Large rpm drop

[crackedback]

With 18-20 initial that cam should idle at 850 with no issues. JMO

I would not hook up ANY vacuum related items to isolate the intake tract. Nothing! Seal all that off and let the engine run as if the intake.carb are the only thing on top of it allowing air in.

Get a known good carb on it. Hopefully the rings aren't killed from fuel.

 

[Mattax]

idle mixture screws 1 turn out from seated, fuel pressure at 6psi, float level checked,...

Pressure and float level are good to know.
These should result in the proper fuel level.
The way to check that is at the site plugs. Depending on the carb, fuel should either be just below the plug, or in the mid area of the glass.

Are they set it as shown on Page 11 or 12?
https://documents.holley.com/199r9934-3rev4.pdf
or as much as 3/32" lower than Holley showns on those pages is OK- esp secondaries.

If the fuel is too high in the bowls, then the mains can easily be dribbling. And if they are much too high, fuel will come out of the boosters until the fuel pump shuts off and the bowls empty to a point lower than the top of booster passage.

 

[Charlesvolare]

I messed around with it for a few days, ended up getting a new gasket kit. It's not perfect but it's way better than before and there's still some things to work on. Timing is ~18 initial, 28 total, no vacuum advance. Transition slots have about 0.030-0.035" exposed, the secondaries are just barely cracked. 6.5 PV, 11.5 in of vacuum in gear. 575-625 rpm in gear, 750-800 in neutral.

I took the car to an charity autocross this past weekend and ran it, and it did batter than I thought lol. Definitely lots of room for improvement in the handling/traction department (rev limiter was set a little conservative, not valve float. 3rd gear was a little too fast for those turns in my car):


Here's my spark plugs as promised:

 

[yellow rose]

I messed around with it for a few days, ended up getting a new gasket kit. It's not perfect but it's way better than before and there's still some things to work on. Timing is ~18 initial, 28 total, no vacuum advance. Transition slots have about 0.030-0.035" exposed, the secondaries are just barely cracked. 6.5 PV, 11.5 in of vacuum in gear. 575-625 rpm in gear, 750-800 in neutral.

I took the car to an charity autocross this past weekend and ran it, and it did batter than I thought lol. Definitely lots of room for improvement in the handling/traction department (rev limiter was set a little conservative, not valve float. 3rd gear was a little too fast for those turns in my car):


Here's my spark plugs as promised:
View attachment 1715465151

The power valve is opening way too late.

Can't see enough of the spark plugs to see for sure, but I'm not sure why you are only running 28 total. Something is really wrong.

From the plugs it looks like you have too much initial and total, but that is an Autolite plug so I'm not sure on how the cad comes off.

Also, it's hard to see WOT A/F ratio without seeing down in the shell to see the fuel ring on the bottom of the porcelain.

 

[nm9stheham]

Forget the ignition timing.... work on your braking points LOL

Glad things are getting there and it is working better.

 

[Charlesvolare]

The power valve is opening way too late.

Can't see enough of the spark plugs to see for sure, but I'm not sure why you are only running 28 total. Something is really wrong.

From the plugs it looks like you have too much initial and total, but that is an Autolite plug so I'm not sure on how the cad comes off.

Also, it's hard to see WOT A/F ratio without seeing down in the shell to see the fuel ring on the bottom of the porcelain.

Power valve was a known good one, ruling out a blown/bad power valve.

I'm running around that timing to keep from detonating on pump gas. I put this setup together last June, blew head gasket early July running ~34* total timing.

After that, milled the heads 0.010" to flatten, kept total timing 30* to play it safe. Initially assembled the engine with the rings on the tight side of kb's spec, butted rings in October and that's when I rebuilt it to how it is now. Detonation may have been a contributing factor to that as well. But idle always been an issue however no matter what iteration of the engine I was on.

Aluminum heads would probably help with detonation and will probably be used down the road if I can find a good deal, but for now closed chambered irons are what I have.

And this is a thread on getting idle adjustment right so let's save WOT for a later date.

 

[Charlesvolare]

I ran a compression test with the plugs out,190-195 psi range, cold engine, to give an idea of dynamic compression.

 

[yellow rose]

Power valve was a known good one, ruling out a blown/bad power valve.

I'm running around that timing to keep from detonating on pump gas. I put this setup together last June, blew head gasket early July running ~34* total timing.
View attachment 1715465182
After that, milled the heads 0.010" to flatten, kept total timing 30* to play it safe. Initially assembled the engine with the rings on the tight side of kb's spec, butted rings in October and that's when I rebuilt it to how it is now. Detonation may have been a contributing factor to that as well. But idle always been an issue however no matter what iteration of the engine I was on.
View attachment 1715465193

Aluminum heads would probably help with detonation and will probably be used down the road if I can find a good deal, but for now closed chambered irons are what I have.

And this is a thread on getting idle adjustment right so let's save WOT for a later date.

Im Not questioning if the power valve is bad or not. I'm suggesting unless your cruise vacuum is 9 or 10 inches you are opening the power valve way too late.

There is not a scenario where I can say a 6.5 power valve is the correct one for any application.

 

[nm9stheham]

I ran a compression test with the plugs out,190-195 psi range, cold engine, to give an idea of dynamic compression.

Yep, that is well on up there for pump premium! The higher CR's will raise the peak combustion temps higher and higher and that could well have helped those rings to expand and butt.