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Author Topic:   Peak RPM for Stock 350
James Ott
Dirt Maniac

Total posts: 131
posted August 31, 2005 04:23 PM  
We were testing last nite and came to the conclusion that 3.42 rear gear is too low for a stock 350 on a 1/4 mile track. The kid said it stopped reving at around 5500 rpm, with a little bit of straight-away to go. I'm trying to work out a few issues all at once. My driver is 12 years old and we have only done go karts and mini cup so were new to full size racing. The other rear I have is a 2.41. Will this work?

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"Winning heals all wounds"

racer17j
Dirt Forum Champ
Total posts: 5390
posted August 31, 2005 07:08 PM  
W are running TH350 tranny and the tires are 225-75-15. The motor is very stock, and needs a little work. We have the 390/410 lift rule and stock duration rule, rochester carb (1.250" venturi) the max tire is 235/70R15 75, 78, OK

racer17j
Dirt Forum Champ
Total posts: 5390
posted August 31, 2005 09:09 PM  
Yeah we had to run it in second gear and that required him to use alot of brakes. I got a set of new springs on ebay cheap we are going to try. Does anybody have any other suggestions?

nate 11
Dirt Freak

Total posts: 316
posted September 01, 2005 06:15 PM  
listen to racer 17j. he's very knowledgeable.

k2dirtnut
Dirt Full Roller

Total posts: 33
posted September 03, 2005 08:23 AM  
Very true nate11 Listen to him

M1
Dirt Freak

Total posts: 257
posted September 05, 2005 09:11 AM  
try finding a set of 3.08's. With the cam rule and a stock carb like that, your not going to want to spin it much higher then 6,000rpm.

If its cracking and popping at 5,500 I would have to guess the valve springs are weak or something with the distributor.


maximus
Dirt Roller

Total posts: 21
posted September 06, 2005 02:54 PM  
I run on a 1/4 mile semi-banked and I have a th350 running in 2nd with 4.30 gears in the rear end. My rpm when I hit the corners is 5800. If you are going to run in 1st a set of 3.08 should work nicely.

racer17j
Dirt Forum Champ
Total posts: 5390
posted September 06, 2005 08:04 PM  
racer17j about 6 years ago I was running pure stock with 3.08s th350 in 1st gear 305/60 hossiers and my rpm upon curve entry was 6000-6200 rpm. The 4.30s have just came out about 6 months ago for the stock metric rearend. I got mine at a local speedshop.lol

James Ott
Dirt Maniac

Total posts: 131
posted September 07, 2005 03:22 PM  
We talked to the guys at the track and most with stock bottom ends are running 2.73 and the rest are running 3.08 but they got some work done on the bottom end and they say they never twist em more than 6500. I'm thinking that the cam thats in there will not make any power up there any way. I want the kid to have fun and learn and not be worried about hurtin motors. We tried the car in second gear but its tough on brakes, which is makes more for the kid to worry about. I'm thinking on running the 2.73

racer17j
Dirt Forum Champ
Total posts: 5390
posted September 07, 2005 05:21 PM  
I think some of the S10 pickups have 4.30s in them stock.

not sure what years had them....maybe 2000 and up.



James Ott
Dirt Maniac

Total posts: 131
posted September 14, 2005 02:28 PM  
We have an Invitational Race coming up on Sunday so I'm going to give it a shot with the 2.41s I'm going to use some 205-70r15 tires with 82.5 roll out. We get lucky and not get lapped...the kid needs some seat time!

MIKE S
Dirt Roller

Total posts: 5
posted September 15, 2005 11:53 AM  
James I ran a 1980 Monte carol about 14yr ago. I had 273 rear gears that I believe came stock in the car
with a turbo 350 trans that I ran in first gear. I also had a 350 motor double hump heads with 194 valves and Z28 valve springs. The motor turned between 5800 and 6300 depending on track conditions. I believe I ran 225-60-14 and 235-60-14 tires.I am not sure if the tires were 14 or 15 inch tires.The track was a 1/4 mile Simi bank track the car was hooked up and would run in the top five in the main.That is with a turn out of 40 to 50 cars. Good Luck

James Ott
Dirt Maniac

Total posts: 131
posted September 15, 2005 07:22 PM  
Hey BTW those 4.30 gears are stock GM items that were optional in Caprice and Impala. Maybe cop car stuff?

racer17j
Dirt Forum Champ
Total posts: 5390
posted September 15, 2005 07:40 PM  
Hey guys I just wanted to let you know that the kid ran his first race tonite. We were last in the first heat race, 4th in the second heat. He refused to start at the rear for the feature so he started his earned 10 place and ended up finishing 12th in a 40 lapper. The car was no rocket but it did well. Thanks for all the help and suggestions! This is the best racing site ever!

