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Username Post: New HEI for 70's built 350. What spark plug gap        (Topic#136378)
murfs66 
Senior Member
Posts: 1841
murfs66
Loc: So Cal San Diego
Reg: 03-20-06
07-19-06 10:57 AM - Post#971886    

I have a new HEi system that I'm converting over this coming weekend and need to kinow the gap on the plug I should use. The plugs are just the plain autolites I believe. I heard somewhere you need to regap when getting a HEI. Help please.
Line-up.......
64 chevelle 350/350
64 chevelle SS "Project"
66 chevelle 350/350
66 ferd stang (wifes) had to be different!
http://www.picturetrail.com/murfs66






 
MikeB 
Senior Member
Posts: 9523
MikeB
Loc: Plano, TX
Reg: 08-28-03
Re: New HEI for 70's built 350. What spark plug gap
07-19-06 11:22 AM - Post#971887    
    In response to murfs66

GM initially set the gap at .060" when the HEI came out in 1974, and then changed it to .045". That was because the plug gaps would open with use and plugs started fouling. With platinum tips plugs, electrode errosion is not much of an issue, so .060" is safe. For a standard tip plug use .045-.050".

Now, I don't know if all HEIs are capable of putting out the same high current spark. I doubt the control module and coil in a $100 import HEI are as good as the original GM HEI, and they're certainly not as good as an MSD. Then there's the new imported MSD HEI for $150. Is it any better than the $100 models? I don't know.

1982 C-10 SWB pickup -- Unmolested, original paint, 250 six, 3-on-the-tree
(Soon to be 350 w/Vortec heads & TH350)

Sold my 55 sedan in June 2014, having owned it 11 years.


 
murfs66 
Senior Member
Posts: 1841
murfs66
Loc: So Cal San Diego
Reg: 03-20-06
Re: New HEI for 70's built 350. What spark plug gap
07-19-06 04:22 PM - Post#971888    
    In response to MikeB

Thanks. I read somewhere that delco remy (GM) is made by the same company as the imported $100.
Line-up.......
64 chevelle 350/350
64 chevelle SS "Project"
66 chevelle 350/350
66 ferd stang (wifes) had to be different!
http://www.picturetrail.com/murfs66






 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
Re: New HEI for 70's built 350. What spark plug ga
07-19-06 05:06 PM - Post#971889    
    In response to murfs66

You are mistaken, the Delco Remy and Delphi ZZ dists are made in the same factory as the Pro-Form.

The $100.00 and less junker ones are made in another factory, much less quality, same place Pro-Comp are made.

ALL HEI, .045 MAX. The reason the gaps god closed down was the larger gap overworked the in cap epoxy coils, causing more heat and failure, and overworking the HEI modules to failure as well. Olds tried .080 gap, but so many units failed, they went back to .045.

The factory HEI I have in my 1986 GMC Safari is set even closer, .035.

 
DragRacer383 
Super Senior Member
Posts: 4807
DragRacer383
Age: 6
Loc: Arkansas
Reg: 07-17-01
Re: New HEI for 70's built 350. What spark plug gap
07-19-06 05:09 PM - Post#971890    
    In response to murfs66

I like 45. I believe a hot spark is what is about,not how big it is.

BTW I wouldn't try Platinum plugs, Leave them for the computer controlled daily drivers that go 100,000 on plug changes. On a High compression motor they can give you preignition issues.
Later,Glen


 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10706
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
Re: New HEI for 70's built 350. What spark plug ga
07-19-06 07:56 PM - Post#971891    
    In response to murfs66

Quote:

I have a new HEi system that I'm converting over this coming weekend and need to kinow the gap on the plug I should use. The plugs are just the plain autolites I believe. I heard somewhere you need to regap when getting a HEI. Help please.



I love the plain old Autolites better than anything. I have always used .040 and the truck runs great. I experimented with larger gaps, but noticed the engine started harder when the gap was increased beyond .050
~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
four27rat 
Senior Member
Posts: 529

Loc: Atlanta, Tx
Reg: 08-22-03
Re: New HEI for 70's built 350. What spark plug gap
07-20-06 02:42 AM - Post#971892    
    In response to murfs66

you may already know this but the HEI is going to require a keyed hot wire of at least 12 guage.the wire that was running to the points coil will not work.

 
1967ishC20 
Senior Member
Posts: 271

Loc: San Diego
Reg: 02-28-05
Re: New HEI for 70's built 350. What spark plug ga
07-20-06 03:38 AM - Post#971893    
    In response to IgnitionMan

Ignitionman, always enjoyed and trusted your advice, but I thought PRO-FORM was also an import product.

 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
Re: New HEI for 70's built 350. What spark plug ga
07-20-06 04:11 AM - Post#971894    
    In response to 1967ishC20

Take the module off a ZZ dist, or crate dist, and read the word(s) on the rear plate. Dot matrix either says "Singapore" or "Hong Kong", that ain't Phoenix, Boise or Louisville.

The Pro-Forms are good quality, and the other PRO just isn't. You would be surprized at the places in China where stuff with "Made in Australia" or "Made in New Zealand" stamped on it.

