ok, well with the new intake (slp/edelbrock base) it seems that the car has more torque and I can't hook, and belive me I have tryed at the track, it just won't hook. Also the car still dies at about 4800 rpms, and I didn't see any improvements in ET's or MPH. I'm thinking that 3.73's are just to steep, and that 3.23 or 3.42 would be better for hooking and mph. After all every one I talk too seems to run great with those. What do you guys think?

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85 Z28, 355, edelbrock base, SLP runners (old style) 58mmTB, ported plenum, stock cam, fuel reg, TES headers, flowmaster, 3.73's, shift kit, MSD 6a, 305 hypertech chip (YUUUCK!) best prior intake mods: 14.6 @ 94, 2.02 60' temp: 78deg, 80% moist, on radials.
69SS, black, 3,73's, TH400, 402 BB, roller everything (solid 246@50 622 lift)+stud-guirdle, 67 Vette heads ported and o-ringed, about 10:1 cr KB pistons, should be done this summer, goals: 500hp and lots of fun

 

I say go with 3.23's

and try out my camshaft.

ODB


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*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
White 1986 Irocz, 305 with iron #416 heads,
383 with aluminum TFS heads,
Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, Vigilante 2400 lockup converter, 3.25:1 Ford 9" rear, Mcreary Road-Stars, SLP-stainless 1.75" shortie headers & Y-pipe, single 3" Borla exhaust, Linginfelter-TPI camshaft part number 74216 pulls 17" vacuum solid. Cam specs 213/219 @.050 114-LSA, sometimes advertised at 216/219 @.050 112-LSA .462/.470 lift @1.5:1 ratio. Using Harland Sharp 1.65:1 roller rockers. MSD-6AL, billet distributor, multi-retard, blaster-3 coil, and RPM switch. SouthSide machine subframe connectors, SSM lift-bars, Moroso 4" underdrive crank pulley.

N/A runs 10.9 @124,
Crack-runs 10.3 @135
haven't run at track since Oct-99

 

How about some sticky tires instead? Or swap camshafts for one that will pull at the higher RPMs instead of die off. That'll give you more HP and make the gears work better for you. If you want to switch, go for 3.42's. They're a good gear for your current mods.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Couldn't of said it better myself Kevin

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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN93, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL, Holley 9mm wires, fastchip, Bosch O2sensor, Bosch in-line pump(w/stock pump), SLP headers & catback,short shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

 

ok guys, cam change is a no go...I don't want to pull that intake AGAIN. I saw a 90 camaro running 13.9, and according to its owner will do 13.7 with 1.8 60's on DOT. His mods where k&N, cat back and chip. No headers (I have seen the motor myself) and 3.23 hooked to MT DOT's I belive. (made me feel really good too....with my 14.6...well 14.9 for that night). So do you guys thinks its a good idea? ODB you seems to think so...the way I see it is if I can hook again and get better mph it should get me better ET's, since the engine will still produe power crossing the line VS dieing off...correct me If I'm wrong...and one more thing, my buddie's trubo stang gain 3 tenth by going 3.73 to 3.23...and it runs 10.9 all day....

 

Your other choice would be 28" tires instead of 26". That'd make your 3.73 gears act smaller, like 3.42's or so. I forget the math.

 

The real answer to your question lies in what RPM you are crossing the finish line. You want to cross the finish line at maximum horsepower in your 1:1 gear. What are your RPMs when crossing the finish line? If you are over 4500rpms then swap to the 3.42's or 3.23's. However, if your RPMs are 4200 or under then your gearing is fine. Between 4200 and 4500 is a who knows situation since I am guessing that your max horsepower is somewhere in there.

Tim

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• Program your own PROMs!. Read my article to get started!
• Research and Experiment before asking questions.
• This is not a chip store. Go to the classifieds if you want someone to sell you a chip or give you a BIN.

TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

I cross the line at about 4750. It's hard to tell but I think I get best resulst if I shift at 4500, an it seems that at the end of the 1/4, the engine is "stretching" to get to 4700. I would say crossing at 4500 would be the best...I could be wrong...I don't know...

 

I would keep the 3.73 gears and replace the cam and port and polish,or replace the heads.You are probably getting plenty of air in,but not out.Exhaust seems to be the biggest restriction on GM V8's

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We need Perry Mason

 

and that cost $$...and I really don't wanna take the intake apart again...plus I know one of my wheel bearing is going out...I'm just trying to get some feed back on the right gearing, cuz I think it's what's hurting my times (among the chip of course)amd I already have exaust done on it.

 

By exhaust I meant the exhaust ports on the heads.When I rebuilt my L98 I fully ported and polished my stock heads and it pulls hard till around 5600 rpms now.

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We need Perry Mason

 

of course I forgot to mention that I'm not running L98 heads but a fare more worst head: 882's.
but to come back to my post, am I wrong to think that 3.42 or 3.23 would be more apropriate since I don't have top end rpms? it would favorise the strong torque at low and mid rpms. I always though that gears such as 3.73's were for engines that can rev high and/or don't have much bottom end in order to get the car out of the hole and get in the higher rpms faster. wrong? right? tell me....

 

Yes I agree.I was looking at it from the other angle,where you fix the rpm problem,which might make the 3.73 gears work better for you.I tend to favor a higher gear ratio for drag racing.