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"Winning heals all wounds"

James Ott
Dirt Maniac

Total posts: 131
posted September 27, 2005 07:20 PM  
Took apart the motor with the oil trouble and found it had a severe caes of cylinder wash-down. The bores were carved up. After some poking around found out that this is caused by repeated flooding of an engine. The guy I bought the car off had an old Q-jet on it and he said it kept flooding out the motor. Lesson: fix that flooding carb

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"Winning heals all wounds"

racer17j
Dirt Forum Champ
Total posts: 5390
posted September 27, 2005 08:33 PM  
HEY IM NEW WERE DO YOU RACE AT

Eljojo
Dirt Forum Champ
Total posts: 968
posted September 28, 2005 04:15 AM  
Ah HA! After all the great advice Racer 17J has given I finally see one where he's WRONG!
Q-Jets are fine carbs---they just need to be prepped for a round trackin!

eenfield
Dirt Maniac

Total posts: 116
posted September 28, 2005 03:07 PM  
Eljojo, Ill second that!

James Ott
Dirt Maniac

Total posts: 131
posted September 28, 2005 05:08 PM  
We did put a two barrel on it, but the damage was already done. I mean I only started the motor once with the quad and man did it flood! Come to think of it a Quad either works awsome or it don't... no in between! Anyway the motor needs a rebuild
Thanks for all the help guys. And my 2 bbl works fine

OvalRocket34
Dirt Forum Racer

Total posts: 81
posted September 28, 2005 08:01 PM  
Racer17j

How do you determine final drive with rollout figured in? I mean I know how to do it between the tranny and the gear but not figuring the tires in... Thanks!

sc1 racing
Dirt Freak

Total posts: 419
posted October 04, 2005 12:47 AM  
we didnt find the peak rpm but we did find the breaking rpm in a bone stock bottom short block. ussally it stays 6500-7200. but a buddy drove the car friday night and had it in 1st instead of 2nd gear and it turned 8900 for 3.25 laps then threw 4 rods out of the block

robhbk24
Dirt Freak

Total posts: 372
posted October 04, 2005 03:23 PM  
i'll try this ? on here and see if i can get an answer. i'm running a pg (1.82) in low with a decent 331 chevy turning approx 7200 on a 3/8ths mile moderately banked oval with a 89inch tire. next week i'm heading to another track that is a big half with decent banking. alot of our guys are able to run the same gear both places but i can't they turn around 5-6 hundred more rpms there than we do at our normal track, i was going to put 3.23s in and try that but there is an issue with the bearings so i put in 3.08s figuring that if it's not enough i can go to my 87 inch tire or 86 inch to get the rpms up. my ? is am i on the right path here? how many rpms diff will there be between the 42s and 08s? i did the math an it figures about 700. how many rpms do you gain per inch of tire? and would i be better off fixing the 3.23s and running those? 17J up until a year ago there were a few places carring 3.36s for a 7.5 i think national was one of them but i haven't seen them advertised in a while aside from that i have found.2.14,2.21,2.23,2.41,2.56,2.73,3.08,3.23,3.42,3.73,4.10,4.56. any that i missed??i would love to see them make 3.55 and the 3.36 were avaliable at one time

sc1 racing
Dirt Freak

Total posts: 419
posted October 04, 2005 03:40 PM  
you can swap bearings on the pinion shaft easy, and a new bearing isnt more than 10.00. if car is handling good i wouldnt mess with tires. i asume you got the 3.23 out of a 90's car or truck.if so just go get a pinion bearing for your car. any part store will have them...

robhbk24
Dirt Freak

Total posts: 372
posted October 04, 2005 03:51 PM  
yeah i know but that woulda required me to drive to the store and well.lol. actually i don't know what the gears are out of i bought them years ago and used them for a while in another rear with this one it's almost like the pinion won't tighten up enough i think the bearing needs to be spaced diff not sure. not really worried about the handling vs tires this track has wide sweeping corners and long straights, add in the fact that our tracks up here in the cny area exspeciall the one i'm headed too (nur) our usually very dry/slick and the same day i am running they are also running 2 classes of sprints (mini and full size) a 100 lap 3000 to win pro stock race ( kinda like a stock framed late model thier payin 125 to start home track rules) mini stocks, sportsman mods ( ne mods with a lesser motor and smaller tires) plus the pure stock street stocks. we should be last on the sched or 2nd to last before the mini stocks so with all that racing on top of an already dry slick surface add in the fact that the weather up here will prob only be high 50ish maybe low 60s and it'll be early afternoon the place should be like an ice skating rink tha's why i'm leaning in 3.08 direction. how much diff ill there be between 42,23 and 08s assuming nothing else changes?thanx, and btw sc1 8900 rpms dman i woulda loved to here that from behind the wheel that thing musta been screamin.lol

sc1 racing
Dirt Freak

Total posts: 419
posted October 04, 2005 06:05 PM  
id probably stick with the 3.08 for insurance.

the car sounded like it was fixing to take off.and i almost took off waving my arms at him to kill it..well he killed it ill post some pics of it tomorow. it has enoungh rods hanging out of the block to decorate like a christmas tree..

robhbk24
Dirt Freak

Total posts: 372
posted October 16, 2005 12:02 PM  
sc1 thanks the 08s worked awsome, one prob though, it rained for 8 days before the race and it rained at 2pm start time, stopped raining the s****ed the track twice packed it in, we ran first heats, that was the roughest track i have ever been on, was sitting in turn 3-4 waiting for the national anthem and trying to get the corner flaggers attention to get him to take a shovel and get the last smooth spot out of the corner dug up.lol. anyways got all the heats in and it started pooring, eventually gave up and rescehd for today which rained out again now they are rescheduling for the spring.gotta love racing

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