Ran accross an old article that was talked about here on this forum around a decade ago..... based upon glossing over some threads here on this forum over the last few months, I think a lot of you might benefit from this data, so I am re-posting. I have much more data I might post in the future for the L98 guys based upon my personal results.

Interpolate the data as you please....

This is for the LT-1 guys, this motor is a stock LT-1 with a manual transmission on a chassis dyno. This shows the results of a few of the most basic bolt-ons.

Base stock motor baseline:

278 rwhp @ 5000 rpm
319 rwtq @ 3800 rpm

Add 52 mm Throttle Body

281 rwhp @ 5000 rpm
322 rwtq @ 3800 rpm

(As expected, not a lot with a throttle body increase, especially on a stock motor)

Add March Pulley & K&N cold air box with filter

291 rwhp @ 5000 rpm
329 rwtq @ 3800 rpm

(not bad, better than most might have thought)


Add 1.6 roller rocker arms & Fresh valve springs

307 rwhp @ 5300 rpm
340 rwtq @ 4000 rpm

(I suspect a good part of this 16 rwhp gain is from the fresh springs.... the added rpm adds credence to that thought)

JBA Shorty Headers

317 rwhp @ 5500 rpm
350 rwtq @ 4300 rpm

(These headers probably would have seen better results with a modified motor internally)

Final increase over stock with the Full Torque Curve:


Bone Stock baseline........Finished.Mods......Diffe rence

rpm....... HP........TQ.......HP.......TQ.......HP. .....TQ
2500.....147.......309.......158.....332 ........11.......23
2800.....166.......313.......178.....334 ........12.......21
3000.....179.......314.......190.....334 ........11.......20
3300.....199.......317.......213.....339 ........14.......22
3500.....211.......317.......228.....343 ........17.......26
3800.....231.......319.......250.....346 ........19.......27
4000.....243.......319.......265.....347 ........22.......28
4300.....259.......317.......286.....350 ........27.......33
4500.....267.......312.......296.....346 ........29.......34
4800.....277.......303.......311.....340 ........34.......37
5000.....278.......292.......317.....333 ........39.......41
5300.....277.......275.......316.....313 ........39.......38
5500.....274.......262.......317.....303 ........43.......41
5800.....n/a.......n/a........307.....278.......n/a......n/a
6000.....n/a.......n/a........305.....267.......n/a......n/a

Just bolt-ons and now up to 317 rwhp.... for you guys that do not dragrace, understand, that with practice, this is enough power to row yourself well into the 12's with a strong clutch and some sticky tires.

 

Great info!!! Thank you for posting.
I have not seen underdrive pulleys for the LT1 Corvette. Where can they be had?

 

I just got a set off ebay for $50.
http://www.ssd4u.com/streetsmart_210.htm

 

I'd research it first. I remember hearing about problems with pulleys on later C4's. ATI is usually considered to be the best.

http://www.atiracing.com/products/da...ts/damserp.htm

http://www.aspracing.com/gm.htm

 

good info

 

Oh I see.... they're combo's on the LT-1....

 

Uh-Oh, what type of problems???

 

thats great stuff man

 

Strap on a cat back(my slp pro flow gave me 12rwhp when it was stock), and you have 330rwhp.A tune may give you an additional 10. That just about puts you at a stock C5 Z06 .

 

http://forums.corvetteforum.com/sear...rchid=10206791

 

Sounds alot like my car when I first got it in 98 (1993 coupe). I had:

K&N + cut lid + March pullies
Crane 1.6 RR with new replacement springs and pushrods
Watson Longtubes no cats stock exhaust.
4.09 gears.

12.7X @ 111 mph all day long

What is amazing is not just the peak power. Look at the difference in power at 4500 + rpms in hp and torque.

 

I'm curious about the pulley set you bought for your LT1, since the crankshaft pulley is also the balancer on an LT1 the price seems incredibly low. Most replacement balancers with stock diameter are quite a bit more money. Have you installed your pulley set yet and if so do you notice any engine vibration? Can you post a picture by any chance? Thanks.

 

Some great info there. Underdrive pulleys seem to be a pretty good deal, adding HP and possibly MPG. How badly do alternator underdrives affect power output? Our cars have alot of electrical components that could be adversly affected. I mainly use my Sled for road trips so I wouldnt think that long term highway driving would take a toll but what of city driving? Would alot of short hops around town eventually result in battery discharge sufficient to affect starting? I live in a small town so I rarely run enough to get to operating temps much less replace the amps lost to cranking. Of course recharging the battery would be a good"excuse" to take a little cruise wouldnt it??

Anybody running underdrives experience any bad effects to their electrical components, especially in a early L98? Thanks and sorry about the hijack.

 

It doesn't take much to wake up an LT1, though I'm not a fan of underdrive pulleys on a daily driver.

 

That was one of my questions/concerns about these as well. The ATI is an actual replacement balancer though. It's very expensive and comes in 10% under drive.

Thats another big concern. I have too many electrical accessories already. I wonder if anyone is running one with an EWP on a daily driver.

 

As far as the L98 is concerned, well all know you the intake is the biggest problem. I've got a lot of common mods to mine and I still feel like its holding me back. I'd feel lucky to make 270 rwhp.

 

Me 2 years now

 

Nice Post; really looking forward to the L98 data

 

Neither Me !

 

I had the march pullies but they were discontinued about 8 years ago. they were $550 + back then (cdn). AFter the balancer broke (due to the shoppe hammering it) I went with ASP. Asp is top quality.

I used the ud pullies for 6 years as a dd. No problems whatsoever. with my big sound system on at night with the headlights the interior lights would dim just a tad at idle only. any movement and the rpms are always above 800 so there was no problems at all.