I am looking at my options for improving the performance of my 96 Corvette LT4.

I have done a lot of searching on the web and the LT engine still seems to be a hard engine to get any info on.

It would be nice to aim for 400RWHP+

A sensible starting point that appeals to me would be:

LT4 hot cam kit with better springs
Headers (long tube though shorties look a lot easier to fit!)
ECM tune
Open air box
Lightweight flywheel
Throttle body (maybe?)

I am also wondering about stroking it to a 383 though am finding it hard to find a kit or shortblock.

I am in the UK so bear in mind there are very few people who know anything about building these engines over here. I'd want to build the engine myself though would need to get the machine work done.

Due to the horror stories I have heard of over here if I were to go the 383 route I think it may result in less pain if I could get a "ready built" short block from the USA.

Any experiences from anyone who has built up a good strong LT engine?

I am not trying to do it on a real budget because I know that won't work out. I actually think it may be an idea to buy a block or a used LT1 to build up and save my LT4.

I would like to keep the stock rear gears (3.54:1 Dana 44) because they're great for highway cruising and get good economy.

Another option of course may be to build up a lower compression strong engine for supercharging....

Happy New Year from England! Malc

 

Happy New Year

Here is a site where you can get a rough ideal what to expect with hot cam, headers, tune etc.

http://www.corvetteactioncenter.com/...96/96perf.html

 

To know what to suggest we would need to know your intentions for the car after it is built. Do you want low end torque and acceleration? Do you want to win on the drag strip? Are you taking it onto a race track? Do you want to drive it on the street and have lots of go when you step on the gas pedal?
From my experience the LT4 is more of a top end performer than a low end torque engine. To change the engines characteristics and keep it driveable will require careful selection of components. It may also lead to reliability problems if not done properly.
Let us know your expectations and you can get much more specific assistance.

 

Hi, it's more for useable street performance including high speed highway use - I took it to Germany last year and want to take it more to Europe to enjoy their fast roads...

I quite like the way the LT4 loves to rev.

Your remarks about matching components echo what I have been finding trawling the web.

A few years ago I had an LT1 auto 'vette and wanted to build that up and it took me ages to research who could do the head work, what cam, etc. In fact that was harder being an auto with 2.59:1 rear but with my 6-speed it should be easier to get the revs where I want them for performance.

P.S. I didn't mod the LT1 because I bought a Callaway Twin Turbo instead!

Malc

 

LT4 hot cam kit with better springs--Nice start

Headers (long tube though shorties look a lot easier to fit!) - Long tubes, shorties won't be much help. Delete the cats, egr, etc if you can. Maybe Borla mufflers. I have Magnaflow high performance 3" in/out and it is too loud.

ECM tune - Yes, that will make a difference.

Open air box - Can't hurt, might not make any difference though.

Lightweight flywheel - Others will have to chime in, I have an auto trans.

Throttle body (maybe?) - Not unless you get the intake and heads ported.

 

Your ideas are very good though I would go with long tube headers (do you have emissions testing in england /europe?).

I always recommend the lightweight flywheel. Im running fidanza 12 lb aluminum in my 93 lt1 and am very happy with it.


You cant go wrong with the hotcam kit. Hotcam kit is great in that it includes the hot cam (218/228 .525/.525 112 LSA w/ 1.6:1 roller rockets), roller rockers 1.6:1 ration, lightweight hats, and springs. However be advised the springs are the weakpoint of the kit. The springs in this kit are not much better than stock.

Also you should know that there is a little bit better technology out there with cams nowdays. Newer cams have faster ramp rates than hotcam. While the hotcam has .525/.525 lift, it doesnt stay there very long. Some of these new cams spec around .570ish w/ 220ish / 230ish duration, 114 LSA. Now, I dont know if you give up some low end TQ for high end gain w/ these newer cams.

With a manual transmission, and LT4 heads, Id at least consider these newer cams. Id talk to Lloyd Elliot (a well known LT1/ LS1 tune/porter )and see what he recommends.

All this said, I made 353 rwhp/355 rwTQ on my 93 with LT headers, hotcam kit, pcmforless tune, and mildly ported lt1 heads.

Also, if you are in there doing the grunt work of a cam change, Id get your heads worked over by either Lloyd Elliot or AI induction. With your LT4 castings, you could save yourself some money vs. buying expensive trick flow or AFR castings.

I like your idea about a blower too. Whatever cam you put in there, be aware of the LSA. You want that number as high as possible.

A guy on the camaroz28 website made an extra 40 rwhp with one of these newer cams vs. hotcam on his supercharged car (a whole different animal) when he swapped cams.

Good luck !

 

I may seem a bit paranoid here but I can virtually assume there is virtually nobody in my country that knows how to effectively port LT1/4heads.

I have known so many people here that have had engine work done that have been disappointed.

For those reasons I feel I would need heads ported or any trick machine work probably to be done in the USA by someone well recommended.

These are also reasons I'd think about buying worked heads and/or block assembly from the USA as I don't really want to ship my parts out and be off the road for ages.

Thanks for the cam suggestions. I'll also speak to those you suggest and hopefully come up withat least 2 plans: 1) building a good normally aspirated engine (probably with larger displacement than 350 inches) and 2) building a purpose made strong engine specifically for supercharging.

I'd love to fit shorty headers as they look easy and long tubes look a PITA though they're probably not that bad if bought with bullet cats.

