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Author Topic:   Gears, RPM's and track ET's
'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-11-2002 08:55 AM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
I was at the track this weekend and noticed that I was crossing the finish line and around 5200 RPM's for the 1/4 mile. Is this optimal? I am running a 26" tire and 3.89 gears. Should I move up to 4.11's or 4.30's?

I shift at around 6700 RPM's, car seems to get the best times around there.

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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear

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'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-11-2002 09:55 AM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
O.K., I figured it out from another post. Went to Randysringandpinion.com and it looks like I need something in between 1.11's and 4.30's.

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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear

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'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-11-2002 10:06 AM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
O.K., what RPM should a car be crossing the finish line at? Peak horsepower?

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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear

[This message has been edited by '69Stang (edited 11-11-2002).]

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madmanmike
Journeyman

Posts: 18
From: brenham,Texas,washington
Registered: Oct 2002

posted 11-11-2002 05:58 PM     Click Here to See the Profile for madmanmike   Click Here to Email madmanmike     Edit/Delete Message   Reply w/Quote
What was your 60 ft 1/8 mile time,mph and 1/4 mile time and mph

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'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-12-2002 08:40 AM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
Madmanmike: 60 foot 2.008, 1/8th mile 8.22 @ 93.7, 1/4 mile 12.51 @ 115.89.

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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear

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Rory McNeil
Gearhead

Posts: 1210
From: Surrey, B.C. Canada
Registered: Nov 2000

posted 11-12-2002 11:10 AM     Click Here to See the Profile for Rory McNeil   Click Here to Email Rory McNeil     Edit/Delete Message   Reply w/Quote
With those numbers, I`d have to ssume that you are running regular street tires, your MPH is more than sufficent to run deep in the 11`s with decent traction. But you are wasting almost 1/2 second with those lame 60 foot times. Time for good slicks & maybe some suspension work. And yes, you do have room for some lower gearing.

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78 Fairmont 428 4 speed [email protected]
80 Fairmont 302 5 speed [email protected]
85 Mustang NHRA Stocker under construction, 302 5 speed
59 Meteor (Canadian Ford) 2 dr sedan 332, auto
74 F350 ramp truck 390 4spd

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Mike_R
Gearhead

Posts: 151
From: Indianapolis, IN 46237
Registered: Feb 2001

posted 11-12-2002 12:30 PM     Click Here to See the Profile for Mike_R   Click Here to Email Mike_R     Edit/Delete Message   Reply w/Quote
Considering you have a toploader 4 speed, I say run the lowest gear (highest numerically) you can run and still make it through the 1/4 mile. This is even more important if it is a close ratio tranny.

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kcode
Gearhead

Posts: 2590
From: alvaton,ky,usa Suburb of Bowling Green, M&M #79, MCA #29208
Registered: Jun 99

posted 11-12-2002 01:25 PM     Click Here to See the Profile for kcode   Click Here to Email kcode     Edit/Delete Message   Reply w/Quote
Re-calculate your numbers. At 115.89 you should be 5800+ rpms, which is still low for your combo. But at 5200 as stated you are at 104 mph, unless you have a hidden overdrive somewhere.

Mike

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'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-12-2002 03:36 PM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
I miscalcilated. That's were I thought I "saw it" after crossing the 1/4 mile line. I probably also let off the gas at the same time. 5800 RPM is the right number for my gears and tires. What should I be crossing at? 6500 RPM's??

And your right I am using street tires and I obviously can't launch or drive this thing for sh** yet. I'm considering getting some ET streets.

I was looking at 4.11 gears and that would have me crossing around 6300 RPM's. 4.33's would have me crossing around 6600+ RPM's.
Which are better for the application in your opinions. I shift around 6700 RPM's but I suspect my peak power tob 6300-6600 RPM's (no dyno time yet).

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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear

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Mike_R
Gearhead

Posts: 151
From: Indianapolis, IN 46237
Registered: Feb 2001

posted 11-12-2002 03:48 PM     Click Here to See the Profile for Mike_R   Click Here to Email Mike_R     Edit/Delete Message   Reply w/Quote
In my oppinion, with the 4 speed tranny, I would still go for the lowest gear possible where you can just barely make it through the 1/4 mile. The 4.33's do look about right. That is assuming you stick with 26" tall tires. According to my calculations you would be turning right around 6500 RPM at 116 MPH. That still gives you a couple of hundred RPM before you reach that shift point of 6700 RPM. I'm assuming that 6700 is the maximum RPM you want to turn the engine.

If you bolt on ET streets it's going to start grabbing and pulling the engine down. Then the gears will be alot more needed. With the tires and 4.33's it would very possibly drop you right into the 11's.

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Dad Vishus
Gearhead

Posts: 540
From: Moscow, Iowa, USA
Registered: Dec 2001

posted 11-12-2002 04:09 PM     Click Here to See the Profile for Dad Vishus   Click Here to Email Dad Vishus     Edit/Delete Message   Reply w/Quote
What camshaft are you running?

