I made 480 rwhp with edelbrock shorties, cat converter, stock midpipe and flowmaster muffler. I knew that there was more power to be had due to the fact I was using only 1 cat converter and a pretty restictive y-pipe.

After changing the entire exhaust system out to flp longtubes, 2 cat converters, custom single 3" exhaust and dual magnaflow mufflers (strait thru) my engine made 525 rwhp and gained torque everywhere above 3500 rpm. I was impressed with the new exhaust, but it wasn't cheap.

 

I'll add my little bit here. I think for LT's to work to their full potential the rest of your combo have to have the need for them. The original poster mentioned he has some minor head work and intake work with the hotcam, I personally don't think that's enough motor to get the full potential from LT's, shorties in his case will be fine, maybe change to a different style with 1 3/4" primaries will help a bit more.

Take my car for ex., stk. heads and cam and stk. motor with the stuff listed in my sig. Stk 3:42 gear, stk. d/c's between the borla and my SLP d/c headers. I dyno 305/320 @ the wheels and the car runs consistant 13.30's now @ almost 105mph (fastest ever is 13.23@103). No programming done to the ECU (HPP3 is only for fans and scanning use). In my case since I don't have any major mods done I don't think LT's would help me too much, the extra costs wouldn't justify going this route.

I don't think my shorties are even maxed out yet, I probably could do heads/cam and see improvement from that now, with LT's there may or may not be a gain which can justify the amount of money that would need to be spent for them to be worth the install.

I know my engine setup has enough to get me into the 12's, my only obstacle right now is that even with DR's I can't hook worth a damn (still 2.0 60's), that's why in my case I've pretty well left the engine alone and now working on getting what I have down to the ground, and that's the reason why there's a Spohn TA under my car now waiting to be tested this spring.

Getting back on topic, people need to look over their combination more thoroughly before diving in with their mod plans, just because a part has the promise of delivering the results you are looking for doesn't mean it will work with your already done mods, other alternative pieces may deliver better results without the extra costs or hassles.

 

Well, like I said, I've already put in the order so it's too late now. I never bought the edelbrocks that are in there now, so I guess I'm not really spending any "more" money. The LT's will be the first headers I've bought.

As far as the headwork is concerned, in my opinion, it's more than just "minor". They were fully ported and polished, multi-angle valve job and 2.02/1.6 valves were installed. Also The intake was ported an LT4 Hotcam w. 1.6RR . I have a 52mm throttle body +150shot when I need it.

Taking into consideration the mods I've done, how much of a Torque increase would you estimate I get with the LT's?
Thanks.

Ps. BEFORE the head/intake work was done, I was putting out aprox.
320/320 N/A and 440/490 torque on the spray. All numbers are at the wheels mind you. With the heads done, I hope to see in the area of 485-500 at the wheels now that I've got the tranny fixed and a custom ECM.. Fingers crossed

 

you'll probably find that you gain 15-20ft-lbs around 2500rpm and that figure will slope off to around 5-10 by 4500 and -5 to -10 at redline (7k-7.5k rpm or so, i'm assuming). Peak horsepower will be up a bit, average hp gain will be 5-10, and mainly low-mid. You're gonna pull harder low-mid range and still pull hard up top due to your heads/cam, but you'll find that your top end hp isn't going to be helped really. You're 60ft and ET will drop if you can hook up but trap speed may be close to the same or minimally better.

Go dyno with your shorties then dyno with the new LT's and let us know what the results are. Make sure and post the graphs so we can see what happened

http://www.carcraft.com/techarticles...st/index1.html - that's an interesting article...just thought you might wanna see it.

 

That's exactly what I plan on doing but don't hold your breath. It's about -25 right now so I'm not going to be installing anything till, at the earliest, some time in April. Then I'll do a base line run with the Edelbrocks, throw on the LT's and run it again.
I'll post the results, but I don't think it'll make any difference with the way people think about the whole LT vs Shorty issue. There are people on both sides that just won't think differently about the issue (what header they prefer) regardless of whatever Dyno charts they see or whatever write-ups they read.

I am happy I posted this thread here 'cause I got a lot of helpful responses and I learned a couple of new things. Mainly that LT's are more suitable on some applications (head/cam cars) than they are on others (stock/bolt-on). That's not to say Shorties or mid-lengths are bad, just that they too are more suitable for some set-ups than others.

Thanks guys. I'll post some pics of the JetHot's when they arrive.

 

ok, I didn't know your heads were "fully ported and polished", I went with your first post where you said you had "head work" done, that could mean anything. Regardless, in your situation since you didn't have to buy the headers that were on the car originally I would say "good job" going the LT route. With the mods you've done you probably have plans to do more later so LT's if you don't get the full potential from them now you will see it later when you do more work on the engine.

Couple q's unrelated to this thread:

Your 11.70 et's were run on the spray yes? What et's do you run on the motor?

When you did your heads and put in larger valves, was there any problem with the valves AFA piston/valve clearance? I take it your shortblock is still original correct?

I see you're in Scarborough, we should hook up this year sometime at the track for some runs.

Tony

 

I run 12.90's w/SLP's, Flowmaster cat-back, gutted cat. M6 '95Z28 running full weight, ie: even stock rims on BFG DR's. 3.42 gears. Seen a .2 and 3mph increase going from stock manifolds to SLP's, no other mods other than NGK TR55's at that time (and gutting the cat while I was at it-->may have helped)

Hope this helps.