There are companies that operate in the "one or two parts" method, They make the majority of products in China, and add just one or two little parts, like a coil or cap, made outside of China, that give them the ability to mark that product "Made in (Fill in the Blank)" and not the real, honest "Everything Else Made in China".

There are things done in this industry that are kept as secret as possible, and stuff like this can get confusing if you don't have an inner view of things.

The people that make the Pro-Form products are good people, use knowlwedgeable hired help in their factories. The factory that manufactures the other PRO stuff uses the same type labor force as Ikea does, prison labor, a captive, very low paid workforce. This is how Pro-Comp keeps the pricing down, and how the quality isn't there with some products, an always changing labor force that isn't paid much per DAY.

It gerts intriguing when you see the way tbnings are done within an industry, sometimes, it just doesn't make any good sense. Pro-Comp's ONLY intentions are to both put every little manufacturer out of business, and flood the market with their dubious quality knock-off products. People on a lot of websites are posting their less than happy experiences with Pro-Comp products, this isn't just a random incidence on this site.

Please don't view all this as a flame or defaming of a product line, it isn't. It is what you may consider a Public Service Message. Caveat Emptor, To the Buyer......BEWARE.

Another way to put it is, "The bitterness of poor quality long remains, after the sweetness of cheap price is forgotten".

 
murfs66 
Senior Member
Posts: 1841
murfs66
Loc: So Cal San Diego
Reg: 03-20-06
Re: New HEI for 70's built 350. What spark plug ga
07-20-06 04:15 AM - Post#971895    
    In response to 1967ishC20

Thanks for the info guys. I'll probably stick with the autolite plugs. I opted out this last weekend to get the delco remy one for $50 used and instead I got the cheap billet dist for $60,because it was new in the box and shiney.I tell you the shiney things are very attractive and they tend to pull you in. I hope I'm satisfied with this one. What do you guys think? will it work ok?
Line-up.......
64 chevelle 350/350
64 chevelle SS "Project"
66 chevelle 350/350
66 ferd stang (wifes) had to be different!
http://www.picturetrail.com/murfs66






 
MikeB 
Senior Member
Posts: 9523
MikeB
Loc: Plano, TX
Reg: 08-28-03
Re: New HEI for 70's built 350. What spark plug gap
07-20-06 05:32 AM - Post#971896    
    In response to murfs66

Ignitionman -- Since you're on a roll, which MSD external coil do you recommend? As I recall, you said one was junk and one was a good quality U.S.-built unit.

Also, I'm considering an MSD 8360 since my HEI is up against my firewall. Should I look at anything else?

1982 C-10 SWB pickup -- Unmolested, original paint, 250 six, 3-on-the-tree
(Soon to be 350 w/Vortec heads & TH350)

Sold my 55 sedan in June 2014, having owned it 11 years.


 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
Re: New HEI for 70's built 350. What spark plug ga
07-20-06 01:02 PM - Post#971897    
    In response to MikeB

Good luck with that $60.00 Pro-Comp junker dist I have been warning people to stay away from.

MSD used to have andover Industries, in Andover, Indiana, manufacture ALL the Blaster coils, but...MSD's product cheapaning department moved the RED Blaster coil production to a comp[any ion Mexico, Pro-Bobbin, and simce then, the RED Blasters have had nothing but l;ayer shorting issues. I have seen them murder both HEI and MSD boxes in less than 30 seconds.

The MSD 8200 chrome coil is still made by Andover, still great quality. But...if you want to save some serious fundage, get the SUM-G5215 chrome coil from Summit, it is the SAME coil, made on the SAME assembly line as the MSD 8200 is.

I can't comment on the site about small body HEI's. Others can, but I can't.

 
MikeB 
Senior Member
Posts: 9523
MikeB
Loc: Plano, TX
Reg: 08-28-03
Re: New HEI for 70's built 350. What spark plug ga
07-20-06 01:10 PM - Post#971898    
    In response to IgnitionMan

IgnitionMan -- Thanks. I'll send that Dave guy a PM when I'm ready to get a small body HEI.

1982 C-10 SWB pickup -- Unmolested, original paint, 250 six, 3-on-the-tree
(Soon to be 350 w/Vortec heads & TH350)

Sold my 55 sedan in June 2014, having owned it 11 years.


 
murfs66 
Senior Member
Posts: 1841
murfs66
Loc: So Cal San Diego
Reg: 03-20-06
Re: New HEI for 70's built 350. What spark plug ga
07-20-06 03:29 PM - Post#971899    
    In response to MikeB

Hpoefull it works for awhile for me. Also how do you hook it up. I know the wire from the ignition(hot start) needs to be changed and goes to the HEI,but what about the "R" wire from the starter silnoid? where does that go? I have 2 wires coming off the silnoid.
Line-up.......
64 chevelle 350/350
64 chevelle SS "Project"
66 chevelle 350/350
66 ferd stang (wifes) had to be different!
http://www.picturetrail.com/murfs66






 
TennSS 
Senior Member
Posts: 117

Loc: Memphis
Reg: 06-03-02
Re: New HEI for 70's built 350. What spark plug gap
07-20-06 04:19 PM - Post#971900    
    In response to murfs66

Plug gap size is dependent upon how strong your ignition system is. For example, with an HEI system, you must have a coil and module that is strong enough to jump a wider gap. We always recommend .055" with our systems and have for many years. If you open up your gaps on a system that is not strong enough to make the jump, you will experience a miss, etc. We have always had good success with Autolite Platinum plugs.
The wider gaps do lead to more power/performance because they explode a higher percentage of your fuel mixture-as long as your ignition can jump them.

