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Discussion Starter #1
As a lot of you know I’ve been fighting junk cams.... anyway that is behind me so now here is the current issue. Sbc, Edelbrock performer heads, cam and intake on a 355. 650 Holley dual feed new MSD distributor. 10.5:1 Keith Black flat tops been running 92/93 pump gas. I’ve been fighting a dead spot when you stab the throttle and have absolutely black and carbon nasty plugs, even fouled a few. I’ve been all over the map with jets, power valves, timing you name it. Earlier today I was out for a test drive and just let it rap up to about 7k, and the belt flew off for some reason at that point. Shut it off, coasted to the corner put the belt back on and came back to the house. Soooo, now I’ve got 67 primary jets, 75 secondary jets. 6.5 power valve not exactly sure where the timing currently is because I’ve been doing the twist it and see how it reacts thing. The car usually runs right around 200 on the temp but now it continues to climb and after about ten miles it’s 230 and climbing still. Any thoughts on what in the hell is going on and why I can’t get the dead spot out of it? Played with the pump cams and everything, getting pretty irritated with the whole thing and now the temp issue to add to it. Any input would be welcomed.
 

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Is your carb a double pumper or vacuum secondaries?
 

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not exactly sure where the timing currently is because I’ve been doing the twist it and see how it reacts thing. Any input would be welcomed.
^^^
Fix this first.
Get a timing light and do it properly.
Guy
 
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Discussion Starter #5
I’ve set it at 10 and 12 (among others) base and saw zero improvements. Using a dial light I ran it between 25&38 total and still saw the same issues. I’d be happy to set the timing and lock it down and find the problem elsewhere but that just isn’t happening. So where is the problem? Everything is new, I’ve tried ported vacuum, manifold vacuum, jets. If someone wants to tell me where to lock down timing, what jets to put in, ported or manifold vacuum. Tell me the theoretical setup that should work and I’ll put it in! I’d be happy to just set the timing but that tells me nothing about anything else that could be the issue.
 

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How much mechanical advance do you have? Also, auto or stick?

All I can tell you for timing is what has been working for me. Similar on both my small and big block, both with autos. Feel free to give it a try, it may or may not work for you.

I‘ve been running 16-17 initial, 18 mechanical all in by around 2500 and 10 degrees of vacuum advance on manifold vacuum with great success. Using a VC-302 vacuum canister on an MSD pro billet HEI.

That timing, along with tuning the carb, gives me good throttle response and no flat spots. Note I’ve got an auto, and am also running vacuum secondaries. One key with vacuum secondaries is to make sure your secondary spring is not too light or they open too quickly.

Right now with the MJ 467 I’m running the same but have the vacuum advance disconnected per Mark’s instructions, and still running well.

I will note that the vacuum secondaries carb is easier to tune on my small block than the same size mechanical secondaries was, and the vacuum secondaries carb performs just as well as the mechanical secondaries does on that motor.

On the big block, I’ve had nothing but vacuum secondaries.

Edit: BTW - since I have had good success with that timing on many engines, I use that as my baseline now. I set the timing to pretty much that first, and then tune the carb around it not messing with the timing anymore. So far, with that timing, I’ve always been able to then tune a carb to be very well behaved.
 
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Discussion Starter #8
It’s an TH400 with a manual valve body and a 3,400 stall. I guess I’ll try putting more timing in it but the dang plugs are absolutely nasty black. I leaned it out a bunch till it was flat then went the other way. Tried a 2.5 power valve and that certainly wasn’t the answer. Can you see any reason why any of this would cause it to slowly keep increasing in temperature all of a sudden? That’s new as of today.
 

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Start by reading Ignition 101 sticky at the top of the Ignition forum. Ignition affects vacuum which affects your carb.

Basics: You say you have an MSD distributor, no mention of which one. Typically you will want to install the black bushing, the largest one. Set initial timing to 18 degrees, total centrifugal shoud be 36. Do you have a degreed balancer, timing tape or dial back light?

On top of that, you'l want 10-12 degrees of vacuum advance, most cans have more than that, there are various ways to limit it, some like to argue about it. Make the choice that works for you.

Even with your vacuum advance unhooked, you can work on your WOT acceleration once your centrifugal timing is set.

A stumble usually indicates lack of fuel. With the greater ignition advance in your distributor, you should be able to close your throttle blades, so your idle circuit and transition circuit is working as intended. This alone may fix it once you correct idle speed.

You say you have a 650 Holley, what is the list number? That will clarify exactly what it is and how to best tune it for your application.

Other questions: Is your car automatic or manual? What is your rear gear ratio?

Devin
 

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For your heat issue, this is what I did to fix my heat problem.
new 180 thermostat, Weiand high flow water pump and most important, full manifold vacuum.
Runs at 180 all day long and 185 at idle.
Definitely get your timing right first. That will affect heat too.
I also had a stumble with a Holley, rebuilt it, changed a few things, jets, squirters, etc. couldn't fix it. So, I didn't give up, I just selectively interchanged it with a new Holley. fixed.

It sucks throwing $ at the problems, but sometimes you look at an issue and that's been kicking your ass for awhile and you just have to open up the wallet.
 

