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You want idle advance 20-24 (12 base +10-12 degrees of VA). Mechanical advance generally about another 12 degrees so that gets you to 35-36 at 2500-2700 rpm which is where SBC want to be
SoCal805, I agree with your recommendations... but if the distributor is set to provide 12°-14° initial "mechanical only" timing, you would shoot for an other 20°- 22° of mechanical advance in addition to the initial. The VA should not be considered when determining total mechanical advance. When the VA is connected, you could see a total of 46°- 48° of advance (mechanical + VA) during light throttle cruising... and that is fine.

OK, lets waste volumes of time and effort on "TESTS", instead of getting right down to it, and fixing it the right way in the first place. shall we.
Dave, I understand your point and agree that the OP would probably be a lot better off with swamping out their non-VA distributor to a VA distributor... but unfortunately, the OP's MSD #85551 cannot accept the addition of a VA canister.

The test doesn't cost anything (but some time) and is just a piece of mind for the OP before they consider spending $$$ on a new distributor with VA. The "test" is only duplicating how a properly set distributor (with VA) would preform at idle... and if there is enough of a rise in vacuum level to support the purchase of another distributor.
 

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SoCal805, I agree with your recommendations... but if the distributor is set to provide 12°-14° initial "mechanical only" timing, you would shoot for an other 20°- 22° of mechanical advance in addition to the initial.

The test doesn't cost anything (but some time) and is just a piece of mind for the OP before they consider spending $$$ on a new distributor with VA. The "test" is only duplicating how a properly set distributor (with VA) would preform at idle... and if there is enough of a rise in vacuum level to support the purchase of another distributor.
Yes mechanical advance 2500 rpm + whatever initial is set at without VA would = "total" advance. Op would need to use timing light to see A. what initial timing is at idle and B. what it is at 2500-2700rpm

But his core issue is low engine vacuum at idle so a simple timing advance with his current dizzy will show if that brings up engine vacuum enough to resolve his brake booster issue.. If so he would be better served dealing with dizzy mods vs installing a hydro boost. However if not that that would be the direction to go regarding his low engine vacuum issue

Not withstanding, a non VA dizzy on a street car is not ideal and a VA dizzy, set up properly with VA control, should be used
 

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Discussion Starter #23
OK. So, I checked the initial timing and it is around 14 degrees. I had about 10-12Hg. I advanced to 22 degrees, adjusted the idle, and was around 12-14 Hg. I will be doing a compression check later this week.
 

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Discussion Starter #25
I'm back. Happy New Year. Life and the holidays sidelined me for a minute. I'm open to opinions and or diagnosis. It would seem that everything is ok with the engine. I did vacuum checks from the manifold and from the front and rear of the carb.

The car sat for a few years until recently. I pulled the plugs and they all look like it had been burning really rich and or oil.

At 14 degrees initial timing I pulled 10hg. 9/10 bounce at the manifold. 20Hg at approx 2200 RPM.
At 22 degrees initial timing I pulled 12-14Hg. bounce at the manifold. 20-22HG at approx 2200 RPM.

I can tell that the booster is engaging when brakes applied vs when engine is off. (I should have disconnected while running, but it slipped my mind) The brakes are actually too soft and go near the floor. Which is confusing because I did not think 10Hg was enough for the brakes. I obviously have other problems with brake system but not necessarily vacuum. I will be upgrading to Wilwood disc all the way around. Finding vacuum for that system is what started all of this. What is the opinion of whether or not to still go Hydroboost?

I ran the engine several times and got it up to temp several times during the vacuum testing. Regardless of timing, it still burned rough (stinking of exhaust), but was not black or blue. Not too cloudy. (I have video) I let sit for a week, started it to move car in the garage and pulled the plugs. Found oil weeping from #6 and evidence of it in #4.

I did a compression test. Cold engine. (Had to move alt, ac, headers, and z-bar) #8 164psi #6 159psi and all others 160 on the nose. If solid compression, where is the oil coming from? I thought it may be valve seals and the compression test would expose that.

Suggestions, diagnosis, comments, or advise?
 

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at 22 degree initial timing, with VA (if you set up a controlled VA using a stop plate), 14 hg should be enough for power brakes. On the low side though

Rich, your carb may need attention in jets and or metering rods to lean it out. Given the car has sat for long periods maybe the floats are just stuck up to high causing the rich condition.

Good your compression is solid.
 

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Discussion Starter #28
Thanks SoCal. My research says that I can lock out my existing dizzy and control timing via the Sniper EFI. Hopefully, this would solve the idle vacuum and the rich burn in one go. I'm pretty sure this carb is too big. It came with the 355 I had before and I thought it too big for that one. It's a Holley 770 dbl pump. Any ideas about the oil in the spark bung if compression checks out?
 

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Car runs rough, vac needle moving around...forget about the distributor timing for a minute and go verify your valves are adjusted correctly.
 

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Discussion Starter #30
I'm pulling the engine for paint and other things. I will do a valve check then as well.
 

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A compression check will not determine the condition of the valve stem seals.
 
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It's a Holley 770 dbl pump. Any ideas about the oil in the spark bung if compression checks out?
The 770 may be on the big side depending how its jetted regarding rich condition.

EFI can be fussy to get dialed in but should be a more stable platform once set up right which is something you may need to get done by someone experienced with the Sniper

A leak down test would show if your valves are sealing and since you are pulling the motor easier to do than in the car with headers and Z bar. If the motor is coming out just change the valve stem seals if unknown age or condition
 

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Discussion Starter #34
Can I use the leak down tester keep the valves from falling when I change the valve seals? Is there a sure fire way outside of the air compressor, rope, or take off heads?
 

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Can I use the leak down tester keep the valves from falling when I change the valve seals? Is there a sure fire way outside of the air compressor, rope, or take off heads?
Why do you want to change valve stem seals?
 

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Ok fair enough. Some guys like bungee cord, some guys like air pressure.
 

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Discussion Starter #38
I see an air tool that you can use. I heard it's easy enough to make. I have a 20 Gallon Husky air compressor and am not sure if it's enough.
 

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OP

I have done it both ways, compressed air and rope. IMHO the rope is "safer" way to do it and certainly quieter. Especially if the rings or valves are letting air go by keeping the compressor running all the time. Also the compressor can push the piston all the way down so if pressure diminished the valve would drop into the cyl.

When I did valve stem seals a few months ago I just used about a 2' piece of 1/4" rope. Slide it in the spark plug hole (tie knot on end that stays out of the head) and then just rotate engine to bring piston up so rope fills the space and holds the valve up. Repeat.
 
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