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Author Topic:   RPM & Gear for 3/8
Burque
Dirt Forum Racer

Total posts: 98
posted October 06, 2004 11:37 AM  
Well guyís this will be my last race of the year and it will only be my fifth, do to my car not being ready for beginning of the year. Well I race on a 3/8 medium banked clay track that is usually tacky. Iím running a 355 with flat tops, 480-lift cam, 1.6 roller rockers, headers, original Torker intake,and Holley dbl pumper. For wheels Iím running about 86 roll out with 11 inch track. My gearing is 6.07, T350 in first 2.41 in the rear.

Well Iím am getting my b u t kicked good out there! I hit about 5800 rpms at the end of the straight but start to feel a high end miss. I figure it is my distributor maxing out with the original module. But these guys can pull away fast and are beating my like bye 3 to 4 seconds per lap.

What my questions are should I run more gear or does it sound like Iím just underpowered for this class? Most guys in my class are running closer to 6500 to 7000 rpms and running a 6.20 all the way up to 7.10(6.50 average). I can change gear pretty easy, but as to horsepower money and the end of the year got me beat! Also with the change of gear and rpms what can a stock bottom end handle? Thanks any help appreciated.

Flanndad
Dirt Freak

Total posts: 255
posted October 06, 2004 12:08 PM  
Big question, did you spend money on a good balance job.

I run around that gear with my 406 (6.12).
A 355 needs to be run with more rpm's, I would think you would want to be up around a 6.80 or 7.00, with stock bottom end.
Some around here are running 7.50 or even more with good bottom ends. (Good Parts, Good Balance job).

iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted October 06, 2004 12:17 PM  
we run on a 3/8 medium bank also but we are limited to compression a stock rod motor can handle 7000 for a long time but if you are running a hydrlic cam with stock lifters you dont want to turn over 6300 or so plus depending on your valves springs you dont want to turn much over 6000 we run a 620 to 683 gear on a 3/8 track depending on the motor we run at the time some of the motors we run are solid cam and need to turn 6800 or a little more, One of the cams we used this year was around 480 lift and we needed to turn it around 6300 to get where we needed to be.
some people on here will tell you that a stock module falls flat after 4800 rpm wich is true if you dont run a alternator but with a alternator you can turn a stock module 7000 with no problem i have seen guys run 7000 with no alternator and still not miss a beat
As far as your miss goes try a different module and check your valves springs,plug wires,float level,try unplugging your tach i have seen that be a problem also

Burque
Dirt Forum Racer

Total posts: 98
posted October 06, 2004 01:19 PM  
The valve springs Iím running are Z-28 spring not sure the lift but fairly new, on a set of 441 heads milled 10 thousands. The distributor I pulled out of an old Elky, changed the cap and rotor. The miss is only at the end of upper rpms donít know if its just a miss or valve float? I will change to a MSD module this week.

As to gears I have a set of 2.73 and can get some 2.56 pretty easy. With the 2.73 it will put me at 6.87 and 6.45 with 2.56. In the toolbox to pull 6300 I would have to change to a 6.60 and 6.80 to pull 6500.

I can use the 2.73 most likely but the 2.56 will only pull a little over 6100. I also have two T200 with a 2.74 ratio and with my 2.41 already in it would put at a 6.60 which would give me 6300. I donít know how well a 200 would hold up but I do have 2 of them. Does anyone have any info on how well they hold up cause that could be an option to if theyíre any good! Thanks again

robhbk24
Dirt Freak

Total posts: 372
posted October 06, 2004 01:46 PM  
i ran a stock metric 200 for 2 seasons with no cooler before a rebuild.never had any problems i pulled on the track in first shifted manualy into 2nd and left it there.the third season i ran it with a better converter and clutches it worked a little better but not really noticably.

Burque
Dirt Forum Racer

Total posts: 98
posted October 06, 2004 02:06 PM  
Did u ever run it in first cause thats what ratio i need for a 6.60. (2.41 X 2.74= 6.60)

robhbk24
Dirt Freak

Total posts: 372
posted October 06, 2004 03:23 PM  
never tried 1st, i rand second with 3:23 on a 4/10s mile high bank. i've been told that 2nd gear in these is a 1:52 but i have a hard time believeing that i am running a pg with 1.82 and 3:42s now and i am turning almost the same rpm. my tranny was from a late 70s malibu i read in hotrod one time where the 2nd gear ration was 1.96 or something like that. i think 1st gear would work fine the biggest prob with these trannys not holding up was shifting, for drag purposes or even mild street i would not recommend them because the do not take hard power shifts well but for our use just putting them in gear and going they hold up fine.

racer17j
Dirt Forum Champ
Total posts: 5390
posted October 06, 2004 04:28 PM  
I think I am going to just switch the gear and go from there. If next season its to high of a rpm I will have the funds to change it by then. Thanks for all the info guys. Hope to keep up this last race!!HAHA

Speedway65
Dirt Freak

Total posts: 344
posted October 07, 2004 12:17 PM  
Wr run TH350 in 2nd with a 3.73 rear gear and a 82 inch roll and turn around 6200rpm.We ran it with 4.10 gears and it turned around 6800 rpm or more.

Burque
Dirt Forum Racer

Total posts: 98
posted October 07, 2004 12:42 PM  
Thanks for that info Speedway but with a money shortage I would not be able to buy new tires this year.

rico 08
Dirt Forum Champ
Total posts: 1139
posted October 07, 2004 01:14 PM  
350 turbo 1.52 2nd 2.52 1st
200 metric 1.48 2nd 2.48 1st....supposedly,a friend of mine runs a 200 and has had good luck.I run the same gear as you and with 82 rollout tires(imca)i turn 6200 on a small 3/8.

waltonjr1
Dirt Forum Champ
Total posts: 516
posted October 07, 2004 01:15 PM  
I ran the same metric 200 for three seasons and loved it. Big difference from a heavy turbo 350. If you use the one with the eltronics on it thats the ones that dont hold up.


Burque
Dirt Forum Racer

Total posts: 98
posted October 07, 2004 02:09 PM  
The ratio I pulled from the toolbox is 2.74 1st and 1.57 2nd. Electronics? Is that the one with the back up lights on it? Didn't know there were different ones. I have the ones with the back up light plug on them. I still am a little weary on the T200 but I am also weary about floating a valve or winding a stock rod and crank too much.

robhbk24
Dirt Freak

Total posts: 372
posted October 07, 2004 03:44 PM  
don't hold me to this but i believe that the 200 used in 78-79 was diff from the 80 up till they switched to the r4. i think that is why my gear ratio was diff. i have pulled a couple of later model 200s and they even look a little diff as far as pans and outside goes. it's poss that the original 200 metric from 78-79 may have had a diff gear ratio. mine says metric on the pan thats how i identifid it it came from a 78-79 malibu with a 350 that some kid my friend went to college with had. he got the car impounded when he got caught running beer and ciggarettes over the border to canada when he got it back it was stripped pretty bad i ended up with the tranny.lol thats what i was told

STREET16
Dirt Maniac

Total posts: 158
posted October 08, 2004 09:02 PM  
Gears won't cure a miss. Z28 springs are usally good to about .550 lift - so you should be OK there. If the ignition module doesn't fix it, see if you can borrow a carb from someone.

    

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