The Stovebolt Site Forums The Parking Lot Big Bolts 1954 GMC 630 ?'s

Hi All

Am purchasing a'54 630 series with a 426ci engine. Haven't seen the truck in person yet. Present owner says it needs a new master cylinder and I haven't been able to find anyone that sells them or a kit to rebuild them. Thought someone here may have a source?

Anything in particular I should be concern with with this series of truck? It's presently a fire truck.

Thanks

Tyler

What is the problem with the master?
Might just need a good cleaup, or a kit, or can be resleeved if badly pitted. Take it appart and inspect.
J. F.

Hi J.F.

Don't know what the problem is yet, just want to be prepared. I'm sure it will probably need to be rebuilt at least. Know where I can find a kit? Thanks for replying.

Tyler

Hy Verdigris, welcome, I come up with Raybestos MK148 for your truck, this is a repair kit for your master cylinder. As Santerre has said you could always have your master cylinder sleeved if it is pitted too badly for a simple honing to clean it up, the master cylinder assembly does not appear to be available any longer. RockAuto has Raybestos MK148 available for $19.16, hope that helps.

A simple easy way for honing cylinder to remove moderate pits and small imperfetion is to take a piece of coat hanger, a section of about 20" long fold in half, with a piece of Emery clothes or sand paper inserted at the bottom of the fold in between both rod, and with a motion of back and forth, turning it with a cordless drill. Do not stay at the same place, always move. Finish with a lighter grit and do not remove more than necessary.
Make sure everything is clean well after, reassemble using sone brake fluid to lubricate the parts, reinstall and bleed.

If everything sat for long time, you might want to take all wheel cylinder and clean, and maybe maybe honing them, flush all the system good. Brake fluid is hydroscopic, Wich will absorb moisture and corode the inside of stuff. Also, might as well replace all the rubber hoses, never a bad investment in my book.

J. F.

3B and JF

Thank you both for the advise and where to find a kit.
Yes, I will be going over everything on the brakes. It's always nice to be able to stop when you need to.

Thanks again.

Tyler

I also have a '54 630 fire truck, I got a master kit on eBay, cheap. Al extension on top of master is easily corroded, easily clean up on a lathe. Looking for wheel cylinders, blew out rubber, so need to take wheels off to get casting number, no original PN's work, mine has 1890 rear. Will keep you in mind when I find casting numbers.

My rear axle was 6.5 ratio, long, slow trip home from Alabama to Colorado, even with OD trans. Got rebuilt 4.33/5.59, much better now.

Rebuilt head, milled .090", new valves, runs good, orig. t-stats no longer available, adapted modern one. Way too many hot (always on) wires in it.

Ed

Hi Ed

How do you determine your trucks axle ratio? Yes, please let me know if you find the casting no's for the wheel cylinders. Like I said before, I'm assuming the brakes will need everything so I want to be prepared.

I can't seem to find much out on the 426ci that's in it. I'd like to find out what it needs for plugs, points, condenser, timing, etc.
Guess I should try to find a shop Manuel for the old girl.

Thanks for the info. Appreciate it.

Tyler

There are shop manuals on eBay from time to time. Inside of glove box has engine, trans, rear axle and ratio. The 426 is within the largest series of GMC 6 cyl. engines. 318? 426, 477, 503. Many interchangeable parts on largest ones. Cylinders are separate from block, as is head separate from cylinders as is common. Several different carbs., manifolds, depending on COE or conventional. Later 503's had .437 valves, early had .375, don't know break, 426 may be all .375. Engine SN should start with 426xxx, etc., stamped on left side of block, very rear, close to firewall, difficult to read.

Plugs are common GM of that vintage. Cannot observe timing mark on flywheel because peep hole covered by tin cover which cannot be turned, left rear, high on block, next to firewall. Put wood stick or such in #1 spark plug hole, turn engine 'tail compression comes out to find TDC, put marks on harmonic balancer.

Distributor drive not like normal GMC, offset drive under base of distributor, works fine, though.

Make sure to oil valve stems, tap with rubber hammer or 2 x 4 piece of wood to make no valves are rusted, prevent bent pushrods. If find a bent one, be gentle. Parts are rare.

Ed

Ed, how are those front wheel cylinders with the pistons I made holding up? That was a fun project!
Jerry

Great, thanks Jerry. I got a two speed rear with 4.33 high, installed it, put a correct Tru-stop disc brake in(the disc in there was 2" too small, would lock up when applied, would have to back up to get it to release) drove it around for a while, one rear cylinder failed, drove it around some more to test out the two speed on the manual brake only, waiting to take rear brake apart to replace. Engine runs great after new exhaust valves, guides, milled head .090" , fresh air intake.

Ed

Thank you again, Ed, for the info. I'll watch e-bay for a manual and make sure things are oiled and free before starting.

Tyler