What size plug gap are you running on your 350? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

TIMSPEED · 01-08-2004, 04:12 PM

On the little spec sheet under my hood, it says I should be running an .060 gap...imho, that's HUGE! I run a .045 in my vette (and that has aftermarket HEI).
I'm currently running a set of Bosch Platinum's (just single electrode's) and I pulled one, and the gap was at like .035...so, should I open it to .060, or what?

*Zilverado* · 01-08-2004, 04:23 PM

Tim,

Mine's a 305, but I use .035 as well. Of course, I'm not talkin' high performance.

bigd65 · 01-08-2004, 04:31 PM

Go to .045, that is a good all around gap. i have the HYPERTECH POWER COIL, and tried the .060 and could tell it was week. i even went to .050. i am now at .045. I dont think .035 is enough for an HEI, you loose to much spark energy.

78chevstepside · 01-08-2004, 04:58 PM

With a hei I vote for .45

TIMSPEED · 01-08-2004, 06:11 PM

Well, I just gapped them at .060, and I must say it's a MUCH smoother idle...but that "miss" is still there...I think I have a spark plug wire that's bad causing the slight problem...gotta check the resistance now.

*67Fleetsidedream* · 01-08-2004, 06:27 PM

I tried the .045 gap on my plugs and it caused my truck to die and run really rough. So I put it at .035 and is purs like a kitten.

bigd65 · 01-08-2004, 06:58 PM

do you have HEI or points. points wont handle a .045 gap.

Tim, it may be smoother, but i bet you will feel a slight lag on acceration. i did anyways and as i said, i have a power coil.

**old Rusty C10** · 01-08-2004, 07:06 PM

Ive always run .045

**swervin ervin** · 01-08-2004, 07:47 PM

Plug gaps went from .035 to .045 when they went to HEI with the coil in the cap. Then when they went to the external coil like the TBI trucks use, in 87, they went back to .035.

With my MSD distributor and 6AL, I run .055.

*1FaastC10* · 01-08-2004, 07:49 PM

i've always run .045

TIMSPEED · 01-08-2004, 10:42 PM

Why would my VECI sticker say .060 plug gap??

allthrtl · 01-08-2004, 11:42 PM

Is your motor stock? If not, don't bother looking at the sticker....it's meant for the stock engine running ALL the smog garbage......If your running a GM HEI distributor, that they made forever, gap it at .45....

TIMSPEED · 01-09-2004, 12:26 AM

Well, .060 seems to be doing swell. Except it's pingin under little throttle, like a MOFO! Filled up with 87 octane, doh!

Blue Beard · 01-09-2004, 01:27 PM

If it's pingin, try adjusting the timing just a bit.............

Tom · 01-09-2004, 01:45 PM

I run .55 on both my vortec headed, MSD'd motors.

**swervin ervin** · 01-09-2004, 04:06 PM

Personally, I never heard of or seen a stock GM vehicle with .060 plug gap. .045 is the biggest gap I've heard of. To run a .060 gap, you would need a real high energy ignition system. More than GM ever put into any of their stuff.

Here's the ticket. If you are running a stock GM HEI coil in the cap distributor, gap the plugs at .045. If you still have a miss, and as long as the plugs are new, buy a set of wires.

01-08-2004, 04:12 PM	#1
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	What size plug gap are you running on your 350? On the little spec sheet under my hood, it says I should be running an .060 gap...imho, that's HUGE! I run a .045 in my vette (and that has aftermarket HEI). I'm currently running a set of Bosch Platinum's (just single electrode's) and I pulled one, and the gap was at like .035...so, should I open it to .060, or what? __________________ I have a few cars... See Them Here

01-08-2004, 04:31 PM	#3
bigd65 Registered User Join Date: Mar 2000 Location: Clute, TX. Posts: 1,935	Go to .045, that is a good all around gap. i have the HYPERTECH POWER COIL, and tried the .060 and could tell it was week. i even went to .050. i am now at .045. I dont think .035 is enough for an HEI, you loose to much spark energy. __________________ 2004 Silverado Crewcab 1972 Chevy Monte Carlo 2017 Chevy Tahoe

01-08-2004, 06:11 PM	#5
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	Well, I just gapped them at .060, and I must say it's a MUCH smoother idle...but that "miss" is still there...I think I have a spark plug wire that's bad causing the slight problem...gotta check the resistance now. __________________ I have a few cars... See Them Here

01-08-2004, 06:58 PM	#7
bigd65 Registered User Join Date: Mar 2000 Location: Clute, TX. Posts: 1,935	do you have HEI or points. points wont handle a .045 gap. Tim, it may be smoother, but i bet you will feel a slight lag on acceration. i did anyways and as i said, i have a power coil. __________________ 2004 Silverado Crewcab 1972 Chevy Monte Carlo 2017 Chevy Tahoe

01-08-2004, 07:06 PM	#8
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	Ive always run .045 __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

01-08-2004, 04:23 PM	#2
Zilverado Account Suspended Join Date: Nov 2002 Location: Winnipeg, Manitoba, Canada Posts: 798	Tim, Mine's a 305, but I use .035 as well. Of course, I'm not talkin' high performance.

01-08-2004, 04:58 PM	#4
78chevstepside Registered User Join Date: Nov 2002 Location: lacenter, washington Posts: 718	With a hei I vote for .45

01-08-2004, 06:27 PM	#6
67Fleetsidedream Wiseass secured himself a BAN Join Date: Nov 2000 Location: MOON!!! Posts: 2,282	I tried the .045 gap on my plugs and it caused my truck to die and run really rough. So I put it at .035 and is purs like a kitten.

01-08-2004, 07:47 PM	#9
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Plug gaps went from .035 to .045 when they went to HEI with the coil in the cap. Then when they went to the external coil like the TBI trucks use, in 87, they went back to .035. With my MSD distributor and 6AL, I run .055. __________________ Mike 1985 Chevy C-10

01-08-2004, 07:49 PM	#10
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,399	i've always run .045

01-08-2004, 10:42 PM	#11
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	Why would my VECI sticker say .060 plug gap?? __________________ I have a few cars... See Them Here

01-08-2004, 11:42 PM	#12
allthrtl Available for Adoption Join Date: May 2003 Location: Lubbock Tx Posts: 177	Is your motor stock? If not, don't bother looking at the sticker....it's meant for the stock engine running ALL the smog garbage......If your running a GM HEI distributor, that they made forever, gap it at .45.... __________________ 1983 C10 SWB 2001 Silverado SWB 1995 Corvette

01-09-2004, 12:26 AM	#13
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	Well, .060 seems to be doing swell. Except it's pingin under little throttle, like a MOFO! Filled up with 87 octane, doh! __________________ I have a few cars... See Them Here

01-09-2004, 01:27 PM	#14
Blue Beard Registered User Join Date: Jan 2003 Location: Washington State Posts: 8,831	If it's pingin, try adjusting the timing just a bit............. __________________ 1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo

01-09-2004, 01:45 PM	#15
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,748	I run .55 on both my vortec headed, MSD'd motors. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.



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01-09-2004, 04:06 PM	#16
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Personally, I never heard of or seen a stock GM vehicle with .060 plug gap. .045 is the biggest gap I've heard of. To run a .060 gap, you would need a real high energy ignition system. More than GM ever put into any of their stuff. Here's the ticket. If you are running a stock GM HEI coil in the cap distributor, gap the plugs at .045. If you still have a miss, and as long as the plugs are new, buy a set of wires.

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