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#43470 06/24/2003 3:30 AM | Joined: Mar 2003 Posts: 10 Member | | Member Joined: Mar 2003 Posts: 10 | I have freshly rebuilt GMC 302. Rebuild kit came from Kantor, $795 I think. Rebuild was supposedly done by a reputable high performance engine rebuilder. I believe it is a 1953 motor.
I plan to run Mobil 1. The stock oil filter has been replaced by a screw on type. I'm wondering at what RPM I can run safely on the highway.
My 51 1-ton has 5.14 gears so with my 33" tires I would be turning 2600 at 50 MPH. I will be shoping for an overdrive. 0.80:1 would bring me up to 62 MPH at 60. I'd like to be able to drive 65 or faster.
What's a max RPM for highway travel?
Thanks
Sidehill | | |
#43471 06/24/2003 1:27 PM | Joined: Nov 2000 Posts: 427 'Bolter | | 'Bolter Joined: Nov 2000 Posts: 427 | Sidehill: You can take that 5.14:1 stump puller and replace it with a '67-'72 4.11:1 out of a 3/4 ton automatic and it's a two hour bolt in job that will cut your rpms down by 25%, which in your case is a HUGE improvement. I did to my '51 3/4 ton (which had the same rear) and it will really make things a lot easier on your truck, and you. Here's a link to the swap: 1951 3/4 and 1 ton two hour rear end swap I think you'll find this a lot less surgery and effort than putting in an auxillary transmission or overdrive setup. | | |
#43472 06/24/2003 3:24 PM | Joined: Jan 2000 Posts: 206 Member | | Member Joined: Jan 2000 Posts: 206 | 302's were rated from the factory at 3400 RPM. Many had governors set for this speed. It really doesn't help to run a stock 302 any higher than this, hp/torque are limited by the airflow capacity. | | |
#43473 06/24/2003 4:23 PM | Joined: Jul 2000 Posts: 504 Member | | Member Joined: Jul 2000 Posts: 504 | One reason original 302's were governed from the factory is because they were built with heavy cast iron pistons.. Overspeeding them was hazardous to the health of the rods and crankshaft..Although modern aluminum pistons lessen the stresses, 3400 rpm should still be considered an upper limit..
I agree with Kook, the rear gear swap is the place to start..
Bill M
53 GMC Hydra-Matic
Home Page
http://home.comcast.net/~bd97/index.html
When you argue with a fool, two fools are arguing..
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#43474 06/25/2003 1:20 AM | Joined: Mar 2003 Posts: 10 Member | | Member Joined: Mar 2003 Posts: 10 | Gentlemen
Thanks for the info. I had been trying to remember what 4.11 third member fit.
As for the RPM's I was guessing 2800, so 3400 is much better than I had hoped. With just 3000 I'm tempted to keep the 5.14's. At 3000 RPM with my 33" tires I would be going 57 MPH. With an 0.8:1 overdrive I would be going 71 MPH. Plenty fast!
I hate to give up the 5.14's because of the rough, rocky, high altitude roads around here. I once had a 53 GMC with a 228 motor, and a 4.56 diff with Detroit Locker, and was always wishing for lower gears for crawling up the jeep roads.
Yeah I know, kinda nutty, but it's way more fun driving jeep trails in a '51 2-wheel drive than in a built 4-wheel drive.
Sidehill | | |
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