Otherwise stock 305 with performance cam
 

I am running a '91 chev truck 305 with a 700R4 trans in my T-bucket. Having never used a performance cam before, I was very pleasantly surprised at the increased performance with the Erson E110024 streetfighter cam. It doesn't spin the tires as easily off idle, which is a good thing, but it really comes alive immediately. No bog, even with the tight torque converter, this thing really flies. Super Stock style burnout yesterday. Brake torqued it in drive and it upshifted to 2nd with the tires burning and the front tires sliding. When I left up on the brake it just stayed in 2nd and went on down the road with the tires smoking. Very impressive for a little 305. The on road performance is very similar to what I had with the 355 with a stock cam. It pulls strong all the way up to upshift at about 5200 rpm. And the street manners are still very nice. Very glad I did the cam change. Looks like the best of both worlds to me. And now with the lockup torque converter wired up to control manually, I expect some real good cruising mileage. Thanks again for the great advice. BTW. It was almost 65 here yesterday so it was a nice day for a drive in the bucket. Merry Christmas. Allan

What rear gears and rear tires?

3.08 rear gears and P295x50 on 15" rims. Yeah, I know. It's geared for cruisin' . About 1560 rpm @ 50 and 2100 rpm @ 70. What more could I want. All that play power and a great cruiser as well.

Something is wrong. 700R-4, 3.08:1 and 295/50R15 should be 1900 RPM @ 70 MPH, and 1350 @ 50.
Is your torque converter locking up? Is your speedometer calibrated? It should be an 18 tooth drive gear, and a 42 tooth driven gear.

Okay , I actually never checked the ratio other than walking alongside as I rolled it along and watched the driveline. It may be 3.23 or 3.42. Not sure, just a guess. It really doesn't matter to me. I just like the way it runs. I have checked the speedometer against my GPS and know that I am going 70 or 71 when the speedo reads 65. So, just saying the tach reads about 2100 in lock up when the speedo reads 65mph. The speedo is electronic and programmable, but is close enough for me , 40 is actually about 41 and 50 is almost 52. Not far enough off to mess with.

Big Al, glad the cam change gave the results you were after. Did the cam give you a bit of "rump rump"? I remember that you were hoping for a bit of "idle music".

Big Ed

Might be a 2.41 ratio:

w/26.7" diameter tires and 1560 RPM= 51.44 mph

2100 RPM= 69.24 mph

Thanks Mark. :thumbup: That sounds just about exactly what I am running for rpm @ mph. The rearend is an early front loader GM used from '55 thru '64 . When I bought a pinion seal, and gave the guy at the parts counter the part number off of the old seal, it referenced a '57 chev. Now if I ever blow it up :eek: with those super stock style burnouts :D I'll have an idea what ratio to look for. Of course I would tear it down and do a tooth count to confirm, before I ordered any parts . Allan

Big Ed. Just a little. Sounds really nice. :D Not quite the smooth as a Singer sewing machine sound that it had. I really don't think that I could have made a better choice as far as cams go. If I bring the car up to 40 mph and then let off the gas so that it switches into overdrive and then switch on the lockup clutch in the torque, the rpm drops way down to about 1100 or 1200. Then I set the cruise control. :cool: So I wouldn't want anything more radical. I was surprised to have that much vacuum loss though. Used to have almost 21 in hg, now is just a little over 15 in hg. Not a concern, just a little surprised. Allan

You guys are forgetting about the OD. I didn't bother figuring out the actual gear because the OP indicated a definite lack of interest.
Figuring 2.41 is close, because a 3.42:1 axle with the 700R-4s 0.70:1 OD gives 2.38:1
In which case, the correct speedometer gears are a 17-tooth drive gear, and a 44 tooth driven gear.

I thought you had a corporate 10-bolt rearend (don't ask me why I thought that), the 2.41 was a fairly common ratio for them.

But I cannot remember a '58-'64 application that would have had a 2.41 ratio. That ratio wasn't used during '55-'57, 3.36 was as high as they got IIRC. I know it prolly doesn't matter that much one way or the other but I wonder if there was a 2.41 used from the factory during the "Hotchkiss" era.

Thanks, whyholdback for your interest. :thumbup: Yeah it looks like cobalt327 forgot about the 700R4 with the .70 overdrive. I actually read his post as 3.41. :rolleyes: . My bad :spank: . Yeah. it would be nice to know the actual ratio, because I am always asked that along with the other usual questions. IE: eng., trans., cam,. So considering that the tire height is 26" (just measured) and the engine runs about 2100 rpm @ 70 mph., what do you suppose my rear axle ratio is ? 3.42:1 ? BTW, I am running a 39 tooth driven gear against a 15 tooth drive gear (if I remember correctly) and the speedo still runs slow. Not really wanting to change speedo drive gears, as they are not cheap. But as I mentioned, the speedo is electronic and programmable, but is close enough for me. I know how much it is off, so I drive accordingly. I did program the speedo when I had the TH350, and if I remember right, you can't get it exact anyway. Did you know that as tires wear, distances from point A to point B increase ? :mwink: I used to have to keep records of my mileage for tax purposes at my last job. I used to set my trip meter in my driveway and reset at the mine entrance. As tires wore down, the trip distance would change from 32.6 min with new tires to 33.1 with worn.

Back and forth here, so you say that 3.36 was a pretty common ratio for '57 ? Just like to know what to say, other than I don't know, when people ask. According to what whyholdback has calculated, that would be really close with the .70 overdrive and 26' tall tires. Thanks, Big Al

Last I knew you had a TH350C. :confused: Oh well.

From my notes- I don't know who to credit it to: "55-56 had 3.70 with a standard trans, 4.11 with the OD trans, and 3.55 with the auto trans. In 57 they went to 14 inch tires and then they used a 3.55 with a standard trans and 3.36 with the auto trans."

When I did the walk alongside while watching the driveline, I know it was less than 3 and 1/2 turns, I actually thought that it was real close to 3 and 1/4, so it most likely is the 3.36:1 ratio. Thanks, Big Al