A few 250 questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

T and S · 10-14-2015, 07:16 PM

Finally started working on my in liner, clean-up, paint re-gasket, etc... It has electronic sparky, weber carb, stock intake and exhaust manifolds. It has been sitting in my shop a little over a year. I haven't checked compression, but motor feels good turning it over, seat of the pants feel.
I pulled the plugs, the center 2 look good. Outside 2 on each end had a little oil around the threads, I figured valve seals leaked down some, and also looked like it may have been running a little rich.
Friend of mine has a cam that he bought for a square body back in the 80's (he told me the lift on it, but it slips my mind ) I could probably get for free, it has never been used. I picked up this motor from a guy here on the boards, I don't know much history on it, but I heard it run in a video.

Should I: A) leave it alone and run it stock.
B) install cam and see what it does.
C) install cam, headers. Will I have enough carb for that ?

I don't want to open a bucket of worms, I want it to be reliable.

**jayoldschool** · 10-14-2015, 07:28 PM

Keep it stock. Get it running well, tuned properly, leak free.

T and S · 10-14-2015, 09:10 PM

That's what I am leaning toward, I just thought I would get some opinions from different peeps.

TJ's Chevy · 10-14-2015, 09:17 PM

A cam with a little more lift and duration won't hurt anything. Long as the lift is no more than .450. But if it runs ok, compression is good and even, doesn't smoke, I'd tune it up and enjoy it. Run some good oil in it since its an older engine.

scuderia · 10-14-2015, 09:22 PM

If you decide to run the cam make sure it's been stored properly (on end) or just make sure it's straight. Was just reading how they can bend under their own weight if stored flat...

T and S · 10-15-2015, 07:13 PM

I think he told me the lift was .520 or something like that. I didn't realize cams would bend from storage.

T and S · 10-16-2015, 10:10 AM

Also, I am thinking of running the high mileage Mobil 1 10W 30 oil in the motor. Is at the top of the list for motor oils.

TJ's Chevy · 10-16-2015, 10:28 AM

At .520 lift you'd be at around at least 260 duration which would be to much for a stock engine. That lift would also require beefier valve springs. Yep, old engine like a good oil. Oil with high zinc in them is preferred to help save the cam.

GRX · 10-17-2015, 10:37 AM

Agree with others above. Get it running with no leaks and be happy. You can worry about performance parts later.

Stock was around .390. 520 lift at the valve is high for these 250s. Pretty much race applications. For that you would definitely need new springs. And probably need the valve guide tops milled down so the valve spring retainers don't cut the umbrella seals. And do not forget new lifters for the new cam.

Cams and cranks can and do bend if not stored properly.

10-14-2015, 07:16 PM	#1
T and S Registered User Join Date: Dec 2013 Location: Oak Ridge, Mo. Posts: 301	A few 250 questions Finally started working on my in liner, clean-up, paint re-gasket, etc... It has electronic sparky, weber carb, stock intake and exhaust manifolds. It has been sitting in my shop a little over a year. I haven't checked compression, but motor feels good turning it over, seat of the pants feel. I pulled the plugs, the center 2 look good. Outside 2 on each end had a little oil around the threads, I figured valve seals leaked down some, and also looked like it may have been running a little rich. Friend of mine has a cam that he bought for a square body back in the 80's (he told me the lift on it, but it slips my mind ) I could probably get for free, it has never been used. I picked up this motor from a guy here on the boards, I don't know much history on it, but I heard it run in a video. Should I: A) leave it alone and run it stock. B) install cam and see what it does. C) install cam, headers. Will I have enough carb for that ? I don't want to open a bucket of worms, I want it to be reliable. __________________ If you don't like this pound sand ..... Last edited by T and S; 10-14-2015 at 07:19 PM. Reason: add info

10-14-2015, 07:28 PM	#2
jayoldschool Moderator Join Date: Dec 2012 Location: ON, Canada Posts: 2,170	Re: A few 250 questions Keep it stock. Get it running well, tuned properly, leak free.

10-14-2015, 09:10 PM	#3
T and S Registered User Join Date: Dec 2013 Location: Oak Ridge, Mo. Posts: 301	Re: A few 250 questions That's what I am leaning toward, I just thought I would get some opinions from different peeps. __________________ If you don't like this pound sand .....

10-14-2015, 09:17 PM	#4
TJ's Chevy Registered User Join Date: Mar 2013 Location: Southern Oregon Posts: 10,384	Re: A few 250 questions A cam with a little more lift and duration won't hurt anything. Long as the lift is no more than .450. But if it runs ok, compression is good and even, doesn't smoke, I'd tune it up and enjoy it. Run some good oil in it since its an older engine. __________________ 1966 Chevy C10 "Project Two Tone" http://67-72chevytrucks.com/vboard/s...d.php?t=596643 1964 GMC "Crustine" semi-build:http://67-72chevytrucks.com/vboard/s...d.php?t=665056 My youtube channel. Username "Military Chevy": https://www.youtube.com/channel/UC_h...fzpcUXyK_5-uiw

10-14-2015, 09:22 PM	#5
scuderia Registered User Join Date: May 2014 Location: SAN FRANCISCO Posts: 447	Re: A few 250 questions If you decide to run the cam make sure it's been stored properly (on end) or just make sure it's straight. Was just reading how they can bend under their own weight if stored flat... __________________ '66 C10 SWB '64 C2 roadster '38 Indian Scout Flattracker '70 Triumph T120R '81 Laverda Jota

10-15-2015, 07:13 PM	#6
T and S Registered User Join Date: Dec 2013 Location: Oak Ridge, Mo. Posts: 301	Re: A few 250 questions I think he told me the lift was .520 or something like that. I didn't realize cams would bend from storage. __________________ If you don't like this pound sand .....

10-16-2015, 10:10 AM	#7
T and S Registered User Join Date: Dec 2013 Location: Oak Ridge, Mo. Posts: 301	Re: A few 250 questions Also, I am thinking of running the high mileage Mobil 1 10W 30 oil in the motor. Is at the top of the list for motor oils. __________________ If you don't like this pound sand .....

10-16-2015, 10:28 AM	#8
TJ's Chevy Registered User Join Date: Mar 2013 Location: Southern Oregon Posts: 10,384	Re: A few 250 questions At .520 lift you'd be at around at least 260 duration which would be to much for a stock engine. That lift would also require beefier valve springs. Yep, old engine like a good oil. Oil with high zinc in them is preferred to help save the cam. __________________ 1966 Chevy C10 "Project Two Tone" http://67-72chevytrucks.com/vboard/s...d.php?t=596643 1964 GMC "Crustine" semi-build:http://67-72chevytrucks.com/vboard/s...d.php?t=665056 My youtube channel. Username "Military Chevy": https://www.youtube.com/channel/UC_h...fzpcUXyK_5-uiw

10-17-2015, 10:37 AM	#9
GRX Registered User Join Date: Jul 2010 Location: MD Posts: 1,937	Re: A few 250 questions Agree with others above. Get it running with no leaks and be happy. You can worry about performance parts later. Stock was around .390. 520 lift at the valve is high for these 250s. Pretty much race applications. For that you would definitely need new springs. And probably need the valve guide tops milled down so the valve spring retainers don't cut the umbrella seals. And do not forget new lifters for the new cam. Cams and cranks can and do bend if not stored properly.



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