plug gap.. hei dist. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tim21391 · 06-21-2009, 06:44 PM

what do i gap the plugs to im swapping to hei from points..

**leddzepp** · 06-21-2009, 06:47 PM

0.030 is what I use on my HEI.

**WorkinLonghorn** · 06-21-2009, 06:56 PM

leddzepp,really? My books show .35 for points and generally .45 for HEI.
I converted to HEI (skip white-ebay) and left them at .35for 12,000 miles then 2 weeks ago decided to try .45. MORE POWER. Maybe 5% more. But I notice that mileage went down a tad.
Try .45 on yours and let us know the diff. WLH

**Stocker** · 06-21-2009, 08:44 PM

Quote:

Originally Posted by WorkinLonghorn

My books show .035 for points and generally .045 for HEI.

This is what I have always heard, and always done.

prostreetC-10 · 06-21-2009, 06:59 PM

.35 if for points type dist. You want .45 and even more if you are running an MSD or some other control box. Check the manufacturer's recommendation but .45 on a HEI with no box

tim21391 · 06-21-2009, 07:07 PM

im getting ready to run accell

**leddzepp** · 06-21-2009, 07:13 PM

Guess I am wrong. My truck runs great though.

**WorkinLonghorn** · 06-21-2009, 07:23 PM

Try it leddzepp,you're gunna like it!

prostreetC-10 · 06-21-2009, 07:43 PM

With the "seat of your pants" dyno, the average motor will not feel much diff from .35 to .50 but you will get better burn at the correct gap.

**El Jay** · 06-21-2009, 08:43 PM

What engine?
When GM started using HEI's back about '75, plugs were gapped at .060".
In '77 they changed the gap to .045", except for the 250 c.i., I-6.
The plugs for the 250, were gapped at .035".
The 350's equipped with R44TX plugs had the gap set at .060".

My service manual stops at '77 (I save everything!), so I don't know what other changes they may have made after that.

So, I'd say that .045" would pretty much get you in the ballpark.

dwcsr · 06-21-2009, 08:49 PM

I have mine at .050 with the Skip White HEI setup and R44ts

gcburdic · 06-21-2009, 09:17 PM

good stuff here....

prostreetC-10 · 06-21-2009, 09:56 PM

Typically...the hotter the ignition, the wider the gap you can run. That's why the MSD's can run into the 60's but cylinder compression ratios come into play. This is why you need to stick to the manufacturer's recommendation for gap. If you got a used one from a friend, set it at .45 and go!

**WorkinLonghorn** · 06-22-2009, 12:22 AM

WLH wrote;

Quote:

I converted to HEI (skip white-ebay) and left them at .35for 12,000 miles then 2 weeks ago decided to try .45. MORE POWER. Maybe 5% more.

ProstreetC10 wrote;

Quote:

With the "seat of your pants" dyno, the average motor will not feel much diff from .35 to .50

Maybe my 350 wasn't average?

I'm telling you I gained maybe 10 HP which I definately felt "seat of pants" (which I don't consider any more sensitive than the next guys).

tim21391 · 06-22-2009, 12:27 AM

its the original 402 that came with the truck (1972) but its been rebuilt in 2004

Camper Power · 06-22-2009, 12:37 AM

the gap stayed the same till 87 and only the EFI engines had a different gap, the carbed HEIs after 76 stayed at .045

prostreetC-10 · 06-22-2009, 12:49 AM

ah.....you are also asking the BBC PS questions huh?

Camper Power · 06-22-2009, 12:50 AM

BBC is still at .045 from what my book is telling

Rippin-J · 06-24-2009, 07:34 AM

currently running 35 on HEI, going to regap to 45 today. great thread! thanks.

jay6891 · 06-24-2009, 08:07 AM

The book that I got from Jacobs Electronics stated that the optimum gap would be .10. Hard to believe. Tried it anyways. Truck ran great. Only problem was that after about 6 to 9 months the struck would not start. Seems like the plugs would burn up. Never at home either. So I would have to change plugs and it would start right up. Went back to .075 on the gap and have never had a problem since.