With the other specs. you list, if its a solid and you have oil restrictors, turn er up. 4V heads like RPM. With a properly prepped motor even with stock rods with good bolts, 7000 is not too high. KV has run stock rods with good bolts all along and believe me, they have seen 7500 + many times. The only times a rod has failed was when a bearing spun.

If its equipped with a hydraulic cam, then 6800 or so is enough. Without oil restictors, all the oil wants to end up in the top of the motor at high RPM. If a 4.30 gear gets you about 6700 or 6800 in the traps, then that's what I'd do.

Again, depending on your valve train, a 4.56 would work even better. If you street drive the car much, thats going to be a bit short though. If you should happen to get taller race tires, that will make a 4.56 even more do-able.

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'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-12-2002 04:43 PM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
My solid roller cam spec's out at 234 intake and 236 exhaust with .588 lift, 110 LSA. It pulls hard to 7000 RPM, I shift at about 6700 RPM's based on what I THINK and FEEL the peak horsepower is. I don't know. I got better times when I began shifting at 6700 RPM's instead of 6400. The times might even get better if I shift at 7000 RPM's, I just haven't had a chance to experiment.

It is a small cam however, so it might peak at 6000 RPM's, but it doesn't act or feel that way. I'm comfortable running it to 7000 RPM's because I do have the oil restrictors in place, ARP hardware, and the assembly was dynamically balanced. I do think that I'll pick up a couple MPH with the gears and slicks too, so around 118 MPH at the line.

I guess I'm hearing 4.33's are the way to go. Just seems like a lot for running around on the street. Let me know your opinions.

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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear
-------------------------12.51 1/4 mile @ 115.89
60 foot 2.008 (ouch)

[This message has been edited by '69Stang (edited 11-12-2002).]

[This message has been edited by '69Stang (edited 11-12-2002).]

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Rory McNeil
Gearhead

Posts: 1210
From: Surrey, B.C. Canada
Registered: Nov 2000

posted 11-12-2002 05:47 PM     Click Here to See the Profile for Rory McNeil   Click Here to Email Rory McNeil     Edit/Delete Message   Reply w/Quote
The only real way to find out what RPM your engine likes is to experiment. But first I would get tires. I wouldn`t waste my $$ on drag radials, oe ET Streets. A true drag slick will be better, without a doubt. Especially with a stick. A pair or 8 1/2x26 MT ET Drags are sufficent for a 11 second car, & will fit with no modifying the wheelwells.A 9x28 slick will also fit, but it gets fairly close to the front of the wheelwell. Plus, the taller tire hurts you gear ratio. Also, it`s OK to let the engine rev a bit in high gear. On my 428, I normally dump the clutch at 6000-6200 rpm, shift at 6000, but the engine is normally hitting 6600-6700 RPM going thru the traps. ONce you have decent, repeatable 60 foot times, try shifting at different rpms.The ET slip will point you in the right direction. But you need traction first, or you just "spinning your wheels", so to speak.

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78 Fairmont 428 4 speed [email protected]
80 Fairmont 302 5 speed [email protected]
85 Mustang NHRA Stocker under construction, 302 5 speed
59 Meteor (Canadian Ford) 2 dr sedan 332, auto
74 F350 ramp truck 390 4spd

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Dad Vishus
Gearhead

Posts: 540
From: Moscow, Iowa, USA
Registered: Dec 2001

posted 11-12-2002 05:47 PM     Click Here to See the Profile for Dad Vishus   Click Here to Email Dad Vishus     Edit/Delete Message   Reply w/Quote
With the 60' time you report, I'm assuming you are spinning alot. That combo with shorter gears and tires that hook up are probably going to bog the motor or otherwise launch pretty ugly. Do you have any type of traction bars? If not, the springs will wind up and may cause wheel hop. Slapper bars will help that, if you don't have them already.

Once you do get it to hook-up, you'll find out where your next weak point is. A stock 9" carrier will spit out the pinion gear sooner or later.

Seems to me like you are real close to having a race only car. You can probably gain in E.T. by improving 60' times while all the time making the car less streetable. At some point the chassis will start flexing making more mods a necessity, like frame ties and/or a roll cage.

If you have a nice 69, I'd think pretty hard about doing much more to make it faster on the track, if it were mine. We came to the same point years ago with KVs 70. We got into the 12s in street trim with slicks and open exhaust. The car was too nice to cut up and we started looking for a better candidate to make a racecar out of. 69 and 70 fastbacks are the ultimate bad-a$$ looking street cars to my way of thinking. If I had a nice one, I'd make it a streetable hot rod, as it were, and find something else to race.

