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Surge problem on new motor.

I got my vacuum gauge on this morning and I only have 4 in vacuum hot idle in gear. So my power valave is right on the edge of being open and closed at a slower cruise. So I'm going to try a 2.5 power valave so it's closed at a steady cruise like it's intended to be.
 
Heimedw said:
I got my vacuum gauge on this morning and I only have 4 in vacuum hot idle in gear. So my power valave is right on the edge of being open and closed at a slower cruise. So I'm going to try a 2.5 power valave so it's closed at a steady cruise like it's intended to be.
Click to expand...
You were right on your vacuum being low with that cam....I think you are headed in the right direction.
 
Well I put the 2.5 power valve in and I still have the issue. I check the timing again. At 2000 rpm I have about 20 degrees. I have 9 degrees at idle and about 30 total all in about 3000rpm. I'm at a loss not sure what way to go?
 
Bummer, I think the power valve switch should run better long term.....buy obviously there is another issue. Does the car have the surge when you open the carb up in park at a fast idle or just driving?

9 degrees of timing initial is retarded. I think that would make it labor some...especially with that cam. Try advancing it. 36-38 total is what we shoot for if the gas allows it. I'd at least advance it and see if it changed your problem.
 
When it does this touch the break pedal just a little without changing RPM.
If it goes away it's the converter.
By touching the break pedal the converter becomes
locked up.
 
I advanced the timing 2 degrees and it made it better? Should I add more?
 
Yes. Keep going. You can probably go to a max of 40. If it doesn't ping. But peak power is usually 36-38 and 40 is not necessary. But it sounds like you need more idle-fast idle timing for sure.
 
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If the carb you have is a “race” carb, more than likely what you’re experiencing is why race carbs often make poor street carbs.

Carb part number?

I’d look into borrowing a “known good working” carb from a friends street car that isn’t experiencing the issue you’re having.

With some of these new carbs, without having the ability to read the a/f ratio in real time....... you can really end up chasing your tail.
 
Heimedw said:
I advanced the timing 2 degrees and it made it better? Should I add more?
Click to expand...
Be careful advancing the initial timing, until you know how much mechanical advance is in the distributor.
When you advance the initial, you usually need to shorten the mech advance, to keep full advance in check.
 
Agree, If you have 21 degrees in your mechanical advance.... It may need to be dialed back some by limiting the the movement. But it should be close at 17 initial and 38 all in. You will need to limit the mechanical advance if you only can run 34 total but need it at 18 at idle. That is a 16 degree mechanical advance. But with a large cam it should bleed compression, hopefully you can run 38 total.
 
I bump it yesterday to a max of 14 initial and 35 total and the issue is getting better. Im a little afraid of detination because are fuel in Ontario suck big time with 91 being are premium fuel and not having as good a additives in the fuel as the US. I backed it back to 12 and 33. Bs67 did say to much timing at cruise could cause this problem. My msd has two blue springs and blue bushing in it so should I try to slow down the ramp rate or speed it up more? Advancing the timing seems to be helping so if I speed up the ramp rate that should make it better?
 
If more timing is helping my thinking is taking timing out at 2000 is going to make it worse. My guess is advancing it is compensating for a lean condition on your carb..
You may need to shorten your mechanical timing as well if you want to be at 33 total and it likes more at a idle.
Speeding the ramp rate may help but I think we are just compensate for the carb not getting enough fuel in the rpm range you are struggling with.
 
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With as much hp you have and problems.....need to weld a bung on the exhaust and measure a/f ratio's. Lean can be expensive...and when your trying to feed a monster...need to not guess.
 
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The car is actually running on the rich side.

20190908_171203.jpg
 
PV is not the issue and is the wrong direction. Motor in the rr has 5.5 inches at idle and I run a 10.5. PV only contributes when the mains are on and at low vacuum. Not the case at cruise or idle.
 
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What’s your rear gear ratio. If it’s say 3.23 and at 60 your running 2400 you have a stall converter at 2600. It might not be locking in just yet. Only a suggestion. Won’t cause any backfire issues though. Curious.
 
Your engine definitely seems to want more initial, which means you will probably need to recurve the distributor(not hard). But you gotta get the timing settled before moving on to the carb or you'll be fighting a losing battle.... more timing at idle, will increase your vacuum a substantial amount and then you adjust the carb from there. Advance your distributor, at idle, until vacuum just starts to level off... that should be the happy place or you can even back it off two degrees from that point and still be good. But yes you have to watch your curve and total timing.
 
My guess what's happening is my vacuum at idle is 4.5 and I have to run my low speed jets at 11/8 to idle well then as I tip into the throttle my vacuum is jumping up to 15 and the motor is starting to draw in to much fuel and causing my surge and popping from a stop. Then adding timing is helping burn that fuel.
 
I'm running 355 gear. I also thought it was the convertor stall at first but I don't think adding timing would help like it has.
 
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