1961 corvette -283/230 & 283/245 cylinder head blueprint specs question.

[Lewis B.]

Seeking any&all oem cylinder head blueprint specs for 1961 corvette 283/230 and 283/245 engines.particularly interested in the oem combustion chamber c.c. Specs for these engines.also interested in obtaining any hard copy documentation of the blueprint specs,oem or otherwise.any information or help in this area for any 283 corvette cylinder head part number and/or casting number would be greatly appreciated.

[Joe L.]

Re: 1961 corvette -283/230 & 283/245 cylinder head blueprint specs question.

Seeking any&all oem cylinder head blueprint specs for 1961 corvette 283/230 and 283/245 engines.particularly interested in the oem combustion chamber c.c. Specs for these engines.also interested in obtaining any hard copy documentation of the blueprint specs,oem or otherwise.any information or help in this area for any 283 corvette cylinder head part number and/or casting number would be greatly appreciated.

Lewis------


The same GM casting number cylinder head was used for both the 230 and 245 HP 1961 applications, GM #3774692. The combustion chamber size was 59.7 cc, nominal. Since these combustion chambers were as-cast, there could have been some very slight variations in size.

[Lewis B.]

Re: 1961 corvette -283/230 & 283/245 cylinder head blueprint specs question.

Joe,thanx for the fast reply!the 59.7cc spec is the one i am questioning.what is your source for the 59.7 cc spec?-the source i have to work with uses the 59.7cc spec for the combos in question.this same source uses a 54.9cc chamber spec for some later 283/220 type engines with same allowed head casting numbers,piston dome,ect,ect. Of course i would like to be able to use 54.9 if i can .im at 570-437-2201 in pa. Est.if u care to discuss or i can call u.

[Joe L.]

Re: 1961 corvette -283/230 & 283/245 cylinder head blueprint specs question.

Joe,thanx for the fast reply!the 59.7cc spec is the one i am questioning.what is your source for the 59.7 cc spec?-the source i have to work with uses the 59.7cc spec for the combos in question.this same source uses a 54.9cc chamber spec for some later 283/220 type engines with same allowed head casting numbers,piston dome,ect,ect. Of course i would like to be able to use 54.9 if i can .im at 570-437-2201 in pa. Est.if u care to discuss or i can call u.

Lewis------


I cross-checked this from information in "Chevrolet By The Numbers" as well as a few other sources I have available to me. The combustion chamber volume for the 3774692 head is 59.7 cc. I don't know of any small block heads with a chamber volume of 54.9 cc. Some earlier 265 and 283 heads did have a volume of 55.7 cc, though. All of these volumes are with stock inlet and exhaust valves installed. Keep in mind that these combustion chambers are as-cast and have a plus or minus of 1 cc.

Combustion chamber volumes may increase with successive valve jobs since as the seats are reground, the valve face recedes further into the head, increasing chamber volume.

[Lewis B.]

[Duke W.]

Re: 1961 corvette -283/230 & 283/245 cylinder head blueprint specs question.

NHRA specs are not the same as nominal OE specs. NHRA allows "cleanup" cuts on the deck and heads, so allowable deck clearance may be less than the .025" OE nominal, and allowable head volume may be a cc or two less than typical factory production.

That's why back in the day "stock" Z-28s with 5.13 gears, slicks, and some work on the suspension ran in the 12s versus close to 15 seconds for one off the showroom floor with the standard 3.77 axle.

Engine "blueprinting" using allowable NHRA specs helped along with a big help from headers and open exhaust, which the 30-30 cam really responds to in the mid to upper rev range.

If you go with a 283, why not build it to 270 HP specs? It will be a good deal faster. BTW, I've already designed a "cheater" Duntov cam that will work better with manifolds (assuming headers are not allowed) than the OE design, but it's still stock lift - basically the Duntov lobes with slightly different indexeing and a wider LSA. Think mechanical lifter version of the L-79 cam.

Duke