FrontEngineDragsters.Org Forum
Drag Racing Discussions => Front Engine Dragsters => Topic started by: masracingtd1167 on April 28, 2015, 11:57:00 AM
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We have been talking about tires a lot lately how about gear ratio's for a powerglide ? I have been using a 1.80 low gear and I am told that I should use a 1.69 . Have any of you tried both and what did you find . Thanks Bill
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I'll second that. Been looking at new planteries for my powerglide with differant ratios. What's the benefit of a 1.69 over a 1.76 or mas's 1.80?
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I have 1.69 low in trans.No info yet sorry. I had some guy name Parks tell me DO NOT get 1.80 go with 1.69 low. I lucked into a coan max duty aluminum carrier shorty shaft with 1.69 at less than half price and had 10 runs on it. Kind of seemed like fate.
More wheel speed with higher gear getting up on tire and not as voilent is what I took as reason. Heck what do I know I just listen to those who run fast and have lots of experiance with FEDs.
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I chose a Torqueflite because it has 2.45/1.45/1.00 thinking the lower first gear combined with 4.56 rear gears will make my converter work better at multipling torque. I'm a hand brake guy have I made the wrong choice? I want a car I can drive.
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Bill brian has run both and swears by the 1.69.
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I chose a Torqueflite because it has 2.45/1.45/1.00 thinking the lower first gear combined with 4.56 rear gears will make my converter work better at multipling torque. I'm a hand brake guy have I made the wrong choice? I want a car I can drive.
I think of it this way, I run a 3 speed (T400) and run a 3.90 or even a 3.50 gear. With the low gear launch the converter is done doing its job right at the hit. The motor will stay in it's peek torque if you shift it right and the tall gear will give great MPH without buzzing the motor. You do not need a 4.56 gear or a killer converter with a 3 speed.
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Hi buds:
Say Can someone have anything to say about the starting line ratio for a FED?? Some generalities? Have talked and read some with people and they always relate to a heavier or suspended car. just thought this should go along with the talk here.
Here is a sample of info for conversations sake. Page 155 and 156.
https://books.google.com/books?id=SOIYFkfXdocC&pg=PA155&lpg=PA155&dq=starting+line+ratio+for+dragster&source=bl&ots=8IVq331lYu&sig=dwdICBWUpeXfLR0cIT2JzY2M2wA&hl=en&sa=X&ei=QV9AVcpLhMWiBOiugPgM&ved=0CC0Q6AEwAg#v=onepage&q=starting%20line%20ratio%20for%20dragster&f=false
I will be facing this whole issue when we dyno the engine. So thanks to everyone for sharing. 8)
Luke
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yes for you guys running decent power a 1.69 is the way to go but one important thing none of you have mentioned is that with the higher ratio your spit is much more favorable as well, this helps with your fuel curve as well as preventing the RPM fall back on the converter........In fact some of you guys would benefit from an even higher first gear......one of the posts above mentioned it generates higher wheel speed.......That is not true with a shallower gear.....
just food for thought
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Look at this way. Suspended RED's weight in 2000 lb area for most part. FED's in the 1400 to 1600(heavy) are. You need the tq multiplacation of lower gear(bigger number) to get the heavier car going ,but not so much with lite weight car.
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Not saying 3 spd is wrong. It is lot heavier and lot more rotating mass.Some have been built under 100#. While there are lots of parts for3 spd's ,theres nowhere near the parts as for PG and well built pg can handle 2500 hp. As for rpm range. Glide will drop plus or minus around 900 to 1000 rpm pretty narrow power band will be larger.
Need someone with racepak to post there stage,hit,shift rpm,fallback and time between leave and shift,Wouldbe great if someone had same info for 1.69 and 1.80.
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What I am thinking is to change the rear from a 4.56 to a 4.71 and put in the 1.69 low I think this would help my first half numbers .
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thats not much of a starting line ratio change.......it takes you from an 8.02 to a 7.96 .........will help on the split though
what size and tire roll out are you using?
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I run the 12x31 Goodyears .
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thats only about 96 inch roll out .......is this an 1/8 mile set up or 1/4 set up? that is a very steep gear for 1/4 with only 96 inch roll out.....?what is RPM in the lights.I guess I would need to know alot more about your set up......