06-21-2009, 06:44 PM	#1
tim21391 Registered User Join Date: Jul 2007 Location: Salina, Kansas Posts: 1,998	plug gap.. hei dist. what do i gap the plugs to im swapping to hei from points.. __________________ 1972 C-10...402/400..flowmaster 40 series 1967 Mustang 347 stroker/C-4 1966 Mustang 289/3-speed 2013 Mustang V6/6speed w/300 ponies I may be 23, but i sure do knows 67-72s are sexy! Its not MPG its smiles per gallon! build started 11/25/08 build thread: http://67-72chevytrucks.com/vboard/s....php?p=2993796

06-21-2009, 06:47 PM	#2
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,037	Re: plug gap.. hei dist. 0.030 is what I use on my HEI. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man RIP FleetsidePaul

06-21-2009, 06:56 PM	#3
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,886	Re: plug gap.. hei dist. leddzepp,really? My books show .35 for points and generally .45 for HEI. I converted to HEI (skip white-ebay) and left them at .35for 12,000 miles then 2 weeks ago decided to try .45. MORE POWER. Maybe 5% more. But I notice that mileage went down a tad. Try .45 on yours and let us know the diff. WLH __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

06-21-2009, 06:59 PM	#5
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: plug gap.. hei dist. .35 if for points type dist. You want .45 and even more if you are running an MSD or some other control box. Check the manufacturer's recommendation but .45 on a HEI with no box __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!

06-21-2009, 07:07 PM	#6
tim21391 Registered User Join Date: Jul 2007 Location: Salina, Kansas Posts: 1,998	Re: plug gap.. hei dist. im getting ready to run accell __________________ 1972 C-10...402/400..flowmaster 40 series 1967 Mustang 347 stroker/C-4 1966 Mustang 289/3-speed 2013 Mustang V6/6speed w/300 ponies I may be 23, but i sure do knows 67-72s are sexy! Its not MPG its smiles per gallon! build started 11/25/08 build thread: http://67-72chevytrucks.com/vboard/s....php?p=2993796

06-21-2009, 07:13 PM	#7
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,037	Re: plug gap.. hei dist. Guess I am wrong. My truck runs great though. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man RIP FleetsidePaul

06-21-2009, 07:23 PM	#8
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,886	Re: plug gap.. hei dist. Try it leddzepp,you're gunna like it! __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

06-21-2009, 07:43 PM	#9
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: plug gap.. hei dist. With the "seat of your pants" dyno, the average motor will not feel much diff from .35 to .50 but you will get better burn at the correct gap. __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!

06-21-2009, 08:43 PM	#10
El Jay Gone to greener pastures Join Date: May 2007 Location: Gateway to the Delta Posts: 7,354	Re: plug gap.. hei dist. What engine? When GM started using HEI's back about '75, plugs were gapped at .060". In '77 they changed the gap to .045", except for the 250 c.i., I-6. The plugs for the 250, were gapped at .035". The 350's equipped with R44TX plugs had the gap set at .060". My service manual stops at '77 (I save everything!), so I don't know what other changes they may have made after that. So, I'd say that .045" would pretty much get you in the ballpark. __________________ '69 Chevy 1/2 T LWB Stepper: Daily Beater '72 GMC 3/4 T Fleet: Another Daily Beater '72 Plymouth Gran Coupe: ? "Ah women. They make the highs higher and the lows more frequent." Friedrich Nietzsche "Never kick a fresh turd on a hot day." Harry S. Truman GUN CONTROL: Never having to say, "I missed you." Always fire two warning shots into your attacker's chest area before putting a bullet between his eyes. Paraphrased from Louis Awerbuck

06-21-2009, 08:49 PM	#11
dwcsr Hollister Road Co. Join Date: Apr 2005 Location: Houston Posts: 6,131	Re: plug gap.. hei dist. I have mine at .050 with the Skip White HEI setup and R44ts

06-21-2009, 09:17 PM	#12
gcburdic Restoration Virgin! Join Date: Jan 2008 Location: Huntersville, NC Posts: 8,298	Re: plug gap.. hei dist. good stuff here.... __________________ Geoff with a G 1968 Chevy C10 SWB The Mistress 1972 Custom Deluxe C20 Suburban A Suburban Named Isabella 1966 Ford Mustang Mama's High School Graduation Present

06-21-2009, 09:56 PM	#13
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: plug gap.. hei dist. Typically...the hotter the ignition, the wider the gap you can run. That's why the MSD's can run into the 60's but cylinder compression ratios come into play. This is why you need to stick to the manufacturer's recommendation for gap. If you got a used one from a friend, set it at .45 and go! __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!

