Engine evaluation

[Dan D.]

Re: Engine evaluation

Your right Duke, and in a way it is sad. I experienced the character of a 327/360 (it was FI) up to 1070, and that engine and that car was a great feeling and I will probably miss it. But I am now 69, the engine is 48, the gas is terrible, but some things change and life goes on. I have yet to see how well it does and how well I like it. "Character" is a good way of expressing it. -Dan-

[David H.]

Re: Engine evaluation

First, let me clearify that the engine had antifreeze in the base when I got it and had been sitting for close to 15 years I think. That is why I "opened it up". That plus I like to know exactly what I have and what I am looking at.
Let me also clearify, as many of you know, that I am a purist at heart and prefer to go original any where and any time I can when it is practical. If I felt that I could run this motor on todays gas I would and I will. If I felt that I could run solid lifters and an original cam I would and I will.
I have had a lot of advice pro and con on all of this and now it is up to me to decide the direction that I want to go.

At this point I feel fairly confident that I can make it work as an original 340hp engine with solid lifters, original cam. If necessary I can use octane booster if all else fails.

I cant begin to tell you how much I appreciate all the input into this subject and what a great education I am getting into the Corvette world.
I truly want this car to be an appropriate representation of what it was designed to be.

~Save the Wave~

dlh

[Joe C.]

Re: Engine evaluation

First, let me clearify that the engine had antifreeze in the base when I got it and had been sitting for close to 15 years I think. That is why I "opened it up". That plus I like to know exactly what I have and what I am looking at.
Let me also clearify, as many of you know, that I am a purist at heart and prefer to go original any where and any time I can when it is practical. If I felt that I could run this motor on todays gas I would and I will. If I felt that I could run solid lifters and an original cam I would and I will.
I have had a lot of advice pro and con on all of this and now it is up to me to decide the direction that I want to go.

At this point I feel fairly confident that I can make it work as an original 340hp engine with solid lifters, original cam. If necessary I can use octane booster if all else fails.

I cant begin to tell you how much I appreciate all the input into this subject and what a great education I am getting into the Corvette world.
I truly want this car to be an appropriate representation of what it was designed to be.

~Save the Wave~

dlh

I'm happy to hear that you'll maintain it's original character. You are rightly concerned about detonation with 93 octane pump gas. If you use gas from one of the reputable brands, like Shell, Mobil, Exxon, BP, Sunoco, and stay away from the discount brands, you will have no trouble at all, PROVIDING THAT YOU PAY CLOSE ATTENTION TO YOUR "AS BUILT" COMPRESSION RATIO. In order to do this properly, you and your engine builder must determine (accurately measure) vital statistics such as combustion chamber volume and piston to deck clearance. These values, as well known entities like head gasket compressed thickness and piston dome volume (for Speed Pro L2166NF-.030 is 5.3cc), and derived entities like ring land volume and head gasket volume must all be plugged into the appropriate equation, such as:

http://www.csgnetwork.com/compcalc.html

or preferably

http://www.diamondracing.net/cocalc.htm

Your engine had an advertised static compression ratio of 11.25:1, but with moderately wide tolerances, the compression ratio on the lowest cylinder could have been as little as 10.5:1! If you "blueprint" your engine, engineering it for an honest 10.75:1 - 11.0:1, then you will be happy with its performance, so long as the timing, coolant temp, primary fuel metering, and spark plug heat range are all reasonably close to optimum. You should NOT have to dope your fuel with any TEL additives, avgas, Cam 2, etc etc.

Is this engine the original motor? If not, does it possess all of the correct information on the stamp pad except the VIN? If not, then you should seriously consider decking the block. This will eliminate the factory variance in piston to deck clearance among all 8 cylinders, and bring your engine build to the "next level".

[Timothy B.]

Re: Engine evaluation

I agree with Joe in the post above.

If you look for a Chevrolet shim steel gasket you can find them on ebay, they measure .022 thickness.

Also, it's a good idea to degree camshaft to make sure it is ground to correct specs. If you build a engine assuming certain compression ratio based on a intake valve closing point you need to double check camshaft to be certain it's at spec. GM book says 160 lbs cranking pressure for healthy engine but I have read 190-200 lbs is good for pump gas with hp street engine.

If you use the stock solid camshaft, the only way to manage compression without decking engine is with head gasket selection and piston dome unless you get into different compression heights, custom pistons or advance camshaft.

If it is a original engine I would keep the bore as small as possible .010-,020 and order pistons. Don't finish hone until new pistons arrive to custom fit skirts to bore...

[Joe C.]

Re: Engine evaluation

I agree with Joe in the post above.

If you look for a Chevrolet shim steel gasket you can find them on ebay, they measure .022 thickness.

Also, it's a good idea to degree camshaft to make sure it is ground to correct specs. If you build a engine assuming certain compression ratio based on a intake valve closing point you need to double check camshaft to be certain it's at spec. GM book says 160 lbs cranking pressure for healthy engine but I have read 190-200 lbs is good for pump gas with hp street engine.

If you use the stock solid camshaft, the only way to manage compression without decking engine is with head gasket selection and piston dome unless you get into different compression heights, custom pistons or advance camshaft.

If it is a original engine I would keep the bore as small as possible .010-,020 and order pistons. Don't finish hone until new pistons arrive to custom fit skirts to bore...

Tim,

Personally, I think that degree-ing a camshaft is BS, unless you are building a race engine. Otherwise it's an easy way for the machine shop to justify extra work done and compensation therefor. We degreed the camshaft in my 327 and found that it was ground 1 degree retarded from their spec of 4 advanced. I installed it at 5 advanced rather than 3 advanced. Most times, cams are within 1 degree either side of spec, which makes NO discernable difference in DCR or performance. The farthest from spec that a camshaft was, which I degreed was 2 degrees.

200 psig seems to be the rule of thumb for cranking pressure, but I can tell you that a certain 327 I am familiar with has cold cranking pressures of 225-235 psig. It experiences no detonation at optimal spark timing running on good quality high test (93 PON) pump gas.

The absolute BEST way to manage compression ratio, is to further unshroud the intake valve. You must be VERY careful doing this. Chambers can safely be opened to 68-69cc on a closed chamber 461 head if the casting is "select" and the work is done carefully. Angle milling or flat milling will tailor the volume to exactly where you want it, and 58 cc is achievable.

If decking the block is an option, and good strong connecting rods and fasteners are used, then achieving quench distances as low as .032" is safe for a street motor. This modification goes a long way in making an engine more detonation resistant than another one of equal SCR but larger quench distances. Sixties era engines with .025" nominal piston to deck clearance, were built with large tolerances in deck height, which, when combined with .022" gaskets yielded max quench distances on the order of .057". 1964-65 vintage SHP 327's which used double head gaskets had quench distances on the order of .079"!

Joe