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Chasing a ghost in a 350 SBC.

8K views 43 replies 8 participants last post by  cdminter59 
#1 ·
Year One Power Crate 350 with the Edelbrock E-Tech package, hyd roller, RPM air gap, Pro Systems XC built by Patrick, Dynatech Musclemaxx headers, older MSD Pro Billet, 6AL, Blaster II coil, Moroso Ultra 40 wires. The problem I'm having is it acts like there is a miss somewhere. This engine has about 250 miles on it, and the miss is getting worse. I changed plugs, and they looked like they came out of a fuel injected engine. Perfect color. Cleaned the cap, and rotor, made sure the pick up in Pro billet was clean, switched to another 6AL, rewired the 6AL straight to battery to make sure it was good. 14.7 VDC constant, readjusted the rockers, ran a compression test, 160psi across the board, checked all wires individual with a spark plug, has good fire, and it advances with engine speed, tried two different carbs, checked fuel pressure 7psi, checked all 8 primary tubes from cold with a thermal heat gun and 5 of 8 were ranging 400 degrees after 1 min of run time, and three were in the 250 to 290 range. Is there anyway the Pro billet could be causing an erratic spark issue? I'm at a total loss this far. Thanks for any information
 
#12 ·
Changed carbs back to the Edelbrock and the problem went away. There is still a slight bogg in the Eddy, but it's because of the secondaries not opening soon enough. But at least this tells me that the Pro Systems carb has some trash or something going on there. It's very strange why it's running great now. Like I said, chasing a ghost!!!
 
#14 ·
FWIW, I have seen more than a few problems lately with old muscle cars trying to run gasohol, which is pretty much all thats available in my area. Vapor lock issues in the summer, surging under cruise, etc which can be eliminated by running actual gasoline. I wonder in the pumps have more than 10% alcohol like they claim. Old rubber parts in the fuel system are also a problem with the new gasoline.
 
#16 ·
UPDATE: I took the 4150 apart and found a nice piece of fuel line trash, I built 6-AN fuel line, wedged in one of the passages of the primary metering block. Also found another great piece of fuel line trash blocking the hole in the secondary pump outlet. Anyway, played with three steps of PV, ended up using 5.5, and dialed the idle mixture screws to 7/8 turn out from seat. Re adjusted the idle transfer slots on primary side, and adjusted idle speed mainly with the secondary idle adjustment. Then started playing with pump arm gap. Adjusted to have a slight gap in the pump arm and pump lever.

Then came timing. To make a long story short, initial timing is a crazy 24 degrees. With heavy springs installed for a slow curve, and used a silver stop bushing. Total timing at 3000 is now 34 degrees. Car starts great, idles great, is very responsive, has almost zero transition into the secondaries on a double pumper, and pulls very hard from 2800 to 6000 rpm. Still a bit concerned with having 24 degrees initial, but there is zero pinging. Anyway, thoughts and comments are welcome. I believe my rear end gear is a 3.08:1 instead of the axle code stating 2.56:1. I'm turning 2500 rpm at 65 with a 27" tire.
 
#34 ·
Then started playing with pump arm gap. Adjusted to have a slight gap in the pump arm and pump lever.
Just to be sure- the gap is only at WOT, not at rest (idle), right?

Still a bit concerned with having 24 degrees initial, but there is zero pinging.
I'm guessing the cam is fairly 'healthy'. If that's the case, absolutely nothing wrong or unusual about the amount of initial timing.

BTW, good job on the carb tuning as well as the timing. A LOT of guys stumble (npi) on this.;)
 
#20 ·
With some of the aftermarket camshafts it will take alot of initial timing. There is nothing wrong with it. Check the total timing at 3500 rpms and above to make sure all the mechanical advance is in at 3000 rpms. The silver bushing allows 25 degrees advance. Check out this website for 10* and 14* advance limiter bushings it sounds like you will need them. Tuning MSD Distributors. Usually it takes one blue spring and one light silver spring to get the advance all in by 3000 rpms. Use a vacuum guage to tune your carburetor. Adjust the idle mixture screws out to get the highest vacuum reading.
 
#28 ·
That could be a possibility. They do take a long time to warm up. You don't have a spare Performer RPM you could try do you? Maybe a buddy might have one on the shelf? Have you checked your coil lately? Here is how to check it with an ohm meter. How to Test an Ignition Coil
I don't have a buddy with a spare Vortec RPM intake. And yes, I swapped out two different MSD Blaster 2 and Blaster 3 coils. Same effect. It's not in the ignition.
 
#31 ·
This might sound out of line but I had a tach some years ago do what you are describing. It was intermittent miss fire at times then other times a miss that was consistent around 3k then disappear. I unhooked that tach and the problem went away for good. Just a thought.
 
#35 ·
I read in one of your post about the trash you found in the 4150 carb. What type fuel filters are you using? Most manufacturers recommend a 100 micron filter at the tank. Also a 40 micron filter in the line up front. Another interesting thing I read the other day is not to use teflon tape on any gas or oil fittings. It said to use a paste type sealer with teflon in it. I used Permatex 59235 when rebuilding my engine last year. You have replaced everything in the ignition system and it hasn't fixed the problem yet. How about your fuel. Gas with 10% ethanol has a shelf life of about 3 months. The ethanol absorbs water from the atmosphere. I have heard of using a timing light to watch the gas as the carb squirts the gas. IDK but it is said you can see water in the gas. Here is the article (advertisement) i was reading. USA Fuel
 
#36 ·
I was using a summit racing summit racing 110 gph mechanical pump. I had installed it over the winter along with some other changes is why it took me so long to figure it out. I would swear that our description sounds just like my nightmare. It cost me a small fortune to figure it out.
 
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