BTW: I'm adding Hooker LT's to it ONLY because I want the SLP's on the less modded '94 Trans Am, the '95 will go from bolt-on only car to LT4 conversion w/hotcam.

I will say this though - changing plugs on the SLP's in worse than doing an intake manifold gasket change, make sure you utilize the industries head shielding and all the wire protection you can, many, many wire burns.

 

In 6 pages, there seems to be less than 5 FACT-BASED posts.

Let's see if I can help with some facts:

- Stock Eliminator LT1 cars (stock non-ported heads, stock displacement, near stock compression, stock intake, stock TB, stock lift cam, etc. . ) are running in the mid-low 10's NA. They use ultra-long duration cams (260+ @ .050"), Hooker Super Competition LT's, and high stall converters (5000+ rpm) to get there.

- NASCAR engines use LT headers.

- Thunder Racing did a shorty versus LT dyno test on a 350 LT1 with ported LT4 heads and CC306 cam. I don't remember the exact numbers, but it picked up around 30 - 35 ft-lb low-end torque, but only about 5 - 10 rwhp. If you want the exact numbers, call Thunder, ask for David, and ask him about Hoffpauer's car (pronounced Hof-power). The shorties were 1 5/8". Perhaps the gains would have been less if he had 1 3/4" shorties.

- The initiator of this thread indicated he had Edelbrock shorties. Unless they changed their design, Edelbrock uses a "dual diameter primary", which means 4 tubes are 1 5/8" and the other 4 are only 1 1/2" (!!!). I had a set on an '89 Firebird that were constructed this way and, yes, I measured them myself.


It seems as though cars with longer duration cams (Stock Eliminator and, to a lesser extent, CC306) pick up more from LT's than stock cam cars. This actually agrees very well with the theory of operation.

You see, during the exhaust stroke, the piston is pushing exhaust out the port and through the header. With an LT header, think of the exhaust as a train travelling down a tunnel. When the piston decelerates at the end of the exhaust stroke, the train (exhaust), because of its mass/momentum, wants to continue travelling at the same speed. Basically, the caboose (piston) is throwing on the brake. So what happens? The train separates. When gasses (exhaust) separate, the molecules get farther apart and the pressure drops. So, at the end of the exhaust stroke, you've actually pulled a vacuum on the chamber. With a long duration cam, the intake valve opens and allows intake air to be drawn in by the vacuum.

Now, if you shorten the exhaust header tube, there is less mass/momentum of exhaust gas, so you don't as much of a vacuum pulled on the chamber. However, a shorter tube has less restriction, so it will flow better at high rpm.

Also, short duration cams close the exhaust valve too early to let the LT header pull a vacuum on the chamber. They also don't open the intake valve early enough to allow intake air to rush in and take advantage of the vacuum.

So, the most power can be obtained by using an LT header with large enough primaries to not cause a restriction, and match the cam to the header style.

Mike

 

Yeah, the 11.70's were on the bottle. When we got to Cayuga that night it was just about to close. I managed 3 passes. 11.90, 11.84, 11.75. Never got the chance to see what she'd do N/A. I'm hoping now with the headwork, I'd run 12.80. Only time will tell. We'll see next spring if I can find an insurance company and bring the car back out.

There were no problems installing the larger valves. Atleast, not anything my mechanic told me about. Yes I still have the stock shortblock. Next winter, I plan on going to a complete "forged" rotating assembly. Low compression 355 with an ATI and 12# boost. 550RWHP here I come...

Yeah I live in Scarborough, how 'bout you? I'd gladly meet up with you and go down to the track sometime.

 

Great link!! It's so much better to see real data than just going with what people think is better.

Dan

 

hey 93 formy, good move with the jet hots. Should see a big low end difference. For me I cannot keep the car from spinning the tires. If you can get your car to hook then you will book. That should drop your 60-foot bigtime and increase your et alot, especially if youve got alot of work done.

 

I guess now i will post on this. Have to agree with Mike above.Dont you think the big time racers in NASCAR would be running shorties or mids, if there was more power there.Kinda blows up the shorties and high RPM theory.I agree the car set up has a lot to do with it.The guy that didnt gain from LTs has some probs.And Frank ,I would like to see you put some LTs on,11's would be there.My input.

 

I didnt feel like reading through 6 pages of posts, so sorry if this has already been said. I would only switch over to long tubes right now if you can find someone to buy your shorties. If not, any shorty header will flow a hell of alot better then stock manifolds, so i would spend your money elsewhere at this point in time. My 2 cents.

*EDIT* I guess i should have read more then just the first page, i didnt know you had already ordered long tubes

 

Have you bothered to look around? You're like one of the only people advocating 1 3/4 mids...and if I see you post your "I ran a 12.0 with mids" one more time I think I'm going to scream! How about people take what they want from this thread and you stop pushing your "mids own!" BS...people are tired of hearing it.

 

Well, I don't know about that. After looking at the actual test results of headers when they break down primary size and primary length, the 1 5/8" mids are the right headers for me also.

1 3/4" LT's are not always the best choice. They will not make for faster times on all cars. In fact, in many cases, they can be slower than mids.

LT's are great, and so are mids. Just depends on the setup.

You do see him post a lot about the fast time that he has with mids, but I understand the reason for it. WAY too many people automatically think LT's are better.

I could have just as easily went LT's, but chose not to because the mids will give me better gains in my car with my future cam, stock heads.

Dan