Cam selection for bored/stroked 68 L36

[Charles F.]

I have a 68 L36 that has been bored and stroked. The stroke is 4.25 and the bore is 4.35 [will be 100 over, sleeved]. This is an oval port; 100cc chamber; stock exhaust; stock intake; stock quadrajet carb; 3.70 rear; A/C; power brakes and steering; three surface valve grind.

What say you about the best cam choice ? Please be specific as to cam model number, where to get it and where to get full specifications.

Thanks

Chuck

[Joe L.]

Re: Cam selection for bored/stroked 68 L36

I have a 68 L36 that has been bored and stroked. The stroke is 4.25 and the bore is 4.35 [will be 100 over, sleeved]. This is an oval port; 100cc chamber; stock exhaust; stock intake; stock quadrajet carb; 3.70 rear; A/C; power brakes and steering; three surface valve grind.

What say you about the best cam choice ? Please be specific as to cam model number, where to get it and where to get full specifications.

Thanks

Chuck

Chuck------


You could use the stock L-36 cam. It will provide an excellent, streetable cam even with your increased engine size. Replacements for this cam are easily available as has been described in other recent posts.

If it were me, however, I'd use a retrofit hydraulic roller. Not some "wild" grind, though. You want a very streetable piece. I'd go with something like the GM #24502611 which has 211 degrees intake duration and 230 degrees exhaust duration at 0.050" lift and .510", intake/ .540" exhaust lift with a 112 degree lobe centerline.

You won't be able to use the above with GM lifters, though. You'll need aftermarket, retro-fit hydraulic lifters as available from Comp Cams, Crower, Iskendarian, and others.

Also, with the GM roller cam you ABSOLUTELY MUST use melonized distributor gear of GM #10456413. If you use this cam, do not make a mistake on this.

[Duke W.]

Re: Cam selection for bored/stroked 68 L36

In any engine restoration where "more power" is desired, the first order of business is massaging the heads.

If you merely stroke an engine, it will make about the same peak power as before at the same mean piston speed because power is always limited by head flow, but average power will be greater over the useable range due to the greater average torque from the greater displacement of the stroker.

With your approximate 505 cubic inches, the problem will be more torque than the chassis/tires can handle in the lower gears, so I would trade some low end torque for top end power.

If you massage the heads and retard the OE cam 5 degrees from the OE indexing, you will achieve the above objective and still have OE reliability and reasonable rebuild cost as long as you keep revs to a level that is safe for whatever rotating/reciprocating assembly you have. With proper head work this configuration will make peak power at in the 5000-5500 range with useable power to the 5500-6000 range.

You will also still be able to light the tires at nearly any speed in first and second gears, but it should be manageable. In fact, it will be as docile as the L-36 in normal driving - no lumpy, bumpy idle and 5 MPG fuel mileage of a long duration/high overlap cam, but it will be substantially stronger across the rev range when you boot it as long as the tires can get some bite.

Converting to a roller hydraulic cam is expensive, and the money is MUCH BETTER spent massaging the heads.

There is no magic camshaft, manifold, carburetor,... whatever that will make substantially more top end power without screwing up the low speed torque, low speed operating behavior, and idle characterisitcs while substantially increasing fuel consumption.

Peak power is all about HEAD FLOW!!!

I know of a certain OE appearing massaged-head L-71 that is stroked to 4.25" with the OE cam retarded 6 degrees. It's actually pretty docile in normal driving and makes peak power at about 6000 with enough torque to get instantly sideways in second gear if you're not careful. The peak RWHP was choked down because it has the OE sidepipe system, which is VERY restrictive, especially for a stroked SHP big block, so the owner's next project is to install some less restrictive pipes under the OE covers, and just live with the increased noise.

There is a nearby thread on the current L-36/68 OE replacement camshafts.

Duke