GREGGPENN

On the TPIS website, they indicate (in the MiniRam description) that the main difference between the L98 and the LT1 is the intake. Specifically, the description say they have the same basic heads, cam, etc....

Obviously the LT1 has a bigger, better exhaust. So, if you put this exhaust on an L98, added a MiniRam or LT1 intake --with a tune (if necessary), would you end up with the equivalent of an LT1 motor?

If not, what would be the difference(s)? Things like the location of the distributor don't apply, but the WAY it works would.

Gregg

_twisted_

reverse cooling of the LT1

TIMSPEED

As Twisted said...
The main difference between L98 and LT1 is the reverse flow cooling heads...
However, if you take an L98 (89-91) and stick a MiniRam on it, those #113 heads are pretty good, so you'll be close to LT1 power levels.
MiniRam + Cleaned-Up #113 heads + ZZX Camshaft =

88BlackZ-51

I dont see why not. Even the exhaust makes a huge difference.

88BlackZ-51

Thats alot of cam. Do you know guys who did that, If so how did it turn out?

Curveit

113 heads work well and may suite you, but LT-1s flow a good bit better. The best port job on 113s I've heard of, only hit around 230-240CFM which is about what LT-1s flow. It would be cheaper to buy new heads,than to get them ported, and you get heads that flow better than either. If the ZZX cam is the one with 239*, it's too big; you'll lose a lot of bottom end power. Cam choise depends on how you want the car to perform.

Aggravated4life

Yeah,the intake is a major role,even though the LT1 was a new design over the older sbc set up.

Look at the ZZ4 chevy crate engine...it puts out 355 HP and is basically a stronger internal L98 motor with a carb intake.It uses stock 113 heads,carb set up,and ZZ4 cam.
What exhaust you use on it can affect it too...point is,a good intake can push the L98 into the 300-350HP range and make it similar to an LT1.

Dave Emanuals Book on sbc engines,theres a section about the LT1,and it was quoted the biggest bump in power came from the LT1's intake design,its short runner style boosting an extra 50 HP over an L98 with TPI.

85L98-84L83

Add some rear end gears and you will be in the 11's.

GREGGPENN

Really? That doesn't sound right... See the threads below....

http://forums.corvetteforum.com/show....php?t=1880792
http://forums.corvetteforum.com/show....php?t=1875788

I would agree that mildly ported 113's are probably close to LT1 heads but @ 200CFMish....

gp

Curveit

Sorry GREGGPEN... brain malfunction.( I'm old, and often stoned ) I don't fool with LT motors and was probably thinking Vortecs (239/160 @ .500"), or LT4s (250/180). How about L98s @.500" 196/170 and LT1s 214. Thats 18 CFM difference, which is still a pretty good bit. A port job would bring them up to match. I like AFRs myself...180-260/207 and 195-280/211.

GREGGPENN

Here's the deal...

I looking at swapping intakes. After a couple of threads someone posted a like to a superrod shootout of intakes. Though installed on a 383 motor, it provides the best comparison I've seen. From the comparison, I have a better understanding of the intakes.

Specifically, I was surprised at the straight-line HP curves on the miniram and HSR. Also, that very little was given away at the bottom end vs the gain up top.

I am obsessing between 1.75" large tube runners (ASM), an HSR, or mega-ported SLPs (as shown on CorvettePlenum). To be honest, I'd pick a superram but it's been discontinued, I've heard too much about engineering issues, and the SEMI-siamesed SLPs seemed like a good alternative. (aka mega-ported SLPs).

Then I discovered the SLPs have smaller runners than the larger ASM or TPIS versions. An eBay'r measured an older set at "a hair over 1.5". He didn't even say 1 5/8". OUUUUUCH!!!!! With that in mind, I feel the 1.75" large tubes could flow as well as "mega-ported" SLPs....

I also looked at the HSR pretty hard at first (especially because I have a hirise hood -- eliminating clearance issues). But, I left that train of thought because I didn't want the low-end losses. After looking at the TPI shootout article, the stock TPI vs the HSR look closer than I would have guessed. Plus the high-end gains are IMPRESSIVE!!!!