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If your plugs are black and fouled, too rich. When I had the Performer RPM heads on my 355, they liked 32* best. Ran one silver and one blue advance spring and had 12* mechanical advance with 20* initial with my vac advance on ported.

I ran a 650 dp too...until you get the rich part figured out you can’t really do too much else.
 

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Also borrow another carb if you can
 

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Not sure I can offer much. But....

My 350, stock 882 heads, Eddy performer intake, Summit HEI, 30 year old Holley 1850 vac secondary carb, likes 18 initial, and about 14 mechanical. The vacuum does not play much at WOT tuning.

My first suggestion would be to go back to a 6.5 or orig spec power valve.

Set the timing with a light. Maybe try 16-18 initial, and add 16 ish by mech via springs and stops.

Then set the idle mixture screws. All four if you have them. Do that with a vacuum gage, or best idle by ear. Then make sure the cold start idle screw is not causing issues, you have to pull the carb to access it, is under the baseplate.

Then set the curb idle.

Maybe do all this, then pull the carb again or other wise look down the carb and make sure the throttle blades, as you have them set, are in the acceptable location below the idle transfer slots.

A country boy check is to pull a vacuum hose off the intake at idle, if it speeds up, there is too much fuel still.

Make sure you dont have excess fuel dripping when the carb is off or idling, ie, correct float levels, and the rear bowl gaskets, both of them, are not old, damaged, or otherwise leaking.

If all this is good, it should start, run, idle, etc.

For the bog, I would start with the pump cam adjustments. There is specific Holley guidance on this and it works. They should move immediately when you touch the gas pedal.

Then fool with jetting. In most of my tinkering, too lean main pri jets will also create a bog, so i go that way, find the bog and go up.

For an at car, even with a hi stall converter, I like a vac secondary. For mech secondary, you may have the added effort to get the pump shot to coincide with the stall speed, ie, the pump fuel shot is used up revving the engine, the converter loads up and it needs more gas. I have not needed this but just a thought.

The pump activation has been the key element for me.
 

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One would think of all the info on CORRECT timing and vacuum advance degrees setting, and source, it would be a slam dunk to get it right, but.....

"Right now with the MJ 467 I’m running the same but have the vacuum advance disconnected per Mark’s instructions, and still running well."

"12* mechanical advance with 20* initial with my vac advance on ported."

This, and all the rest of this load of total misinformation being emitted here would be absolutely hilarious, if it weren't totally criminal.

No need to do it right, there are so many ways to completely mess it up, and more than a few are listed in this topic. Not worth trying to get the OP to do it right, and then incur the wrath of a handful of timing experts.

I'm gonna go work on BBQ'ing lunch correctly, now, thankfully, there won't be 17 other people insisting I cook the food some sort of strange way. .
 

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It’s an TH400 with a manual valve body and a 3,400 stall. I guess I’ll try putting more timing in it but the dang plugs are absolutely nasty black. I leaned it out a bunch till it was flat then went the other way. Tried a 2.5 power valve and that certainly wasn’t the answer. Can you see any reason why any of this would cause it to slowly keep increasing in temperature all of a sudden? That’s new as of today.
Wait for the engine to cool down then remove the thermostat,then sit it in a pot of water and bring the water to a boil.Watch to see what the temp of the water is when it starts to open,if its a bad thermostat it won't open at all.
Water starts to boil at 220* just in case you don't have a heat gun to see what the temp is.You could also use the family cooking thermometer because the boiling water will keep it clean.
Stuck thermostats happen all the time and always at the worst time.
 

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A stuck thermostat can blow the radiator hose off. I drove 10-15 minutes before it happened. Happened to me twice in the early 1990's. Got into the habit of replacing every 2-3 years.
 

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Hi Dave. I agree with you, normally I would have the vacuum advance connected to manifold vacuum and set to be pulling about 10 degrees at idle. I’ve got one adjustable canister set up per your instructions with the crane adjuster plate in front of the pull tab with a tapped and set screw. I was running it exactly as you recommend with my old 454, initial, mechanical and manifold vacuum advance. And this is what I recommend the OP to give a shot.

But, as I also mentioned, the engine builder of my new engine that I just installed said not to run vacuum advance at all, so to keep my warranty valid, I’m running it as he said to run it. Everything else is set up as you recommend and the way I ran it on my old 454, just running with vacuum advance disconnected for that reason. In my case it seems to be running just fine.

As for a BBQ lunch - sounds good. :thumbsup:

One would think of all the info on CORRECT timing and vacuum advance degrees setting, and source, it would be a slam dunk to get it right, but.....

"Right now with the MJ 467 I’m running the same but have the vacuum advance disconnected per Mark’s instructions, and still running well."

"12* mechanical advance with 20* initial with my vac advance on ported."

This, and all the rest of this load of total misinformation being emitted here would be absolutely hilarious, if it weren't totally criminal.

No need to do it right, there are so many ways to completely mess it up, and more than a few are listed in this topic. Not worth trying to get the OP to do it right, and then incur the wrath of a handful of timing experts.

I'm gonna go work on BBQ'ing lunch correctly, now, thankfully, there won't be 17 other people insisting I cook the food some sort of strange way. .
 
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