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I run 1/4 mile . Right now I am crossing around 9000 but I think that's where my motor wants to be . I have never dynoed it but I think it is a little shy of 800 hp . Last time out I ran some high 7.20's at 183 .At some point I would like to run 7.0 pro with it so I am looking for a little more !
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well that now makes sence to me........I should have asked about your combo before I assumed anything....... I agree that the change to 4.71 would be a good move with the 1.69 low...... its not much help on the starting line but you should net a sizable gain with the shorter 1-2 split allowing a longer run at first gear as well as caring a higher level of enertia into the shift much less RPM drop at the shift keeping the rpm up where the engine is happy....
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OK Bill, I've been running a 1.68 [ light carrier] 1'st gear for about 6 years. We changed from 1.76 because we could hit the slicks a little too hard sometimes, so 1.68 helped off the line, helped with tire shake, and the motor would climb quicker after the shift because the drop between 1.68 and 1:1 is closer. Our 60' improved too.
So here are some RacePak numbers;
Hemi,1.68/ 4.56, ET 7.21, shift 9317, converter flash [ after shift] 7960 rpm , 185.4 mph, @ 9214 rpm , 31x12x15
Hemi 1.68/ 4.71, ET 7.22, shift 9444, flash 8462 [ looser converter] , 184.2 @ 9500, 31x12x15
Hemi 1.68/4.56, ET 7.07, shift 9130, flash 8037, 189.4 @ 9400, 33x12x15 tire
RR SBC 1.68/ 4.88, ET 6.99, shift 9660, flash 8700, 188 @ 9921, 31x12x15
RR SBC 1.76/ 4.71, ET 7.06, shift 9879, flash 8108, 188.5 @ 9700, 31x12x15
The converters are flashing at different RPM's because of different 7" converters, but keep in mind more HP = higher flash points.
Hemi makes 870 HP, RR SBC makes 850 HP, but 100 lbs lighter than Hemi
1.76 x 4.56 = 802 start-line ratio
1.68 x 4.56 = 7.66
1.68 x 4.71 = 7.91
1.68 x 4.88 = 8.20
1.80 x 4.56 = 8.20, but less 1/4 rpm, and more likely to spin tires at hit.
I hope this info helps !
Jon Hansen
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Jon That's exactly the kind of imformation I was looking for ! I am really not sure where my motor falls of because I have never dynoed it . My heads are old Comp eliminator 18 degree heads Done by Jimmy Bell and they flow very well 391 cfm at 850 lift so I think this thing wants more rpm . Thank you so much for the info ! Bill
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Bill, WOW 391 cfm, that's more than my RR iron SBC heads flow, 357 cfm, so yes I think your motor wants more RPM. We run 9500-10,000 rpm. The more the heads flow the better it runs at higher RPM. In some cases the more they flow, you need more RPM so you can get the air speed you want for more HP. Parks A/ND 14° Chevy heads flowed over 440 cfm, so they needed a converter that flashes at 9200 rpm, and launch no lower than 9000. With their 5.37 rear gear the finish line rpm is around 10,500 . And they own the A/ND record at 6.76, but they need the high rpm to get enough air speed with their monster heads.
Your .850 lift is close to what we run .937" and again we run a lot of 7.0's, 189 mph with my 4.88, and 31x12x15 GY .
I assume you have good valve train parts for higher rpm. One tip we learned is for years we used Ti valves with a SS tips, but our team and other teams learned that when we started running 10,000 rpm, the tips broke off at the retainer grove, so we all run solid Ti valves with lash caps, no more problems.
Ask your cam guy what rpm range you should be running at, no sense over rev it beyond it's power band.
Have Fun !
Jon Hansen, Hayden Wheels
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Jon and Bill,
Since you both run SBC hitting 10k are.I have a question have either of you ever ran the lash cap /lock piece.I think you both will know what I am talking about they are made so lash cap is made as part of the locks. Not to jsck thread but since Jon had mentioned valvetrain and I have these sitting here,thinking woule eliminate kicking lash caps off or breaking them,for what ever reason crap happens.