Damon

I'm currently screwing together a super low-buck 305 for my brother whose team is going Lemons Racing next year. They're stuffing the world's cheapest and most plentiful motor (305 SBC) into a lightweight RX7. In theory, it should be competitive with a good HP/weight ratio.

And when I say cheap, I mean REALLY CHEAP. Competitors can claim your motor for $500.

Just running a carb on top of this thing, obviously. The distributor is an issue, though, because we have no ROOM for a large cap HEI in the RX7 and an aftermarket small cap distributor would cost half as much as the whole car!

I came up with the idea that we would run a cheap junkyard computer controlled small-cap HEI distributor but without any computer controls. Effectively, a "locked timing" distributor on the cheap. We don't care about advance mechanisms since we're always going to be at 3500+ RPMs and part throttle/fuel economy don't matter when you spend most of your time at WOT.

Thoughts, comments? Anything I'm missing here that maybe you guys know about that would be an issue using the distributor in this manner?

Thanks in advance.

Damon

Nobody's tried this? C'mon, I can't be the first one!

RBob

iTrader: (1)

I haven't done it, but I know that quite a few boat engines are set up this way. With no ECM interface to the ICM it will run in bypass or limp mode.

A proper ICM will have limp mode advance that kicks in somewhere in the 1600 - 2000 RPM range. So be sure to set the desired full advance above where this kicks in. This built in advance is helpful in getting a hot engine started as there won't be as much advance during cranking.

But then again, if hot cranking is an issue just need a kill switch on the coil power feed and flip it once the engine is rotating.

RBob.

Damon

Thanks, RBob. That's one of the things I was hoping to confirm. I had heard they might give some small "one step" bump in advance around 2000 RPMs when not run by an ECM. I'll just consider that the "start retard"!

The plan is to set the timing around 32-36* at 3000-3500 and let let it just fall back to wherever it happens to drop when it comes back down to idle. Now, I don't know how much it will fall back, but lets assume for a minute it's 10*. So at idle it would be around 26* and then it'll kick up to the full 36* again when the RPMs come back up. We can totally live with that behavior. Aside from starting out in 1st gear, the motor's never going to be below 3000 RPMs again anywhere in the race.

My concerns are more around issues of dwell and rotor phasing. Now, I admit I'm looking for problems that may not exist, but I don't want to kill a coil every 2 hours because this thing runs some funky amount of dwell without an ECM controlling it. Or burning up coil wires and distributor caps because it's firing when the rotor and distributor pole aren't properly lined up with eachother.

Remember, this thing's gonna be hammered on for 24 hours straight. Longevity matters. That's why I try to use factory stuff as much as possible. It's usually very reliable and spare parts are cheap if you need to do a quick repair in the pits. I just don't know if I'm severely compromising any of that longevity by using a CC-HEI without the "CC" part.

naf

iTrader: (7)

I have seen far too many ccc systems running without the ECM controlling the distributor, some running for YEARS that way, to imagine this would be a problem. AND these were generally not subject to careful and thoughtful preventive maintenance.

The timing step for the LG4 ICM comes in pretty low, maybe 1200-1500. I think you'll be happy with it.

Fast355

iTrader: (2)

AGREEED^^^

Also far too many carbureted, non computer boats running around with small cap HEI distributors from 3.0L through 8.1L for a longetivity issue. I believe the timing advances about 16* above 2,000 rpm if memory serves me correctly.

Damon

That's a good point, naf. Kinda hard to argue with that.

16* of built-in advance would be fairly excellent, Fast. Wasn't sure it was even going to be that much. Cranking the motor over shouldn't be a problem if the distributor's going to do me the favor of knocking 16* off of a 36* full-advance setting.

Fast355

iTrader: (2)

http://bpi.ebasicpower.com/pc/BPIDELCOESTV8/MER10A

Damon

The one I use will be somewhat less expensive.

I got 'em stacked up like cord wood from the various car engines I've converted over from EFI to carb. Thanks for the link, though.