Okay I know carb to TPI comes up a lot on here as I did a search. I am just looking for a few answers that pertain to my car.

Its an LG4 Z28. I am thinking about going to TPI. I don't want anyone coming in here and say go get a bigger carb heads etc because that has nothing to do with going to TPI.

What I want to know is if I got an 85 or 86 intake, wiring harness, computer can I still use the LG4 heads? I know 87 and up use the center bolt heads with the different angle intake bolts.

For a cam, do I need the 305 TPI cam, or can I get something like an LT1 cam that seems to get some good reviews from some threads on here? I know it will need to be changed I am just wondering what would be better to start with.

As well for the pump in the tank can I just get an inline pump? If so what would you guys recommend? ( I know its must be capable of 40 PSI)

 

My understanding is that the LG-4 flat tappet cam is almost identical to the roller 305 TPI automatic "peanut" cam. Small, but computer-compatible, if only to get it up and running.

You can't easily bolt any factory roller cam (L-98, LT-1, etc.) into your 84 block- it's for flat tappet cams only. A mild flat tappet aftermarket cam would be your best bet if you plan on upgrading. Something with under 210* duration @ 050 on a 112-114* LSA if you want it to work well with the stock TPI chip. You can go bigger but it won't help much without a custom chip.

Early LG-4 305 perimeter bolt heads like yours are almost identical to later 305 TPI heads. Same sized valves, runners, combustion chambers, etc. An 85-86 TPI will still use the early style intake bolt pattern that is compatible with your 84 heads. In short, no need to change your heads if you get a compatible year of TPI intake.

Some things that will still be different on your engine vs. a true TPI:

1. Your 84 LG-4 has a rather low compression ratio of 8.5:1 thanks to heavily dished pistons. TPIs were all around 9.5:1. You'll be a little down on power vs. a true TPI motor, but it'll run OK.

2. Your stock LG-4 exhaust system uses more restrictive exhaust manifolds and exhaust system all the way back to the tailpipes than any TPI engine. Again, it'll run, but you'll be down on power.

Yes, you can use an in-line EFI fuel pump to feed the TPI. You can even re-use some of the factory fuel lines. Your carb'ed car will have both a 3/8" feed line and a 5/16" return line just like a TPI, but they pop out of the frame on the passenger side down low in the engine bay vs. a TPI that would pop out on the driver's side up higher in the engine bay.

 

Thanks for the info.

I am from canada as well so I don't have all the AIR on my 84 from factory as many US guys do, will that reduce the restriction on the exhaust?

So the cam I have is fine to get it up and running, well thats good enough I guess, I could just run that till I can get a better cam down the road.

Does TPI support a significant increase in milage over carb, everyone seems to think this, I was just wondering if its true. I hear people said they got 25 with there TPI and switched the carb and dropped to 20 and under.

What about the charging system, does the alternator plug in change, or could I just wire in my old 84 alternator system?

Gas lines I did notice run opposite, is there anyway to route them to the passenger side... I guess I will get to figure that out when the time comes.

 

The air injection system doens't affect the flow of the exhaust system. Your LG-4 will still have little 2" outlet exh. manifolds, 2" down pipes into a 2-1/4" y-pipe, 2-1/4" cat and 2-1/4" exhaust all the way back to the muffler.

TPIs were 2-1/4" manifolds to 2-1/4" down-pipes to a 2-3/4" y-pipe and about 2-3/4" through the cat and all the way back from there.

TPI could give you a bump in mileage. Depends how far off your carb setup is right now. I would think it could probably give you 2-3 MPGs even if both systems were working/tuned properly.

Not sure about the alternator. I know later TPI engines had slightly different plugs on the alternators than the old carb engines had (and were on the opposite side of the motor when they went to serpentine driven accessories). Don't know how different an 85-86 TPI alternator/wiring harness would be than your 84 setup. Probably have some work to do there, though.

Fuel lines is up to you. I would go swipe a set out of a junkyard TPI car, or just order up some new ones. I've seen people just keep using the stock lines and then looping some flex line up and over/around the engine, but that's kind of a rig job. Kinda stuff I would do but never recommend to anyone else.

 

Okay, once again having a Cat is not a must in Nova Scotia unless the car is newer then 1990, plus my LG4 actually has True Duals running off it, but they are probably the 2 inch manifolds. Does a TPI engine require a cat to work properly?

Fuel lines I just replaced that not long ago, so I don't really want to do it again, I will have to look into rigging it once I get a setup.
I am just trying to make sure I have everything clear before I get one, so that way I am not stuck with a car that won't start and stuff.

How much pressure is on the return line, or is it like carb, minimal?

 

When I did my carb to TPI swap, I used an 87 TPI setup and wiring, but had it modded to a 90-92 setup and changed the ecm to a 91 so I could eliminate the MAF and run Speed Density.

My Engine wiring was separate from the body wiring so I was able to use the stock alt wires, oil pressure wire, and coolant temp wire.

I installed a Crane Cams Powermax 2050 camshaft since I had a manual, if I had an Auto I would have had to upgrade to a higher stall converter.

I did this swap over 4 years ago and I think it turned out pretty good, motor didn't last too long though, bearings went bad 6 weeks later.




Here is a video of the car after I did the swap,
http://www.transamws6.com/video/ZepherWS6.mpg