Hot Rod Forum banner

1 - 20 of 46 Posts

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #1
Well here's the deal. I have a 350 bored .040 over, trick flow 23 degree heads, Comp cams .480 lift I/E cant remember duration or any other numbers of the top of my head, Victor JR. intake, speed demon 750 DP, complete MSD ignition. Any how the the cam builds power from 2200 to 6100 RPM and the whole set up is very strong in the mid to upper RPM range. I have a four speed muncie with a 3.73 posi out back. This car is boggy under 2000 RPM and I was wondering if switching to 4.10s would help much. It runs about 2300 rpm going down the highway. Im not concerned with fuel mileage and its just a weedend cruiser. Any way do you guys think this is a reasonable swap or should I stay with the 3.73's?
 

·
http://teamrfc.gospelcom.net
Joined
·
1,742 Posts
What would help the most is if you changed the Victor JR to a Performer RPM or Performer RPM air gap. The Victor JR has a power band of 3500-8000. The performer RPM is 1500 to 6500. That would match your combination much better and give you the bottom end you are looking for. I would leave the gears alone.

Adam
 

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #3
I don't really want to change the engine at all because im very happy with the power it produces. The low end bog isn't even really a problem. Im more looking for a quicker car.
 

·
Premium Member
Joined
·
2,370 Posts
Yes, 4.10 gears would get you into your powerband quicker. You didn't mention what kind, if any, stall converter your running. This is what is going to launch you right into your powerband.
 

·
Premium Member
Joined
·
2,370 Posts
Oops . . . guess I should pay more attention lol. If you going to keep your intake setup then I would look into the steeper gears than the 3.73's.
 

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #7
Alright then just for a referance what do you people with 4.11's turn for RPMs going down the highway.
 

·
Premium Member
Joined
·
2,370 Posts
It depends on the size of your tires and the gear ratio of your transmission. Give us those specs and we can tell you.

This is only a weekend driver right lol?

I have a 3speed auto (3rd gear being 1:1), 4.10 gears, 26" tires and turn about 3000RPM at 55-60 mph
 

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #9
The tires are G60-15 mickey thompson indy profile S/S. I don't know the tranny ratios but it is a muncie four speed and I think it is an M-21 but i could be an M-22. The car was originaly a big block.
 

·
current hot rod: CTS-V
Joined
·
1,821 Posts
2300 rpm's going down the highway with 3.73s? That seems a little low. What do you consider highway speed?

My dads 66 Chevy has G-60s 4.10's and 4 speed. It turns close to 3000 around 55.
 

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #11
Highway speed 65-70. You bring up a good point getto. Ive thought that myself. It wouldn't be the first thing this guy lied to me about. It is a true posi but i don't know how to figure rear end ratio. I know its ring gears divided by pinion gears or something anybody know.
 

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #13
Fire stone that would be helpful but i don't know my gear ratio on my transmission. Any body know the fourth gear ratio on an M-21 muncie.
 

·
Premium Member
Joined
·
3,519 Posts
? 3.73 is PLENTY for that setup. THats not a very big cam or high end intake. If he wants into his power band can dump the clutch like you're spozed to.

K:thumbup:
 

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #16 (Edited)
Well hold on now this is an RPM engine. Cam specs as follows, Duration 280/280, lift at .50 .480/.480, 110 lobe seperation. Now I know that I could rev it up and go from there but my exhaust is loud and i would rather not have to rev up a few grand in the middle of town.

Thats odd. Using the calculator the firestone gave me it tells me that with 3.73s and 1.1 ratio I should be turning just under 3000 to just go 55. Currently I've been running around 2300-2400 to go about 70. That all doesn't add together. Was I lied to and does this car have highway gears?
 

·
Registered
Joined
·
864 Posts
NovaSS350 said:
Was I lied to and does this car have highway gears?
that would be my guess, with your rpm at speed, it'd probably be 2.73 ish rear gears
 

·
Hotrodders.com Moderator
Joined
·
1,642 Posts
4.11s

Put the 4.11s in it. It should run like a raped ape.

Yes, it's true that the low gears do get old buzzing down the highway, but I guarantee you that it will run like a rocket with the big gears.

It has always amazed me that many hotrodders will build an engine with all of the bells and whistles but pay no mind to the gear ratio.

I would rather have the low gears and a junkyard engine vs. a high dollar engine and 2.73s.

More than likely, the boneyard engine with a set of gears will out run a modified engine with highway ratios (at least in an acceleration contest, and not to mention the added smiles you get from being planted in the seat.
 

·
I dun learned sumthin
Joined
·
248 Posts
Discussion Starter #19
Well this opens up a whole new box of worms. I mentioned this previously but does anybody know the caculation to determine rear end ratio by the number of teeth on the pinion and ring gear. I tried to find it in the knowledge base and found a lot of online calculators. But I would rather be able to pull the cover off the back and know for sure what is in there.
 

·
current hot rod: CTS-V
Joined
·
1,821 Posts
NovaSS350 you were lied to, 70 at 2300rpms is a 2.73 gear. I would not go with 4.11's unless you are strictly concerned with your 1/4 mile time. With the 4.11's you're going to top out before you hit 120mph. If it were me I'd go 3.73's. Going from 2.73's to 3.73s will be a huge change, it will make your car will really jump off the line
 
1 - 20 of 46 Posts
Top