91-Z

Had Hedman shorty headers installed last week along with new cut to fit Moroso wires, Bosch platinum plugs, Accel cap and rotor, MSD coil, and also removed the smog pump and all related parts. I put a pulley in place of the smog pump and had a 2.5 inch y pipe custom made as well.

Took it to the track Sunday hoping to see mid 13s, I ran three times with these results. 1 2 3

60'- 2.13 2.11 2.06

1/8 9.28 9.16 9.24
78.62mph 79.60mph 77.91mph

1/4 14.38 14.34 14.48
96.61mph 95.82mph 94.96mph

I got pissed after those three runs and said to hell with it. Any ideas or suggestions. It was about 91 degrees and cloudy when I ran but my car has run consistent 14.00 to 14.10's all day before in the heat at 97.xx mph. My best run is a 13.82 and I usually run in the 13.90 to 14.00 range all the time. Any help will be greatly appreciated, as I am ready to push this car into the river.

Thanks

Paul

BryanJ

I live in Madison and about two weeks out at the dragstrip in Lena mine I ran .5 slower in my 96 z. I guess its just that humid lately.

91-Z

I could understand running slower if I had not done anything to the car, but you would think that the headers and smog pump removal would make up for the heat, I guess not.

91TPI5.7

Dont forget. The headers release a lot more heat under the hood that the manifolds did. And you do lose some low end power after headers but gain on the mid and top, show a list of mods to see what area may need help.

91TPI5.7

Just saw your sig, sorry. Umm, all the intake work you did sure helps when you get in the high rpms. Try to siamese your runners, plenum and intake, flattens the torque curve. do a custom prom that advances timing, and spark , and stuff. And try a new torque converter, assuming you have an auto. there is other lil mods like an air foil, adjustable fuel pressure regulator. All this stuff compliments one another on tpi motors, and should net you some lower ET's. hope this helps.

Jim85IROC

iTrader: (2)

The speed density computer may take a few hours of driving time to adjust to the new fuel & air maps. Or... you may need a custom PROM.

David 91RS/Z28

Get that flowmaster muffler off and install a good 3" catback. The gains from the headers will not be seen until you unchoke the rest of the exhaust.

tpi_roc

David is the man to listen to



(although his website could do without the midi's )

91-Z

Hey Dave,

I could understand not being able to see gains from the headers with a flowmaster on the back, but I already have a 3" catback, the only changes made to the car were the headers and removing the smog system. Car was always in the 13.90-14.10 range before the header install. I am not as worried about not getting faster as much as I am that my car SLOWED down up to half a second and 4 mph.

Paul

chevy power

can the computer adjust the air/fuel stuff by itself after run'n awhile? i did a new heads/cam/intake set up and it idles at 2,000 rpm now, i only had it run'n 5 mins, but i figured stock computer can't work right now w/ all these mods. should i drive it for couple hours then, u think the idle will go down or what?

nsimmons

you have a vaccuum leak, or your tbi's way off

BadSS

I was there 2 weeks ago this coming Saturday in the white 86 IROC with the stock hood. It was a hot one!!!! Mine did OK with LONG cool downs in the 88 degree weather. Can't say if it was off norm or not,, that was the first trip in full street trim (minus the skinnies and slicks), and just the "before" to see how much this StealthRam is going to give me.

Hey 91Z - do you have adjustable fuel pressure regulator? Did you change your timing? David is right about the Flowmaster if it's a "stock replacement" dual out design. If you've ever seen one cut open the actual muffler portion of the thing is very small,, too small,, but don't think that is your immediate problem.

David 91RS/Z28

I was going by your sig. It says you have a flowmaster muffler. Is it a 3" flowmaster catback or just a replacement muffler? Also, if you have an AFPR try bumping up the fuel pressure. It may need a bit more fuel. Sorry, don't know what else to tell you.

BryanJ

BadSS, was that the Iroc that Brock used to own it looked like you had some pretty good times out there. When are you going for the Stealth Ram run you think?

Mark A 91Formula

iTrader: (3)

I'd start looking into prom burning if I were you. You've opened up the intake and the exhaust so you've changed enough to really start to NEED a little chip work. You could drive around all day and the computer will learn enough to compensate for the changes, but thats only at part throttle. The "learn" function will do nothing for WOT and thats where your issues are. Bare minimum right now would be to get a hold of a scanner and see what the computer is doing.

Ed Maher

Unless i read your post wrong, seems you say you 'had' those parts installed. If thats the case, then who knows what your mechanic screwed up in the process. For example:

- Cut to fit wires, maybe he didn't get one put together right and you have weak spark on a hole.

- Spark plugs. Incoreect heat range causing a little detonation that you didn't have before.
--- OR, incorrect plug gap, perhaps he thought he was helping you out by setting them a little wider and now you again have weak spark in some holes.
--- OR maybe he dropped one while he was installing them, closing the gap up to way under spec, and didn;'t bother to regap it
--- OR it could just be the platinum plugs. Platinum plugs have atendency to retain heat. They're an absoilute no no in power adder cars for this reason, and i also think they are a bad idea in any high performance application sinc ethe same idea applies, just on a less cataclysmic scale

- Timing. Maybe while he was doing your tune-up for you he though he'd adjust your timing. Just this week i had to correct a mechanic because he said he sets all thirdgens base timing to 0'. That would sure give up some power. OR the opposite, he thought he'd help you out and advance the timing some and now you're getting knock.

