Compression test results

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Well the saga continues . . . .thing was running great and then this
20220402_102627.jpg
 
Not that it’ll help your current predicament...... but......
It looks nice!!

Hopefully you didn’t venture too far from home.
 
PRH said:
Not that it’ll help your current predicament...... but......
It looks nice!!

Hopefully you didn’t venture too far from home.
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Thanks ! It's most likely going to be a pretty garage ornament for the next few months
 
GREEN GHOST said:
Well the saga continues . . . .thing was running great and then this View attachment 1715899902
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Coming to the party late. I got a 408 stroker engine from Blueprint that came with a 750 VS carb. The engine ran OK except for low speed where it was very lazy. Plugs after just a few minutes of running were black, pig rich. Could not put a vacuum gauge on it to adjust the idle mixture because the gauge needle was going crazy because of the valve overlap. Long story short: Changed the power valve in the carb from 6.5 to 4.5 and that cleaned everything up. Very responsive at low speed now. May even test going to a 3.5 at some point.
 
Ricks70Duster340 said:
Coming to the party late. I got a 408 stroker engine from Blueprint that came with a 750 VS carb. The engine ran OK except for low speed where it was very lazy. Plugs after just a few minutes of running were black, pig rich. Could not put a vacuum gauge on it to adjust the idle mixture because the gauge needle was going crazy because of the valve overlap. Long story short: Changed the power valve in the carb from 6.5 to 4.5 and that cleaned everything up. Very responsive at low speed now. May even test going to a 3.5 at some point.
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Nice, from what I'm reading it sounds approx 1/2 of your manifold vacum. . .I'm pulling about 13 at idle so I was going to go up to a 6.5. .. with your big cam maybe a 3.5 would be right for you
 
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GREEN GHOST said:
Nice, from what I'm reading it sounds approx 1/4 of your manifold vacum. . .I'm pulling about 13 at idle so I was going to go up to a 6.5. .. with your big cam maybe a 3.5 would be right for you
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For the record, the power valve does not affect idle. It can’t. There are videos to prove this out.

Several folks on here have tested it and found that this is correct.

The correct way to set power valve opening timing is 3-4 less that cruise vacuum and then tune the rest of the carb for that.

Also, I’ll point out that if you delay power valve opening more than it should be and it runs better, it’s a sure sign the primary main jets are way too big.

To tune for that, plug the primary power valve off with a plug. Drive the car and get the speed up to cruise on the main jets. Drop main jet sizes until you start to get a slight lean surge and then go up 2 sizes and leave the primary main jets alone. You should never have to touch them again unless a big change is made like you moved to very high elevation, cam change or some other modification.

Once you do that, put the power valve back in and tune for WOT by increasing or decreasing the Power Valve Channel Restricters, which are the holes behind the power valve. And by changing the secondary main jets.

That’s the proper way to tune Holley. For starters anyway.
 
Rat Bastid said:
For the record, the power valve does not affect idle. It can’t. There are videos to prove this out.

Several folks on here have tested it and found that this is correct.

The correct way to set power valve opening timing is 3-4 less that cruise vacuum and then tune the rest of the carb for that.

Also, I’ll point out that if you delay power valve opening more than it should be and it runs better, it’s a sure sign the primary main jets are way too big.

To tune for that, plug the primary power valve off with a plug. Drive the car and get the speed up to cruise on the main jets. Drop main jet sizes until you start to get a slight lean surge and then go up 2 sizes and leave the primary main jets alone. You should never have to touch them again unless a big change is made like you moved to very high elevation, cam change or some other modification.

Once you do that, put the power valve back in and tune for WOT by increasing or decreasing the Power Valve Channel Restricters, which are the holes behind the power valve. And by changing the secondary main jets.

That’s the proper way to tune Holley. For starters anyway.
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Haven't dove into carb tunning yet. Just remember reading as a basic rule of thumb the pv should be approx 1/2 the size of your manifold vac measurement at idle.
 
Has the reason for being left at the side of the road been determined yet?

Fuel issue?
Spark issue?
Mechanical issue?
 
PRH said:
Has the reason for being left at the side of the road been determined yet?

Fuel issue?
Spark issue?
Mechanical issue?
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It's getting fuel, test & confirmed msd box / coil are working, leaning towards mechanical issue... punched it cruising at approx. 40mph, smelt gas for a second and then it just starting running very rough, smoke out of exhaust pipes. Almost knocking like it's misfiring. Started a couple times running super rough, smoke out exhaust, backfiring through carb and then died. Now won't start . . Going to dive deeper later today but can't be good lol.
 
GREEN GHOST said:
Haven't dove into carb tunning yet. Just remember reading as a basic rule of thumb the pv should be approx 1/2 the size of your manifold vac measurement at idle.
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Yes, that is frequently said and is completely wrong. This misinformation keeps popping up (and I think Holley tech is still telling people this). It's only close if you have a very mild cam so idle vacuum is high (and well above cruise vacuum). I suppose they tell the average 350 SBC owner this to keep them out of trouble? :realcrazy:

Idle vacuum has nothing to do with the power valve. Someone already mentioned that a place to start tuning is 3-4 inches below cruise vacuum. Not idle.

