Hydraulic cam in a solid lifter engine...

[John P.]

Disassembled my 64 365HP L76 engine today. The engine has not run since 1973 and was locked up. Turns out that 7 of the wrist pins were frozen. The rest of the engine is in remarkable condition. Curiously, the cam part number is 3732798. This number indicates that it is a hydraulic cam used in 250 and 300 HP engines. What issues if any are caused by running a hydraulic cam in a solid lifter engine?

Thanks,

John

[Duke W.]

Re: Hydraulic cam in a solid lifter engine...

No issues. It's just a cam and lifter swap. The OE 30-30 cam is notoriously torque-shy, but I'm surprised someone would detune it down to a base engine cam. It must have been done long ago as that cam was replaced by the ...929 in '67 for both original build and service part for earlier engines back to '57.

If you want to go back to a mechanical lifter cam use the LT-1 cam. If you want a hydraulic cam use the L49/82 cam, but install it four degrees advanced from the OE indexing of 114 ATC inlet POML.

Both with provide SHP type engine characteristics, but won't be totally gutless down low.

Duke

[Joe L.]

Re: Hydraulic cam in a solid lifter engine...

Disassembled my 64 365HP L76 engine today. The engine has not run since 1973 and was locked up. Turns out that 7 of the wrist pins were frozen. The rest of the engine is in remarkable condition. Curiously, the cam part number is 3732798. This number indicates that it is a hydraulic cam used in 250 and 300 HP engines. What issues if any are caused by running a hydraulic cam in a solid lifter engine?

Thanks,

John

John------


I expect the reason the piston pins were frozen is that all lubrication had left the pins and dissimilar metal corrosion had occurred between the aluminum pistons and the steel pins. You're lucky that the same thing had not occurred between the pistons and cylinder walls.

[Gene M.]

Re: Hydraulic cam in a solid lifter engine...

Your rear end ratio and transmission M20 or M21 should have a voice in cam selection. If the car has a 3.36 or higher (lower number) make sure it has a wide ratio before selecting one of the Chevy higher performance cams. As a driver and 3.36 gears I would use the base engine cam if you want to really drive it. If the cam was changed odds are other things were also.

[Timothy B.]

Re: Hydraulic cam in a solid lifter engine...

That camshaft with the domed pistons probably made for a interesting combination.

[Duke W.]

Re: Hydraulic cam in a solid lifter engine...

Low rev detonation would likely be a problem because the base cam exhaust closing is much earlier than the OE 30-30 cam, which raises the dynamic compression ratio. I recommend no more than 10:1 SCR for base cam engines. The LT-1 cam will tolerate up to about 10.5 and about 10.25 for the L-79 or L-46/82 advanced four degrees on 93 PON fuel.

If the L-46/82 cam is used in a 350 or longer stroke configurations and not advanced from the design 114 deg. ATC inlet POML it will tolerate up to about 10.5.

Duke

[John P.]

Re: Hydraulic cam in a solid lifter engine...

How about this cam from Comp Cams? Nostalgia Plus, N+30-30s.
<http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=232&sb=2>
Looks like a possible alternative...

Thanks

[John P.]

Re: Hydraulic cam in a solid lifter engine...

Gene,
The car has its original 3;08 posi. I verified this last night. What a strange combination...

[Duke W.]

Re: Hydraulic cam in a solid lifter engine...

Comp cams has quality problems and they do not Parkerize their cams, which aids break-in. My first choice is Federal Mogul, which offers all OE cams manufactured to the GM prints including Parkerizing. Crane is my second choice, and they manufacture the cams I designed.

A 3.08 axle with a CR four-speed mated to a 30-30 cam engine is a difficult combination to deal with, especially if you live in hilly areas. It's like a five-speed that's missing first gear.

This is the likely reason why the engine was detuned with a base engine cam that makes 30 percent more torque at low revs than the 30-30 cam.

Duke

[John P.]

Re: Hydraulic cam in a solid lifter engine...

Thanks Duke!

It sounds like the LT1 cam is the way to go, and perhaps a gear change in the rear end is in order.

John

[Duke W.]

Re: Hydraulic cam in a solid lifter engine...

I suggest you drive the new engine configuration with the existing gearing and see if you can live with it. Rather than change that nice 3.08 highway cruise axle, consider changing the transmission gearing. You can replace the clutch gear and counter gear to convert the Muncie to a wide ratio, but then you have that huge 3-4 gap.

IMO a better option would be to replace the Muncie with a Super T-10 with the 2.88, 1.91, 1.33, 1.00:1 ratio set. That yields an overall first gear ratio about equivalent to a CR Muncie with a 4.11 axle, but you still have a fairly tall highway cruise gear. This ratio set is "progressive" in the sense that the largest inter-gear ratio is between first and second, and the gap narrows as you work up through the gears. This is best for a road car.

Piston choice could be either the OE type forged or KB 157, which will allow a reasonable CR with a thin head gasket.

Your engine has the first design 327 rods, which are a failure waiting to happen. A set of Eagle SIR5700 rods is the best value $250 insurance policy you will ever buy.

Depending on your objectives and budget, you can get close to 300 SAE corrected RWHP from a "327 LT-1" with usable power up to the 7000-7200 range with the LT-1 cam and second design small block production valve springs. The OE forged steel Tufftrided crankshaft is virtually indestructible as long as you don't oil starve the bearings or let some machine shop grind it, which will remove the hardened surface; and combined with the better rods will make for a bottom end reliable to well beyond valve float speed of about 7250.

I have some documents I can send you on how to do this. If you're interested, send me an email via the TDB.

Duke