lt4 coupe

So im in the middle of putting a blown LS-3/T-56 Magnum in my 69 Chevelle and my 96 LT-4 decides to display a strange noise from the #1 cylinder. The car is completely stock drive train wise as far as I can tell and has 56k miles. We will be pulling the drivers side head and likely the oil pan. If its piston/ring land/wrist pin and is repairable without pulling the motor, that's the plan, as I don't want two cars apart at the same time. If it ends up being rod bearing or there is cylinder damage, we will pull the motor and rebuild it with new pistons, rings, bearings, seals gaskets and valve springs, etc., but plan to keep the rest stock, with the exception of cam and long tubes (for now).

Question is, LT-4 Hot Cam or something else/better? We will be doing long tubes regardless if the motor comes out, since I already have muffler deletes and X-pipe. I will be deleting the cats and getting non-smog long tubes. At that point we will likely be figuring out mufflers since we both (the wife) like loud, but not necessarily strait pipe. =)

I have heard guys in the past say that cam and long tubes alone really wake up the LT-4 and makes a huge 1/4 mile improvement, so if the motor does come out, why not? Ill likely bump up the compression some with the new pistons as well...

drcook

The LT4 engine already has higher compression than the LT1s do. How much higher are you thinking and how are you going to deal with the higher compression ?

LT1's in 96 had 10.4:1 and the LT4's had 10.8:1 compression ratios.

If you have to get into tuning a 1996 you will find that you have other hurdles to jump.

The computer can handle a Hot Cam, that is what I am putting into my '96 LT1. However, there are more modern cam grinds that won't require the computer to have tuning required.

If you don't want to go to the expense of acquiring the hardware and software required for for tuning a 96, then standard compression pistons and a Hot Cam or a modern equivalent is the way to go.

The 96's are a 1 year only interface and you have to buy the Jet DST software and hardware and (in my opinion) a Windows XP machine to run it on. I have a dedicated XP laptop that I will use to tune my car. I am going with new heads, headers, cam. 1.6:1 rockers, bigger injectors, etc.

As such, I have to adjust the settings.

I have looked at the files from both the LT1 and LT4's and there are subtle differences.

lt4 coupe

Thanks for the reply. I have a tuner here in Las Vegas that has tuned these before but it has been many years. I had an appointment to have him see the car today and verify he can write to it, but we had to reschedule to Friday.

I was thinking right around 11:1 since Chevy always has safety margin built in. If it wasnt for the fuel tank I would just have him tune it for E-85 but I dont want to run a fuel cell. What more modern cams do you recommend? Lets say worse case scenario, he cant tune it anymore vs a best case scenario (he can tune it) cam?

Are you saying the stock computer, un-modified, can account for the Hot Cam only or cam and long tubes/mild other mods? It seems the hot cam with factory manifolds is a waste, no?

Kevova

Stock PCM will accept Hot Cam without tuning, not that tweaking could add a little bit more. TPIS , Lloyd Elliott, Advanced Induction, all have more aggressive tuning required lt4 cams.

drcook

comp cams also has a cam that requires tuning, they actually say so on their website

mtwoolford

LT4 Hot cam with matching springs is one of the few bargains available for an LT4 engine, you won't be disappointed; and it is a "drop in", assuming of course that the one year non adjustable pedestal mount roller rockers are in good shape.

lt4 coupe

56k miles. I'd say quite likely?

93 ragtop

Quote:

Originally Posted by mtwoolford

LT4 Hot cam with matching springs is one of the few bargains available for an LT4 engine, you won't be disappointed; and it is a "drop in", assuming of course that the one year non adjustable pedestal mount roller rockers are in good shape.

As a bonus, because of the popularity of this swap, you can get a very good tune by mail order. Companies such as pcmforless.com or pcmofnc.com will probably do it at a very reasonable rate.....
FWIW, GM used to sell a kit called Hotcam LT4 top end kit. Best I remember, it was a Lt4 intake, heads, and a hotcam. With headers one of the magizines claimed it made 429 hp on a LT1 shortblock.

lt4 coupe

So he was unable to connect through the ALDL. He has a harness that you unplug the car connectors from and plug directly in. He gets a connection indicator, but no response from the ECM.

He said 1 of 2 things. Either it's been flashed previously by someone like Hypertech which changes the firmware to only talk to them, or the ECM may have been compromised when the battery charger I was using wigged out.

The OEM radio died at the same time so it is highly probable. But he said he has a program he needs to dig up, that allows a forced reflash to OEM, he wants to try first.

I'll keep you guys posted, thanks a bunch for the input!

drcook

One of the last board members that toasted the ECM had to unsolder 2 of the chips, put new ones on that were reflashed back to stock.

if all else fails

https://www.mamotorworks.com/Corvett...-1996-690022-1

I do have a stock LT4 bin or as the Jet software identifies it, .jcl that can be used to restore an ECM. I can create one, change the vin and email it to you, if you ask nicely.

lt4 coupe

Ok sir, I appreciate the help. I'll let you know.

drcook

One last question that I just have to ask, you stated the tuner had done these in the past. Do "these" mean 1996 Corvettes or LTx Corvettes in general ?

As I said above and what works for the 95's and before will not work on the 96's.

lt4 coupe

Yes sir I was aware of that and he had already mentioned it. We talked about how 95 was OBD1 and 97 is 24x.

dizwiz24

Not a fan of doing higher compression, that will just annoy you when you want to go boost later.

(yes, lt1 /4 are just as good for boost as the lsx series)

jayjones

Did you get the initial issue diagnosed? Curious what you found.

lt4 coupe

Yeah, not going power adder on this car. Lol

I misunderstood my dad, the plan is to pull the head and oil pan THIS weekend. Most everyone who has heard it is going wrist pin.

I'll let you guys know ASAP.

For now I'll try to find a mail order tuner who will delete the smog so I can run slick long tubes...

KyleF

As has been discussed on other threads a full point (10.0 to 11.0) of compression nets 4% power increase. Based on a magazine test.

As a 350hp motor that is 14hp. Say you runner a better Cam/Headers and have a 400hp motor. Bumping the compression will net you a whopping 16hp and cause a lot of potential issue with tuning an knock, not to mention additional stress on components. I would stick to stock compression. The Juice is just not worth the squeeze. You wouldn't even be going up a full point from the LT4 stock motor.

Kevova

96-97 LT1/4 are the same. Lt4 is only in a few 97 firehawks and Camaro SS.

93Polo

Dated but an idea of dyno #s:

https://www.grandsportregistry.com/dyno.htm

Plenty of cams out there. I always like the Crane/GM 846 cam 222/230. Newer options are likely available.

I would also give CamMotion a call. They do LSx and LTx cams, good customer service and they make power.

lt4 coupe

So I have the Canton road race pan on the way. I was going to order headers today based on the above recommendations. Lingenfelter doesn't show them on their site anymore.

American Racing only lists options including mid pipes and cross over. I already have X-pipe so I don't really want to pay $1800.

Exotic Muscle only has smog options. Im running full smog delete (currently in the works during rebuild).

Does no one make a slick (no smog) long tube?