Putting a Caprice engine (L05-7) into a 92 g30 van (has L80e trans)

[Schurkey]

For the 383 the guy said that I’d need a different flex plate.

Because of the crankshaft bolt circle diameter; or because of balance?

Balance might be a legitimate reason. Not so with the bolt circle size.

 

[Danboquist]

Because of the crankshaft bolt circle diameter; or because of balance?

Balance might be a legitimate reason. Not so with the bolt circle size.

He didn’t say, but I googled it and it seems the answer is balance. The weights that are welded on the flex plate..

 

[Schurkey]

It also occurs to me that maybe the engine ships with a flexplate intended for a 4L60E torque converter, and you'd need one that fits your 4L80E...but if the balance is the same, you'd just use the one from your original engine if it's in decent condition. Might want to ask the engine builder why the flexplate it ships with isn't compatible.

 

[Danboquist]

It also occurs to me that maybe the engine ships with a flexplate intended for a 4L60E torque converter, and you'd need one that fits your 4L80E...but if the balance is the same, you'd just use the one from your original engine if it's in decent condition. Might want to ask the engine builder why the flexplate it ships with isn't compatible.

I will do that. Now I’m concerned about having to reprogram the ECM.

 

[L31MaxExpress]

You are likely going to have to reprogram the ECM regardless if you change from the stock engine setup at all. Either engine will run with the stock ECM, but far the way they should. Years ago I ran a 406 small block on the stock 350 TBI system with the only change being the 46mm bored TBI and 80# injectors. Ran well as it was and really ran a lot better with chip tuning. The flexplate on my 383 is a SFI rated heavy duty replacement for the stock 350. The crank was balanced so that it used a standard weighted 1-piece rear seal style flexplate and a standard neutral balanced L31 style balancer. Will he accept the core regardless of its internal condition? Might be worth knowing.

 

[L31MaxExpress]

The biggest issue you are going to run into is a roller cam, any roller cam will have signifigantly different valve timing than the OE cam, which alters the vacuum signal at various throttle positions and loads. The PCM will adjust the fueling based off the 02 sensor in closed loop, but during open loop operation such as startup warmup and heavy throttle the PCM does not use the 02 sensor and fueling will not be accurate. The cam change will also likely alter the amount of timing advance the engine wants at various rpms and loads. You can crutch this a bit with fuel pressure and base timing changes, but those are global adjustments rather than being able to fine tune the PCM mapping.

 

[Danboquist]

You are likely going to have to reprogram the ECM regardless if you change from the stock engine setup at all. Either engine will run with the stock ECM, but far the way they should. Years ago I ran a 406 small block on the stock 350 TBI system with the only change being the 46mm bored TBI and 80# injectors. Ran well as it was and really ran a lot better with chip tuning. The flexplate on my 383 is a SFI rated heavy duty replacement for the stock 350. The crank was balanced so that it used a standard weighted 1-piece rear seal style flexplate and a standard neutral balanced L31 style balancer. Will he accept the core regardless of its internal condition? Might be worth knowing.

I don’t have a core and don’t know where I could get one, but I can ask.
The information that you gave earlier about the cams helped me a lot. I was able to talk the salesman past his knowledge and now he is just the middle man between me and the owner. Helped me a lot.

 

[Danboquist]

The biggest issue you are going to run into is a roller cam, any roller cam will have signifigantly different valve timing than the OE cam, which alters the vacuum signal at various throttle positions and loads. The PCM will adjust the fueling based off the 02 sensor in closed loop, but during open loop operation such as startup warmup and heavy throttle the PCM does not use the 02 sensor and fueling will not be accurate. The cam change will also likely alter the amount of timing advance the engine wants at various rpms and loads. You can crutch this a bit with fuel pressure and base timing changes, but those are global adjustments rather than being able to fine tune the PCM mapping.

This is an excellent explanation. I get it. Timing advance ,fuel/air mixture, fuel line pressure. All because of the cam.
So can I run 383 with TBI? I guess if the heads will allow such an intake it is possibly ok.

 

[L31MaxExpress]

I don’t have a core and don’t know where I could get one, but I can ask.
The information that you gave earlier about the cams helped me a lot. I was able to talk the salesman past his knowledge and now he is just the middle man between me and the owner. Helped me a lot.

When it comes to TBI combinations and cam changes, about the only thing that can be expected is to expect the unexpected. There are so many different factory tunes that GM used it is impossible to know how every tune will respond to a given change. My best advice is keep the engine as close to stock as possible. I have had good luck using the 6395 marine cam in one, the Melling MTC1 flat tappet in others, a GM F/Y car LT1 cam in a few and a stock 1996 LT4 cam in another. The LT4 cam I ran actually came out of a TBI 355 a buddy of mine built for his 1987 1-ton suburban. He tried running it on the stock tune and it gave him fits. I put it in the 355 I built for my G20 to replace the MTC1 and it ran flawlessly on the 1992 G20 van ECM I was running at the time. I put a GM 300 HP 350 crate engine into a 1992 TBI truck years ago as well. It ran very well on the stock tuning with 68# cop car injectors and the base timing bumped up to about 10* BTDC. The non swirl port heads on that engine wanted a lot more timing. I think the 1992 ECM was a bit more capable of running a modified setup than the 87-91 ECM was. The electronic transmission trucks and vans have a faster processor and better code than the 87-91 ECMs and even the 92 ECM used with the 700r4s as well.

 

[L31MaxExpress]

This is an excellent explanation. I get it. Timing advance ,fuel/air mixture, fuel line pressure. All because of the cam.
So can I run 383 with TBI? I guess if the heads will allow such an intake it is possibly ok.

if the intake bolts up, should be able to get it to start, run and drive. The 383 will actually make a slightly larger cam tamer than the equivalent cam in a 350. It is all a balance and unfortunately there is no magic bullet to say, do A, B, C, D, skip E, change F and it will work.

I had a 406 running on TBI, GM had a 366, 427 and 454 on TBI. They also offered a 502 for TBI 454 applications as a crate engine years ago snd Mercruiser had a 383 and 502 TBI as well.