My Camaro originally had the HSR since I bought it. L98 is running off factory heads and cam, only a little internal work done to it, like being bored .40 over and new rocker arms. People have been telling me that it's practically against the law to run a HSR on stock cam and heads, as it is a high-end intake on a low-end engine.

I have been disappointed with the car's performce for all that has been done to it and I'm starting to wonder if the intake is truly the problem, it's powerband does not match the powerband of the engine. So what do you think? I really don't plan to upgrade the heads and cam, I don't want to go over the top with the engine... but do you think another intake would be better, maybe one that has more of a low-end powerband? Heck, do you think even the stock intake would perform better on my engine than the HSR?

 

If your sig is current, then your problem is the cam / heads. The HSR starts to make power right when the stock cam is all done - even if they do claim +40hp on a stock engine. You've got some good bolt ons - you just need to finish it off.....

If you put the TPI back on, you'll pick up the low end power that the HSR takes away. If you don't want to mess with the heads and cam, then that is probably your best option.

Also, that TB is too big for a stock engine - a 52mm would be a better choice.

 

I'm with bubba on this. Heads and cam. If you ONLY drive it around town, then a torquier intake like the TPI would work. But don't get me wrong, it's not gonna be a night and day difference. ...and if ya get on it much, you may be dissapointed because you'll lose a little up top with the TPI. I wouldn't have put the HSR on, but since you got it that way, I wouldn't take it off either.

No matter WHAT intake you run, the stock heads and cam are gonna hold you back. Unfortunately, the stock pieces just aren't up to today's performance levels. The next step really is heads and cam. No shame if you're not up to doing that, but it is what it is.

As for the 58mm TB, it's really not a big deal on an intake that's already is able to flow TOO MUCH air. On a TPI, where high port velocity helps torque, the 58 total overkill, but even then it's debatable whether or not it hurts. Some swear all day that the bigger TB helps, some swear all day that it hurts. I've never seen a test prove one way or another on a TPI. But yes, it's more than you need, no doubt. -but since ya already HAVE it, no sense gettin' rid of it!!!

 

Eehh... that's what I was worried about. I've been considering just getting some used ZZ4 heads and cam for cheap and putting those on there and seeing how they do. I don't want to spend a lot and I know the ZZ4 stuff is at least a slight upgrade over what I have now.

 

I have a stock l98 that i put a HSR on and im am extremely happy with it. The tpi was nice, but i wanted to go fast for cheap. I really havent even got to it on the highway, but driving it on the street there is a huge differnece. I too know that the heads and cam are holding me back, but it still is fun to go from spinning tire halfway thru 1st to hooking and launching like a bat out of hell. I can def fell the difference with the hsr and am never going back to tpi. I have owned the car for 4yrs and wish i switched a long time ago. With what ever u choose best of luck and hope u r pleased

 

Has the engine been tuned? The HSR completely changes the VE of the whole engine. Your engine probably runs really rich and a simple tune will get rid of the sogginess down low and get a bit more power up top.

You don't have to spend big money on heads to get good power. Check these out. Great power from those for a very nice price. Then maybe a Comp XE274 and you'll be laughing (after a tune.)

 

I would't mess with either the intake or TB but I do got to ask you if you know what has been done to the chip at all? Maybe some tweeking in the prom might change your mind on things.

 

That was going to be my next point. I have a adj maf and that helps, but i have the burn1 and also have to adj ve tables. With my reativly stock car, and a stock tune, i lean out the maf and in turn richen the fuel mixture. helps out alot compared to keeping the stock setting on the maf. When i first started the car it would idle and run like crap. but know that i adj the maf i have tons more power. Now i cant wait to start plugging away at a custom burn

 

I am buds with two guys from PCMForLess and it has been custom tuned to the HSR and everything else the car has. I did notice a nice difference with the new tune, but the car is still only running low-mid 14's when it should easily be hitting 13's with what it has.

Someone posted those $1000 heads... exactly why I don't really want to get new heads, I don't want to spend that much. I'd much rather get something like these here for fraction of the cost of new heads.

 

Why so against nice heads though? I'm sure you spent good money on your car, or good money on those mods if they didnt come with the car.

Obviously used heads will be cheaper, just be careful of what you buy. Those heads have 72cc chambers. That will lower your compression, plus that auction still has 5 days to go up quite a bit.

