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Old 12-07-2009, 03:39 PM
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stroker 383 or 350 rebuild

I am ready to start my rebuild next week. I have a lot of research and am trying to put it all together. I would like to get advice from people who have considered a stroker. Simple tips on the do's and don'ts from experience

I have a 1975 Corvette L-48 with TH400 auto, 3.55 or 3.73 rear, performer manifold, ac, dual exhaust (no cats), double hump heads (match ported and milled to 60cc chambers). The tranny has been rebuilt, engine compartment is finished and waiting for the motor

I am looking for a budget build that is 350-400 hp which is drivable and dependable (does this sound reasonable?)

I am trying to keep it as reasonable as possible without compromising reliability, but have enough gains to justify stroking over a 350 rebuild. I am looking for the most power for the buck and still maintain drivability and reliability

will the rest of the drive be ok with this HP and TQ

will the 2 bolt main be ok

i want to stay in the rpm range of the performer (0-5500 rpm)

should i rebuild the Q-jet or get something else, if so what

will the double hump head be ok, they are match ported and milled which reduced the chambers from 64cc to 60cc

if not, which heads are the best bang for the buck

which kits are better (I am currently looking at eagle and scat)

should I go with the long or short connecting rods

which roller cam is the most aggressive that will provide enough vacuum

I have a good shop to build and balance whichever kit we get
My heads and intake manifold will be ported to match

My local shop will be ordering the parts as well as the complete rebuild and machine work. They will be balancing ANY kit I go with to be safe

What is the Differences with the same build as a stroker or not (HP and TQ)


thanks for the help, I know its alot of questions but the more you know, the more you realize you don't know

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Old 12-07-2009, 04:45 PM
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I would rather have a 350 with good heads than a 383 with stock heads. If you are on a budget then get proper heads first.

check your gear ratio and be sure of what you have. A 75 vette with an auto trans will most likely have a 3.08 gear. what are the rpms at 60mph and how tall are your tires?
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Old 12-07-2009, 05:33 PM
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Here's my oppinion...... Keep the double hump heads(especially if they have the 2.02 valves maybe mill them somemore to get around 10/10.5cr using flat-top pistons...hyperutechnics, and take the money you would have spent on heads and get a smaller converter. Stroke it to 383 and use the 6" rods. Use a cam with about 240'ish degrees@.050 duration and 106/108 LSA for low and mid-range power. Huge torque..up to your limit of 5500/6000rpm with a converter that will let it idle while in gear. Make sure about those rear gears.
6sally6
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Old 12-07-2009, 05:57 PM
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i think a 240ish duration is a little high for what he is trying to accomplish, i would say closer to 228-230ish. that is if you go with the 383, if you go with the 350 i would stay around 218-220ish, those head are going to restrict you some but not too bad, if they have had some work done they should be able to flow around 220-225cfm at max lift. i would stay away from the eagle cranks they have some rumored quality issues, i would go with a scat 9000 cast crank, a set of eagle sir rods (5.7, there is no gain from the 6.0 rods), i went with a set of 18cc dished KB pistons, with a 60cc head this would put you up around 10.2:1, you may want to look for a little more dish to put you closer to 9.5:1. if you find a good mech who can rebuild the Q-jet i would go with it, if not go with a decent 650 Va-sec for the 350 or a 750 va-sec for the 383. you do want to really look into the gears in the rear of the car. an easy way is to jack the rear end up, put a piece of tape on the driveshaft then spin the tire counting how many times the driveshaft makes a turn before the tire make a full turn, if it only turns 3 times then you probably have a 3.08, if it turns 3 and half times you probably have a 3.42, if it turns 3 and 3/4 times then you probably have a 3.73, hope this helps some
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Old 12-07-2009, 06:11 PM
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Quote:
Originally Posted by 6sally6
Here's my oppinion...... Keep the double hump heads(especially if they have the 2.02 valves maybe mill them somemore to get around 10/10.5cr using flat-top pistons...hyperutechnics, and take the money you would have spent on heads and get a smaller converter. Stroke it to 383 and use the 6" rods. Use a cam with about 240'ish degrees@.050 duration and 106/108 LSA for low and mid-range power. Huge torque..up to your limit of 5500/6000rpm with a converter that will let it idle while in gear. Make sure about those rear gears.
6sally6

your typical flat top is still -5 to -7cc, combined with a 60cc head and a proper .040ish quench you would end up with about 11.5:1 not 10:1
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Old 12-07-2009, 06:22 PM
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Find yourself a rebuildable 400sbc engine core (400 block and crank) and rebuild it using dished pistons 5.7 rods and your heads.

nice Hyd roller cam: GMPP LT4 hot cam 1.6 rockers retrofit roller lifters.
218-228@.050" .525" lift 112LSA fine with a stock GM 12" th350 torque converter and your mid3.xx gear. Your heads will wake up a bit more with some deeper port work. The higher the valve lift the more the further/deeper porting helps. The bowl under the valve ,short side radius, and valve guide boss shaping contouring and raising the port roof a bit are key areas that need to be addressed.

The 400 is the way to go.