 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10706
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
Re: New HEI for 70's built 350. What spark plug ga
07-20-06 06:40 PM - Post#971901    
    In response to murfs66

Quote:

Hpoefull it works for awhile for me. Also how do you hook it up. I know the wire from the ignition(hot start) needs to be changed and goes to the HEI,but what about the "R" wire from the starter silnoid? where does that go? I have 2 wires coming off the silnoid.



Be sure to use a 12 guage wire for power to the coil to prevent a fire. HEI coils draw a lot of current.
~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
Trucked_up 
Valued Contributor
Posts: 4946

Loc: 315 er
Reg: 03-23-02
Re: New HEI for 70's built 350. What spark plug ga
07-21-06 12:18 AM - Post#971902    
    In response to IgnitionMan

I might be wrong,but,when when GM introduced the HEI,it was primarily to deal with the spotty lean mixtures in the early days of emission laws.The lean mixture need a high voltage to jump the large gap required to get combustion started in the cylinder.Getting rid of maintenance prone points was good also.When emissions are not a factor,like on many mild street performance engines running richer mixtures,maybe only 20K volts are ever necesary to light off combustion,considering the plugs are fairly clean.
From what I've been told,it's not the voltage but the duration of the spark that's important.Being that a tradtional HEI is still a Kettering type ignition,the spark duration is still somewhat short.I'm thinking this is the reason for the popularity of MSD type ignitions.
My experince with HEI's is limited to work done on my several modified older GM 6 cylinder inline engines.In my case,an HEI GM unit offered no performance advantage over a points distributer in good shape other than the issue of points wear.But muliple spark ignitons did show improvement at lower speeds.

 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
Re: New HEI for 70's built 350. What spark plug ga
07-21-06 06:07 AM - Post#971903    
    In response to murfs66

Check the fuse box for a terminal marked either IGN or Ignition for battery voltage in both RUN and START ignition switch/key positions. If you have both, then, 12 guage wire through the firewall to the BATT term on the junker Pro-Comp will do for now.

If you don't have the volts in the START position, then add the R terminal wire from the solenoid to the BATT and the system should power up on the required full battery voltage correctly. Tape the resistor wire up and tuck it into the wiring loom cover over the top of the engine at the firewall, and it will still be workable, and in place, if you ever have to go back to a resisted system.

 
murfs66 
Senior Member
Posts: 1841
murfs66
Loc: So Cal San Diego
Reg: 03-20-06
Re: New HEI for 70's built 350. What spark plug ga
07-22-06 04:29 AM - Post#971904    
    In response to IgnitionMan

Thanks ignitionMan. So your saying that I dont need the R wire hooked up it may need to be if I dont have enough volts? I'll try it today and get back to you guys on my progress. Thanks again all you guys.
Line-up.......
64 chevelle 350/350
64 chevelle SS "Project"
66 chevelle 350/350
66 ferd stang (wifes) had to be different!
http://www.picturetrail.com/murfs66






 
ranman 
"2nd Year" Silver Supporting Member
Posts: 10706
ranman
Loc: The cold wet and windy O...
Reg: 03-10-01
Re: New HEI for 70's built 350. What spark plug ga
07-22-06 05:45 AM - Post#971905    
    In response to murfs66

Quote:

Thanks ignitionMan. So your saying that I dont need the R wire hooked up it may need to be if I dont have enough volts? I'll try it today and get back to you guys on my progress. Thanks again all you guys.



With the points system, the R wire is what powers the coil while the engine is running. It provides less than the full 12 volts to the coil to save wear on the points. It is temporarily bypassed with a full 12 volts when the ignition is in the start position.
You do not want less than the full 12 volts going to an HEI distributor, so the R wire will no longer have a use....... unless at some point you decide to go back to a points type distributor. That's why Ignitionman said to tape it back into the wiring harness instead of just cutting it off.
~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
If plants ruled the world, would they regulate oxygen?


 
murfs66 
Senior Member
Posts: 1841
murfs66
Loc: So Cal San Diego
Reg: 03-20-06
Re: New HEI for 70's built 350. What spark plug ga
08-02-06 06:09 AM - Post#971906    
    In response to ranman

Sorry to bring this one back up,but is there anything I can do to make my "junker pro comp" work better. I have a chance to get another module and coil from another car. Will the swap make it a better unit than the one I have. Its an accell unit in the other car.
Line-up.......
64 chevelle 350/350
64 chevelle SS "Project"
66 chevelle 350/350
66 ferd stang (wifes) had to be different!
http://www.picturetrail.com/murfs66






 
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