johnsonm

I am very familiar with the search function on this site and it has gotten me through nearly all the questions I have had up to this point.

I have just completed a LG4 / T5 to 350 and T-56 swap. The transmission portion went well, except for not using dedicated pressure plate bolts or having the flywheel and pressure plate balanced before installation, the first time (I would recommend both of these to anyone).

I am leaving the computer controlled carb and distributor from the 1986 LG4 running the 350. Everything runs well, but I feel I may be lacking a little in performance and mileage from the stock PROM. I have searched for PROM options and gotten several answers, most aren’t real definitive.

1.Lots of people swear by the ZZ retrofit computer and PROM, these are for automatic transmissions and delete the EGR correct? What issues will come about from using an automatic chip in a manual car? I would also like to keep the EGR.

2.I have heard to use an aftermarket chip. Some say these work great, others say too much advance, and all they do is ping. Anyone know about the how much advance a Hypertech or JET chip uses?

3.I have thought about using an L69 chip. My 1986 model LG4 came with a knock sensor and higher compression than earlier models (supposedly). What is the possibility that it also came with the upgraded or more aggressive spark timing?

4.I have installed a timing tape on my balancer, so I can get a pretty good feel for my advance and where it is coming in. My question is, can I check the equivalent of what would be “mechanical” advance on my feedback system. I have unplugged the 4-wire connector and increased the RPM’s. I have unhooked the vacuum line to the MAP sensor and increased RPM’s. I have unhooked both and increased RPS’s. All give me a different result. Is there a correct way to check? Has anyone swapped a chip into a 1986 feedback system and checked the rate of advance, and could possibly share their results with me so I may know where to begin.

I don’t think PROM burning is really the answer for this situation. I may be wrong, but from what I have read, there is very little info available on custom proms for feedback systems. I’ve got the carburetor adjustment down from all the old schoolers on here.

Big thanks to everyone for all the good questions and information, this is a great site! Who would have thought that a 20 year old beater could bring so many enthusiastic and knowledgeable minds together.

Thanks!
Matthew Johnson

five7kid

iTrader: (14)

First, welcome aboard.

Now, you started with something close to what I have, only difference being the manual vs. auto tranny. I had an "aftermarket" chip in for 6 years, a couple of months ago I put the stock chip back in - couldn't tell a lick of difference.

You can't really check the advance as you suggested. I've never tried it, don't know if it can be done (assume it can), but datalogging is the only way to know. Disconnecting the ECM connector puts it into limp-home mode, with only the advance built into the module. Although, I haven't tried the disconnecting the MAP sensor thing. Best thing you can do is try different base timing settings and comparing performance.

Vader was talking about doing some CC carb PROM tuning, haven't heard how he's made out.

What cam are you running? I was thinking again on the drive into work today how well my setup runs. We're planning on taking it to the track again this weekend, my son is going to run it in the High School class this summer. Auto makes that a little easier, as you might imagine.

Oh, the cam question. Makes quite a difference in how the system responds.

johnsonm

five7kid,

Thanks for the prompt response.

The cam is the old stand-by Performer knock off, 262/272 dur, .420/.442 lift. Not the best, but not the worst. Goes right along with everything else about this engine. The heads are old 76 cc smoggers (3973487). They do have 2.02 valves strangely enough, but no screw in studs. So... ok but nothing special. The block is a 4-bolt truck block, 40 over, with 4 relief flat top pistons. This was all kind of assembled out of parts that were laying around. It's a lot stronger than the 305, but I haven't gone to the track to find out how much stronger. All these pesky details to figure out.

I'm dissapointed to hear the chip makes no difference. I guess next you'll tell me all the work I've done to increase EGR flow won't help my gas mileage. I would have thought that cramming cumbustion chambers with inert "filler material" instead of fresh air and fuel would have gotten a few mpg. Guess not.

When advancing my initial timing, I guess there is no such thing as too much, until the car won't start or I get detonation? I'm at 12 degrees now, just keep cranking it up until one of the two above happen. Correct?

I would be interested in hearing how times at the track go.

Thanks!

Matt

five7kid

iTrader: (14)

That's a pretty mild cam and pretty lame heads. Your compression is going to be very low, so you're probably going to lose power with too much advance before you have problems starting or get detonation.

You'll see a lot more improvement with a better cam and better heads than you'll ever see messing with the chip.

FWIW, I'm not saying the aftermarket chip I had was the cat's meow. It wasn't the ZZ4 conversion chip, which eliminates the EGR function. With the exception of the heads, my set-up is a close clone to the ZZ4 conversion, however, with a better torque converter and better exhaust. You could argue the heads are better as well. Using various conversion formulas you see out there, the sea level converted track #'s translate to about 365 flywheel horsepower, slightly higher than the ZZ4 crate (the ZZ4 conversion, I've heard, produced about 310 net flywheel HP as-installed).

johnsonm

Thanks,

yeah, ok the heads suck, I'll get to work on procuring a better set. Better to spend the $ on decent heads than a chip at this point, gotcha.