Need some help with putting my 383 together. I bought a '77 Corvette and pulled the motor to put in my '69 but I want to make some changes. Its a 350 2-Bolt Main (ugh) bored .030 over with a Scat 383 Crank (383ci) It had a Fuel Injection setup but i'm swapping over to carb so I have an Edelbrock Performer RPM Air-Gap Intake and Mighty Demon 750cfm Mech. Sec. Carburetor. The heads are Edelbrock Victor Jr. 210cc Intake, 65cc Exhaust, 70cc Combustion Chambers and 2.08" 1.60" Valve Size. I know they may be a little big for a street engine but i'd like to make them work. Has 1.6 Stainless Full Roller Rockers and 7.8" Magnum Push Rods. The pistons are Sealed Power H859CP .030 Over Press Fit Pistons which I believe I should change to get more compression and would love to hear some suggestions/thoughts. The cam is a Comp Cams 12-213-3 .501"/.501" Lift, 292/292 Degree Advertised and 244/244 Degree Duration at .050" Lift with 110 Degree Lobe Seperation which I also think needs to be toned down quite a bit, I think I would prefer to stick with a Hydraulic Falt Tappet Cam for now. The cam is advertised for 2500-6500 RPM and this car is going to be driven probably everyday this it is nice out here in Upstate NY. I believe the Rods are 5.7" GM Pink Rods which I will most likely re-use. I appreciate any input or help you guys could give me! Thanks again!

 

 

Ran great! Very strong but didnt come in down low which i'd like. Its pretty much completely torn down now, compression I believe to be right around 9:1 with those pistons and the 70cc heads which I would like higher than that.

 

That sounds like a great engine, and will work well with that cam, but you need loads more compression, I reckon 11:1 or a bit more would be great on high octane pump gas. That will bring in the bottom end "off cam" hugely though changing from fuel injection to carb will likely reduce the response down low.

 

I should ask, auto or stick? Diff ratio? Those things will also be important factors.

 

4-Speed Muncie M21 Transmission, not sure on rear gear yet but if its not 3.55 then its being switched the 3.70, if its 3.55 i'll just leave it.

 

I really want this to have good street manners so I think I should get a less aggressive cam, also I like simplicity so thats why i'm going back to carb haha, if something breaks on this engine I want to be able to fix it in a day. For pistons I have never done engine work and have no idea what to look for or anything so i'm hoping to get some recommendations haha but i'd like to be at around 10.5 compression, so with 11:1 pistons and 70cc heads I should be right around there I believe.

 

You've got a stick, you'll have enough gear. I still say give it enough compression leaving the rest alone and I think you'll be very happy. Will be a killer street engine. But you need the compression to get the low end better with that much head and cam.

 

In the '77 this cam loped like a son of a bitch and just really was too much in my opinion for a street car, with higher compression would it help "tame" it?

 

I'd re-assemble and angle mill the heads to near the max practical. Use a shorter seat duration cam, and if that's not enough low-end torque change to an intake with a full divided plenum but with the same rpm range. You should consider a custom cam.

http://www.lunatipower.com/Product.aspx?id=2929&gid=401

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=78&sb=2

 

Posted in another forum and i've heard a lot of the same that I should just up the compression and run it, I think thats what i'm going to do.

 

Yup. That cam will want 11:1 and a 4.11 gear. It doesnt make much torque or come on til about 3500.
Theres better hyd flat tappets. Honestly in a 350 once you approach that 240@050 mark you ought to think about a solid flat tappet if you cant go roller
Even a smaller solid youll love, dont be afraid of some lash it wont hurt anything.

Id use the best dual plane you can find or a small single plane if you gear it (Team G for instance)acient design but they work and keep up with larger intakes.

Are those pistons flat top, domed, how far down in the hole are they? Nothing wrong wiht a 2 bolt main either guys run em hard all the time. If you line bore it use studs
If you want more later on you can go roller and make use of those cyl heads. Dont know that compression "tames" it but it allows the cam to make the power its supposed to..part throttle response, torque. Youll hear guys minimze it saying oh its only xx percent, run low compression then complain about a lazy acting (and sounding) motor.
. You need it, really changes the way the car behaves.

If your head is a little on the big side, not quite enough gear run a little smaller solid cam maybe in the 230s somewhere. It will be night and day difference.

 

They are dished pistons, not sure how far they are haha (not an expert by an means). Id like to find a better hydraulic flat tappet if I could find one that will work, Id also like to be closer to 10:1 compression. I think with my heads and those pistons im around 8.9:1. For intake I already have an rpm air-gap so I think im good there.

 

Yikes, that is a little on the low side, gotta get that compresion up and plan well. No compromises will make ya happy when you start driving it. All gotta work together, doesnt need to be fancy

Many yrs ago the car mags used to push low compression cammed up motors let me tell you they suck! lol
Then out come the extreme energy cams to try and make them work, cant say it was a good idea.

 

Milling the heads to achieve a smaller combustion chamber will get your compression to what you want. It's not a free lunch , but much less expensive than rebuilding the engine with new pistons (which also requires rebalancing ).
Your intake is great with a good street carb, but the "Air gap" does lose some bottom-end punch because of the lowered plenum divider. But just very little , I'd run it as is first.
Did you look at the cam link I listed above ? The Lunati Bootlegger cam listed was found on Amazon last nite @ $60.05 after shipping (only one left now). it's 108* LS is more inline with what your 383 would really like. Advertised seat duration on the intake is 269* with 224* @ .050 .

 

Sorry, just checked Amazon and they've added $99 to the price !!!!!! (I scored tho')

 

I'd just add compression and a tight quench to what you have. Compression will add power throughout the entire rpm range, sound crisper. have better throttle response and get better mileage. A tight quench, .035" to .040" max will make the engine more eficient and be less prone to detonation. You will never make the power of a high compression engine with low compression.

Mike

 

Sounds like about 370ish HP gross.

What components did you end up going with? Particularly the cam?

I hear popping in decel on the vid? Running a bit lean perhaps.

damn related threads option

 

IKR?! I get stymied about once a month

Jebby

 

Decel popping is cool in some circles. Enough that GM mapped it in their fuel management maps for the C7 iirc.