FocusGhia

I have an 88 IROC 305TPI (89,000 on the clock) auto (2.72 posi) with decat, I've descreened the MAF and a pair of K&N's and a TB airfoil are on their way..

I hit the track for the first time this weekend and my best result was:

60ft ET: 2.344s
330ft ET: 6.627
1/8 ET: 10.142 @ 71.29mph
1/4 ET: 15.810s @ 84.76mph

That was with holding it on the brake at 1,500rpm then once it's rolling giving it full throttle, tyres chirp and it goes. The track was cold and REALLY slippery. I was told the tyres I have are real hard, I did maybe a 4s burnout on them and that got me to 15.8 instead of 16.0 I had been running all day.


What would be my next mod?
I can't go higher than 3.42 on the rear gears due to the price of gas in the UK and I was hoping to change other things before doing the gears.


Question 1:
What sort of difference would headers, porting the plenum, a shift kit, a hypertech (or similar) chip and say softer (NOT slicks) 275 tyres make? And would I be in any danger of breaking the diff or transmission with the tyres?

Question 2:
After fitting that lot, what sort of difference would fitting 3.42 gears make?


BTW: The transmission refused to change into 3rd after half a dozen runs, let it cool down a couple of hoursd and ran again and it was ok for half a dozen runs. I'm assuming the fluid is getting too hot and I should fit a cooler?

BadBowtie88

Well, for one, don't try to hold the brake when you launch. All your doing is binding the car up. I tried this idea with the '88 IROC I used to have. I ran 3 times, twice holding the brake, once off idle. The two times I tried to hold the break, I was actually causing tire spin. I ran nearly a tenth and half faster just off idle. If you just put on some DR's you're not going to break anything. You're not gonna be sticking that hard. I would go with the gear change to 3.42's and headers. You'd be surprised what that'll get you if you slap those DR's on there. Good luck!

SLP IROC-Z

iTrader: (1)

hmmm im lookin at ur time slip ya posted, it seems taht ur car is doin real well to the 1/8th mile where u trapped 71mph. however then u look at the 1/4m mph and its only 84, with a 71mph 1/8th speed ur 1/4m trap should be around 90-91. is this because of ur transmission not shifting out of 2nd gear? that sounds like whats slowing down ur 1/4m ET. if thats not the case then, are u sure ur cars in good tune? going by that that means ur car is falling off at the upper end of the track. low fuel pressure, things like that can cause a loss of power at the top end of the track. id look into all that stuff before doing any more modding. if u found ur bug and fixed it and got the car to trap around 90mph u could possibly hit a 14.9, 15.0-15.2s for sure.

just some food for thought, when my car was pretty much bone stock it trapped 93.25mph and i pulled a 15.1 witha 2.3 60ft and a 9.99 or 10.00 1/8th.

SLP IROC-Z

iTrader: (1)

oops ****ed up

FocusGhia

On that run the car did shift into 3rd, on the run where it didn't I trapped at 83mph.

The car does need a serive actually, new plugs and so on.

The car does feel sluggish in3rd I do admit, even on the road. I've had it on a rolling road (dyno) and the air/fuel is bang on all the way up the rev range at about 6%.
I put it down to the tall gearing as the car wakes up at about 90-95 and accelerates hard as the rpm has obviously risen andthe engien is making some power.

I'll put an adjustable fuel pressure valve thingy in there with a gauge on it and check it again on the dyno to see what is going on with the fuel pressure and if it's ok adjust it to say 50psi.

Well spotted if it is the fuel pressure!

I've been checking some online stores and I was thinking of some 275/50R15 BF Goodrich Drag Radials on 15x10 Weld Draglites (the backspacing on those is only 5", is that enough?).

Is that the right tyre/wheel size combo?