pontiacgp said:
I would agree. When my MSD Box went out it started as just an odd miss and eventually started backfiring while accelerating and then timing went to hell. When I put a new ignition box in it ran better then it had in awhile.
Holley Carb Tuning Problems --- Help
- Thread starter CdnCutlass
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I would agree. When my MSD Box went out it started as just an odd miss and eventually started backfiring while accelerating and then timing went to hell. When I put a new ignition box in it ran better then it had in awhile.
The plugs look like a nice tan.
The distributor I have does not have a module, it only functions with an ignition box.
The best way I can describe the problem is that at 5500rpm its hits a wall power wise, makes a clattering/popping, if I let off the throttle and shift gears it recovers after a second and keeps pulling until it reaches that rpm again in the next gear.
The distributor I have does not have a module, it only functions with an ignition box.
The best way I can describe the problem is that at 5500rpm its hits a wall power wise, makes a clattering/popping, if I let off the throttle and shift gears it recovers after a second and keeps pulling until it reaches that rpm again in the next gear.
I still would like to see a fuel pressure gauge to ensure something is not causing it to run out if fuel, otherwise I think I would start to lean towards what the above post are saying with a possible ignition box failure, I would put a $40 gauge on before I changed out a $250 box tho
what valve springs are you running? It sounds like the valve springs could be too light and they are floating at 5500
pontiacgp said:
They are the springs that came on the patriot heads. Patriot does not put the specs out there, all it says is they are good for.575 lift. I wonder if they are offshore...
You could always call Patriot and ask them, I would hope an aftermarket head with a decent spring could run to 5,500 rpm, that's not a lot of rpm for a valve spring to withstand, if this were my car I would still be leaning towards a fuel issue, and maybe ignition. You have to just start eliminating things, get a fuel pressure gauge, call about the springs, and maybe swap out the ignition parts, or put a 5,400 rev limiter in it and keep driving it 
Don't rule out the plugs - Had the same problem but @5200. That camshaft is about all in @ 5500 and those heads are just starting to breath. Thats a lot runner for your set-up and killing your bottom end - not helping your other problems either.
lilbowtie said:
I pulled apart the fuel filter. Its clear so no issues there. I have a fuel pressure gauge on order picking it up Saturday, so by Monday afternoon should know what's going on with the fuel system.
The plugs I use are RC12YC champions. What would cause them to be an issue?
When I bought the Patriot heads on their site they recommended the 225's for 383 c.i. and up builds. I put the flow numbers into camquest at the time and they made more projected power than other heads regardless of brands. The only thing that changed the power band rpm was the cam selection according to camquest. I thought they were large for a small block. What would have been a more ideal selection for my engine that would rev max around 6000rpm?
When I talked to Comp tech support they said the XE274 cam was good to shift at 6000rpm, I guess that's why I am hung up on that target number.
Pulled the valve covers, a quick inspection did not show any issues.
I should also mention when I had the old HEI ignition system in I experienced the same problem, even after the Pertronix Flamethrower Upgrade kit.
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