64 327/300 Cam question

[Gary D.]

My 327/300 64 with original intake, exaust, and carb. has a crane WG996 cam in it. I have very little vacuum under 2000 rpm. Do you think I need a different cam or do I have another problem. This causes the engine to run like you are in 4 gear with no gas when ever you are not on the gas.
Carb, Dist have been gone over. Thank you in advance.

[William C.]

Re: 64 327/300 Cam question

What are the specs on the crane cam? What is the condition of your distributor relative to the match between the advance curve and the cam? Is the vacuum advance properly matched to the specs of the cam? I can almost assure the answer to the last three are NO, No, and No. Either get rid of the boy racer cam or retune the rest of the components to work with it, noting that depending on the cam specs, a match may be difficult to obtain.

[Duke W.]

Re: 64 327/300 Cam question

The original mild hyraulic lifter cam used in medium performance small blocks from 1957 to 1966 is no longer available, but it's 1967 replacement can be bought at NAPA (CS-174) for about fifty bucks. It's operating behavior is identical to the original, but it's easier on the valve train. It was probably used in 10 million small blocks over the next two decades. That's why it's so inexpensive. It's still a high volume item.

It's a good cam for the OE as-machined components - pulls 18" Hg manifold vacuum at 500 idling in neutral and has stump-pulling off-idle torque.

Your other option is to turn it into a "Special 300 HP" engine with the McCagh Special camshaft, but that requires going completely through the engine. (See the Fall 2010 Corvette Restorer.)

Duke

[Joe C.]

Re: 64 327/300 Cam question

My 327/300 64 with original intake, exaust, and carb. has a crane WG996 cam in it. I have very little vacuum under 2000 rpm. Do you think I need a different cam or do I have another problem. This causes the engine to run like you are in 4 gear with no gas when ever you are not on the gas.
Carb, Dist have been gone over. Thank you in advance.

Gary,

I am finding that the Crane WG996 is a reproduction of the 962 (L46/L82) and is identical to the old 151 (L79) for all practical purposes. In which case, your idle vacuum, @ 800 RPM is probably in the neighborhood of about 15 in-hg.

OEM #3863151, 350 HP, L-79 327

WG-996 (Cam only)
WG-996Kg
151H
Hyd C
222 222
306 306
.447” .447”
110/118

That said, and although the WG996 copies two of GM's more versatile and popular SBC camshafts, this setup will not produce the idle vacuum that you are looking for on a typical L75 engine, which is as stated in the above post.

If I were you, I would replace the Crane unit with a Sealed Power CS 174, but that is ONLY after I determined what the as built static compression ratio of the engine is. If the engine was rebuilt with 5.3 cc popup pistons, then it is NO LONGER COMPATIBLE with the L75 (929) cam or reproductions thereof! If the pistons have been "upgraded" to popups, which will produce (nominal) SCR of (about) 10.5:1, then the engine will ping like hell with the 929 cam installed in it..........unless you retard the hell out of it and/or use race gas and/or retard the hell out of the spark timing.

If the engine was rebuilt with SCR unmodified from original (nominal) 10.0:1 and showing 4 eyebrow cast flat tops, then the installed Crane WG996 is leaving a moderate amount of torque and power "on the table".

In either case, I would not install any of the "experimental" cam lobe swapped "designs" in any engine of mine.

[Stuart F.]

Re: 64 327/300 Cam question

Just as a sidelight to this subject; my ongoing investigation of the various Carter AFB carbs used from 63 thru 65 on L-75/L-76 engines bears out that anyone with a 63 L-75 running a 3461S carb on a driver car would benefit by changing to one of the later 3720S series models for improved driveability. The 3461S was extremely taylored for the L-76 engine in 63 with the 097 cam. I didn't realize just how much until I began to bench compare them side by side. Actually, I believe the 3461S may flow about 50 cfm more, and all the jets and air bleeds are consistent to this end. Even the secondary air valve has lighter weights. I recently ground one from my donor 3720SA to lighten it for testing and found the 3461S still lighter than my modified piece.

If anyone wants to compare notes on this off subject matter, just send me an E-Mail or P.M. and we can began a dialog to pass on some knowledge.

Stu Fox

[Joe C.]

Edit Post Number 4

EDIT POST NUMBER 4:

The "edit" function has "timed out".

