HEI Installation - No Vac Advance Problem

Just like the title says, I've installed the HEI, set 5 deg initial timing, hooked up the advance and ran it hard. I'm not having the same advance problems that most others have noted. Currently running the best I've ever had it running since I've owned it. I pulled it back in the garage, put the timing light to it and revved it. Distributor is 6cyl even fire with ground points and NAPA odd fire pickup, rotor, cap and vac advance all for '75 Buick w/ 231. Did I do something wrong, or did I just get lucky?

 

good deal clint, sounds like you did everything right. if yours is like mine you won't have to touch it for years. i still carry an extra module though, just in case. how did you solve your clearence issue?

 

Sounds great! I've been slowly building / converting an even fire HEI to odd fire for my Jeep. The only parts I need now are a set of plug wires and the dust cover for the coil. My points setup runs fine, but after reading your post, I believe I'll now be changing to HEI sooner.

 

I think I saw the other day in the junkyard that an 8cyl dust cover will fit the odd fire cap. The even fire 6cyl cover has the screws in the wrong spot for the odd fire cap.

I was running a Delco points dist with vac advance. It ran good, but this HEI did away with some of the popping I was getting, especially on decel, smoothed out the idle, and the throttle response is quick. I haven't taken a new mpg reading yet, but going to do that soon.

Anyway, I'm not a lucky person, so I'm scratching my head on this one, but I used the standard '75 Buick HEI vac advance from NAPA, if anyone wants to give it a try and see if it works for you, too. G' luck.

 

Thanks for posting that Clint (Mr. March!). Do you know what the vacuum rating is on yours?

The vac advance diaphram on mine was blown when I got it so I never hooked it up but she runs great without it.

NAPA has a book with several pages of vacuum advance canisters just for the HEI. Some with the vacuum hose connection coming out the end and some with it coming out the side (so you have clearance to the fan). Also, they've got all different vacuum ratings to pull the timing advance at different amounts of vacuum.

 

I don't know the vac rating, but I should. Thanks for the tip on the NAPA big book. I'll check it out next time I've got some time just for intellectual property.

Also forgot to mention this GREAT resource. Used this write-up to modify my distributor. What a great reference, lots o' pics. I mean, if I can do it, ANYBODY can do it:
http://www.cjoffroad.com/writeup.asp?WU_ID=21&noAdd=1

 

That's the one I used.

But I found an oddfire right before I started. I removed the vac can because of clearance problems.

Silicone plugged the opening in the dist and tap and screwed the vac advance plate to lock it.

No problems without the vac advance. True it only has mech advance now but it runs smooth during accel and decel.

You're right it runs the best it ever has.

Matt, I think I might have an extra dustcover in the garage. If you're interested I can check.

 

Infact, since posting this I've decided I'd like a little more advance. Over time I've slowly crept up the timing to 12deg initial. I guess at first I was just afraid of running that far advance for fear of toasting a valve, but I definitely get better performance that way. I've got this one little spot in the midrange throttle under load in overdrive, though, where it wants to bog down a bit. For verification, I disconnected the vac advance and it seems to be more pronounced. Just for test, I bumped up the initial to 15deg and it seemed to get better. My hypothesis now with the folks having problems with too much vac advance is not the advance module being too sensitive for the odd fire, it's that the 2g draws a ton of vacuum. I'm running a Holley 4bbl and thinking that the ported vacuum may be less than the 2bbl. I haven't confirmed this yet. Anyway, I'm wondering if there is a way to add a touch advance, maybe just 2 or 3 deg, at the spot just after mid throttle where ported vac starts to drop off, and just prior to WOT when the mechanical advance seems to build up. Or, maybe I'm putting the cart before the horse and need to play with springs and weights first.

 

Spring for sure. Mallory used to have (sell) a variety pack on springs. It sure helps if you have access to a dist scope and know the cam specs. If not, maybe you can borrow Sammy's adjustable timing light. It will show you when your weights come into play and what changes yu have made with spring changes. Very interested to know how you come out.

 

Old thread, just FYI for archive:
Use V8 HEI parts for both plug wires and dust cover. The V8 plug sets cost the same as the V6 sets, but you get two additional lengths of wire for free so that you can pick and choose wire routing around your accessories. Use '76 Buick Skylark with 350 as your application at the FLAPS counter. The dust cover on the V8 is the same as the V6 odd fire and extremely plentiful in the junkyard.

 

Yep, I ended up getting the dust cover from a chevy V8 HEI. It bolted right on.