Phoenix'97

I start to run into problems because no one has done what I want to do. The only guys I can ask are the TPI guys and especially those with L98s, both the F-body and Corvette owners. However help is almost non-existent since some of those guys are modding or already have modded their TPI engines over to LT1 style intakes and better flowing heads. So I am left with an assumption game. The 1991/1992 L98 would have been the closest thing to the LT1 and with nearly the same compression ratio. So, I am left with reading material on L31 Vortec head swaps on stock L98 engines with TPI intakes and trying to figure things out from there. Some guys have used the ZZ4 camshaft with the L31 Vortec heads without problems although I am not certain they made the modification to allow for more lift and swapped out springs and so on. However, using the stock B-Body LT1 camshaft may be all that I need when paired with this combined set-up, and if I can get away with as much increased compression as an engine builder deems safe for 91 octane gasoline.

I regret swapping over to my shorty heads due mostly to the pain of changing spark plugs when factory style exhaust manifolds made the process so much more easier. Then, if I want other modifications done, such as removing my hydraulic power steering for an upgraded electronic steering unit, and doing other new-school technology upgrades, those shorties are going to be in the way. Fortunately a racing parts company actually made improved reproductions of the factory exhaust manifolds which exist for race cars because of the room they give on the SBC block. So, if racers do use these factory exhaust manifolds then they can't be that bad. Plus, I feel like my shorties have reduced some of my off idle low end torque. The car was better before I swapped them, so in the future those shorties are going bye-bye.

ACE1252

Racers only use the stock manifolds because they are forced to due to series rules/restrictions....so the argument that the stock manifolds are great for performance is nonsense. The stock manifolds are terribly restrictive and should not be considered for any kind of a performance build. I've got the numbers to back it up because I left them on the car after my CC503 swap. I dropped 0.4 sec and picked up around 5mph in the 1/8th mile after only swapping from stock manifolds to long tubes. The results speak for themselves.

If you want nothing more out of a F-body but "butt-o-meter torque", I personally think you need to find a good clean 3rd gen L98(or a diesel truck) and sell your 4th gen before you screw it up bad enough to where you can't get anything out of it other than scrap metal value.If you have money to burn, move forward with your plans. If not...you need slow your roll on what you are thinking on doing with that '97.

Phoenix'97

I was not making an argument. I was just stating that they offer this product and for anyone who may be looking for factory exhaust manifolds for their LT1 or to use them on a first-gen SBC, then this place offers them. I am aware that the stock exhaust manifolds are restrictive but after fooling around with aftermarket shorties, I can say that I am not happy with my decision and that the room those restrictive manifolds gave for spark plugs and wires was so nice compared to weaving fingers in and out of oddly kinked and curved mandrel bent tubes.

I am not selling my car for a third-gen and I am not swapping engines. So it is perfectly fine to modify for racing but to give me a "butto-o-meter torque" monster, well that is just downright absurd? I have a very specific set of guidelines for this build: EPA rated fuel economy can not be reduced but improvements are welcome and try to improve low and mid-range torque as much as possible with a small camshaft.

Now, I have been contemplating using either the B-Body LT1 camshaft or the ZZ4 camshaft with cast iron LT1 heads and keeping my LT1 intake. However, I feel like I am missing something from this to peak the torque curve as much as possible.

merim123

iTrader: (11)

ACE1252

When you start talking SBC heads on the GEN II platform just to move the torque curve a few hundred rpms lower, absurd does start creeping into the picture.

Phoenix'97

I am a college student and money is getting tight trying to keep my 1997 Trans Am going. As much as I like the fourth gen corvettes, I really don't want to buy a second car. My daily driver is my 1997 Trans Am, it's not a spring/summer only car which is why my performance goals seem so backward to those who focus on squeezing as much power out of these cars and their engines as you possibly can. I basically want a grocery store car but more significantly, I want a second generation L98 which is what I want to turn my LT1 into. Can it be done? Yes. The question however is how to go about it and do it right. I need as much torque production off idle and up to 5000 RPM as you can get with a small camshaft that is fuel efficient. The TPI intake will help to peak that torque curve to get the most out of it within the RPM band the car spends most of it's time in. That is the game plan...

Phoenix'97

Okay, so let me forget about the L31 Vortec head idea. I will have to stick with LT1 heads but desire the cast iron heads. Now I need to figure out how to get a TPI base made that will fit onto my LT1 heads. Either that or spend the money to have a machine shop modify and add material to a factory TPI head to get it to match and bolt on to LT1 heads. Either way, customization is going to be required.

The Batman

iTrader: (4)

There are cheaper, more effective ways to accomplish your goals. Gearing would be a good start.

merim123

iTrader: (11)

ACE1252

The only thing I did to my Z28 when it was my daily driver ('99-05) was a cold air intake and catback exhaust. I kept everything else stock. Like you, I was in college....and I was married. Didn't want to compromise my daily driver for some HP. Could not afford it. I didn't start significant mods until I had another daily driver, it was paid for, and more of a backup car/toy.

