So,.. Two tings
 

First: As I contemplate accomplishing a much needed tune up on my 350 SBC, I want to convert to HEI for my near daily driving of it. It seems those who went with a GM HEI distributor had the best results. (Yes?). In the wisdom out there, will this be the best to ensure the OEM tach will continue to function? (I read somewhere that someone put in an HEI from an '83 with very good results).

Second: I also want to install a 3 point seatbelt and shoulder harness. (The driving here in southwest Florida is very reminiscent of many demolition derbies I've attended)! I notice a 1/2" to 5/8" hole in the posts/panel behind the driver and passenger side panels. They have a "plug" tack-welded over them. I'm wondering if there is a threaded nut, etc., behind there to accept the mounting harness? (It almost seems like GM was anticipating the eventual reality of a required 3 point restraint system and got ahead of the curve). If this isn't the case,... anyone installed a sealtbelt with shoulder harness in their truck?

Happy New Year!!

Re: So,.. Two tings
 

Yes ,install HEI . spark plugs need to be re gapped to .045-55

Yes, It's a plastic plug in the pilar not tack welded . 3 point seat belts bolt right in for about $175.00 :chevy:

Re: So,.. Two tings
 

I think member t korinek sells nice aftermarket 3 point seat belts. Other board vendors may also, I just seem to recall seeing his shown somewhere. Factory 3 point belts extremely rare.

OEM tach will function fine with or without an HEI. If you do swap in an HEI, you might consider adding a tach filter in the wiring. Some folks run them, some folks don't, worth reading up on before you install - lots of threads on here about it. LMC and several other places sell them.

Re: So,.. Two tings
 

70 C20 - 3 point seat belts - I had a plastic plug over a threaded nut. Can't remember the thread, but it was a standard size.

Re: So,.. Two tings
 

You may already know this: you'll have to source a 12 Volt ignition hot to power the HEI. Your original ignition hot (+) to the coil is voltage reduced for the point system and not sufficient for the HEI upgrade. Search the the forums here for the conversion.

Steve weim55 Colorado

Re: So,.. Two tings
 

The holes in my 67 cab for the three point seat belt holes
at the top of the cab are 7/16 diameter x 20 thread per inch.

Re: So,.. Two tings
 

HEI is a great upgrade and highly recommended, but it’s not just plug n play and has to be setup right. As already mentioned, you’ll have to replace the original power wire with an un-resisted 10-12 gauge wire so you’ll get full voltage to the HEI, and the plug gaps need to be adjusted to .045. To set it up, you have to verify your mechanical advance weights and center plate to see how many degrees of advance it gives (you want 20-22), change the mechanical advance springs so you’ll get full advance between 2500-3000 rpm, and verify your vacuum advance degrees (you want 10-15). If my memory serves correctly, GM HEI #19212081 or #1104067 should work well and you’ll only need to change out the springs and vac advance with those units. Just verify compatibility of those part numbers and you’ll be good to go. Get Crane’s vac advance kit (99600-1), it includes the springs and has an adjustable vac advance that will get you setup nicely. After all that, time it to 36-38 degrees total, plug the vac advance in to manifold vac, and it’ll be running like a champ.

Seat belts are real easy. Most vendors sell them with all the correct hardware. You just have to figure out which ones you like and the price point you're comfortable with.

Re: So,.. Two tings
 

Here's a really good thread from dmjlambert on replacing the resisted power wire:

http://67-72chevytrucks.com/vboard/s...d.php?t=708975

Re: So,.. Two tings
 

Some where on here someone did a swap with an s10 seat belts.His reason for doing the swap with the s10 is because he knew that the s10 belt would lock up in an accident.The after market seat belt suppliers couldn't give him a yes or no answer.