06-22-2009, 12:27 AM	#15
tim21391 Registered User Join Date: Jul 2007 Location: Salina, Kansas Posts: 1,998	Re: plug gap.. hei dist. its the original 402 that came with the truck (1972) but its been rebuilt in 2004 __________________ 1972 C-10...402/400..flowmaster 40 series 1967 Mustang 347 stroker/C-4 1966 Mustang 289/3-speed 2013 Mustang V6/6speed w/300 ponies I may be 23, but i sure do knows 67-72s are sexy! Its not MPG its smiles per gallon! build started 11/25/08 build thread: http://67-72chevytrucks.com/vboard/s....php?p=2993796

06-22-2009, 12:37 AM	#16
Camper Power Registered User Join Date: Feb 2008 Location: Grande Prairie Alberta Posts: 261	Re: plug gap.. hei dist. the gap stayed the same till 87 and only the EFI engines had a different gap, the carbed HEIs after 76 stayed at .045 __________________ eh 1970 Chevy C20 daily driver 1975 GMC Jimmy 4x4 project 1966 GMC C10 Dad's project Last edited by Camper Power; 06-22-2009 at 12:38 AM.

06-22-2009, 12:49 AM	#17
prostreetC-10 My Carbon Footprint Join Date: Oct 2008 Location: Orygun Posts: 5,527	Re: plug gap.. hei dist. ah.....you are also asking the BBC PS questions huh? __________________ A quick "pedalfest" *Still getting loose (carb test)* 496 Initial fire up video!



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06-22-2009, 12:50 AM	#18
Camper Power Registered User Join Date: Feb 2008 Location: Grande Prairie Alberta Posts: 261	Re: plug gap.. hei dist. BBC is still at .045 from what my book is telling __________________ eh 1970 Chevy C20 daily driver 1975 GMC Jimmy 4x4 project 1966 GMC C10 Dad's project

06-24-2009, 07:34 AM	#19
Rippin-J OurLadyofBlessedAccelerat ion Join Date: Aug 2007 Location: Denver, CO Posts: 148	Re: plug gap.. hei dist. currently running 35 on HEI, going to regap to 45 today. great thread! thanks. __________________ _______________________________________________ 1968 Chevy C-20 w/ 396 1997 HD Sportster 1200 street tracker 1994 Chevy 1500 Silverado

06-24-2009, 08:07 AM	#20
jay6891 Car Knocker Join Date: May 2001 Location: jefferson,arkansas Posts: 664	Re: plug gap.. hei dist. The book that I got from Jacobs Electronics stated that the optimum gap would be .10. Hard to believe. Tried it anyways. Truck ran great. Only problem was that after about 6 to 9 months the struck would not start. Seems like the plugs would burn up. Never at home either. So I would have to change plugs and it would start right up. Went back to .075 on the gap and have never had a problem since. __________________ 68 c-10,91 sportside bed,350 .030 over,4 bolt,10-1 comp,2.05 intake/1.94 exhaust,1.6 Harland Sharp roller rockers,edelbrock rpm cam and intake w/750 carb, 700r4, 3.73 gears,Jacabbs Electronic Igntion w/Accel HEI distributer and super coil. ZR-1 roll pan, filled tailights. Blazer tank. Hidden hitch. 2 1/2" Flowmaster 40's. Parts bought but not installed>> ford 9" posi with disc. CCP front and rear lowering kit 4/5. Cab corners,foor boards,rockers, cab braces, Phatom grill, Painless wiring kit.

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