Clutch adjustment needed?

[Joe C.]

Re: Clutch adjustment needed?

Tim

Photo attached (I hope).

The cam is a CS1145R..........a faithful reproduction of the original LT1.

The fact that it has electronically controlled dwell is in your favor, and, of course eliminates two potential problem areas.

Check the inside of the cap for carbon, and gap the plugs at .032" first. Then go through the timing as I indicated.

The photo shows no PCV or other ventilation system. So......how are you venting the crankcase? You MUST vent the crankcase otherwise you'll suck oil into the chambers via the valve stem seals!!!! Recommend that you connect your port at the rear of the block to the air cleaner housing as it was originally. Remove the cap and run a hose from the oil fill tube to the 5/16" tube at the forward base of the Edelbrock. Use a PCV valve from a 1970-72 LT1 in-line on this forward hose. You may also use a replacement PCV for a 1963 Corvette. Either of these are available from your local auto parts store.

ONLY AFTER all of this is done might it become necessary to fool with the carburetor mixture. The above procedure must be your baseline, and represents a proper setup. There is a strong possibility that mixture adjustments will not be necessary.

[Domenic T.]

Re: Clutch adjustment needed?

Disconnnecting the VAC is not a very elegant way to correct a lean surge problem, which appears to be the case here.

IIRC John increased his jet size by one over OE, which eliminated the lean surge.

In addition to the massaged heads is has the Special 300 HP camshaft, and the two modifications combined to lean out the cruise mixture enough to cause lean surge.

See the Fall 2008 Corvette Restorer for more info on the subject.

It would help if the OP would state the exact model year, engine and transmission option - also whether the configuration is OE or modified in any way.

Duke

I think you mis-understood my post.


Disconnecting the vac can would be an elegant way to find the problem.

By no means did I mean fo him to run it all the time like that.

So maybe I'll try saying it this way.

To see if your vette is at the point of moving the timing because your vacume is fluctuating your timing via the vacume can at the distributor,
1-Disconnect the line and plug it.
2- if problem go's away?
3- By all means re-connect the line and now you have found your problem.

DOM

[Steve D.]

Re: Clutch adjustment needed?

Joe
There is a threaded connection in the intake manifold behind the carburetor. Would I get proper ventillation if I screw an el into the manifold, screw a PCV valve into the el and then connect the valve to the crankcase vent tube at the back of the block? Steve

[Steve D.]

Re: Clutch adjustment needed?

The current combination of intake manifold and carburetor doesn't allow use of the original air filter set up because of hood clearance. Also, my oil intake is a 64 without the side vent tube. I previously had a rubber hose running from the vent tube in the rear to the 5/16 connection in the front center of the carburetor, but did not have a valve.

[Steve D.]

Re: Clutch adjustment needed?

I just looked at the oil fill pipe and it does has a small vent tube; it just doesn't have an extra bend like the 63. Was your original suggestion to vent from either the front or the rear, or from both the front and the rear?

Steve

[Steve D.]

Re: Clutch adjustment needed?

I reset the timing and the surging went away, so the surging was a self inflicted wound.

I set the initial at 13 degrees at 700 RPM with the hose to the can plugged. At 2500 the advance is 38 but it continues to advance a bit after 2500. I will start looking for some stiffer springs
With the can connected at 700 RPM advance is 29 degrees meaning the can is adding 16 degrees which seems to be in spec. All of this was done with the crankcase vent tube open, but not connected to the carburetor. I will add a PCV valve to the circuit and go through all of this again.

Thanks everybody.

Steve

[Joe C.]

Re: Clutch adjustment needed?

Joe
There is a threaded connection in the intake manifold behind the carburetor. Would I get proper ventillation if I screw an el into the manifold, screw a PCV valve into the el and then connect the valve to the crankcase vent tube at the back of the block? Steve

No. The crankcase vent system needs both an inlet and an outlet. The proper way to do it is to draw filtered air from the air cleaner via a 1" rubber hose to a special stamped steel fitting/tube into the hole at the back of the block near the distributor. This fitting/tube is sold by Paragon as part no. 1057:

https://www.paragoncorvette.com/corvette-parts-catalog/c2/#/6/zoomed

You will also need a special long bolt to fasten the tube to the hole in the crankcase, Paragon 13585K.

A hole must also be cut into your generic air cleaner base just above the throttle linkage to allow installation of a flame arrestor/90 degree elbow. These can be found at most speed shops or online dealers like Jegs or Summit. A short piece of 1" rubber hose will then go between the sheet metal tube at the back of the block and the flame arrestor/90 degree elbow in the base of the air cleaner. This comprises the filtered inlet side of the circuit.

The suction side (outlet) will consist of a short length of 1/2" diameter rubber (reinforced fuel) hose going between the fitting already present on your Edelbrock's base (your picture shows it capped), and the capped fitting on the oil fill tube. You must regulate and govern the air flow in the circuit, and that's the job of the PCV valve, which is a pintle of varying diameter working against a calibrated spring. Its original location was at the oil fill tube. A Purolator PV679 will do nicely. Use the 1/2" fitting at the base of the carburetor. It's purpose is for the PCV hose! There is no need to put a fitting into the intake manifold (the plugged hole that you refer to is for the power brake booster), and I don't understand your reasoning for wanting to do so.

