Burnin plugs

[Anonymous]

HI I'm looking for some input on why i'm having problems with my 2 center plugs burning up. I race this car in the wissota mods and i run a 750 alky carb. 13 to 1 comp. The head is a ported 240 head with 190 and 1.6 valves Where getting 221 cfm flow on the intake with a holman and moody intake. We just got it rally running strong and scuffed a piston. I have the right piston to cyl. clearance. I'm running 36 degress of timing. The engine is built to run about 7000 rpms. I went to the coldest plugs i could find. I went from the stock campion# 18s to 9's which helped.. The other plugs are burning nice.

 

[Anonymous]

Is the scuffed piston also from one of the middle two bores?

 

[addo]

I'm wondering if it's too well-exhausted on the centre pair. What about a cam grind with greater LSA on #3 and #4?

 

[80broncoman]

If you think the intake or exh flow rate needs some adjustment on a certain cyl you could experiment with a higher or lower rocker ratio on those two.
Just make sure if you up in ratio you have eough valve spring clearence.

 

[Anonymous]

Yes its # 3 cyl. And the pipes are all equal lenght. I had a pipe builder figure the pipe length that i needed to run the rpms. I've raced these engines for a while and had some leaning on cyls but not like this. It was always the end cyls. On the flow bench the ex. was about 170 or a little less. on all cyls. I used to run these motors up to 7500 rpms and never have a problem.

 

[rbohm]

8) might have a vacuum leak in that cylinder runner that is causing a lean condition. likely right at the gasket, but also the valve guide might be a bit loose.

 

[Anonymous]

My knowledge of alcohol burning engines is pretty limited but I'm going to take a shot at this anyway. As an engine fuel, alcohol is a completely different animal than gasoline. Alcohol runs a lot cooler which is why you have to run cooler plugs. I had a friend running a SBC on alcohol. He had to drill and tap the cooling passages at the deck and then install restrictors to help distribute the flow of coolant better. I'm wondering if your two middle cylinders are running hotter. The other option, at least on the scuffing issue, is that the two mid cylinders are getting too much fuel. I have a 300 setting here that was running an unheated intake. It wiped out #3 & #4 cylinders. It was a stock engine on gasoline.

 

[Anonymous]

I check the intake gasket and it was fine. The valve guides are new and are not loose. I'm taking the head and intake in to the head shop to have them flow it with the intake on it and see what happens.