Technical help during problem determination

[Harry S.]

Re: Technical help during problem determination

More help with "shudder"/"stumble" - does it continue to run but somehow "roughens" up or does it actually stop for a split second and relight it self? If it occurs when you ask for a "little more", I'd look at the spark advance.

Loren, I'll be on that also.

Thanks

[Frank D.]

Re: Technical help during problem determination

Well hood clearance actually was an issue on my stock 250hp dual snorkel air cleaner - and not where you'd expect. The PS snorkel just touched the reinforcing lateral rib in the hood....a little judicious tweaking of the snorkel took care of that. Yeah, no hot slot, on these cars; but I think the point was made...

One final alternative is to add an electric "booster" fuel pump if its determined to be vapor lock, not something most Corvette guys want to do but many hot rodders adopt the fix. Then the hot fuel is being pushed towards the front of the car (with the electric pump near the fuel tank) instead of the mechanical pump trying to suck it from the front.

[Gerard F.]

Re: Technical help during problem determination

Harry,

Try some of this fuel line insulation:



Works for me on my 67. Also check your timing advance.

[Gerald L.]

Re: Technical help during problem determination

Might someone offer a part number for the distributor long tip rotor mentioned above? Thanks.

[Scott S.]

Re: Technical help during problem determination

I would check your fuel pump pressure, low pressure can cause a vapour lock.
Off on the Road Tour tomorrow.
Scott

[E B.]

Re: Technical help during problem determination

Harry, just pop the hood and see if this helps. Ed

[Leif A.]

Re: Technical help during problem determination

Might someone offer a part number for the distributor long tip rotor mentioned above? Thanks.

Here ya go...

https://www.parts123.com/parts123/yb.dll?parta~dyndetail~Z5Z5Z50000370a~Z5Z5Z5AAGCY~P15.00~~~~S5IY1FFX4R64201117870a~Z5Z5Z5~Z5Z5Z50000370a

[Harry S.]

Re: Technical help during problem determination

1932015 should be it.

[Dick W.]

Re: Technical help during problem determination

1932015 should be it.

That is the standard Delco rotor that was used for many years. If I remember correctly the article that Bill Sangrey wrote for the Corvette Restorer
magazine referenced an Accel rotor as having a longer tip.

[Harry S.]

Re: Technical help during problem determination

Just got the coil out. Here is the test.

Meter .4 resistance in the wires.

087 in the car Primary 1.6, minus the .4 gives you 1.2 Secondary 7,910
087 spare Primary 1.6, minus the .4 gives you 1.2 Secondary 8,003
NAPA Primary 1.7, minus the .4 gives you 1.3 Secondary 7,940

Thoughts?

[Harry S.]

Re: Technical help during problem determination

Still working on the bug. Quick question.

What MSD coil is the best replacement for the Delco 087 coil. Is it the MSD 82023 or the MSD 8222? It's for a 327/250.

Thanks

[Robert K.]

Re: Technical help during problem determination

I was reading this thread and saw information related to the carburetor and heat sink comments. There was a discussion about installing a insulating gasket between the intake manifold and the carburetor(s). Has anyone ever heard of a product from Heatshield (https://www.heatshieldproducts.com) being used on the underside of the intake manifold to aid in this problem? It is "foldable" and can be "wrapped" around to conform to the shape needed. Would this material aid in limiting the heat to the carburetor(s) to effectively help resolve this problem? The company advertises its use on the C5 LS-1 but really doesn't talk to much about the C2 Big Block cars.....

Thoughts from anyone or just wishful thinking?

[Timothy B.]

Re: Technical help during problem determination

Hi Harry,

This may have been mentioned already but have you wired the heat riser open and plugged the hot slot holes in the intake manifold.

On more thing I was thinking if you can't find any joy is could you have some voltage issues when the engine compartment heat soaks. This could be at the firewall plug and lead to low voltage from the ignition switch to the coil primary and a weak spark when opening the throttle blades and the mixture goes lean for a moment.

It seems related to heat and electrical resistance may be something to think about. I guess you could get the condition to repeat itself and jumper a known 12v to the ballast or coil and see if that makes it better.

[Harry S.]

Re: Technical help during problem determination

Think I found the problem, Coil and distributor cap. As soon as I set the timing, dwell etc. and take a ride I'll know.

Later

[Gerard F.]

Re: Technical help during problem determination

Harry,

When you check the timing, check your plugs. Been through a similar thing with my 67/327. Could be some fouled plugs due to valve leaks. Probably common on cars that get used only once in a while. A change of plugs and an oil change with some STP makes a difference.
The insulation of the fuel line from pump to carb also made a difference on mine, I found the fuel line touching the block and the radiator hose.