1967 427 3/2 JD Questions

[Vader]

I'm doing some research for an acquaintance. I've performed a couple of unproductive searches, and hope that someone here can give me details or direction.

The car in question is a '67 convertible, 427 L36 (sub-code JD) with 3-two barrel H2600s and a Powerglide. The car is bone stock (show variety).

The questions are:

• Are the heads iron on the L36? Casting numbers? I know the L71 used aluminum heads, but...
• Is the L36 a hydraulic lifter design?
• What are the cam specifications / part number?
• From what I've been able to determine through web searches is that the CR is 10.0:1, but the owner reports having heard 11.0:1. Any clue which is correct, or niether?
• Short (standard) deck height on the old 427?
• Torque converter K-Factor (stall RPM)?
• Standard 105# valve springs, or did they install real springs in '67?

I know - I don't ask for much...

I'm curious about the heads and valve train, since it may get a "stealthy" roller retrofit and decent lift with shorter duration to keep the cylinder presure down enough to run 91 octane pump gas, without detonation. I (we) don't want to open the chambers, install dishes, or ¼" heads gaskets. If at all possible, dynamic cylinder pressure will be controlled via the valve timing. It doesn't get many 1320 runs, unless they happen to be the distance from the entrance to the booth at the show. He'd like to be able to achieve a bit more driveability without frequent visits to the local airport for 100LL.

Any help will be noted and appreciated, even if simply a link to more information.

 

[midyear]

Heads are cast iron on all 67 BB's except for L88 and L89 engines. The L36 and the L68 both used oval port cast iron heads.

L36 used a hydraulic cam/lifters

comp ratio @10.25

The engine is a standard deck bb chevy

I have an L68 tri power powerglide 67 convert. I installed a small roller cam and had flat top pistons built. I now have @ 9.50 comp, runs on 89 octane without a problem. Orig powerglide stall speed was @1800, I did not like it and put in a 700R4 9 years ago. The car now will run on midgrade gas and get 20+mpg (best of 22.6) on the highway. My best 1/4 mile time is only a 13.20, I feel a larger cam could/would make it quicker, but I am happy with the car overall and cant see changing a good combo.

Dennis

 

[67HEAVEN]

Vader,

midyear is correct in his information, as usual.

The L-89 aluminum head option was based upon the L-71 engine, therefore the common confusion about L-71's having aluminum heads. The actual option code is L-71/L-89.

 

[67HEAVEN]

How's this for info? Right here at
http://www.corvetteactioncenter.com/specs/1967/67id.html

 

[Midyrcoupe]

Vader,

I have the same roller-cam mod in my '66 L36 that Midyear described except I used the stock pistons. I have around 10.5:1 and it runs on 92-93 octane with out a problem. I would also recommend changing over to hardened seats and SS valves to insure happiness in the land of unleaded pump gas.

 

[Vader]

Thanks for the info and the link. I should have known to poke around the board a bit more. Having moderated a rather busy tech site myself, I should have looked first.

It's good to hear that at least two of you have gone the way of the roller, and have had success. Given the potential early BBC lifter issues, I thought a roller was prudent. It is almost a necessity to get the kind of lift and ramp I'm considering.

I was of course thinking Race-Flo SS valves on both sides. I was also hoping that the heads were iron so the seats could be induction hardened between the machining and final grinding to survive the leadless fuel with fewer problems. When heads are off, magged, and inspected, I'll decide whether to recommend bronze guide inserts or not. Either way, the seals will be PTFE and spring pockets and stud bosses will get the once-over.

Thanks for the deck info as well, since that should help with initial push rod length selection for final geometry check. I'm going to push hard for the acquisition of real valve springs and Comp or Crower forged CrMo rockers. The oval port specification is also quite helpful.

The hope is for a relatively easy rework of the bottom end, with only a balance, rings, and bearings, and concentration on the heads and cam. If necessary, the pistons would be changed, but stroke will remain stock.

I should at least be able to collect some options and pricing now.