flabound11

I know this isn't the normal question but I figured it would be the best place to find an answer. I have been working on a Mastercraft with an LT1 Corvette engine. I知 not very familiar with this setup so let me tell you what I know. The boat was a scrap yard find, I知 following several mechanics to get this running. The engine and electronics were in pieces when I started, just about every electronic part has been replaced. I had to replace the crank sensors, fuel pump, and one coil pack, to get the engine to run. I had the ecm program checked and the correct updated Indmar LT1 corvette program is on the computer, it was bench tested and is functioning properly. It appears to run fine at idle, when you snap the throttle or accelerate faster than a turtle, it pops and backfires at 3000RPM it starts to run fine again. I have a fuel pressure gauge on the engine and the PSI is correct. I have checked compression. I have removed and cleaned the injectors. I have checked the module with a known good test module (Northstar ignition). I have checked the advance and base timing. The TPS has been replaced. Here is my question, I was looking at some pictures of another Mastercraft and noticed the heads were aluminum. After doing some research, I discovered they also put the LT1 in cars not just Corvettes, the horsepower difference is - car 260hp, Corvette 300hp. Apparently the difference between the car LT1 and the Corvette LT1 is they put aluminum heads and a different cam in the Corvette LT1. Those changes wouldn't have this kind of affect if it had a holly carb and a distributor, however, I知 not so sure about this MPI setup with distributorless ignition. Can anyone weight in on this and tell me, (I already know the motor has cast iron heads), if it also has the wrong cam could the popping and backfire and poor performance be a result of this?

Pliant

This should be interesting how did you get a NorthStar ignition module running with a mefi 2??? Mefi advances the timing so the fact it runs is saying a lot. Who burned the new tune on the ecm

flabound11

Indmar did it, came like this from Mastercraft. Bob at Mefiburn checked out the computer

Pliant

I take it this engine is not orignal (cast heads) . is it all original or better said does it have a car intake manifold or is the manifold original stuff and the injectors are they original or aftermarket....never mind that's a complete different animal intresting

http://www.enginebuildermag.com/2014...hevrolets-lt1/

flabound11

Looking at pictures of other Mastercrafts with the LT1 engine, it looks like it's all original. The block and heads are what I think are from a car, they look the same but are not the same. An extra crank sensor in the block, an extra coolant sensor in the head, cast iron heads.

BUP

iTrader: (9)

I will add some info. Indmar did a lot of these back in the day LT1 installed in Mastercraft boats. I have worked on plenty of them back in the day as well. Indmar used the Northstar DIS waste spark system instead of the Corvette Optispark distributor.

Indmar plugged the hole for the distributor hole and again used the GM Northstar DIS waste spark system from GM Cady Northstar engines.

This set up was 4 coils units mounted to the front of the engine with 8 spark plug wires coming out of them. There is no CAM sensor on this app and uses 2 crank sensors as per Indmar called lower and upper crank sensors. The ICM = ignition control module to the crank sensors has 6 wires as 2 of them are a shield for each of the Crank sensors and then 2 wires per for the crank sensors themselves. Anyways just some info on the ignition side of this.

airjunky

iTrader: (2)

The king cobra had a similar deal. The dohc caddy motor pulls the cyl position from wheel on center of crank.the king replicated that from a trigger mounted on the flywheel. Uses the caddy style icm.purely i pull this from old memories.. I put one of these on a jet boat back in the day just cause it was cool. About the time they came out with the 383 corvette ski boat. It was more than the corvette by 5 grand . You are a ambitious fellow. I would of plugged a 350mpi mag in it and sold off the lt1 bits to some purists. That first gen dis system was not kind to the people