Spark plug gap

« **on:** August 18, 2018, 08:11:18 PM »

Anyone have any recommendations on spark plug gap?
BBC 11.5 to 1 427

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« **Reply #1 on:** August 18, 2018, 08:49:31 PM »

What kind of ignition do you have?

« **Reply #2 on:** August 19, 2018, 07:52:50 AM »

Mad distributer ran with a coil

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« **Reply #3 on:** August 19, 2018, 07:54:00 AM »

MSD

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« **Reply #4 on:** August 19, 2018, 07:54:45 AM »

MSD distributer with external coil

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« **Reply #5 on:** August 19, 2018, 10:20:31 AM »

Start out with the factory recommendations for plug gap and adjust up or down in .005" increments to optimize performance.

The recommended starting plug gap is probably going to be .035", depending on the plug design.

https://www.rockauto.com/en/catalog/chevrolet,1969,corvette,7.0l+427cid+v8,1040904,ignition,spark+plug,7212

https://www.rockauto.com/en/catalog/chevrolet,1970,corvette,7.4l+454cid+v8,1040926,ignition,spark+plug,7212

MSD's rule of thumb based on compression:
Up to 10.5:1 .040-.045
10.5 to 13.0:1 .032 - .040
Over 13:1 .025 - .032

The higher the cylinder pressure, either from dynamic compression ratio or supercharging, the harder it is for the ignition system to push the spark across the plug gap. If you are not turning the RPM that you should, try closing the gap.

« **Reply #6 on:** August 19, 2018, 11:52:16 AM »

Thanks good info have a little sputter at Cruz and idol seems to go away when I put my foot in it and comes back when I take it out or if I put my foot in it and run flat out it seams to come back when held there thinking it may be fuel since I just went from 1 850 to 2 660 and tunnel ram it ran good last weekend and this weekend issues last weekend at end of the trip I got low on fuel and fuel pressure dropped as if I picked up some crud of the bottom of the tank I changed the filter fuel pressure is good now but problem is still there

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« **Reply #7 on:** August 23, 2018, 08:17:22 PM »

What is the history of the 660s??? Those carbs can be a bitch to dial in just right..
Ray

« **Reply #8 on:** August 24, 2018, 05:57:43 AM »

Yep that was it the floats where a bit high and the squirter need some fine tuning

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« **Reply #9 on:** August 25, 2018, 12:42:50 PM »

Again, do you know the history of those carbs?? Did you buy them recently? I had two that were among the stuff stolen from my storage unit. I'd be really interested as to where you got them if it was recently..
Ray

« **Reply #10 on:** August 25, 2018, 05:28:28 PM »

.30 gap and u should be good , that’s what I run with tunnel ram and 750s dp

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« **Reply #11 on:** August 25, 2018, 09:54:18 PM »

We have had them for long time we had if that tunnel ram set ups I guarantee they're not the ones u are looking for

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