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7 members (1946chevytruck, Gdads51, 55shaker, Swami29, Otto Skorzeny, 3800GUY, tclederman),
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Mod | | | Forums66 Topics128,114 Posts1,056,604 Members48,448 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Jul 2006 Posts: 707 Shop Shark | | Shop Shark Joined: Jul 2006 Posts: 707 | Who has done this swap? Can I use the mounts from the donor '81 1/2 tonner? Will the thermatic fan fit behind the AD radiator? I think I'll want electric fans anyway. Opinions? What else might confuse me?
1951 3800 Be the change you want to see. -hotshoe
| | | | | Joined: Jul 2006 Posts: 707 Shop Shark | | Shop Shark Joined: Jul 2006 Posts: 707 | Okay, next question then: What should the plug gap be on the '81 250 I6?
1951 3800 Be the change you want to see. -hotshoe
| | | | | Joined: Mar 2004 Posts: 874 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 874 | The shop manual says .035 plug gap for a 1981 250.
You could use the original 250 mounts, but they would need some cutting/welding/fab work on the frame side.
The radiator will have to move forward and down to accomodate the 250 fan.
I believe the fan on the 250 will be about 4 inches or so lower than your 216 fan. (measuring from the crank centerline) | | | | | Joined: Jul 2006 Posts: 707 Shop Shark | | Shop Shark Joined: Jul 2006 Posts: 707 | Thank-you. The old plugs came out clean at .045-.050, and the new ones went in at .038. So I guess my timing will be a little reatrded from spec, but that's okay by me as I like to lug my engines: I imagine it gets me fuel economy. I'll let you know about that tomorrow, as I have a 250 mile trip to knock off through the coast mountains, and on the return leg I'll be loaded to around 1000 lbs.
So if I delete the belt-driven fan on installation and use electric fans, will there be clearance?
1951 3800 Be the change you want to see. -hotshoe
| | | | | Joined: Jul 2006 Posts: 707 Shop Shark | | Shop Shark Joined: Jul 2006 Posts: 707 | Thanks, Chuck. Is your bellhousing in the same spot, or has the engine been positioned back a bit? I'd like to keep my stomp starter.
Your site, by the way, is nicely set up (not that I'm much of a judge), beautifully written... (that, I am in a position to judge: I, too, was educated at the end of a yardstick by penguins. Do you think it doesn't show?) ...but page 26, at least, is so rife with techspeak that it is barely comprehensible to a Doctor of Just Plain Truckin', such as my ownself. Even so, I enjoyed what I have read, and I will be getting to the rest. But right now it's 04:30 and I have a promise to keep.
Where the heck is your garage? I want to leave Epic #2 there for a bit...
1951 3800 Be the change you want to see. -hotshoe
| | | | | Joined: Jan 2001 Posts: 662 Shop Shark | | Shop Shark Joined: Jan 2001 Posts: 662 | I have no clue where the bellhousing was originally; the truck had a 230/3 speed/open driveline when I got it. I did bump out the front of the floor for bellhousing clearance, and I ran a stock-type fixed fan when I first put it on the road. The fan had about 3/4" clearance with the rad mounted inside the horse collar, instead of on the rear face as intended. http://www.chuckthetruck.com/page16.htmlThanks for the compliments. | | |
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