Is this a good engine?
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Senior User
Joined: Jul 2002
Posts: 279
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From: Anchorage
Is this a good engine?
I've got a 300 from a '78 parts truck that I'm thinking about using in my '58 F250. The engine cranks and seems to run fairly well until the carb runs dry. Apparently the fuel pump doesn't work. In fact, I'm pretty sure the diaphragm has been leaking gas into the oil since about 2 gallons of really thin old-gassy smelling oil came out when I drained the pan. Anyway, I checked the compression and got the following:
1 : 120psi
2 : 120psi
3 : 120psi
4 : 130psi
5 : 125psi
6 : 140psi
I also have a mechanical oil pressure gauge hooked up and read about 30 psi with the super thin oil that was in it. I feel like the bottom end is solid, but while I've got it on the stand, should I go ahead an replace the rings? Maybe get a valve job, too? This engine hasn't ran in at least 3 years (probably 5+) so I don't expect it be perfect right away, but it seems like with a little work this will be a great motor. Here's a short video I took:
YouTube - 300-6 on stand.wmv
1 : 120psi
2 : 120psi
3 : 120psi
4 : 130psi
5 : 125psi
6 : 140psi
I also have a mechanical oil pressure gauge hooked up and read about 30 psi with the super thin oil that was in it. I feel like the bottom end is solid, but while I've got it on the stand, should I go ahead an replace the rings? Maybe get a valve job, too? This engine hasn't ran in at least 3 years (probably 5+) so I don't expect it be perfect right away, but it seems like with a little work this will be a great motor. Here's a short video I took:
YouTube - 300-6 on stand.wmv
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Joined: Apr 2004
Posts: 34,475
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If the '58 is an occasional use vehicle, I'd be tempted to run it as-is. Fresh oil and fuel pump fix of course.
For regular use, a re-ring won't hurt the pocket book too much if it's a DIY job. Maybe peek at the bearings...
30 psi is fine, your compression figs are a little strange as you usually find one low, not one high.
Valve job...it should have hardened seats in '78, so make sure it really needs the work. Valve seals for sure.
Good luck with it.
For regular use, a re-ring won't hurt the pocket book too much if it's a DIY job. Maybe peek at the bearings...
30 psi is fine, your compression figs are a little strange as you usually find one low, not one high.
Valve job...it should have hardened seats in '78, so make sure it really needs the work. Valve seals for sure.
Good luck with it.
Lead Driver
Joined: Mar 2008
Posts: 7,175
Likes: 377
From: Near Los Angeles
The gas-thinned oil concerns me. Hopefully you did not run it very long with that gas/oil mix in it. If you are going to be depending on that engine for anything other than pops around town, I would definately take a look at some of the bearings. Depending on what you find and the expected usage, that would determine whether or not you r&r the bearings.
Spend a bit more and buy a quality fuel pump. I've had brand new pumps fail. Smell your oil periodically. If it happens again, it could take out your bottom end.
You can get a set of new Clevite 77 bearings for about $100.
Good luck.
Spend a bit more and buy a quality fuel pump. I've had brand new pumps fail. Smell your oil periodically. If it happens again, it could take out your bottom end.
You can get a set of new Clevite 77 bearings for about $100.
Good luck.