Yes we have pretty strong emissions testing every year here so decatting isn't an option...d*mn!

Malc

 

Id recommend going long tube headers. Not much gain w/ short tube. Random technologies high flow cats will fit in behind them.

You want 1 3/4" tubes also, not the smaller 1 5/8". Those would just bottleneck you for future mods and you'd have to spend again to get into bigger headers

Also, may want to add an x pipe in place of the center resonator on your exhaust.

I forgot to add:
be sure to get a sprung hub clutch like spec stage 3+ if you go w/ lightweight flywheel.

The heavy dual mass is two steel disks with rubber sandwhiched between them and it can absorb driveline shock from rapid gear engagement.

One you eliminate that 'shock absorber', driveline shock can damage u joints and even twist up half shafts.

A sprung hub disk is what you want in there, it will also help with noise. There is a tiny amount of rattle w/ lightweight flywheel. Typically in wot or lugging up a hill in too high of a gear. Also, a slight knocking in neutral w/ clutch engaged (pedal released). No big issue at all.

The whole flywheel noise issue is blown out of proportion by a few members on this website and most members here (unfortunately) go w/ a less than ideal flywheel. Hot rod magazine showed that even in quarter mile drag race, a lightweight flywheel more than made up for any disadvantage it had at the start line and provided a net improvemnt in quarter mile time(less rotational inertia) vs. Heavy flywheel on the same car.


As for clutch:
Spec stage 3+ has excellent streetability (unlike 'puck'-type spec stage 3) and has held up behind my 470 rwhp supercharged 93 vert.

This is the best choice IMHO. It allows some slip (ex. parallel parking) for street driving and is still very stout.

I would also recommend spec stage 2 kevlar clutch, except I broke out the centr of mine one day at 110 mph. I had to get towed home. I was really happy with that clutch up until that happened.

The thing I like about SPEC clutches is that they engage/disengage like they are new even with many thousands of miles on them.

What I mean is the grab point doesnt seem to get higher and higher off the floor as the clutch wears. OEM and centerforce clutches, I feel a noticeable difference in engagement as the clutch wears.

SPEC stage 2 was the best for this until the center broke out of it. spec stage 3+, also very good.

Both of these clutches are sprung hub.

Good luck.

 

http://elliottsportworks.com/

LE gets 410+ RWHP with his LE2 H/C package on a LT1
http://elliottsportworks.com/home/?page_id=53

Bear in mind OP has to pay freight both ways (very expensive ) if he gets his heads done;
would be cheaper to pay core charge and only one way shipping

 

Do they do a sniffer test that measures emissions or is it just a visual check?

Tune will be harder to accomodate if you don't have anyone familiar with them over the pond.I would think there would be some LS engine tuners somewhere that could accomodate you with the right software.

With shipping being the pain it is do it right and do it once.For immediate use I would go with something like AFR heads and a cam to match(I do like Advanced Inductions grinds on paper-have not run one).Go with long tube headers(if you can)and a Corsa cat-back(do it once and no resonance).
Buy a computer stateside and have a knowledgeable tuner(several in my area)tune it on a running vehicle with similar mods if possible.
An electirc water pump is'nt a bad idea and a new optispark would'nt hurt either when you tear it down.

If your shortblock is sound you are good to go and you can always use the top end on a stroked shortblock later.

Lots of ways to get it done.Figure out what you want/need and do it once.

 

rather than spending who knows how much money porting and rebuilding the stock LT4 heads (with their 2.00 inch diameter hollow stem intake valves), I'd consider leaving those (rare and expensive) LT4 heads unmolested and exploring the option of an aftermarket LT4 head such as those offered by Air Flow Research (AFR), parts numbers 1039 (2.05 inch diameter intake valves) or 1076 (2.10 inch diameter intake valves).

 

Yes I would probably like to keep my LT4 heads, and possibly the entire engine untouched and build up another engine for my car.

One reason is, although there are other (well at least 2 that I know of) 96 CE Corvettes over here (UK) mine is thought to very likely be the only CE with an LT4 6-speed so it's a rare one here. The others i know all have LT1s.

In the unlikely event it ever would be worth anything it can be made back to a stocker by swapping in the original lump.

Before anyone laughs and who really cares about collectability a few years ago you couldn't give a 2nd gen Trans Am away over here now everyone wants one and in fact they look more expensive in the 'States...

Anyway it looks like a pattern is emerging and Lloyd Elliot's name seems like a good one. I found Golen's site a while back though they have some negative reviews. That's not to say they're not good though but there are a few unhappy people out there. Bear in mind, as someone pointed out above, I could spend a disproportionate amount of money shipping parts back and forth to be worked on and returned to me. You'd probably find there's not much difference in me buying AFR or equivalent heads outright compared to me shipping my heads.

A mad friend of mine did ship his LT5 to Marc Haibeck from the UK, had the engine built to 535 flywheel HP, waited a few months to get it back and remains a very happy individual.

However I don't quite have that sort of money...

I have experienced the lightweight flywheel effect in a ZR1 though (his has it also) and you can feel a difference just starting the car up. Haibeck reckons this alone is worth 15hp...

Thanks for all replies so far. As 96_LT4 mentions above it's best to do it once once and do it right!

Yesterday I was at a Corvette meet and there were even more stories about 'vettes being touched by "mechanics" that maybe should be pursuing a different line of work...

Malc