The Stovebolt Site Forums The Shop Area Engine Shop 248 Build Up

Hi everyone,

I'm finally taking the plunge and getting the old 248 overhauled. Are there any tips that i should go for? This is going to be a street driver weekend cruiser with the occasional 50 mile trips.

I'm taking it to Rob's Auto Machine in Hayward, CA.

This is what i have planed so far:
Machine all surfaces and reuse where possible
Rework head (its a 270 head)
hardened seats
Regrind crank
regrind cam
Dual carb zenith intake with Nicson Intake
Fenton Split Headers
HEI Distributor
Full Flow Oil Conversion

I am debating getting:
new pistons that are lighter
Buffalo Enterprises 200r4 Adapter and Trans
New Driveline
New Gears in rear end

Any other suggestions are welcomed. Im dropping the engine off next Friday the 14th.

Just make sure you get the correct pistons for the chamber head your using. There is a high dome and a low dome. You may end up with very low compression if you don't.

From the research i've been doing it looks like my pistons will be flat. Unless i have a 270 h-head, which i do not think i do. My head reads Ferro 2 h25 2194819

Also, does anyone know good donor cars for a 200r4 transmission.

Patrick's lists 2193417 as the 270 H head casting code.

Mid eighties Monte Carlo SS, Buick Grand Nationals, Olds 442, would be the better ones. Just plain Monte Carlo, Buick regal, and Olds Cutlass, would work also.

Awesome info, thank you!

Anyone else want to chime in on the build up?

I think i am also going to have the machine shop grind the lifters in order to eliminate lifter noise.

Also, if i do find a donor transmission, what else should i take off from the car? Shifting linkage? Frame brackets and cross member support for the trans?

I know that Buffalo requires you to make your own brackets for the front mounts.

grind the lifters in order to eliminate lifter noise

What does that mean?

check it out
http://www.langdonsstovebolt.com/tech/noisy-lifters/

It says its for Chevy's, but my engine has the same issue with loud lifters. It could be that the lash is off, so i'll see what the machine shop has to say.

I'm not sold on the problem or the solution.

Your engine doesn't have hydraulic lifters.

Right on, Panic.

Anyone else? A few more days until it goes to the machine shop.

should i have the machinist re-plane the manifold surfaces too?

First of all, If I were going to spend the bucks you are talking about, I would consider a 270 or 302. There just ain't no replacement for displacement. If you have an intake to match an H head, it will work on a 302. If you are having the head worked, I'm sure they will square the valve tips, but worn rocker bushings, rocker shafts and worn rocker tips cause most of the noise. I still have an attachment on my old Sioux 645 that resurfaces the rocker tips. Your lifters will have to be resurfaced if you regrind the cam, but this has nothing to do with noise. I'm sure the machine shop will true the head, but I always true the manifold surfaces. If the head ever had leaking exhaust manifold gaskets, it can be pitted.

Re: the manifold surfacing.
Make sure they are one unit with the heat riser attached so the plane is true for each surface.

I do see the value in building a 270 over a 248. however, this was my grandpas truck and how he had it configured. so the 248 will remain until i can build up a decent 270.

Thanks for the info on the rockers, i might have to look into replacements or see if they can be rebuilt as well - i have no idea what condition they are in.

so it seems that i might need to take my split headers and intake manifold to the machine shop as well.

can you explain this a little more or provide a link. Im not sure what you are talking about.

Is the heat riser similar to what Tom Langdon refers to in putting a plate under the intake manifold that heats it up using the engine coolant?

He is trying to say bolt them together(intake and exhaust) so they can be resurfaced at the same time.

got it, thanks!

anyone know or have a guide as to what color the engine brackets should be? Flat black? Is the manifold a greyish color?

I have been using this information I found on oldgmctrucks.com that Rob English posted:

Scarlet Pimpernel is what many believe to be the original red, not orange paint used on the engines. Rob just calls it GMC Red.

Engine Block & Head......….Scarlet Pimpernel (GMC red)
Cylinder Head (Valve) Cover..........Scarlet Pimpernel
Pushrod Cover..........Scarlet Pimpernel
Exhaust Manifold..........Natural metal or high temp silver powdercoat
Intake Manifold GMC..........Scarlet Pimpernel
Carburetor..........Natural metal - clear coat top - black base.
Fuel pump..........Natural metal - clear coat original pot metal.
Water pump.......Scarlet Pimpernel
Fan blades......black
Air Cleaner..........black
Horn..........black
Starter..........black
Generator..........black
Distributor..........Natural metal - clear coat
Oil filler pipe..........black
Radiator..........black
thermostat housing..........Scarlet Pimpernel
engine water outlet.........Scarlet Pimpernel
Oil Filter Can and cover..........Light Gray

The black on the engine is all glossy black except the generator and starter which are like a satin black. The inner fenders, all the radiator supports and hood closing sheetmetal is that Eastwood Chassis black type of black. Firewall is body color. Bell housing is engine color. Tranny is black. Linkages are all black and steering column is that wierd steering column color down to the box which is black.

Although many on the stovebolt are members of the oldgmctrucks.com, their site is GMC only a few OT posts and they have invaluable information regarding the GMC line.

This is exactly what i needed. Thank you. I'll give them a look tonight.

Got a call back today from the machinist. looks like my 248 is already .030 over and the crank is .020 under.

Is it safe to bore any more than this on either of these components? I know that the blocks are prone to cracking as it is. The block hasnt been fluxed yet either.

Any suggestions as to what i should do?

anyone have an opinion?

I call Egge and ask if the components you'd need are available and I'd have it magnafluxed first.
My orig block turned into an anchor once it was fluxed...

thanks CASO

I think I am going to freshen up my 1948 248. Its a roach

These blocks are as tough as boat anchors. I've seen plenty of them bored .080" oversize with no problems, and the round track racers went even bigger. The crankshaft might go to .030" undersize if necessary, but try doing a polish job if it's still round and straight, and avoid grinding it any more if possible.

Jerry

The factories had a different block policy regarding scrap rate and quality control back in the day.
First, cast iron was cheap and saving a few pounds on a truck meant nothing.
Next, rebuilding or replacing the fixtures that located the cylinders for boring cost money. Cheaper to make all the walls thicker, so a greater error will be harmless.
Trucks are expected to have loonng service lives.