Spark plug gap

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so when you say it falls on its face is it acting like you let off a bit or is it like your hitting a limiter and breaking up?

if its breaking up im fighting the same thing after a gear change...
 
I think you just told me the problem. I had that same Problem with the proform body were it would fall on its face. Those bodys work well with there metering blocks and not others Don't get me wrong Proform makes good carbs. But when you start mixing your own parts thay dont work well. And also I asked what size Air bleed it has on the block cause it might just need to be tuned.
 
75dartsport said:
The carb is a 750 base with proform body, and aftermarket metering. Not sure what it flows? It had 75 front and 85 rear when I bought it. Should I jet it with stock 750 double pumper jets? I had a700 holley on it before.
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He said he has a proform body with aftermarket metering blocks.......
 
valentino automotive said:
I think you just told me the problem. I had that same Problem with the proform body were it would fall on its face. Those bodys work well with there metering blocks and not others Don't get me wrong Proform makes good carbs. But when you start mixing your own parts thay dont work well. And also I asked what size Air bleed it has on the block cause it might just need to be tuned.
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I first had stock Holley metering blocks on my Proform body and now have Quick Fuel blocks on it and it has always worked fine. After installing the Quick Fuel blocks I had to re-jet it and change air bleeds. It's all in the tuning.
 
fishy68 said:
I first had stock Holley metering blocks on my Proform body and now have Quick Fuel blocks on it and it has always worked fine. After installing the Quick Fuel blocks I had to re-jet it and change air bleeds. It's all in the tuning.
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I also said it might just need tuning!!!
 
Thay Do work well with Quick Fuel block and there own meter blocks Fishy! But Holleys gaskits mess match as well And Thay have two types of main bodys one that sopports 4 corner idle Circuit and another that just covers a 2 circuit. I also had one Defective 1 that no matter what I did to the carb It didn't change a bit. It had A Hole that wasn't drilled to were it was suppost to!
 
valentino automotive said:
I also said it might just need tuning!!!
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Yeah I saw that. Didn't mean to be repetitive, just meant that I think any blocks can be made to work with tuning as long as their compatible and have no defects.

valentino automotive said:
Thay Do work well with Quick Fuel block and there own meter blocks Fishy! But Holleys gaskits mess match as well And Thay have two types of main bodys one that sopports 4 corner idle Circuit and another that just covers a 2 circuit. I also had one Defective 1 that no matter what I did to the carb It didn't change a bit. It had A Hole that wasn't drilled to were it was suppost to!
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There are a few types of Holley gaskets but from my experience as long as you use the correct ones your ok. You gotta watch close cause all it takes is one hole to be off and things don't work, I'm sure you know that. The first go around with mine I used a throttle plate to main body gasket for an 800/850 and didn't notice one of the idle passages was off just a little towards the outside and it blocked an idle passage and therefore had no idle a/f adjustment.

Yes, defective parts sure can drive you crazy.:violent1:
 
75dartsport said:
I am running Autoolite 65 plugs in my 360. W2 heads around 10 to 1 compression. Mopar 284/480 hydraulic cam. My question is it seems to pull real hard to 5600 rpm, then falls flat on its face. Doesn't seem to gradually just all at once. I pulled a couple of the plugs, and they were gapped at .025. Would this do it? Im running a msd digital 6al. What would the proper gap be? And is this the right plug for my combo. And before too many people tell me, I know the W2 heads are too much for the cam that is in it. It was just an experiment to see what the heads would do without changing anything else.
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I'm running this box in my Demon. I had this issue with engine cutting out at 5700 too. Then the dyno operator said it sounded like was hitting the rev limiter, though it was set to 6200. So I set it to 8000, the motor reved to 6500 clean as could be. So now I set my rev limit at 7000. I'm running the 508 Mopar cam. I gap my plugs at .050. Set your limiter up higher and make a pass to check. The 508 cam pulls hard to 6500, but I shift car at 5800.
 
moparmanestock said:
I'm running this box in my Demon. I had this issue with engine cutting out at 5700 too. Then the dyno operator said it sounded like was hitting the rev limiter, though it was set to 6200. So I set it to 8000, the motor reved to 6500 clean as could be. So now I set my rev limit at 7000. I'm running the 508 Mopar cam. I gap my plugs at .050. Set your limiter up higher and make a pass to check. The 508 cam pulls hard to 6500, but I shift car at 5800.
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i had the same thing happened years back and just did what you did and all was good after that. very easy fix.
 
Gettin back to the opriginal subject of plug gap....a spark is pretty much a spark. Ain't like a wider gap is gonna add 50 HP or 2K RPM.
 
StrokerScamp said:
Gettin back to the opriginal subject of plug gap....a spark is pretty much a spark. Ain't like a wider gap is gonna add 50 HP or 2K RPM.
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I did tell him what gap I run. But my main point was to tell him it is the box rev limiter that is the issue, no question about it. If he adjusts it way up, the car will respond. On my car, on the chassis dyno, the HP picked up 41 at 5800 with just the rev limit change only. The only other change to the car was to dial up my fuel pressure from 10 to 11. The car picked up 6 MPH in the 1/4.
 
On older MSDs like 6A, the engine would stutter on the limiter. The Digital 6 wont do that, the engine runs smooth on the limit. When I stage on the 2 Step, its smooth. That's why you wont notice as easy when you hit limiter at high limit. But it showed on the chassis dyno though. Lost 41HP from 5700 to 5800, but rev limit was set to 6200. The motor wouldnt rev above 5800 at all.
 
Ok, guys finally made it to the track. Let me say very dissapointing. The car ran low 8's with my old set-up. My first pass 8.67. Bad 60' 1.97. Felt like a dog. Second pass 8.64 still a dog, just wanted to make sure it wasnt me. Running 34 degree timing so i backed it off 2 to make it 32. It ran 8.48. So I decided to re-jet. Took the fronts down from 75 to 73. Went to take the back bowl off and it was dry? Went ahead and put 81 jets in it had 85. Put back bowl on and checked the float and it seemed like it was right. Made a pass and another 8.47. checked the rear bowl and almost empty again? Im going to put the 700cfm back on it and see what it does. I'm hoping the carb is the problem, should have picked up not slowed down almost 1/2 second.
 
I'm not sure. When the car is at idle it took a little while but the bowl did fill up and float level was right. After making a pass and shutting it down, it would be about empty. Just acts like it takes forever to fill the rear bowl?
 
70aarcuda said:
I would run a colder plug then a autolite 65...

a holley 750 dp 4779 comes jetted around 71p- 80s....you gotta lot of jet in the primaries....Does the carb still have the power valve in the primary side?
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my setup is close to yours 360 w2s but my cams a solid and a little bigger.i run autolite 63s at 40 gap and 34 degrees.it goes to 6500 easy.my jets are 72 80 same carb.
 
Take the fuel line adapter fitting out of the rear bowl and check to see if it still has the factory filter in it. If so it may be clogged and that'd explain why just the rear bowl would go dry.
 
75dartsport said:
Still running a mechanical pump.
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I had the same problem with a stock 340 shifting at 6500.The mechanical fuel pump could not keep up with fuel demand.Put a holley blue pump and never nosed over again but then had to check plugs to jet up.plug gap I ran .045
I have ran NGK plugs for a while R5671A-7 or 8 just have to check heat range.
 

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