69 350/300 restoration

[Erv M.]

Does anyone have a lsit of parts necessary to rebuild/restore a 350/300? I am concerned with the SCR, I want a pump gas friendly engine. I have all the original pieces minus the rotating assembly

[Jim T.]

Re: 69 350/300 restoration

Since you do not have the rotating assembly this rebuild could be expensive enough that if your Corvette is not going to be judged you could just buy a brand new 350 from GM that will run just fine on 87 pump gas and give close to 300 HP. The purchase of all new quality parts individually can be more expensive when the rebuild labor is included.

[Erv M.]

Re: 69 350/300 restoration

My car is very original, but it has not been judged. I want to keep it as original as possible so a crate motor is not an option. I can pickup a rotating assembly .010 over very reasobanble locally. I was wondering if someone had a good spec in regards of piston, cam specifications that work well with the original heads.

[Joe L.]

Re: 69 350/300 restoration

Erv-----

If you want to keep it as original as possible, then I'd use a reproduction of the original cam. GM #12364051 is a Crane-manufactured reproduction of the original GM #3896929 camshaft used for your engine, supplied as a kit which also includes lifters. This kit is a very good value. You can also used a GM #14088839 camshaft together with GM #5232720 lifters. This cam is the GM SERVICE replacement camshaft for the 3896929 and has near-identical specifications. However, if you go this route it will cost a lot more for the cam and lifters than if you go the GM #12364051 kit route.

For compression ratio, I do not recommend that you go higher than 9.5:1. For this, I recommend Keith Black hypereutectic pistons of their part number KB 193. If you wish to stay with original compression ratio, use KB 228, but you're going to risk pre-ignition/detonation problems. In fact, even at 9.5:1 you're likely going to be on the "ragged edge".

[Erv M.]

Re: 69 350/300 restoration

Under NCRS judgin does it matter what I have as the rotating assembly? As an example I could go nut and put a hydraulic roller cam to reduce friction and with the grind still have a decent idle thus produce 30 -40 more horses. I want to make sure I have all the infromation before I build it. I am meeting with the Southern California chapter on Saturday, hopefully they can guide me in the area also.

[Jack H.]

Re: 69 350/300 restoration

What you do internally is your business as these components aren't judged. BUT, if you get REALLY radical (highly aggressive cam and hydraulic -> solid lifter conversion), experienced judges will KNOW it's not a stock engine just from the sound of it idling...

[Duke W.]

Re: 69 350/300 restoration

I caution you against filling your engine with aftermarket parts. It is expensive and you may end up with an engine that doesn't behave like a base engine and has poor torque bandwidth. OE quality Federal Mogul and Dana Corp. brand replacement parts are readily available at competitive prices.

There is a lot you can do to a base 350 to improve its performance without affecting external appearance, low end torque, or idle characteristics

As with any OE Corvette engine, the key to top end power is HEADS, HEADS, HEADS, so the first order of business is massaging the OE heads, which is good for about ten percent more top end power and ten percent more useable revs.

A base engine with massaged heads also responds nicely to retarding the OE cam four degrees - adds a little more power and another few hundred useable revs, and the above two internal modifications have only a slight effect on low end torque and no effect on idle characteristics.

On any rebuild, one should very carefully manage the compression ratio, and I consider the limit on a base engine with the OE camshaft to be 9.75:1, which is about the true CR they were build with, not 10.5 or 10.25:1 as claimed by GM. The target CR is usually easily achieveable on nearly any base engine with OE replacement components and proper head gasket thickness, but knowing the deck height/deck clearance is critical to developing a plan before you begin the project. Once these dimensions are known its a simple matter of using an online CR calculator to test various piston and head gasket combinations to bring the CR into the target range.

I have system engineered mechanical lifter 327 SHP engines that make 325-340 honest NET horsepower with the useable power band extending to 7200 and no less than 80 percent peak torque at 2000. Other than replacing the weak 327 connecting rods, everything was OE replacement, and I also have a couple of base engine configurations that might be of interest to you.

All of my projects have the intent of maintaining original appearance and overall operating characteristics, including idle characteristics, while broadening torque bandwith and increasing top end power and useable revs.

I'll be at the SCC meeting on Saturday and can further discuss the issue with you if you like. The first thing I will want to know is what your objectives are for the car in some detail, so think about that.

Duke

[Erv M.]

Re: 69 350/300 restoration

I look forward in meeting and speaking with you. My thought process, unless after the meeting I am convinced there is no hope for my car to be judged well after modest work, is to keep it as original as possible with a modest hp gain.

I would like to rebuild the original block to run on pump gas and get about 350hp from it. I plan on having someone rebuild it as the block is .040 over as is and I want it done correctly. I have the original block, heads, intake, exhaust manifolds, AIR equipment, starter, alternator, distributor, AC compressor. There are a few items I am missing but should be available if I am patient.