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C10 250 swap to 350

Old Dec 4, 2020 | 10:55 AM
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Default C10 250 swap to 350

I'm new and need help in every way but I have a neighbor that can do anything
My wife has a 1971 c10 short bed step side, we have fixed everything so that it all works as it should. Now we want to swap from a 250 six cylinder to a 350 v8 and keep the 3 on a tree.trans.
will the clutch work ( 10" 10 spline ) or can we put a larger clutch and work with the trans? ( say 10 spline 12" ???? )
Is there a different clutch linkage for the v8 ?
I have ordered motor mounts from Brothers...
I was given a completely rebuilt 350 from 68 Camaro and have starter the process of pulling the 250
Any advice and help would be appreciated
Please advise
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Old Dec 4, 2020 | 2:47 PM
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Originally Posted by FREEWILLIE71
I'm new and need help in every way but I have a neighbor that can do anything
My wife has a 1971 c10 short bed step side, we have fixed everything so that it all works as it should. Now we want to swap from a 250 six cylinder to a 350 v8 and keep the 3 on a tree.trans.
will the clutch work ( 10" 10 spline ) or can we put a larger clutch and work with the trans? ( say 10 spline 12" ???? )
Is there a different clutch linkage for the v8 ?
I have ordered motor mounts from Brothers...
I was given a completely rebuilt 350 from 68 Camaro and have starter the process of pulling the 250
Any advice and help would be appreciated
Please advise
Clutch will be ok. I am assuming the transmission is a Saginaw, it will work. I am pretty sure everything back of the engine is ok. All you are doing with reading your post is replacing the engine, and motor mounts, the rest of the drive train should be ok, the drive shaf
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Old Dec 4, 2020 | 2:51 PM
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Clutch will be ok. I am assuming the transmission is a Saginaw, it will work. I am pretty sure everything back of the engine is ok. All you are doing with reading your post is replacing the engine, and motor mounts, the rest of the drive train should be ok, the drive shaft will also work as the spline into the transmission is adjustable, i.e. slide it in, and bolt the U joints into the differential.
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Old Dec 5, 2020 | 3:46 AM
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Originally Posted by FREEWILLIE71
I'm new and need help in every way but I have a neighbor that can do anything
My wife has a 1971 c10 short bed step side, we have fixed everything so that it all works as it should. Now we want to swap from a 250 six cylinder to a 350 v8 and keep the 3 on a tree.trans.
will the clutch work ( 10" 10 spline ) or can we put a larger clutch and work with the trans? ( say 10 spline 12" ???? )
Is there a different clutch linkage for the v8 ?
I have ordered motor mounts from Brothers...
I was given a completely rebuilt 350 from 68 Camaro and have starter the process of pulling the 250
Any advice and help would be appreciated
Please advise
The 250 Chevy is a great motor. It'll last forever if you don't beat it up. That said the 350 should fit in nicely. Might be good to check out your rear axle before you do so. Three-on-the tree? So many moons ago now.

Last edited by oilcanhenry; Dec 5, 2020 at 3:49 AM.
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Old Dec 6, 2020 | 12:13 PM
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Thanks for the input....
I am told that I can put a 11 inch clutch instead of the 10" with this flywheel. ( just think the bigger the better ?) with bigger engine.
The 11 is actually cheaper than the 10 ....

Do you have any thoughts about the 3 speed not holding up to the v8 ?
Will just be a occasional driver for fun not competition

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Old Dec 6, 2020 | 12:17 PM
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I will need to find a home for the 250 if you know someone with a need.
Nothing wrong with it as far as I know ....

Was running fine till I found the the 350, I honestly think the actual miles are less than 60000
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Old Dec 6, 2020 | 12:44 PM
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Originally Posted by FREEWILLIE71
Thanks for the input....
I am told that I can put a 11 inch clutch instead of the 10" with this flywheel. ( just think the bigger the better ?) with bigger engine.
The 11 is actually cheaper than the 10 ....

Do you have any thoughts about the 3 speed not holding up to the v8 ?
Will just be a occasional driver for fun not competition
If it's a saganaw, I don't see any issue with it. The clutch is fine either way, I hold suggest replacing the release bearing unless it is fairly new. You can tell if it needs replaced when you get it out, but for a 20 dollar part, it's worth that to not drop the transmission in 6 months or so to have to replace it.
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Old Dec 6, 2020 | 2:26 PM
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FREEWILLIE71:

https://nastyz28.com/chevy-manual-tr...tification.php

This ought to help you identify your transmission, but Kevinpkp is likely correct about a Saginaw being the transmission.

I'd put some light grease on the pinion shaft bushing or bearing and use a good full synthetic 75-90 or 80-90 gear oil in the gear box.

Probably 3 pints to 3.5 pints or so.
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Old Dec 8, 2020 | 3:22 PM
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Default 11" clutch did not work on 250 flywheel

I had to get a flywheel for the 350 that the 11" clutch would fit.
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Old Dec 8, 2020 | 3:42 PM
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Originally Posted by FREEWILLIE71
I had to get a flywheel for the 350 that the 11" clutch would fit.
Make sure the starter shim (if needed) will engage the fly wheel and not cause damage to the fly wheel teeth.
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