Just my $.02

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'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-12-2002 06:06 PM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
Rory & Dad Vishus, wow, thanks, great advice and comments I appreciate it. I'm definitely going to get some better tires so that I can launch effectively and get the times that are hiding in there. I'm still confused on the gear, but I'm sure either one will work well. This car is definitely 90% hot street and 10% strip so I can really relate to your comments DV. I will keep it from becoming a race car, I like just cruising and "test & tuning' on the street. Having said that, I do have traction bars (under-rider) and sub-frame connectors with better rear leafs, and 80/20 front drag shocks, so the car doesn't wheel-hop at all. That makes me think ET streets for grudge matches and the occasional drag strip event. Gonna have to think about the 4.11 vs. 4.33 decision.....

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'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear
-------------------------12.51 1/4 mile @ 115.89
60 foot 2.008 (ouch)

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kid vishus
Gearhead

Posts: 4538
From: middle of NC
Registered: Oct 2000

posted 11-12-2002 06:15 PM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
I also figure your cam to be good to somewhere around 6400 or so. Ut just doesnt have enough duration to support 7000 and keep making good power. More than likely the reason the car was faster shifting it higher is because the motor is falling into the fatter part of the torque band on the gear change.

Speaking from experiance, you wont see much gain, if any, if you go to a 4.11 gear. It will take more of a change to gain much et. I would suspect 4.33's, or even 4.56's would be best. But, then your street car becomes not so "street friendly". I used 4.71's in my street car awhile, that and a 4500 rpm convertor. It was fun to drive, so long as I didnt want to go very far. I would get the 4.33's, and some real slicks, and have fun with what you got.

Also, if you have 28 spline stock axles and the car hooks hard, you will break one. That will be the first thing that gets broke.

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bluestreek
Gearhead

Posts: 1289
From: Athens,GA
Registered: Jul 2001

posted 11-12-2002 07:48 PM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
I have a set of 4.44 gears setup in a rebuilt open 9" with a steel mini-spool. With 26" tires, the engine will pull about 3500 rpms at 60mph and 7000 rpms at 120 mph. Wanna trade??

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1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, ported TFS alum. heads, ported Stealth 8020 intake, CompCams Xtreme Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi, BFG Drag radials..

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Dad Vishus
Gearhead

Posts: 540
From: Moscow, Iowa, USA
Registered: Dec 2001

posted 11-12-2002 08:17 PM     Click Here to See the Profile for Dad Vishus   Click Here to Email Dad Vishus     Edit/Delete Message   Reply w/Quote
KV beat me to it. I was thinking the same thing about changing from 3.89s to 4.11s not being enough of a change to notice much difference. Imagine us thinking alike!

I'd think a set of Moser axles would be a good investment also. A 4 speed car has no "give" in the drivetrain like an auto trans does. If it hooks up hard, something is more likely to break.

These things do tend to get out of hand also. Several years ago some guys showed up at Eddyville for a quick 16 race, I think. They had the baddest, nastiest, in your face means business lookin 69 fastback I've ever seen. It had a super neat red paint job on it and a monster big block, as I recall. KV might remember better, but I sure remember the car. It may have had a Lenco in it, now that I think about it.

I talked to the guy quite a while and he said the thing started out as a street driven hot rod, basically, and went way wrong at some point. By then it had the steel roof clip left from the original car and that was about it.

Anyway, my point is that if you want to keep your car fairly streetable, you might not want to do too much more. It sounds like you have a cool streeter that is fun to take out and play with. I'd love to have one like that. The 69 fastback is my favorite Stang.

Personally, if that car was mine and I could afford it, I'd put a milder motor in it for the street and build a full blown racecar for your roller motor (with a bigger cam). You've got a really good start on the motor.

Which ever way you decide to go, I know you'll have fun.

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'69Stang
Gearhead

Posts: 180
From: Detroit, MI USA
Registered: Jan 2002

posted 11-13-2002 09:14 AM     Click Here to See the Profile for '69Stang   Click Here to Email '69Stang     Edit/Delete Message   Reply w/Quote
Thanks for the advice guys. I think all I'm going to do is change the gear (4.33) and axles (Moser), get some better rubber for launches, and then just enjoy beating up on all the local chevies

------------------
'69 Mustang Fastback, 351C, Holley 950 HP, New Parker Funnelweb,4-v quench heads ported, 10.75:1, UD pulley, windage tray, Top Loader, 3.89 9" rear
-------------------------12.51 1/4 mile @ 115.89
60 foot 2.008 (ouch)

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kid vishus
Gearhead

Posts: 4538
From: middle of NC
Registered: Oct 2000

posted 11-13-2002 11:20 AM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
It had a glide in it. And BIG BBF wiht one gas dominator on it. It was running around 5.20's (might have been in the 'teens) in the 1/8.

He did say it started off as a fast street car, the progressed to a 10.90 super street car and somewhere along the way got out of hand.

It was the prettiest mustang racecar I have ever seen. It was candy brandywine over a gold base. It also had some black '69 style boss stripes on it. It was gorgeous. I saw it a yr or so later at the ET finals in Topeka, it was running low 8.20's in the qrtr.

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