Stupid ignition timing thing!

[1987cp]

yeah there is a lot of variation in those cans. Unfortunately their characteristics seem to be very poorly documented so I have absolutely no idea how you even pick one unless its a case of randomly finding one that works properly for you.

I'm quite willing to believe that. Possibly the best solution for someone who really does want vacuum advance and wants a can with known characteristics is to get one of the available aftermarket cans and use its manufacturer's recommendations as a guideline.

In the case of HEI, there are definitely several aftermarket vacuum advance canisters available, though since it's on a Ford, I know the whole distributor is aftermarket, so possibly its manufacturer put a can with known characteristics on it.

Efi ftw

That doesn't necessarily solve all your problems. It might be plug and play (sort of) if you keep it stock, but deviate much and you'll be back to the tuning board, only this time you'll need a $200-plus electronic doodad instead of a screwdriver.

[sly]

I miss that 85 Pontiac Parisienne with it's q-jet and HEI.

[import convert]

i think the HEI just has full curve way to soon. i never tried disconnecting the vaccume advance to see if it helpped but like i said at full throttle it was great but partial itd ping. i did feel that the accelerator pump might have needed to be readjusted though. a quick bleep of the throttle seemed to make it stop for at least a second or 2

[gadget73]

adding a shot of fuel to make things stop pinging sounds almost more like lean fuel mix than timing problems. A combination will make things real interesting. Thats really the big problem with carbs and mechanical ignition, especially if you're not overly familiar with it. Carb issues can present like ignition, and vise-versa. Unless you know how to diagnose it accurately and make the proper correction, its never gonna be right. EFI is really no different in that respect, though the method of fixing it is obviously different.

[gadget73]

adding a shot of fuel to make things stop pinging sounds almost more like lean fuel mix than timing problems. A combination will make things real interesting. Thats really the big problem with carbs and mechanical ignition, especially if you're not overly familiar with it. Carb issues can present like ignition, and vise-versa. Unless you know how to diagnose it accurately and make the proper correction, its never gonna be right. EFI is really no different in that respect, though the method of fixing it is obviously different.

[1987cp]

Thats really the big problem with carbs

Especially if you're suffering from low vacuum signal or have a carb that isn't very responsive. I finally ended up just going richer again to get rid of an annoying flat spot on tip-in.

Apparently it's possible to get a carbed performance engine working quite efficiently if you can strike a combination of a cam with a strong vacuum signal and a modern carb that's fairly responsive. One of these days I want to get myself a bigger engine budget and give that a shot. Who knows, maybe I could even do better than 15mpg?