Since your money is tight, you need to focus on making the grades in college and not worrying about mods to the car. Once you get a job putting that college degree to work, get some coin in the bank, then think about car mods.

Fast355

I personally would not touch the F-car cam. I have put it in numerous L31s and it wakes them up compared to the B-car grind they came with that was installed 5° advanced in them. The factory L31 cam is unimpressive in the lower rpm range you are talking about as well. My Express van had a LT4 cam with 1.6 rockers about 8 years ago. It made enough torque down in the 1,200-1,500 rpm range it would pull the van around town and uphill in overdrive with the converter locked as low as 40 mph. I have also had the 395' Marine cam in the same van. In the lower rpm ranges between those 3 cams you honestly cannot feel or tell a difference. However once the tach climbs. The factory Vortec cam is a dog, the marine cam is a bit stronger, but the LT4 cam pulled like a freight train.

I have also had both a Vortec truck intake manifold and a TPI intake on the same engine. The TPI intake and Vortec intake with ports the length of the TPI base plate both felt about the same off-idle up to about 2,500. From 2,500-4,000 the TPI made a bit more umph. From 4,000-redline for all practical purposes they felt exactly the same. The runner length of a TPI resonates strongest around 3,200 rpm and in other areas of the powerband the runners can actually cause torque loss. A dual plane intake makes more torque under 2,500 than a TPI for example. You could consider converting a dual plane LT1 intake to port fuel injection similiar to the Mercruiser MPI intake that is basically a performer rpm with injector bosses added. But bottem line your not going to get the torque you want without adding stroke and thus cubic inches. 6" rod 396 would be the best bet!

moehorsepower

iTrader: (3)

I see nothing wrong into pursuing onto "something different" dept. Its no difference than others wanting to build a 302 or 327 LT1, at times there may be way better options but if you have a goal to try out your idea, Id say go for it, First I would start with asking competent machine shops about your thoughts, but as said, stick to your college, direct all your funds for schooling then maybe go for your goals, Good luck in you search for the torque monster..

merim123

iTrader: (11)

94TAisfast

I'm not sure if I mentioned this before, but make sure your builder has worked on LT1's before you go taking his word as gospel. I was about to go all in with a shop after getting my heads gone over, until he told me that he "knows what he is talking about, and I was off my *** for wanting 12:1 on a street engine." He then proceeded to tell me that what I needed was 9:1, and that if I was going to run 93 from good stations, he would even add another half point. His justification for the factory compression was "manufacturers make mistakes sometimes." This was someone who builds SBC and LS engines left and right, and has a great reputation.


You seem to be falling into that "old school mentality" that a lot of guys think the LT1 fits into. You have a wealth of information right here from people who have built these cars, and you are telling them that you don't agree with them because they haven't put old technology on a newer engine. And if I am not mistaken, the L31 is closer to the LT1 than the L98 is. They share the same head ports and flow numbers according to this link, and other sources you can easily find. If you're so obsessed with torque that you just NEED to have as much as possible, look into RV cams and converting intakes that are designed for towing with a 350.

You will gain absolutely nothing worthwhile from putting L31 heads on your LT1. If you want better heads without porting, get some iron heads from a B-body, which are good for a few CFM more than the aluminum heads. But the aluminum heads let you push a little more compression, so some warmed over aluminum heads would do wonders for your power output.

I was specifically referencing the fact that the shorties don't do anything for power. They are a looks only piece, where long tubes actually help. I switched from shorties to long tubes in the beginning of last summer, and was only a tenth off my record time, with the same trap speed. Previous record was 13.5@104.5 using shorties and race gas, made after making 25 consecutive passes in a day, with Hoosiers at 20lbs, at 65*. New time was 13.6@105, first pass of the night, street tires at 32lbs, at 80*, with a mild header leak at the flange. Long tubes make power, stock manifolds and shorties do not. If people race with them, it's because they're in regulated classes.

I am guessing that you're really new to the modding scene if you're complaining about the spark plugs on these cars, because once you've done them once, they become a snap. It's still a pain, but much less so than the first time. If you really are looking for more torque, then keep your factory heads, get some long tubes, 4.10s, and an intake and tune and you will be happy.


My apologies. I just read all of the replies. I'm in a similar pair of shoes, being in college and modding my car. My car is my summer ride, though. Something to keep in mind, what "feels" faster isn't always what performs better. The L98 intake likely won't help you, if anything it will hinder your performance. The L98 runs out of steam early, so it feels like it's got more low end. It's the same concept going from the LT1 to the LS1. People think the LT1 makes more torque, but if you look at a stock dyno comparison, the LT1 makes less torque and runs out of breath around 5700 rpm, where the LS1 just keeps on going. There are a lot of things you can do to make your car feel better, but I would have to recommend the basic stuff that can be accomplished in a day if this is your daily: gears, intake, exhaust, tune. This will make it a fast car, and it *could* improve your fuel efficiency. Modding for fuel efficiency is one of the dumbest things you can do, because by the time you've installed a new torque cam and exhaust, you've got at least $600 in parts for the engine, and probably the same or more for the exhaust. Add money for the tune, and you have just spent enough money to buy probably about 500 gallons of 91/93 octane. If you got 15mpg city, that could've bought you another 7500 miles of city driving, which assuming you picked up 2mpg you would need to use about 3750 gallons to see a cost savings after modding the car. And that's not including the cost of gears or an intake, which are probably gonna run you another $700-800.