- Exhaust. 2.5" Y-pipe huh. Is it mandrel bent? If not, that could be hurting you as the exhaust has to slow down and speed up as it makes the turns. And 2.5" is overkill on a stock headed, cammed car anyway. Could be losing exhaust velocity (note io said velocity, not backpressure, backpressure is bad, velocity is good, don't make me whip out the old post explaing the difference) even if it is mandrel bent,and thereby slowing you down.


If you did do some of the stuff i mentioned above yourself and you know it's all good, then ignore it. But that should give you some ideas on where you could lose a couple mph with your recent work. I really doubt it's a matter of the chip/fuel unless you were already borderline and now you have a hole or 2 going lean and getting you into knock.

Notice how knock keeps coming up in this. Thats because you won't hear it, your computer will just pull timing and you slow down and sit around scratching your head calling your car a POS yet there is probably one small stupid thing holding you back.

And thats why i harp on the basics. I have $5 on it being something really small and lame causing all this And especially if you don't do your own tune-up stuff, you're just asking for trouble.

BadSS

Yep,, that's the same engine I built for him that his $525 JET chip washed the cylinder walls down. I've done a ton of little,, and not so little things to it and it was a 16 year old electrical nightmare!!! Bad grounds, bad relays, bad sensors, pinched / shorted wiring, fried computer, etc - LOL a real pain.

Thanks for noticing,,, yes,,, I was VERY pleased with the way it was running as hot as it was. I felt sorry for that guy in the old gray 3rd gen that pulled out on the track with me - if I had not been "dialing it in" I would have cut him some slack and not run full out - that had to hurt,, didn't feel sorry at all for the Mustang though. Anyway, I thought I'd have it going and back to the track this coming weekend,, but it's looking more and more like the following weekend.

91-Z - I also agree with Ed, it's probably something minor. Go back through and do all the basics.

Pull the plugs and look at them - check the gap
Look closely at the wires,, roll them over and check for cracks and burns
Check TPS settings
reset min idle
reset base timing
adjust fuel pressure (use a g-tech or go to the track)
As Ed suggested check the crossover pipe - I've seen them crimped so bad that it would negate or hurt performance after a swap to headers. Also seen them rest against the oil pan - and we don't need an oil heater around here - LOL

91-Z

Thanks for all the suggestions guys!

Here we go, the only thing I had someone else do for me was put on the headers and remove the smog system, I did everything else myself, including plugs and cutting the moroso wires. I guess that I will go ahead and change plugs and see what happens. The minimum idle is set, and the tps is at .54v.

No the y pipe was not mandrel bent that may be the problem huh? If I need to buy another pipe what size do you recommend? What do I need to set timing at?

BADSS, Is that Brock Wallaces old car? I worked with him at Gateway when he bought and was building that car. Man that was no fun. That thing was a mess when he bought it. I hope that the motor he put in it is living up to its full potential now because it was weak back then.

Thanks

Paul

u r sofa king we tah did

try one of these....

BadSS

Hi Paul, this is Kevin. I met you down there at Gateway. It was a mess when he bought it???? The thing was a mess when I bought it!!! And it's not been a lot of fun for me to get this thing right either!!!

You know,,, it's hard for me to say the engine was weak,,, since he bought it from me (it was my spare / back up for the SS). No engine can perform up to standards when all 4 cycles are screwed. Induction stroke – the air and fuel was off (stock TPI and way rich – JET chip). Compression stroke - washed walls / rings never really seated (JET Chip). Power stroke - washed walls / rings never really seated plus bad coil, wires, and ECM. And finally the exhaust stroke - the "Y" pipe on the driver’s side was nearly totally collapsed - like what a single 1.5" pipe would flow. Not to mention just a ton of “little things” that all added up (et and money wise). So,, sure,, the car was slow/weak for good reasons – although he did outrun a Cobra and a couple GTs before it really started giving up the ghost.

I’m sorry he didn’t have the chance to see what the car should do while he owned it – and that I didn’t have the time to help him before it was too late. It’s pretty quick now and performing the way it should with the ported TPI / SLP system and a better torque converter being the only major “differences” than when Brock had it. Actually this scenario is good example of why there is more to going fast / faster than just bolting on the parts, or in this case bolting in a hot engine.

Erik formula L98

I agree with Ed about the 2.5" y-pipe. Shouldn't the it be at around 2" to create some backpressure?

Ed Maher

Unfortunately, a bunch of posts from the board previous to the current BB format got eaten in the conversion. Apparently my really sweet post on backpressur being bad was one of them...sigh

I checked the old archives though and found an earlier version of it. OK, so my typing sucked, but take a gander at the timestamp on it. I wrote it at 11:30 pacific time...and i was in PA, lol.

https://www.thirdgen.org/oldarchives...ssages/476.htm

I need to recapture that and make it a sticky or tech article for this site. The myth of backpressure is one of my biggest pet peeves.