Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Keep going through spark plugs, need some advice.
View Single Post
  #8 (permalink)  
Old 04-11-2010, 04:11 PM
eric32 eric32 is offline
Registered User
Last photo:
Join Date: May 2008
Location: ohio
Posts: 2,722
Wiki Edits: 0

Thanks: 156
Thanked 285 Times in 265 Posts
Ok guys here is an update on my engine. I took it up to my dad's house today and he has built engines for many years and really knows his stuff. Now please bare with me many people who know all this stuff will disagree at times on certain things so please be kind to me as I am a rookie and just trying to learn the tricks of the trade. My timing is already set at 16 degrees initial at idle with the vacuum advanced plugged. With vacuum advance hooked up it brings my rpm up about 100 rpm and that is with it hooked up to the timed port at the metering block. I know about timed port vs full manifold but that will be another post. During the winter time my engine idled good and did not have all this spitting and sputtering really bad like it's now doing. Never changed anything just put the one inch spacer on nothing else.

Happens mainly bad at warm up bet mostly goes away after its all warmed up. He adjusted the idle mixture screws and to get the highest idle speed change and it helped smooth out my idle. I did not have my vacuum gauge with me so was unable to see what it was doing. Ok I got it home and I wanted to check where he had them at and he said he went out a full turn which I thought would be a lot so wanted to check with vacuum gauge. I checked the screws and one was one turn out and the other was about 2.5 so I know that would not work correct and they are supposed to be the same. I turned them both all the way back in and went back out 1.5 turns. The idle mixture screws are very sensitive so turning them in either way does affect engine idle so I know they are doing there job and the transfer slot is not exposed too much.

Hooked up gauge and put idle back to 900 rpm and with idle mixture screws out 1.5 turns it now reads a steady 14 inches of vacuum for first time ever and stays there with no fluctuations like before. It seems the engine might want just a hair more on the idle mixture screws but how much is too much? I want to keep this thing as lean as possible at idle but with the best vacuum. Can't go less then 1.5 cause the motor will not idle smooth it will sputter. The missing at idle was even there when I had the pcv valve hooked up before and it made no change in that part. I thought it was the problem with my oil on plugs. Plugs are not oil fouled and still do good when running but outer ring gets black over time.

So that being said my dad said you can see on the side of the plug where it burns its a tan color so it is good where it is. The stock holley carb 600 came with 65 primary and 69 secondary but that is for a stock type motor. Like I said my brother's 305 chevy has the same carb and his motor is nothing performance wise just a smog type engine. My engine I figure would not run correct with that small of a jet setting cause it's a lot more then stock with bigger flowing heads, intake and bigger cam etc.

Will post a picture of what my new plug looks like after one day of running here after bit. Got to go to store so will be back. Thanks for the help guys appreciate it. I also got some better spark plug wires to go on it as well.

Reply With Quote