The Stovebolt Site Forums The Shop Area Engine Shop Help with some advice on my first 250 upgrade.

First off thanks in advance if you take the time to reply.

I've got a 1967 Chevy C-10 with 250 and 3 on the tree that runs very well and doesn't burn any oil. Last year I added and Offenhauser two carb intake and headers to the engine. Nice peppy little truck, I enjoy driving it and it is the most bulletproof old car I own. Built a good number of SBC's in my day but know there are going to be tricks and advice on this motor that i do no know.

This winter I would like to continue on the upgrade for the engine. Goal is still to be reliable but get a nice noise and increase breathing. Not going to tear into bottom end because this engine unless absolutely necessary.

I recently bough a clean 230 head that has been magnafluxed and prepped for stock install. I would like to do a valve job, port, and plane this head. Can anyone give some knowledge on what I can/should do to this head to get the most performance for my dollar?

I would also like to install a cam to give the truck a boost in performance and increase the "lope". Any recommendations on good lift cam?

Thanks again and I look forward to your constructive replies.

First, take that 2-carb setup and pitch it off a bridge into a very deep river so you won't be tempted to try to fish it out again. Inline sixes either need one carburetor or three. Next- - - -go rob a bank. To make the head support the kind of modifications you're suggesting takes money- - - -by the pound. Research "lump port" modification of the cylinder head before you even think about doing any porting or valve size increase- - - -those huge head bolt columns in the middle of the intake ports needs to go away.

Now- - - -do a complete bottom end rebuild before you think about cam, carb, or intake/exhaust work. While you're in there, install a set of 307 Chevy V8 pistons- - - -they're flat tops instead of having the 1/4" dish top of the 250 piston, and you're going to need the extra compression to support any sort of a lumpy cam. The last hotrod 250 I built got a .050" milled head and flat top pistons, and nothing crashed. However, I didn't get stupid on camshaft timing and lift. Anything over about a 270 degree duration cam has no business on the street. If you want an idle lope, take one spark plug wire off. You're going to need a strong foundation to build on, and putting a lot of money into the upper end of an engine in less than brand new condition makes no sense at all.

"It costs money to go fast- - - - -how fast can you afford to go?"

I'm in the process of accumulating the bits and pieces to build a 230 with 3 Harley-Davidson side draft carbs and enough intake/exhaust and bottom end modifications for it to live comfortably at over 7K RPM. I'm expecting to spend somewhere upwards of $5,000.00 before I hear it run, and I'll be doing almost all of my own machine work. The NASCAR tool steel connecting rods alone I'll be using for that engine sell new for over $2,000.00. I'll be using reconditioned "one race" rods from a place that salvages retired round track engines, for a considerably lower cost.
Jerry

Get a bolt in lump kit and give it an install. The install can be done on the work bench. It’s a pretty fun project and will allow the head to breath a bit better.

Here is where you get a kit

https://www.12bolt.com/store/p1/Standard_HI-FLOW_Bolt_in_lump_kit.html

And here are the videos for the installation.

https://www.12bolt.com/bolt-in-lump-installation-instructions.html

You can do a little polishing in the chambers if you want, nice three angle valve job, you can use some good street flo valves if you want.

It’s a pretty good project. I have done two of them.

Myself personally wouldn't spend a penny on ANY Chevy I6 made before the 2002-2009 4.2 (or Atlas) engine. The stovebolt or ANY siamese port head was a lousy design if go fast is what you want. For regular use I love them. If I had to choose an ohv push rod I6 I would use the Ford 240/300 or the thinner block 250. Both have seven main bearings and 12 port heads which are a natural for any kind of port fuel injection and can take a reasonable amount of boost. The Aussies are getting stingier with their 250 12 port crossflow heads but someone is supposed to be making an aluminum one for the 300 Ford. Ones that want to run fast with an inline 6 can just paint the Ford a GM color and put a Chevy decal on the valve cover, then prepare for a lot of tire smoke. Jack Evans out of McKinney Texas has been dead for many years but his 240 Ford I6 dragster was the first to go 200mph and later 250mph in the 1/4 mile---maybe a tad out of reach for the Chevy Stovebolt.

If it was mine, and I have a 250, I would add the 307 pistons for the compression increase, look for a slightly bigger camshaft, have the head rebuilt as it is, clean up the head to block surface, and add HEI ignition. It will sound better with higher compression and run better. You go adding a lot bigger cam will wreck the idle quality. The Lump port inserts work if you spin the engine to higher rpms, they actually work really good, but for a normal old truck, you probably won't notice the performance increase. Dollar for HP gains will be the compression increase, keep the manifolds you have. Be sure to add water heating to the intake if you don't have it already.

And in other news: that's why they run in separate classes.
Like the Ford flathead and OHC Cobra V8 motors don't run heads up?

This is great stuff , at my age I hope I can recall where to find it when I get to getting !

I would talk to Tom Lowe at 12bolt.com and have him do the work. If you are going to do the bottom end why not go with the 292? Same head. JMHO.

Might want to join inliners.org. Their main interest is inline engines that go fast.

John

Bootlegger Adam,
I'm in Columbia, SC. I have a surplus of inline 250ci. Three to be exact. I really need to get rid of them. I'd be happy to supply you with parts you might need. I'd rather not sell them for scrap. Where are you in SC?
Jay (Lugnutz)

A 292 will give you plenty of torque and hp at half the fuel mileage of the 250!

Wow I appreciate all the replies. I'm not sure where the thoughts about me trying to make a high speed power plant came from. Just wanted to liven it up. Sure a bottom end rebuild will happen someday but investing in upgrades as I go has never been money wasted in my experience.

I will check into the lump kit's and I appreciate that advice. No one stated if they had any experience in planning the head.

I have hand ground more heads than I would like to count and dont have a problem doing that again. Will probably go this route if my machine shop price for doing it is to much.

As far as the advice as my intake goes I have had no issues. I have nearly the same exhaust temperatures at each exhaust port after aggressive test drives. Seems to me I am getting a good fuel mixture and burn to all cylinders if that is the case.

Lastly I have upgraded the ignition system. Sorry I figured that was obvious. Thanks for the suggestion though.

If you have any more constructive advice I would appreciate it.

I live in the Greenville area and appreciate the offer for some 250s but dont have the need.