I got in a couple of pulls today after the installation of my mods on my 90 L98 auto vert. I spent some $$ and time and I have to say the before and after comparison leaves me a little The second column shows the results after the following mods:

HEADS: Precision Porting - larger valves .202"/.157", combustion chambers machined to 55.5cc, ported & coated
INTAKE: Precision Porting - port matched to heads & coated
RUNNERS: Precision Porting - 168cc, port matched to intake & coated
PLENUM: ported by me to match the runners
CAM: Comp Cams - valve lift .464, duration @ .050 intake 222 exh 226, lobe separation 114
HEADERS: Hedman 15/8" long tube
CAT: Random Technology

The intake and runners are Edelbrock Hi-Flo and were installed when the numbers in column one were recorded. They just weren't ported. I also had 1.6 RR's, 24lb injectors, K&N filter and Flowmaster II's installed. These parts are still installed and are part of column two's numbers also.

Column One Column Two
Max RWHP: 218 Max RWHP: 241
Max RWTQ: 288 Max RWTQ: 307

I will say that I am still working with Alvin @ PCMFORLESS on the final tune and the car ran rich (11.8/1) but with the time and money I have invested I am still a bit disappointed. I thought for sure the addition of heads/cam/lt headers would be worth more than 23 RWHP and 19 ft/lb of RWTQ. The dyno was a DynoJet and if I had the ability to post the data sheet I would.

Take a look and tell me what the numbers are saying could not be all my set-up can produce. I know L98's are known as torque motors but surely I have done something wrong. Don't get me wrong the car seems to run good. I have not taken it to the track so I do not have an et baseline. I was thinking this set-up would be in the 12's but it now appears I was over enthusiastic. Tell me where I have gone wrong and what you think what I should expect. Sorry for the long post.

90Indy

 

Im no where near a expert but one thing that jumps is is the cam. It just seems pretty mild. Also the A/F plays a big part in tuning. Getting it nailed down may produce more power than you think.

 

The cam selection is based on installing a blower this winter and passing emission's testing. I still find the numbers hard to believe.

 

What do your heads flow for CFM at various lifts? Stock intake style sucks, you won't see big power out of it.

 

Listen to hippy he had exp with TPI and SR/Mini Ram intake and myself too, look at my mods very similer to yours the only diff is your cam lift is less than mine which is .520 with 1.6 RR's. Do yourself a favour put SR upper or mini ram see the diff will result atleast 30-50 RWHP and torque too. Your TPI killing these numbers.

 

Those are good numbers for still having the stock manifold even with porting. I bet it'll lay down some high 12's or some very low 13's.

Are these ported stock heads? Can you describe the rest of your exhaust system? Whats your base timming?

KM

 

Send me a datalog and a dyno sheet and i'll get you another bin emailed to you monday morning.

I would say with a AFR that fat you'd probally see another 8-10rwhp and with timing maybe another 5-6 or so. I usually keep the timing pretty conservative the first time out.. especially with the email tunes because I can work my way up to the right timing via datalogs.

I agree with everyone by saying a intake of some sort should be niext on the list.. SR or mini-ram depending on what you want from the car.

What type of exhaust do you have on the car? I've seen exhaust pick up a car like your around 50rwhp (sami? wasn't that you?)

 

The heads are D-113's and flow as follows:

LIFT CCFM
.1000 86.9
.2000 144.1
.3000 179.3
.4000 215.2
.5000 231.0
.5500 232.3
.6000 242.3

As far as the intake goes, I thought I was getting away from the stock style by going with the Edelbrock parts. At this point I do not want to have to go through the time and expense to do it over again. If these numbers are all I can expect with what I have installed then I will have to just live with it for now.

Alvin, the exhaust tubing diameter is as it came from GM. I have no pre-cats and the main cat has been replace with a Random Technologies unit. I replaced the stock mufflers with Flowmaster II's. I will send you another bin but I will have to fax the dyno sheet as I have no way of sending it to you electronically. By the way, I think you have been more than cooperative and I am not putting my disappointment on your tune. I appreciate all of your help.

I don't want anyone to get me wrong, this car is much more fun to drive than it was as a stocker. I am also not trying to come across as being a whiner. My guess is we all will experience some disappointments when dealing with the world of aftermarket mods. Surely, when the blower goes on my numbers won't reflect similar gains. Surely.

90Indy

 

I bet the tune helps quite a bit. Personally I would chuck the 2.25" exhaust in the trash, that's really holding you back. True 2.5 duals or 2.5"Y pipes with a 3 or 3.5" main will really wake the car up-get some good muffs if you don't have them. Exhaust alone was good for a few tenths.

 

Rebuilt stock heads with bigger valves and some porting
Aftermarket runners
Cam, lifters and rockers
Headers, cat and mufflers

Guys, I think what he is saying is that he expected to see more than
23 HP in return for the $3,000+ I'm guessing he has spent, not to
mention his time. I am betting that another 10-15 hp still doesn't get
him to the place he thought he was going to be by now.

I wonder about the cam selection, too. I know of no reason why a
blower cam needs to have low lift and I've read of others meeting
emissions with more aggressive profiles.

