87draggta

Went tot he track this weekend for the first time this year and I had a weird miss. I have a miss at idle or with a load above 3500. I made 5 1/8mile runs each one progressively slower, 8.0, 8.12, 8.60. 8.90. This is from 7.56 last time out. I was also down about 15 mph from last year. The only change I made over my winter was my intake. I went from a performer rpm to a victor jr. There is an oil leak at both the front and back of the intake, I haven't checked it for vacuum leaks yet. Could a vacuum leak cause this? Oh I also forgot it is backfiring through the exhaust but the timing is right.

Things i have checked and eliminated-

bent push rods
broken valve springs
new plugs
timing
Carb
Gunk in the fuel lines
steady fuel pressure

AlkyIROC

Crossed plug wires ie: 5 and 7? very common to do and the car will still run but with a miss.

With the engine running at an idle, spray some brake clean along the intake flange above the ports on the head. If there's an intake leak, the rpms will increase.

87draggta

I went and bought some intake gaskets and brake cleaner sunday night, but I work weird shifts and havent got a chance to check. Crossed plug wires make so much sense that it's probably that.

87draggta

Finally found it. Turns out my battery was only putting out 10 volts fully charged so my msd box wasn't firing correctly, my intake gasket is leaking, and the needle and seat was stopped up in my rear bowls(some black gunk from my fuel cell.) Anyway I should be runnnin good for my next outing.

brutalform

Those MSD boxes have caused me some headaches in the past. I ran the car with the MSD bypassed ALOT!!

87draggta

I just modified my hei to work with my msd box, so that is always an option. I was just happy that everything was a cheap fix.

xpndbl3

iTrader: (5)

those MSD boxes are very finicky if they don't have 12 volts at least. First thing I check on race cars with a miss is voltage at the box, then the usual suspects.

87draggta

Yeah I checked so much stuff, but I always forget the obvious stuff. I like my msd box until I dont.

car_fixer

I take the small hit on power and run an alternator All the time, and a volt gauge
helps with the what the ? Moments. Foam In your fuel cell going bad?