PROPHET69

Yes, i've posted this in the electronics section but haven't received an answer, traffic here is higher.

Ok, here's my issue, I have an 85 camaro with a carbureted 350 engine... ok, most of you understand my point already, lol. Since Camaro never made stock 350 carbureted engines, i can't find the proper gap that should be given for a 350 engine's plugs. 350 Spark plugs that are used are R45ts. carbed 305's need 0.045 inches according to books while 305 and 350 TPI use 0.035 inches. Should i just adjust for 0.045 inches or what? lol, i just hope buddy who sold me the car didn't lie t be about being a 350 and not a 305.

I'm being fussy about the gap because i've invested lots of new parts on the engine and will invest more later, and if i'm paying lots of dollars to upgrade my engine by a few horses, i want to make sure i squeeze out as many ponies as i can out of ACdelco platinum sparkplugs. Don't want to have pay lots just to screw up in the end in other words.

thanks.

1989GTATransAm

iTrader: (3)

Not sure if anyone will have the "correct" answer. This will most likely be a trial and error situation. I would agree that .035" on the small side and .045" on the long side is what you most likely will be looking at. Maybe try .040" as a compromise and if everthing seems just fine then up it to .045" and see what happens.

With my current setup I run mine at .035". However with my next rebuild and new zero resistant spark plug wires I will be going to .040" for openers.

Fast355

iTrader: (2)

A stock mid-80s truck 350 uses a .045" gap, the TPI/TBI engines use .035" to help eliminat crossfiring in the smaller distributer cap

I run everything that I have at .060" gap. It really helps when you have a hotter than stock ignition setup and you go into tuning and run lean cruise mode.

naf

iTrader: (7)

You would want to run the biggest gap you can without misfire. A lot of things will affect this point..tune, voltage available, coil saturation, wire resistance, compression, rpm limit, load, etc. so an exact, most efficient gap is kind of hard to define (and you probably wouldn't notice the difference in a few thousandths of an inch anyway). .045 is usually a good gap, I'd start with that (especially if you've upgraded your ignition components) then go down if you notice a misfire problem.

PROPHET69

Ok, sounds good, so what you're saying is bigger is better as long as your system can provide a good amount of power to the plugs. In that case, since i'm installing brand new Acdelco wires, rotor and distributor cap, maybe i should start at 0.045 inches in that case. I don't know if i'd want to go bigger considering my ignition coil doesn't look like it's the newest of shape. That would probably be a soon-to-be upgrade, a whole new distributor and coil.

Oh and... since i'm new with fixing up cars, when a car misfires, what is it like, does it just sound like it'll stall or is there anything else i'd notice?

naf

iTrader: (7)

I'm sure you'll be fine with .045. If it mis-fires you'll probably notice it stumble then catch back up.

Sonix

iTrader: (1)

Am I the only one who's going to make a fuss over this? Return those and get two sets of copper ones for the same price.

I set the gap lower, since the only downside to that is lost power. .035" on a high compression, stock ignition 350. If I upgraded the ignition coil and whatnot, i'd go back up to .045" or so.
I'd start low, then once you work out all the other inevitable bugs, you can try opening it up more until you notice it misfiring, then bring it back down to where it worked ok. Remember, as they wear the gap opens more.

PROPHET69

So in other words you wouldn't completely trust a whole 0.045 inches right off the bat? lol, we'll see, it's what i already plugged into my engine, gotta finish the carburetor though before giving her a try

Sonix

iTrader: (1)

well first off I don't like platinum plugs. They're meant for hondas that are really hard to get to the plugs, so you want them to last much longer. They don't make as much power, but last longer. Fair trade off right? ok, but which is more appropriate to you?
Plus you may be reading your plugs whilst carb tuning, which probably will including going through plugs rather fast (tossing them often), so that's $$$ with platinum.

gap - In my case; 10:1 CR, iron heads, old stock ignition. Went down 3 heat ranges, then closed the gap to .035". Once I get all the bugs worked out, i'll probably get a better ignition setup, and open up the gap. But really, one less variable to go wrong is a good thing. I'd rather lose out on 10HP than have a random misfire that is *very* hard to track down.

naf

iTrader: (7)

Sonix's smaller gap is actually a good idea. I've never thought about it that way but I have, in the past, had to drop my plug gap after getting an engine fired up and running. Would be easier to start small and move up. With a run of the mill 350 you'll be fine though at .045.

I agree on the platinum plugs too, they're designed for longevity to increase time between tune-ups. Not just for hondas though.

skyeleighton0

It is advisable to double check that the gap is correctly set to the vehicle's recommended setting when installing spark plugs.

T.L.

Thanks for letting us know, 15 years later...

BASSETT IROC 85

iTrader: (2)

I would run the gap at .045. with a HEI distributor.