Still, I agree with his decision to pause to reevaluate. Get the
current package tuned, live with it for a while and decide whether to
continue. It is a slippery slope.

.

 

Don't be as angry as I was after both my dyno runs. I spent considerable more sums of money and got much the same results. I have tried running richer and leaner on my dyno runs and the best I get is: 249.4 RWHP and 299.7 Max torque. I have been told by several chip tuners that the only way to really nail the non-MaF cars like ours is to tune it on the dyno. They are that sensitive to the parameters. I have been quoted $1000 to $1500 for that type of tuning. Now the good news is that I can run in the 12's with this set up. 12.9 secs in the middle of the hot Summer and as low as 12.6 in cooler conditions. I am making max Torque at 3900 Rpms at 13.6 AFR. My average AFR for these runs was 13.9 .

 

Like I said, sami replaced his catback and phoned me back to say the car picked up like 50rwhp or something crazy like that.. Never underestimate the power of 1 thing not up to par.

 

Indy90, I have a 1985 L98 with some what of the same set up as you do with the exception of my bottom end,and cam. I stroked the bottom end. MY cam set up is 474 lift@.50 220 intake 222 exhaust 111 lobe sep. The only chage I've made so far on the intake system was the base. I have 24lb injectors, K&N filter, Flow master mufflers, and Edelbrock hi flo intake base. The runners, plenum,and exhaust manifold is still stock, . I did swap the stock Iron heads with a set of dart 60 cc chamber alum. heads.(not yet ported or polished) The tranny is stock and the rear end is a 2.73. I haven't had the chance to put it on the dyno. I plan to in the future. If you have better rear gears than I do, than I think you can pass in the low 13's for sure. Take a look at my posted thread "how well did I do?" I post my time on a 1/4 mile track. It was my first time out on a 1/4 so i'm using it as my base time. You headed in the right direction. It just take a little time to get it altogether.

rssshen vette

 

You do realize that with the cam you chose you aren't realizing the higher lift cfm of the heads. So you are only getting 226 cfm out of the head port job, estimated at .460 lift.
I have a 219 and TFS heads, I got 70 hp when all I changed was the cat and the bigmouth setup to a mini. My hp was FLAT from 4000-5600rpms. It just never climed above 275hp now it's close to 345hp. That 275hp pissed me off as I had a stock head/cam car that ran the bigmouth and pulled 276 hp. Your cam has decent duration just not enough lift.
Maybe next year you can cut your losses and step up to a better intake. Are you running 1.6 rockers? If not they will give you a little bit more lift.

 

I am running 1.6 RR's. I understand this will add approximately .030" to my .464" cam lift making the total approach .500". I think my next step will be to go to a true dual exhaust with larger diameter tubing. Your mention of a step up to a better intake also has merit but at this time I really don't want to take things apart and spend more cash so soon after installing the current set-up. Although it is beginning to sound like I did not make the best choices when putting it all together.

I will post my results after Alvin's next tune and the dual exhaust installation.

90Indy

 

I would guess if you go to a true dual exhaust you are going to pick up some power. I don't think you'll see 50 but I'd guess 15-20. If you are seeing 11.8-1 you will definately pick up some power when you get the tune closer to 13-1.
I had a tune around 14-1 for one of my tunes and you could literally hear the car on the dyno struggling to pull RPMs. I don't think your choice of parts is totally off you just need some tweaking. Since you are running 1.6 you are at .494 so that is a bit better for your head flow.
I too didn't think the LTR setup was as shtty as it is. Boy did I find out differently. Drive the car for a while then next year when you aren't pissed about it find yourself either a SR or Mini to replace the crap LTR. Depending what you want out of the car you can decide which path you take. If all out qtr mile is what you want a SR is probably the best but if you decide you want to push your shortblock to a few higher rpms and not fk with the bs of the SR install the Mini would be the intake of choice. Don't listen to the bull about the Mini losing SOOOO much low end tq, it isn't a problem, you just need to change a few other things to take advantage of that intake. Plus since you've installed the aftermarket LTR setup you know the joy of putting that on a car. You can jam a Mini on in under an hour and no where during the install will you be swearing on who the dumbass was who designed it.


P.S. CLIMBED

 

i agree, the heads flow pretty good for 113's, but you are truly only getting around 220cfm or so.......i think it is really hard to make good pwr with only 220cfm imo.

i still dont get why your #'s are so low. my 88 bone stock, and i mean stock was 212rwhp/322 rwtq. i then did the exhaust which the mods are in my profile, i then did some free mods, got the car dynoed again, and it dynoed around 250rwhp/350rwtq. i gained alot with the long tube headers, and i went with the 1 3/4 hookers.


i still think you will gain more with a dyno tune. they are usually $400-$500 in ontario.

 

I guess I just caught this, are you running stock intake runners that have been ported?

 

No, I am running Edelbrock Hi-Flo Runners with their Hi-Flo Intake. Both have been port matched by Bob at Precision Porting.

 

Im feeling your pain, same mods, close to the same specs on the cam same intake and im getting the same power numbers.I talked to alvin and he said the dyno looked good. like these guys are saying maybe its the intake? let me know when you figure it out and ill do the same!