The HSR is similar to the LT intake in that it's a short runner intake. But, it really has longer runners -- which should provide a little more low-end grunt. Since I've driven a few LT1's, didn't notice low-end loss, and liked the extra pull, I'm back to coveting the HSR....

When I bought my L98, the mileage was REALLY low and the price was a HUGE value over an LT1. (I saved about $4K and got a car with 20K less miles that typically available at that time. Being the bargain-hunter I am, I opted for the L98 -- even though I wanted an LT1. This was in 1999.)

I've already improved my exhaust. If adding a short-runner intake will get me in LT1 territory, then I'd go for it. While researching intakes, I've learned more about the overall engine design -- and that changing one part often isn't that simple.

I now understand that the L98 is a "package". The heads aren't super-high flow, the "peanut" cam helps with EPA mileage, the valve springs aren't heavy-duty, and the TPI is designed to build mid-range power. For a manufacturer trying to build reliable cars, this probably helps because few driver's take the engine to it's limits. After all, it's no fun up there!!!!!!!

If I take TPIS's ad for the miniram to heart, then the intake is the only thing that separates me from getting my LT1... (kindof). The miniram is expensive though. The HSR is much less. With the longer runner design, it's seems like a better choice because it keep's its foot in the low-end torque "door".

I've heard many say intakes don't help a stock motor much. And, I probably won't do a cam. I'm not excited about heads/head-work much either -- but porting is an option. After all, I have 113 heads. Earlier vette owners WANT them, so they must not be THAT bad! I've also heard some impressive gains from stock owners who've installed the SR/HSR. That tends to minimize the opinions of those who say the swap is a waste of time.

As long as I feel the long-block of the L98 is close to the LT1, I don't see any reason why I shouldn't make the swap!



gp

(Lights fade as you see me pacing the floor... muttering HSR or ASM or SHORTENED SLP.... HSR, ASM, or SLP.... hsr, asm, slp....)

_twisted_

if I had a hi rise hood, I would have tried the HSR

mseven

Even if you wanted too they incorperated a mechanical rev. limiter, tpi.
I don't think that you can take to heart a "90-125hp" gain as was once advertised for the mini, either intake should be some gain over a stock tpi. Never did a before and after on mine but, I don't think it's worth 50, more like 30 ish?.
I think the LT-1 made the 50 hp. improvment through a combination of things. While the intake may be the biggest gain, when taking into account all the small differences in head flow, cam, and exhaust, while small individually, when added together then produced a 50 hp gain. Doing the heads and exhaust along w/intake on yours will certainly help.

GREGGPENN

TPI = Mechanical rev limiter!!!

That's EXACTLY what I was thinking!!!

GREGGPENN

So you did the mini at a different time than you installed the cam/heads? And, you think 30ish HP gain?

If the heads flow 10% better, the computer (ODBII) is better, and the cam has any diff, and the opti-spark is any better... YOU'D HAVE TO SAY THE INTAKE WASN'T THE WHOLE DIFFERENCE!!!

That's what I was thinking but I thought I might be wrong... It wouldn't be the first time....

OTOH, someone posted a 50HP gain (above 4K rpms) on a stock motor with a SR (dyno'd). Another showed over a .5 second 1/4 time with an HSR on a stock motor. If I understand the conversion correctly .1 = 10HP so .5 = 50 HP. That's at least two people who've shown radical improvement with an intake.

I understand the dyno said overall PEAK HP gain was 4HP but it didn't run out nearly as soon as the TPI!!! I have to assume this is why the HSR was also so much faster.