Please note that 327 with 4 eyebrow cast flat top pistons should produce nominal static compression ratios (SCR) of 10.5:1, not 10.0:1.

Please note that 327 with 5.3 cc net volume forged domed pistons and 1.94"/1.5" valves (62cc chambers) should produce nominal SCR of 11.0:1 when double steel shim head gaskets are used; 11.25:1 with single steel shim head gaskets.

Please note that 327 with 5.3 cc net volume forged domed pistons and 2.02"/1.6" valves (64cc chambers) should produce nominal 11.0:1 SCR when single steel shim head gaskets are used.

[Joe C.]

Re: 64 327/300 Cam question

Just as a sidelight to this subject; my ongoing investigation of the various Carter AFB carbs used from 63 thru 65 on L-75/L-76 engines bears out that anyone with a 63 L-75 running a 3461S carb on a driver car would benefit by changing to one of the later 3720S series models for improved driveability. The 3461S was extremely taylored for the L-76 engine in 63 with the 097 cam. I didn't realize just how much until I began to bench compare them side by side. Actually, I believe the 3461S may flow about 50 cfm more, and all the jets and air bleeds are consistent to this end. Even the secondary air valve has lighter weights. I recently ground one from my donor 3720SA to lighten it for testing and found the 3461S still lighter than my modified piece.

If anyone wants to compare notes on this off subject matter, just send me an E-Mail or P.M. and we can began a dialog to pass on some knowledge.

Stu Fox

Stu,

As you know, a 50 cfm flow capacity won't make any noticeable difference in normal every day drivability. It will add a couple horsepower to max engine output. Certainly no more than about 4-5, at most.

What will, absolutely have a tremendous effect on low/moderate speed drivability is the throttle bore size and, more importantly the ratio of that diameter to the venturi booster diameter. The bigger the booster and it's placement in the low pressure airstream in the throat of the primary throttle bores determine the sensitivity of the fuel delivery at low speeds per given engine manifold vacuum.

I suspect that both these Carters have equal bore sizes and booster configurations; the more significant difference between the 3461S and the 3720S is that the 3461S is likely calibrated richer (smaller diameter metering rods and/or larger diameter main jets) thus tailored to deliver adequate fuel volume to the larger duration/larger overlap L76 engine.

[Michael H.]

Re: 64 327/300 Cam question

Just as a sidelight to this subject; my ongoing investigation of the various Carter AFB carbs used from 63 thru 65 on L-75/L-76 engines bears out that anyone with a 63 L-75 running a 3461S carb on a driver car would benefit by changing to one of the later 3720S series models for improved driveability. The 3461S was extremely taylored for the L-76 engine in 63 with the 097 cam. I didn't realize just how much until I began to bench compare them side by side. Actually, I believe the 3461S may flow about 50 cfm more, and all the jets and air bleeds are consistent to this end. Even the secondary air valve has lighter weights. I recently ground one from my donor 3720SA to lighten it for testing and found the 3461S still lighter than my modified piece.

If anyone wants to compare notes on this off subject matter, just send me an E-Mail or P.M. and we can began a dialog to pass on some knowledge.


Stu Fox

Stu,

Something just occured to me about the carburetor issues you mention. You may want to wait until you have a load of ethanol free fuel in the tank before you fine tune the carburetor.
I noticed quite a change in the way my 66 ran after I switched to ethanol free. I no longer had idle issues or a part throttle hesitation until the engine was thoroughly warmed to operating temp.
All of my carburetor issues disappeared after switching the ethanol free.

Maybe the correct original carburetor is ok as is after the good fuel runs through it?

[Stuart F.]

Re: 64 327/300 Cam question

Michael;

Thanks for the tip. I'm at a stage of cataloging what I have (primarily in the power enrichment parts) and preparing a test plan. I'm still running the replacement 3721SB that I peaked for Florida on ethanol deluted fuel which was doing very well until our recent hot/humid weather. The 3461S I have requires one correct LF venturi cluster (booster) as I received it with an incorrect "tabbed" piece from the former owner. He bought the carb from a well known restorer who has promised to replace that along with a correct top plate with brass vents instead of SS.

Sorry to others on this thread for straying into carbs, but I still standby my recommendation for 63 L-75 drivers (replace your 3461S with a 3721SB for driveability). Trade your 3461S to someone like me with an L-76 who had theirs stolen many years ago and has been trying to find one in the proper date range ever since, Ha!

Stu Fox