My 451 (272@.050 cam) idles at 8" and cruises at 15". A 4" power valve would be very late opening and cause a big lean spot. After extensive tuning I have a 9.5" and it's just about right. :)
 
If the car is running an electric fuel pump, I’d try getting the car started by leaving the pump off.

Sounds like there may be some debris in a needle & seat.
If you turn on the pump and fuel is running/dripping from the boosters, that’s likely the issue........ or the pressure and/or floats are set too high.
 
PRH said:
If the car is running an electric fuel pump, I’d try getting the car started by leaving the pump off.

Sounds like there may be some debris in a needle & seat.
If you turn on the pump and fuel is running/dripping from the boosters, that’s likely the issue........ or the pressure and/or floats are set too high.
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I checked everything at the carb and was driving around for a good 30min prior to this happening. Certainly can't hurt to triple check, stay posted
 
Rat Bastid said:
For the record, the power valve does not affect idle. It can’t. There are videos to prove this out.

Several folks on here have tested it and found that this is correct.

The correct way to set power valve opening timing is 3-4 less that cruise vacuum and then tune the rest of the carb for that.

Also, I’ll point out that if you delay power valve opening more than it should be and it runs better, it’s a sure sign the primary main jets are way too big.

To tune for that, plug the primary power valve off with a plug. Drive the car and get the speed up to cruise on the main jets. Drop main jet sizes until you start to get a slight lean surge and then go up 2 sizes and leave the primary main jets alone. You should never have to touch them again unless a big change is made like you moved to very high elevation, cam change or some other modification.

Once you do that, put the power valve back in and tune for WOT by increasing or decreasing the Power Valve Channel Restricters, which are the holes behind the power valve. And by changing the secondary main jets.

That’s the proper way to tune Holley. For starters anyway.
Click to expand...
My post was poorly written. The comment about the idle mixture was only to say that the vacuum was so inconsistent as to make it unusable, not that it had anything to do with the power valve. Thanks for the reply.
 
Well I'm happy to report as other have recommended that it was a fuel issue ! Very strange even though fuel was coming out of the boosters junk was in the fuel bowls. It looks like holleys hard coating debris made its way in the fuel bowls and was intermittently lodging itself in the needles / orifices. Took all apart, cleaned out, & seems ok. . .back to tuning ! . . .for now
 
GREEN GHOST said:
Just finished testing compression this afternoon, results below are cold & dry. From everything I red the numbers seem higher than what I would've expected for a healthy engine. It's a 500ci 440 stroker with approx. 10.5-1 compression and a small hydraulic cam. Are the higher numbers a result of the baby cam ? Or is the CR possibly higher than I'm thinking?. .. . .cylinder 6 will remain a mystery and I'm ok with that lol. Just getting the spark plug out was a hellacious event that took 15min & had me wishing the car had a 408 in it . . .couldn't imagine a hemi in this thing
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Could be a mix of both but I suspect the intake valve closes pretty quick and is trapping alot more mix.
 
GREEN GHOST said:
Haven't dove into carb tunning yet. Just remember reading as a basic rule of thumb the pv should be approx 1/2 the size of your manifold vac measurement at idle.
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Having the power valve do its thing during part throttle (no secondaries) is a revelation. You won’t experience this with the 1/2 idle vacuum. Like has been mentioned, pick a PV a couple hg less than your cruise reading. Once you dial it all in you can marvel at how responsive your carb (engine) is without having to mash the throttle as much. You have to tune and test to get there.
 
Took the car out after some minor changes & thing seems to be running great. After pulling the carb apart I re- adjusted the 4 corner idle, raised the idle alittle, reset the float bowls, & went up to a 5.5 power valve. Also I swapped from two heavy silver springs to the blue springs in the distributor. Car seems to be running great, starts easy, runs cool, & rips. . . The plugs still look very rich. I didn't mess with the actually timing, initial is around 18 and total looks like it almost touches 40. . . It was recommended that i try champion rc12yc plugs and maybe back off timing alittle. Might just leave well enough alone for now because it seems to be running so well. . .plugs do bother me though, I'd like a cleaner plug.
 
Not sure if the elimination of the initial bog I was getting is due to the larger power valve or timing coming in faster
 
GREEN GHOST said:
Not sure if the elimination of the initial bog I was getting is due to the larger power valve or timing coming in faster
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The power valve doesn’t control how much fuel is added when it opens. The number on it indicates WHEN it opens relative to intake manifold vacuum.

To control or change how much fuel is added when the power valve opens is done with the power valve channel restricter holes. Those are the holes in the cavity you see when you remove the power valve.

I doubt that a 5.5 power valve is opening soon enough for your application.
 
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