New sbc 400 blueprint engine keeps fouling plugs with gas

potent rodent

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u said they have held up do u have 2 power valves ?
 

80BrownK10

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AutoMeter 2698 - AutoMeter Z-Series Tachometers​


I did a write up on the dash mods to get the gage to fit and work. Not hard, but takes some time, but for me worth it. I also use an A/F ratio gage, best tuning tool one could have. Cluster mod etc start on page five. Hope this helps!

Thanks will have to sit and read!
 

matt4426

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Adjust the carb jetting. Cam specs looks pretty good for street use.
 

potent rodent

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Adjust the carb jetting. Cam specs looks pretty good for street use.
thats a pretty aggressive cam for the street , and its on a 110 lsa would be a pain to drive on the street hope he has a good converter
 

matt4426

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thats a pretty aggressive cam for the street , and its on a 110 lsa would be a pain to drive on the street hope he has a good converter
I would think the 110* LSA would give him more low end torque and low to midrange power. The duration numbers are pretty reasonable for a street car too. Got to have some oomph to get a pickup moving. IMO 110* LSA is about as low as you would want for a street vehicle running vacuum brake booster and a stock TC.
 

JBswth

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I think that carb is just too damn big. You can try 1 step hotter plugs, but if that doesn't help, it has to be the carb. It might be jetted for track, rather than street use. Do not try to go hotter than 1 step. You might burn holes in the pistons.
 

JBswth

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Also, you have a racing engine that you are trying to use in a street-driven vehicle, so your plugs are going to occasionally foul no matter what, unless you take it out and race it.
 

Rusty Nail

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Did anyone else notice there aint no pictures of no gawl dang 400 in here nowhere?
Pix or stfu OP.
:mad::pics-stfu:
You prolly aint even got no 400 anyways.
 

HEG77k10

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Here’s kinda the situation now.
I got a autometer afr gauge with an o2 sensor. At an idle right now it’s around 10.7-11.3. Roughly. When I’m driving and just barely touch the throttle it leans wayyy out and stumbles like crazy, gets up to 17 on the gauge. At WOT it runs perfect with no stumble and sits around 13-13.5. Right now primary and secondary jets are 69 and 73. Also changed accelerator pump cam to brown, which is the most aggressive, thought that might change the super lean spike but didn’t make a difference. Going to double check timing but I’m pretty sure it’s where it should be. I jetted down the primary’s to 69 from 73 in hope that it would stop the plug fouling but now it’s has that really lean spike. Any more ideas y’all got is appreciated.
 

Matt69olds

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That’s pretty rich at idle!! No wonder it’s loading up.

Float set too high? Fuel pressure to high? Leaking needle/seat? Debris in the air bleeds?

Once again, call blueprint engines for suggestions. The carb isn’t too big, it’s just not adjusted correctly or something is affecting the fuel curve.
 

Mark Jones

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I had a car with a MSD HEI, I often would wash the engine in the car wash. It started fouling plugs after a while, I would replace the plugs and they would foul again, it was the ignition, since then I had a customer with a HEI, same problem.
 

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