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We need Perry Mason

 

Also, I have the 9 bolt rear end and the gears are expensive.The only cost for me to port my heads was, gaskets, and head bolts.Much cheaper than a gear set,and thats what prompted my first reply.

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We need Perry Mason

 

well guys, I found a good deal on a rear, it's a 10 bolt with disc breaks (a nice upbgrade from drums ) with 3.23's posi out back , the only thing I hate about it is the posi unit, it's one of those "cone" posi, that locks the ohter wheel when one of them rotates faster (in other word, not a clutch posi.., like I have right now). So I'm gonna put it in, try out the 3.23's, see how it perfom, and if it's a go, I'll install my "better" posi in it...and if I hate 3.23's, I'll just transfer the hole 3.73 in it. The way I see it, it'll take care of my wheel bearing and, heack, it has disc break ...and I got it for dirt...
Thanks for the imput guys, I'll keep ya updated on the results.

 

that old theory about crossing the traps at maximum horsepower RPM is nothing but a farce thought up by some bone heads.
The only way to know for sure what a given car/combo likes is to do the tests and find out yourself.

In august of 1999 I had a 3.7:1 third member in my camaro because it was all I had ready at the time. I shifted at 6300 rpm and crossed the traps @121mph & 5570 rpms. I was pulling 1.72 60-ft times.
I swapped in a 3.25:1 third member once it was ready. My trap speed went up to 124mph @ 5015 rpms with 1.58 60-ft times.
As my engine gets more powerful the optimal gear will come down even more.

Building in the traditional method to make high RPM power & scarificing bottom end will end you up with a turd.

Figuring the optimum rear gear ratio is more dependant on engine power-curve and engine loading than it is on your trap speed.

ODB

 

ODB, I so agree with ya...my friend with his turbo mustang gained 3tenth and like 5 mph by going from 3.73 to 3.23...I expect my car to run about 96 to 97 mph, and I'm hoping for a 14.2 pass...all my friends thinks that I'll go slower mph, but I serioulsy doubt it, I have a really good amount of torque down low, so the car shouldn't have any problems pulling threw the gears.
By the way, nice et's....proves that a nice well thought combo runs better than anything else!
later

 

Why wouldnt you want your car to be pulling its max horsepower at RPM thru the traps? By swapping to a 3.25 ratio it looks like your car makes more power at 5000 than it does at 5500, as your trap speeds increased.

 

euuu dude, my car makes about 3hp at 5500...actually it won't go 5500 and that's according to my monster tach...off cours for you guys that read of your stock tach, you see 5500...wanna know what I see? right about 7000rpms....lol so in deed, I want to cross the trap at about 4500, cuz that's where the power is still is, where 4800 is to high, sure it'll go 5000, but from 4700 to 5k, it takes for ever, therefore I belive gears less than 3.73's are better suited for my power band....of course, you look at my 69BB, she make power up to about 7000, so in there I have 3.73 to help the low end...it's all about power band and hp band...trust me, my friend's mustang droped 3-4 tenth by going from 3.73's to 3.23 (3.27??), and so you know he pulls 10.90's all day. he also gain some mph I think and shift at 5250.
And if it makes the car run slower, guess what, I'll drop my 3.73's back in my disc break rear...hehe

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85 Z28, 355, edelbrock base, SLP runners (old style) 58mmTB, ported plenum, stock cam, fuel reg, TES headers, flowmaster, 3.73's, shift kit, MSD 6a, 305 hypertech chip (YUUUCK!) best prior intake mods: 14.6 @ 94, 2.02 60' temp: 78deg, 80% moist, on radials.
69SS, black, 3,73's, TH400, 402 BB, roller everything (solid 246@50 622 lift)+stud-guirdle, 67 Vette heads ported and o-ringed, about 10:1 cr KB pistons, should be done this summer, goals: 500hp and lots of fun

 

Kevin,
Exactly right. My car does make more power at 5000rpms... NOT horsepower, but power (= torque). Horsepower is simply the product of a calculation using torque over a certain time period. Torque is the only direct measurement of power... and yes my engine makes more torque at 5000rpm than at 5500rpm. Most street engine will be the same way.
Horsepower at the top of your gear has very little effect on your E.T. compared to your torque at the shift-recovery RPM. Think about it and draw it on paper. If you accelerate quickly at the beginning of your gears and slower at the top of your gears what happens?
Then reverse the situation saying what if you accelerate slowly at the beginning of the gear and quickly at the top of your gear?
Waiting for RPMs to come up wastes valuable time, and once the E.T. is gone, it is GONE and you can't make it up.
The main reason I shift at 6300 is to optimize my shift-recovery RPM, NOT because my engine makes maximum power near 6300. I pretty much ignore horsepower numbers because they are simply calculated. The actual torque-curve (power band) is what needs to be optimized by your cars gearing.
Once again this is an area where actual vericom testing will show you what the car wants and make it obvious what part of your power band is most important.

Another note. Over the years, adding more rear-gear ratio has been used as a crutch and band-aid fix to help an engine with a weak torque curve, and even more so to avoid any serious tuning efforts. I've seen cars so low geared (700R + 4.56) that they run with a totally dead cylinder and never realize it because the car still feels so snappy off the line. What does that tell you?

I hope this explains the situation a little better, but I'm still open for questions.
ODB