I am about to have my current, non-original, engine replaced with a rebuilt 1969 350-300 "3970010" block. The original engine in my 69 coupe was a 350-350, and I would like to have the new engine rebuilt to that configuration.

Since I will be dropping the engine off for evaluation/tear down next week, I am wondering if anyone has any words of wisdom before I begin this process. The replacement engine is complete, from carb to oil pan and pulley to bell housing. I am planning to use my original exhaust manifold. Although I have discussed my wishes with the shop, we have not gotten into specifics as to exactly what will be needed to bring this up to 350-350 specs. Any suggestions before I take the plunge?

Mark

 

I'd have the heads bowl ported and have the exhaust ports and combustion chambers polished. Manly SS polished vavles and bronze guides. It would probably be wise to up grade to a CompCams XE-262 or XE-268 with a little higher stall. Have some flat top pistons and the heads milled aiming for a 9.0-10.0:1 compression. Having the block decked for a zero deck height would be the best for combustion, and one of the best (performance wise) ways to raise compression. All that is inside the motor, so no one will really be able to see a difference. I've heard NOTHING but GOOD things about the Edelbrock Performer RPM air-gap intake. And it would probably be REALLY wise to get rid of the points and upgrade to electronic internals of the origanal dist, get an HEI or and MSD Pro-Billet (have to have a 6AL box). Some roller tiped rockers would help too. Pending on if you want to look stock a Demon carb or Holley Street Avenger would probably be a nice way to fuel the motor. Since you want to keep the stock exhaust manifolds then atleast get a 2.5'' exhaust with an H-pipe and some decent mufflers. A Meling oil pump would be a nice upgrade, but I've read that the high-volume and high-pressure pumps aren't worth it. The Meling stock replacement should be enough.

That should be a nice 300 solid horse power. Nothing extremely spectacular..but, stout nonetheless....

:cheers:
-Aaron :chevy


[Modified by Aaron-74, 11:26 PM 11/29/2002]

 

Pull the valve covers and give us an idea what heads are on this engine. The heads should be stamped with a 6 or 7 digit number casting # starting with a *3*. There were a few versions available.... some with larger valves for more HP applications. Here's some of the numbers I brought up a minute ago that are the 2.02 intake/1.6 exhaust versions that were probably on the 350/350 version. You can still easily get 350HP without these heads... it would just make it back to the original you are looking for. Then again... maybe this engine had the 1.94/1.5 valves. This list is not even complete, but these are the 2.02/1.6 versions:

340292
3927186
3927187
3928494
3973487
3991492

There are numerous 1.72/1.5 & 1.94/1.5 versions also.

 

I don't think any Corvette ever came with 1.72/1.50 valve set ups. I would atleast go with a newer cam. Those old tech cams are high-rev high HP cams. Zora loved the high RPMs. A modern cam would atleast give a better over all horse power gain.

 

I'm sure there are lots of 1.72/1.50 heads on Vettes across the world. They probably just don't know they were put there if they didn't check to see if they were getting ripped off.

 

FYI: heads with casting # 3973487 were produced in BOTH large & small valve versions ... either 2.02/1.60 ... OR ... 1.94/1.50

BTW, 3973487 w/small valves was common to many L-48.

 

I'm sure thats true. :nonod:

 

Mark:
First ... find out from the machine shop just what needs to be done to the block & heads & crank ... how much if any the block’s deck height may need to be cut ... how much if any the heads need to be cut ... in conjunction with piston choice will be the determinants of what compression ratio you can configure. Quite possible that your heads can be cleaned up and mildly ported w/ better springs ... along with a Comp cam such as Mag 270H, Extreme XE262H or XE268H ... OR Speed-Pro CS1062R ... and likely flat top hypereutectic pistons to achieve 9:1 - 9.9:1 CR ... and an inexpensive, low-rise intake such as Weiand 8004 or Edelbrock 2101 ... and freshen your distributor & recurve it. Save your money ... a properly setup Qjet carb will do VERY well for street 350/350 (probably as well or better than holley or demon) ... if you still have your Qjet carb KEEP IT & have it gone through by an expert for less than a new holley or demon. Roller rockers not necessary for 350/350 ... just fresh OE-type with long slots. Properly tuned this’ll easily do 350 hp on pump gas and be quiet & reliable. Reply later with machine shop’s suggestions for deck & head cut requirements ... & what are casting numbers of your heads ... then you’ll have the info needed for more specific recommendations. Your machine shop may be a Speed-Pro/Sealed Power jobber ... many good cam & piston options there at good bargain. Once you have the machined block's specs ... use an online compression ratio calculator or reply back for help with same. BTW, factory deck height for sbc 350 is 9.025".

 

I definitely agree with Jackson about keeping the q-jet. I gave mine away like a jackass and I kick myself everytime when I think about it. A q-et is the equal to a 750cfm carb (how many stock carbs do you know of have large secondaries) ? Good luck with your rebuild.

 

Thank you all for your excellent responses. I pick up the engine this week and will drop it off at the machine shop on the way back. I will get as many numbers off the block as possible and I will heed advice on the carb.

Thanks.

Mark