Last edited by F-BIRD'88; 12-07-2009 at 06:34 PM.
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Old 12-07-2009, 06:29 PM
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another good combo for a 350 is using vortec heads, a stock bottom end, performer rpm intake, 650 edelbrock mechanical secondaries and a xtreme energy 268 cam, this combo makes right around 375hp at 5700 rpm

when i built this engine i used flat tops and a 750 edelbrock and in a 81 chevy truck with 307 gears and it went really good, and a 268 has a nice idle to it as well
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Old 12-07-2009, 07:16 PM
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if you are looking for a good reliable street machine you might want to go with the 350. it just needs some supin up to got 350 to 400 hp. you will need a cam with a good lift and durtion. like around .450" lift and 230ish duration.
for the carb i would use a eldebrock a 600 or 650 cfm. then for the intake i would use a preformer air gap. i would use the same heads that you have maybe some polishing could be in order. and for the pistons i would use some flat top hypereutertic.
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Old 12-07-2009, 08:01 PM
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Quote:
Find yourself a rebuild able 400sbc engine core (400 block and crank) and rebuild it using dished pistons 5.7 rods and your heads.
I want to stick with the original motor, though I was considering the 400 option.



Quote:
your typical flat top is still -5 to -7cc, combined with a 60cc head and a proper .040ish quench you would end up with about 11.5:1 not 10:1
If this is true, should I use different pistons, that sounds like too much for pump gas



Quote:
you do want to really look into the gears in the rear of the car. an easy way is to jack the rear end up, put a piece of tape on the drive shaft then spin the tire counting how many times the drive shaft makes a turn before the tire make a full turn, if it only turns 3 times then you probably have a 3.08, if it turns 3 and half times you probably have a 3.42, if it turns 3 and 3/4 times then you probably have a 3.73
Thanks, I will try this, there was nothing to ID this, at the shop they did this and said it was between a 350-370, I will go by and try to be more precise



Quote:
Keep the double hump heads(especially if they have the 2.02 valves maybe mill them some more to get around 10/10.5cr using flat-top pistons...hyperutechnics, and take the money you would have spent on heads and get a smaller converter
they are 2.02's, all the porting is done and the 400 was rebuilt with the converter to be chosen after I have the motor specs
I would rather have a 350 with good heads than a 383 with stock heads. If you are on a budget then get proper heads first.



Quote:
I would rather have a 350 with good heads than a 383 with stock heads. If you are on a budget then get proper heads first.
If I go the 350 route my plan is to choose a cam that is on the high end so if I am not happy with the performance I can upgrade my heads and still have a combination that works
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Old 12-08-2009, 08:04 AM
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I would forget the double humps (ported or not). More to a good set of heads than just hogging out a port and putting in bigger valves. power is in the heads.

Your diff should be a limited slip so it should be easy to just spin the drive shaft and count how many drive shaft revolutions are needed to make the tire spin one time around. 3.50 turns of the drive shaft to get one tire rotation will mean you have a 3.50 gear (3.55). common ratios are 3.08, 3.55, 3.73.

A 406cid with votec heads, compcam 280H, and a 2800 stall will even move a car with 3.08 gear. Do a search for impersonator 1 or impersonator 2 and you will see a 525ftlb torque 406 build done by Chevy High Performance Magazine.

build a 355 the same way as a 406 and expect about 13% less output.
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Old 12-08-2009, 08:42 AM
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You're not after max power here, you're after max tq. If you want to stay below 5500 RPM then your double humps with a good bowl job will be more than adequate. If you want to stay at lower RPM you also want to keep the 5.7" rod length. Basically all you need is a new crank, balancer, flexplate, and pistons. Re-use your rods but have them cleaned up, if you're staying below 5500 RPM stock rods bolts will be adequate as long as they are tourqed properly. Also, at this level hypereutic pistons are better than forged. ideal compression will be between 9 and 9.5:1.

For a cam get the Comp cams XFI 260 cam and if you don't mind paying a little extra have it ground on a 108 LSA instead of the 113. (the 113 is for better idle quality, a 108 will give you more power and a more agressive sound)

Most of the other posts took your 0-5500 RPM reqirement and threw it out the window in search of the most hp. This build is one that will give you excellent streetability and the most average power from 0-5500 RPM.
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Old 12-08-2009, 12:01 PM
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I know you want to rebuild your current engine. However, another thing to consider is getting a complete 350 roller engine with vortec heads. That would be a 1996+ 5.7 liter, say from a truck.

then do a rebuild on that with a little more cam. A roller block would be a much better staring point with todays engine oils. This way you would get some decent heads (vortecs) with modern combustion chambers and better designed intake ports.
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Old 12-08-2009, 07:42 PM
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check this out.

http://www.superchevy.com/technical/...ild/index.html
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Old 12-08-2009, 09:13 PM
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383 is your best bet i dont care what heds you got its all inb the bore of your cylinders
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Old 12-09-2009, 09:44 AM
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Quote:
Originally Posted by bigboytoyracing34
383 is your best bet i dont care what heds you got its all inb the bore of your cylinders
wrong. power is all in the heads. adding only 8% more cid doesn't compare with adding 20% more flow. Besides, stock chevy heads are already a bottle neck on a 350, so adding more cids just makes it worst.

check out this page.
http://www.ryanscarpage.50megs.com/combos1.html

over 100 dyno test on different sbc setups.

the first page (8 combos) already shows a 350 with good heads will out power a 383 with stock heads. many other examples at that site showing stock and even modified gm heads being seriously out powered by good aftermarket heads.

like I said, a 350 with good heads is better than a 383 with old school gm heads (ported or not).
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