But if you really want to be a penny pincher, find some one local to a swap with you. You get their stock TPI and they get a HSR and the prom. You might make a bit of pocket change back.

 

Well.

If you got those heads for under $500 i'd set them on the angle mill and shave 'em down to about 60cc. That will do two things, will keep your compression in check, and will change your valve angle making a little more power.

The flow numbers seem to be pretty good, its the chamber size i'm concerned with. I don't get why people order heads with big chambers. Even for a turbo application a small chamber and reverse dome piston is the way to go.

L98's run low 14s high 13s. My cousins '90 vette runs 14.2 every pass, and my buddy's GTA with my tuning goes 13.8-13.9 at aound 95mph every pass. Both with stock L98's, the GTA has headers. Seems like you have everything else right, you just need the heads and cam to compensate your intake, exhaust, and so on. A 224/230 camshaft and some 60cc heads would be killer IMO. It will raise your compression to around 10:1 give or take, which will spike the DCR with the smaller cam, but with good fuel you should be happy. (400+hp happy).

-- Joe

 

Are u sure that it is a l98? My stock 87 350tpi used to run 14.7s all day on street tires. I cant wait to get to the track with the mods ive done. Something is definitly not in line if u are running those #s with that setup. I would dig deeper and find out what is going on. You should be well into the 13s atleast, and with a good slick and launch maybe high 12s

 

"On a TPI, where high port velocity helps torque, the 58 total overkill, but even then it's debatable whether or not it hurts. Some swear all day that the bigger TB helps, some swear all day that it hurts."

FYI.
Ran a comparison to prove the point.
100K '89 Vette L98 ,ZZ4 cam,SLPbig tubes,ported plenum, headers ,3.07,A4

18 runs with stock 48mm, then 12 runs with 58mm BBK.
All same day , no tuning between changes.Just TB swap and set TPS.
No loss of bottom end (as claimed by some) with 58mm; 1.7X all day (MT ET steets)
ET's near enough the same , tank was getting lower at end of day could account for 12.9XX v13.0XX with 48mm
Marginal improvement in MPH.

Slight loss of street drivibility when trying to inch forward in traffic otherwise no change in manners.

Definately not the best bang for $$$ but won't kill your car as some claim
(58mm is for my race 383, already had on shelf)

 

That's been our question of the century... I know a few people that only put in headers, exhaust and a tune and run 13.9's on L98. Sure I haven't ran the car yet with the new tune, but it doesn't feel like there's a HUGE difference in performance, maybe only another .2 or so quicker. I can launch all day long around a 1.8-60ft on street tires so I got a good launch, I just fall flat on the top-end which is making me curious if the intake is my problem.

 

If it falls flat on the top end...the HSR is not the problem. That intake is design for 6500 rpms stock. Heck it will flow plenty enough at 7k for 760hp. So where does it fall on its face at. If its after 5k, its the cam....you need to upgrade.

On my 383, it will pull to 5500 without any problems but I need a bigger cam for 6k which I hope to be doing shortly.

 

I don't see where the 58mm throttle body hurts the runner flow. If anything it doesn't hurt or it helps.

The throttle body needs to flow enough air to keep the plenum around 100KPA at wide open throttle or as close to atmospheric pressure as possible. You want no restictions of the air into the plenum at WOT. This would include the airfilter and intake tract.

 

at least you have a 350 with a better cam than my 305 has.
My 305 is stock and I picked up about 4mph in the 1/4 mile with it. 89mph with TPI and 93 with the HSR.

 

I hit around 96mph in the 1/4. So I'm hitting 1.8-60ft's with a high 90'smph, so I'm doing fairly decent... I just get off to a quick start and then just don't gain much more after that.

 

For something that would be rather inexpensive for a bit of gain, try some 1.6 rockers. Will give you a bit more to work with.
Even with stock heads that cam is killing you.

 

Good info right there thanks for sharing, I to never noticed a loss going with a BBK 58mm TB myself.

 

I will trade you my ported TPI setup off my 91z28 for the HSR you have.

 

Cam, what is your base timing set at? HSR really like aggressive base timing or they tend to be sluggish. I got mine set at 14*, but might be too much for stock heads/cam. As far as fuel psi mines at 35 with 24lbs SVO injectors and I had to turn down the fuel tables from the stock tune. If you ask me I would play with the timing before I messed with fuel tables, unless you like doing things twice. BTW I have another NEW ZZ4 take out cam F/S @ $120.

