gas w/o issues. We've seen several Pontiac engine build with no more than 9.3 to 1 compression pound the rod bearings right out of them simply because they put enough camshaft in them.....FWIW......Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
#33
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you are essentially saying the same as me, except I've removed what I can only guess was misinterpretation. where you lose me is here: Quote:
Are they not parts that you (the engine builder) has chosen to use to get your long block to your desired compression? I agree the cam should be chosen to compliment the compression and intended use, but weather you are deterimining where the compression will be, or where you want it, you are still first looking at the compression; If by chance you are replying to this: Quote:
If this is intending to be a street motor, you can go too much compression very quickly going this way.
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1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
#34
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The 64's would make things more manageable. Along with the autotech pistons. Summit 2801 Cam. That's what I would do if I was stuck with iron heads and could pick what would work best with pump gas. |
#35
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What might be beneficial, is is someone can find a good compression calculator, I seem to be having trouble finding a good one any more. Even with the wallace racing one, I must be doing something wrong, because I seem to be getting 6:1 when I put in specific parameters which should yield closer to 10:1... I think it's the 'head cc' spot that really bunked me on that calculator.
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1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
#36
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Another Option
I know what I'm about to post goes against common wisdom but.... I recently build an engine for a friend that has a 400 in a 72' Ventura. I just did it as a favour at no charge. The car is for his teenage son and he wanted to do it on a tight budget. We tore the engine down and it was .030 over, 8 valve relief pistons and had #16 big valve heads on it. Piston deck height was around .030. The engine had a lot of piston to wall clearance too so I tried to get him to bore it and use "better" forged pistons in it. Wouldn't do it. Just hone and rering it. So I warned him it's going to ping, probably use oil, etc... We wound up putting a 2802 Summit cam in it and a used 2500 torque converter I had laying around.
End result is this car runs very well, no hint of detonation anyplace, and no oil use. Car just ran a 13.80 1/4 mile too! I wouldn't have believed it but in this case it turned out great!
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62' Lemans, Nostalgia Super Stock, 541 CI, IA2 block, billet 4.5" crank, Ross, Wide port Edelbrocks, Gustram intake, 2 4150 style BLP carbs, 2.10 Turbo 400, 9" w/4:30 gears, 8.76 @153, 3100lbs |
#37
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It's obvious the heads have to stay. On an engine like this, with this type of bird, and with restoration in mind, the 12's need to be on the YZ block. So I understand the OP's purpose entirely.
The compression isn't going to be outrageous even if a flat top piston was at or very near zero deck, and could manage pump fuel fine with the right camshaft, I'm doing it with an 068, but I'd recommend a little bigger to keep things a little safer at that compression ratio. It's really going to come down to how much money the owner is willing to spend to accomplish his goal. If he wants to leave it the way it is and use a non adjustable valve train then I see no other choice but to stick an 068 in and button it up, hope for the best. With pistons .040" in the hole the compression has to be pretty dismal anyway. |
#38
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Can you take an image capture of your values?
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#39
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Quote:
http://cochise.uia.net/pkelley2/DynamicCR.html
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Karl |
#40
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If I'm not married to the 12's then I would use the 46's. |
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