Long story short, if you want a fun car, do bolt ons. If you want a fuel efficient and reliable car, buy something else.

Fast355

The LS1 does not make more torque, the LT1 does. Stock for stock the LS1 is not even close until the revs get over 4K. Same thing as a 5.3 vs L31 in a truck. A LQ9 6.0L barely makes the torque a L31 does and only betters it above 4,000. Talking stock for stock. Once you start tuning and adding parts to both yes the LT1 and 350s will start falling behind but the Gen3 will never touch a Gen1 or 2 below 3,500 rpm until you add boost.

Shorties actually do add a good bit of power depending on how bad the OEM manifolds are. The LT1 and LS1 manifolds are some of the better factory parts but even those will see noticeable gains.

TPI intake will make more mid-range torque than about any other SBC manifold. It is probably GMs best truck intake they never put on a truck.

94TAisfast

Do you have any sources on that? I have yet to see an apples to apples dyno comparison between an LT1 and an LS1 that shows the LS having less torque. The stroke is longer, the heads were a better design than the best racing heads you could find for a 350, and had smaller ports, so you had all the torque you could ever need.

I was referencing F-bodies, because that's the car mainly discussed in this forum. And in my own experience, I didn't see much of a gain when two of my friends went to shorties. They came on my car when I bought it, and like I said, I managed to pull an almost identical time in 20* hotter weather, on a shakedown run, with less traction, and with about 20 less octane. So shorties may be *better* to some people, but as far as I am concerned, they aren't worth it when for $100 more you can have headers that will actually help your performance.

The TPI intake peaks out just over 4000 rpm on a stock TPI engine, which has heads that are pretty questionable, especially compared to LT1 heads. So I'd expect to see a torque peak around 4k or maybe even a bit lower if the car has any decent mods.

Fast355

I saw the comparsion first hand on dyno day of a Chevy club between a 295 hp LM7 with an intake, long tubes and tune. A 300 hp Marine L31 with tri-y headers. Then a LQ9 with an intake, tune, long tubes and exhaust. Same dyno, same day, very similar weather conditions. In the 3,000 rpm range the L31 was 40 ft/lbs stronger than the LQ9 and close to 100 ft/lbs stronger than the 5.3. The LS engines make their torque at a much higher RPM than a Gen1 or Gen2. The port size on a LS is substantially larger than a 350. They also have a smaller bore unless you are talking about a 6.0L.

94TAisfast

I would love to see these cars in person. The 5.3 I would understand. The other engines you're describing sound like they were dyno'd in trucks as opposed to the marine engine, which usually wouldn't get swapped into a half ton truck. And the LS makes PEAK torque higher than a gen I/II. And if you care to re-read what I said, I did say "racing heads." And the bore very rarely dictates the torque production, with smaller bores typically making their torque lower in the RPM range, which really doesn't help your argument. There is no comparison between a mostly stock truck engine and a lightly modified marine engine cammed to make all the torque in the world below 3k.

I'm not getting into a pissing match. I replied in this thread to give OP advice, not argue with a keyboard warrior on why he thinks that the 350 should've never died. I wish the OP good luck.

Fast355

Not being a keyboard warrior. Perhaps its to educate rather than saying something blatantly that makes little sense. A marine Vortec 350 IS a truck engine with a different intake manifold that still uses the same intake runners and a cam with slightly more lift, 2° tighter LSA and a few degrees more duration both intake and exhaust. The 395' marine cam is very similar to a factory Vortec cam. Vortec cam is the B-car LT1 cam only difference is it drops in 5° advanced in a truck. 191/196 @ 0.050, 0.414/0.428 lift, 111 lsa and the marine cam is 196/206 @ .050, 0.431/0.451 lift on a 109 lsa and it sits 3° advanced. Truth be known there is very little torque difference between a L31 cam, the 395' marine cam or the F/Y car LT1 cam. So to say the comparison is not valid....That is a long shot. The L31 was also backed to a beefier driveline than the 5.3 or 6L.

ACE1252

Speaking of something that doesn't make much sense.....I like my LT1 machine, but I'm pretty sure the above is ALL kinds of wrong. The LS1 spanked the GEN II LT1 in both hp and torque stock for stock. There was all kinds of guys saying the LT1 was stronger down low, but it was just not the case. The LS1 beat the LT1 everywhere on the curves. The proof to back up that the LS1 wins hands down is in GMHTP, March 2000 issue, page 64.



Stock LS1 vs LT1 Dyno