KeyWestJack

mseven

No everything was done at one time. What I am saying is since I did not just do an intake swap, so it would hard to understand just how much an intake swap by itself made by itself.
OBDII, or opti will not be any performance gain in hp, head flow, a couple of degrees in duration on the cam (very small gain) and exhaust being better (certainly better IMO than L98) would be were the additional gains (aside from intake).
As to the 30 number I posted would be a conservative estimate for an intake only swap. I believe the intake is a big gain, just don't believe it is worth 50hp. I prefer being realistic about gains and not over inflating the numbers. I belive as you add more to the equation (heads, cam etc. etc.)the mini can then allow the combo to make more power.
BTW, I also like the hsr (can't go wrong w/either IMO), you just need some machining for hood clearance.

rlane5

I pick up 5 mph with the LT1 intake conversion BUT it have a good set of heads on it,with a GM HOT CAM. With the stock TPI I got a 1.67 60ft but only would run 13.4s- 13.3s before ruuning out of air. THe intake would not allow the heads or cam to work but once I change the intake the car pick up mph and went 12.6s but had a flat torque curve I tried different cams and intakes but the key is the right heads and exhuast btw I had 3.07 gears at that time, I replace them with 3.73 which I was thought it would pick up e.t. it did not. I put a GM 847 with a SR, the car had good mph but only 1.9s-1.87s 60ft. I realize the key is the right head and exhuast. The LT1s the better heads and exhuast the the L98. PUMP= in and out Intake and heads in, heads and exhuast out
Randy

rodj

"But, I left that train of thought because I didn't want the low-end losses. "
Been done to death on this Forum but compared to a TPI ,losing some bottom end may actually be of benefit as regards getting off the line; more than compensated for by the upper end gains.

So long as you don't do this.
"I put a GM 847 with a SR, the car had good mph but only 1.9s-1.87s 60ft."
At 234 / 242 is probably killing TOO much bottom end.Needs a good convertor to get cam up into working range faster.

As mentioned in every hot up post;the key is the correct combo of matched parts including gears and stall.
One wrong part can make a pig out of a otherwise hot setup.

GREGGPENN

O.K. you have to have the "right combo". I get it.... More often than not, people talk about gearing and stall. But, I have a stick! How does that factor in?

At "launch", I could rev the motor as high as I want before letting out the clutch. Me -- the driver -- controls launch/spin. And, I can shift whenever I want.

I don't know the percentage of sticks vs autos in racing but I know its hard to beat the speed/reliability of an automatic. With a stick, I suppose I could stay in the "power band" by staying the gear that best matches the rpms near the power band.

If I switched from the TPI config to the short-runner HSR, I'd probably run at higher rpms more often. Down-shifts to accelerate could end up being to a lower gear (shifting to second vs third...).

Then there's the issue of the heads. I've heard L98 heads (I have 113's) lose power around 5,500 rpms. I've also heard "valve-float" happens a little past 6 grand. In other words, I'm not sure about life above 5K rpms -- and that's where short-runner intakes start buttering the bread....

I know most people think in terms of racing with talk of the right heads, cam, etc... I'm talking in the context of getting from STOCK 98 performance to STOCK LT1 performance. I want to know if the motor's are really similar and if the externals (intake/exhaust) made the difference.

To be honest, I'm also wondering how a stick factors into this equation. The intake is off my ride and I want to swap. I'm choosing between mega-ported SLPs, large tube ASMs, and a Holley stealth ram.

The HSR provides addl power above 5K rpms whereas the other two intakes primarily improve flow at lower rpms. (They both help with mid torque ratings while extending peak power about 500 rpms).

It's been awhile since I drove an LT car, but I don't remember the low end being "doggy". The LT intake (like the miniram/HSR) should sacrifice low-end power for WINNING high-rpm zip.

I wonder if LT 6-sp owners typically drive at higher rpms than L98 counterparts. After all, that's where the fun is! If so, is the motor prone to failure due to the addl stress. (I wouldn't wonder as much about a car that wasn't 18 yrs old! Obviously, redoing the heads -- and more -- would take car of everything. But, my car has 55k miles. It's not ready for the complete redo yet).

I'm trying to balance the choice between fun now, the best intake for now, the best one for the future, and what parts need to go in the process....

gp