 

the hsr is a better overall intake... period. not only does it breath up top but down low too. so it will make power on an otherwise stock motor. the thing you want is under the curve power, not peaky power that the tpi brings. look at the runners, they arent short but are geared to gain power everywhere. in otherwords... it could feel less powerful but it will pul and pull past what the tpi runners ever could. the tpi is decent but it is fundamentally flawed. instead of going backwards...put in a tame cam that tailors to the intake. like a 224/224 type cam with XFI or XE lobes.

 

I agree with the previous post. You obviously are worried about performance if you take it to the track... Pick up a cheap cam and some decent heads and have fun with it. If you want to digress to the stock intake, don't plan on making performance a priority. Modifying any car is expensive you'll be hard pressed find a 12 second 3rd gen with less than $5K invested; the question is- How fast do you want to go?

 

I think you've got problems other than the intake/cam/heads. If you're only hitting 96mph with a 1.8 60ft, then your problems are elsewhere. The stock cam is good for trap speeds over 100mph . Check the basic stuff like fuel pressure and base timing. Maybe your fuel pump is dying or timing is off. I had my car doing 12.9x at 102-103 on the stock heads with the base timing set at 10 degrees. I backed it off to 6 and immediately went 12.9x at 105-106. The HSR is definitely not the problem and although it obviously isn't helping, I don't think the cam is messing you up that much either.

 

Those are similiar to my car w/o the procharger.. low 14's w/1.8 60 ft times.. I did EVERYTHING to that car and that is all she would do.. I had GOBS of torque and usually pulled awesome 1/8th mile times.. Add a procharger

 

Good luck with your car. I think you know what you need to do. I know that a test I read a long time ago showed a DECREASE in low end performance on a stock TPI with a 1000 CFM TB put on it. It killed velocity and hurt the motor, the stock 502 RAMJET from GM uses a 48 mm TB, VELOCITY. Anyway you can get a stock TB for pocket change, I'd try that just to help the low end.

 

fwiw, I had a Miniram and trapped at 115-116 mph and with the HSR, I still trap 115-116. Same 406 CI, so the HSR can handle my RPMS, I shift/max out at 6000RPM

You have to have heads to breath and a cam to match the heads.

 

Well, I have high hopes for the HSR now that I just put in a LT4 Hot Cam and LT4 valvetrain. Hoping to have the car running by tomorrow. Do you think it's honestly worth to go to a smaller throttlebody instead of my 58?

What about timing... one of you said to bump my timing to around 14, another said around 9, little bit of a difference there. Since I had it timed originally, I completely forgot where it's at, I'll see what I can get it timed to tomorrow once I get the engined re-mounted and hooked up.

 

LT4 hot cam outta wake your engine up a bit. Let us know how it goes when tuned.

A stock TB w/airfoil will provide 700 cfm of dry flow. more than enough for your engine.

 

So you think I should sell off mine and just pick up a stock TB? Really think I'm just pretty much overloading the car with my TB?

 

I dont know. Your engine is FI so you dont have to worry about the fuel being suspended in the air as if it was carburated. Get a hold of a stock one and see if there is a difference. If they both feel the same, then sell the 58mm on ebay for some cash.

 

I may do that this spring. I'll swing by the junk yard and snag a stock TB and see what it does. Hell even better, I'll take it to the track with me and swap'em between runs and see how that goes(true testing right there ).

 

Did you get your car running?

 

Actually... YES I finally did! I made a little thread about it in the TPI section, took me a month and 4 days since the night I started taking stuff off before I got it started again the other day. I only got to work on it for few hours here and there, but whole block came out, fresheneded up, and then went back in with the new goods.

Started it for first time with the LT4 Hot Cam on open headers, sounded tough as hell, but obviously pretty loud, but looked a little tackish/mean with no hood on the car when driving around the neighborhood. Summit screwed up my order with the new headers, which I ordered nearly two weeks ago, and they are SUPPOSED to be here Thursday, so I temporarily put in my old headers to get car going. Now I just need to get my timing set and my shift points readjusted and I'll be good to go. Someday real soon I'll have pics and vids up of the new setup.