Your VAC (vacuum advance can) is in spec and checks out. You MUST limit total travel of the pin in the autocam slot to no more than 26 crankshaft degrees of centrifugal advance, in your case. This is done by means of a small nylon bushing which slips over the pin, thereby limiting total travel to about 26 degrees. You should use a brass bushing rather than a nylon bushing that is included in most restoration kits. Try Accel's spring kit, which comes with a bronze bushing. The other way to limit travel is to bend the heels of the flyweights so that the weights themselves contact the autocam at full deployment, thereby limiting their travel. Use of this method allows adjustability of total centrifugal advance. There is a third method, which involves brazing the slot to shorten it, but that is generally done with engines running 20 or so degrees initial advance thus limiting the allowable centrifugal to only 16-18 degrees to yield the universal total WOT advance number of 36-38 degrees. The rate of deployment of centrifugal advance is controlled by the springs. It is perfectly acceptable to mix/match 2 different springs in order to tailor your rate of deployment to where you need it.

Do you know what the engine's static compression ratio is? Did you make sure that the inside of the dist cap is free of carbon, and that the plugs are clean and gapped properly?

[Joe R.]

Re: Clutch adjustment needed?

Steve,

Nice job on your engine and I'm sure if you follow all of Joe's recommendations your engine will live long and give good service. It will be a joy to drive also.
Please consider replacing the rubber gas line between the filter and the carb. It's not a good idea to put a rubber hose on the pressure side of the fuel pump.
A small pin hole can send a fine mist of gas to your exhaust or spark plug wires that sometimes leak small sparks.
Your setup can cause an instant fire that cannot be controlled.

Just a helpful suggestion. Especially if you have a family.

JR

[Stuart F.]

Re: Clutch adjustment needed?

The PCV arrangement you are describing would be fine for a 64 and up, but the 63 is reversed, and he already has the tube from the port in the back of the block there. I can see it in the picture. This tube just plugs into a grommet in the block and must connect to the PCV valve. The fresh air supply must come in trough the oil fill tube. If he can't connect to the inside of the air filter, then I suggest he just use a vented oil fill cap (hogs hair). Then use an inline PCV to the large tube (port) at the front of the Edelbrock. Don't mess with the plugged manifold port to the #8 runner. Normal 63 manifold has the boss, but it is not drilled and tapped there.

The 63 PCV system was an engineering mistake which was later corrected by a Technical Service Bulletin A.I. 63-10 (and in 64) showing how to add a flame arrestor inside the air cleaner. I blew my valve covers off due to a crankcase explosion because of a sticking PCV valve back in the late 60's. I'm still running this way now, but then I no longer live where the ambient is below zero to duplicate the problem. I have some of the parts to do the alteration, but no will to do it as yet as I need to repair my air filter base first. All the chrome has peeled off the inside over the years. Them Chevy V8's are some tuff engines to eat all that chrome and spit it out without harming the engine - as yet.

Stu Fox

[Joe C.]

Re: Clutch adjustment needed?

The PCV arrangement you are describing would be fine for a 64 and up, but the 63 is reversed, and he already has the tube from the port in the back of the block there. I can see it in the picture. This tube just plugs into a grommet in the block and must connect to the PCV valve. The fresh air supply must come in trough the oil fill tube. If he can't connect to the inside of the air filter, then I suggest he just use a vented oil fill cap (hogs hair). Then use an inline PCV to the large tube (port) at the front of the Edelbrock. Don't mess with the plugged manifold port to the #8 runner. Normal 63 manifold has the boss, but it is not drilled and tapped there.

The 63 PCV system was an engineering mistake which was later corrected by a Technical Service Bulletin A.I. 63-10 (and in 64) showing how to add a flame arrestor inside the air cleaner. I blew my valve covers off due to a crankcase explosion because of a sticking PCV valve back in the late 60's. I'm still running this way now, but then I no longer live where the ambient is below zero to duplicate the problem. I have some of the parts to do the alteration, but no will to do it as yet as I need to repair my air filter base first. All the chrome has peeled off the inside over the years. Them Chevy V8's are some tuff engines to eat all that chrome and spit it out without harming the engine - as yet.

Stu Fox

Stu,

You're absolutely right about the 1963 system being reversed. Since Steve is not interested in originality, it's best that he use the later, improved config since the older system lacks a flame arrestor. More importantly, the old system doesn't provide filtering for the intake air.

The first photo shows the breather tube. The second and third shows how the PCV hose is routed on my '65. Steve has a much neater and shorter run to the front of his Edelbrock:

[Steve D.]

Re: Clutch adjustment needed?

Joe, Joe & Stu

Thanks alot. I think I understand the set up now.

[Steve D.]

Re: Clutch adjustment needed?

Joe

As you suggested, I replaced the rubber hose fuel line with hard line. Thanks for the suggestion.

Steve

[Stuart F.]

Re: Clutch adjustment needed?

I suppose Joe has a point about the rubber fuel hose in theory, but there are many factory correct C-2 Vettes running around with just that. The thing to remember is to use the correct type fuel hose and secure it properly. I use one because I have elevated my carb with a phenolic spacer in order to cool the carb operating temperature (35 to 40 degrees). My steel fuel lines are chrome and I want to keep them for conversion back to priginal some day. Incidently, it is just as easy to misapply the steel fuel lines and have a leak (perhaps more so) due to their flare fittings, and the fittings into the carb are not all that fail safe. The only leak I ever had on my L-76 AFB was with the gasket on the brass inlet fitting. Back in the day, most Hot Rodders used multiple carbs with fuel blocks and hoses. I never saw any one of my friends have any fires. The closest tthing to it was a stuck needle/seat which dumped raw gas into the engine which came out the header stacks as beautiful flames.

Stu Fox