Gold69Swinger
Well-Known Member
My dude. He already told us in his first post that he posted it there and was referred here. This is not new information at all.
SOLVED! 318 2500-3000 rpm idling issue. Don't think its a regular vacuum leak. Swapped 2 intakes, 2 carbs ,and 6 different gaskets still no luck.
- Thread starter PlymouthPontiacEnthusiast
- Start date
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There is a lot of history of his setup over there, components and what they have tried.
Process of Elimination, people are working through it.
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Gold69Swinger
Well-Known Member
Yes...we all already knew this. Care to let people keep doing that or are ya just going to keep posting screenshots and AI nonsense?
TT5.9mag
Two atmospheres are better than one
@PlymouthPontiacEnthusiast try this simple test please, with the engine running, take a spray bottle full of water and spray each exhaust port right near the head on the manifold or header. If each cylinder is contributing equally you’ll get instant steam from each one. Lazy cylinders will take a second to boil off the water. Or if you have a laser temp gun, shoot the temps of each and report back. This is what lead to me finding my issue.
cookietruck
Well-Known Member
While he's at that, spray along the top edge of the intake manifold/head junction too. See if idle changes.
All the way off the choke fast idle cam? Not reading this again to see. Wire it or take the adjustment all the way out so it is out of the equation
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I suggested that and he posted a picture with the fast idle screw backed completely out.
TT5.9mag
Two atmospheres are better than one
It came from google AI. Where everything he posts comes from. It’s garbage.
Following.
I'm going to other direction. There has so been so much bad advice from people whom have clearly never wrenched for a living or whom have product to sell I'm disinclined to participate further.
The amount of AI slop and nonsense on all of these threads is enough to make people leave and not participate. It's ridiculous. The mods need to reel it in.
PlymouthPontiacEnthusiast
Active Member
Alright everyone, apologies for he delay, but I've been hard at work and got a second in person opinion from someone more experienced with built motors and we have discovered the problem, I'm just a dingbat.
The engine, was running fine. Very rich but I'll explain.
This car has an obnoxious short exhaust on it, side exit and straight through flow fx mufflers. So it's loud and this is part of what was throwing me off. I was misreading my vacuum gauge and it was pulling 10in of vacuum, 12* initial, my tachometer read 1600, but the thing was set to 4 cylinder mode meaning it was actually running at 800rpm.
First issue.
Second issue, my power valve was a 6.5 in and was hanging open hence the rich plugs and pig rich exhaust.
So I reached out to a experienced engine builder machine guy who did my Pontiac block, guys 91 years old and sharp as a tack and agreed I needed a 3.5in power valve and it cleaned the idle right up. The carb probably still needs tweaking but I simply lacked the in person experience with engines that aren't just stock 350s and 389s that I was thrown off by the sound and vacuum and idle stability.
Now it runs pretty good, got a little backfiring but I probably need to get the engine under load and drive it. Maybe open the secondary throttle blades a bit and back off the transfer slot on the primary throttle set screw.
Just a lack of experience as this is the first engine I've built that's run and the first performance motor I've ever worked on.
Thank you all even if it was all my fault!
Any further tuning advice would be appreciated with my setup!
The engine, was running fine. Very rich but I'll explain.
This car has an obnoxious short exhaust on it, side exit and straight through flow fx mufflers. So it's loud and this is part of what was throwing me off. I was misreading my vacuum gauge and it was pulling 10in of vacuum, 12* initial, my tachometer read 1600, but the thing was set to 4 cylinder mode meaning it was actually running at 800rpm.
First issue.
Second issue, my power valve was a 6.5 in and was hanging open hence the rich plugs and pig rich exhaust.
So I reached out to a experienced engine builder machine guy who did my Pontiac block, guys 91 years old and sharp as a tack and agreed I needed a 3.5in power valve and it cleaned the idle right up. The carb probably still needs tweaking but I simply lacked the in person experience with engines that aren't just stock 350s and 389s that I was thrown off by the sound and vacuum and idle stability.
Now it runs pretty good, got a little backfiring but I probably need to get the engine under load and drive it. Maybe open the secondary throttle blades a bit and back off the transfer slot on the primary throttle set screw.
Just a lack of experience as this is the first engine I've built that's run and the first performance motor I've ever worked on.
Thank you all even if it was all my fault!
Any further tuning advice would be appreciated with my setup!
Not participating...It's getting air from somewhere. Hoping that the OP will post a conclusion once he gets to the bottom of the issue.
Edit: Looks like he figured it out^^^
Roadblock64
Active Member
Cam lobe not completely wiped but working towards it ? Or completely wiped ?
If it was a Chi-Com Crosswinds Intake in the last 10-12 years they've had bad issues with porosity. Also they made a direct copy of the Edelbrock Performer RPM except that their molds and tools have been... Rode hard and put up wet. There is coreshift and you really need to take a bore scope and check the runners on it and also the plenum area.
A guy in Chattanooga was selling one for $50, a guy I do engine work for bought it and #3 and #7 runner had extra metal so that flow was okay at idle one day, not the next, and if you had tried to floor it- it bogged and the whole engine just essentially fell on it's ***. It was major coreshift as well as MAJOR, MAJOR, MAJOR failure in final machining(non-machining).
Glad you got THAT part figured out, BUT, let's clear something up. The power valve is not on the idle circuit. As the name implies, it's on the...wait for it...power circuit. So, a 6.5 power valve won't open until the vacuum reading gets below 6.5, so it sure AIN'T open at 10hg. Even if it was, it would have ZERO effect on the fuel mixture, because in order for it to do that, there would have to be more air than at idle flowing over the boosters. In short, ifin you wanted to, you could disassemble that carburetor, remove the power valve and throw it in the ditch, reassemble it and start the engine with no effect whatsoever on the idle. Your problem is elsewhere, like idle fuel restrictors, or air bleeds. If you can tell us EXACTLY what carburetor with a part number or list number, we can guide you on how to tune it correctly.
I was just going to ask if You were using a handheld tune-up tach, or one already in the vehicle, & to check the setting/hookup......some old tachs also have an issue with HEI signals depending on the hookup.
Is it backfiring as in spitting/coughing out the carb, or is it combustion of unburnt/excess fuel in the exhaust pipes......or both?
PlymouthPontiacEnthusiast
Active Member
It did it through the carb once or twice blipping it at first but as I revved it up to 4500rpm and back down a few times it seemed to clear up and stat running better.
I was just going to ask if You were using a handheld tune-up tach, or one already in the vehicle, & to check the setting/hookup......some old tachs also have an issue with HEI signals depending on the hookup.
Is it backfiring as in spitting/coughing out the carb, or is it combustion of unburnt/excess fuel in the exhaust pipes......or both?
Just a standard in car tach on the coils. Now that's it's set right it's reading far far more accurately immediately inclined to believe it.
I'm sure the plugs need a good cleaning.
I was just going to ask if You were using a handheld tune-up tach, or one already in the vehicle, & to check the setting/hookup......some old tachs also have an issue with HEI signals depending on the hookup.
Is it backfiring as in spitting/coughing out the carb, or is it combustion of unburnt/excess fuel in the exhaust pipes......or both?
PlymouthPontiacEnthusiast
Active Member
Brawler BR-67255 Brawler 4150 Diecast Carburetor https://www.holley.com/products/fuel_systems/carburetors/street/parts/BR-67255
This is my exact carb I got it as an open box return from Holly directly.
Could I be too much on the throttle set screw and need to open the secondaries for idle? Maybe that's why I was into the power valve at idle?
PlymouthPontiacEnthusiast
Active Member
Yes I took them all out thoroughly cleaned them up it helped
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