Hi Gang! It’s been several years since I’ve been on this forum and I’m finally prepping the fresh rebuilt motor (from and by the previous owner) that was in his garage like building in VT for a few years and in my heated garageMahal for three years. It had a lot of critter debris in the head and block water jackets. That’s all cleaned out and reassembly of the valve rocker drain and head back on block. Bottom end was still clean.
Question: the “Maintenance Manual” for 1947-1954 models on page 208 figure 59 is a diagram showing water nozzles installed in the head to direct cooling water to specific places in the head water jacket. Are they used in the 270? Are they needed? Where can I get them? Jim Carter and LMC don’t mention them and I did a general search on the web and have found nothing. I’m thinking with the water jackets full of coolant, the nozzles aren’t needed??? Whaddya think?
Thanks for reading and I hope everyone is doing well!!! Jim
Last edited by Phak1; 01/27/202512:57 PM. Reason: Spelling and punctuation
I looked in my '51 100 to 350 series and 55.2 100 to 450 series GMC Maintenance Manuals and found no mention of these gizmos. But, I did find them in the 39-54 GMC Master Parts Book.
I'm pretty sure that my '52 228 does not have them and I'm real sure my 302 head doesn't.
What year maintenance manual is your picture from?
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Hey Bill, thanks for the reply. It’s a 47-54 reprint. So it doesn’t cover my exact engine. I’m finding that these things aren’t very popular. Hopefully they are not mandatory. I’m thinking the entire cavity is filled with coolant and doesn’t really need it to be focused by nozzles. Thanks again!
Those look like they could be fabricated by a first year high school machinist student, (back when they actually had those kinds of classes) but since they were discontinued by GMC, I wouldn't waste much time worrying about them. They look like the idea was to direct coolant toward the exhaust valve area of the combustion chamber. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Hey again Bill! Wow, at least people know what you’re talking about when you say “Hens teeth”! I’ve called coast to coast and no supplier has any idea what I’m looking for. You probably saw in my pictures that there’s nothing there. I even found the paperwork for my rebuild, from 2006 and the guy doesn’t remember this specific engine, but remembers the guy I bought it from. Where did you get those numbers in the photo? I tried googling them and all dead ends. Where do I find the GMC engine building authority? If I could find one of each, I got people who can make them. What do you think? Thanks! Jim
Thank you! I was wanting to just skip them but needed someone to validate it. If they stopped using because of clogging back in the day, then I’m good! Thanks!
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
I've got a 248 engine in bits and pieces stashed away. If it has the nozzles, I can use them as a pattern to make as many as necessary. It looks like they're nothing but a piece of blocked-off copper tubing with a spray hole pointed in a particular direction. There's absolutely no reason why someone who has the unmitigated gall to call himself a mechanic shouldn't be able to make them by the dozen. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
So bets are that I will find them on my 302.....and the book says you need to literally destroy them to remove them..... note to self.... be patient you do not have the heads removed yet????
Bob C.
In reading the only manual I have so far, it seems that N0 6 cyl has a tendency to run hot....so did the 216 and to resolve that issue the military installed whatn was called a steam tube...... basically a 3/8 steel line from the temp port of the 216 to the neck of the radiator filler..... remember military 216 ran at 0 rad pressure. When I isntalled my rebuilt 261 stock I retro fitted a steam linesimialr to the 216 BUT installed temporarily a 1/4 ball valve and a see thru vinyl line...... and ran the engine on a test run in the back field with the valve fully closed....stopped, left the engine running and opened the line......for a few minutes the tube flowed only bulbe antifreeze foam then it cleared up...... repeated the test with the valve fully open...... and the fluid was a solid green color with no bubbles. I concluded to remove the temporary fittings and installed the steam line permanently on the 261 and so far, with lots of hard driving, never had a heat issue on the rear cylinder. I my aging memory is correct I detected a pipe plug on the rear of the block between or near NO 5 and 6n cyl which I intend to test out with a view of fitting a steam line.
The military version of the GMC 302 engine had a similar arrangement that routed coolant from the #6 position of the head externally up to the thermostat housing.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
So, to be clear on this concept, which way will the coolant be flowing in that tube ? From the rear to the thermostat housing?
~Charley 1954 Chevy 3100 with 235 “Bud” Follow along in the DITY 1963 Chevy half ton stepside short box 230 1954 GMC 3 ton 302 And several more Chevy camper and work trucks 1979 1987 1996
So, to be clear on this concept, which way will the coolant be flowing in that tube ? From the rear to the thermostat housing?
Yes. Out of the head, forward through the tube and into the bottom part of the thermostat housing.
It will also help clear the "air bubble" that persists at the rear of the head when coolant is changed.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Some body had some "smart" way back to the early days of the war as they adapted the concept of the steam tube to the 216....... mine works well on the 261. I have driven my Chev 261 4x4 on rough trails...rough enough for both gas tank caps to fall off....but the military had little chains so did not loose them....same thing to the cap to the oil refill tube. My after market mechanical water gauge with the very small copper tube actually broke due to vibration where I had coiled the excess tubing. and busted a military double action shock on the drivers side....but I have spares. It is brutal, hot, tight, uncomfortable but its mine!!!! all mine!!!!
Carb is the stock Holley 660-1 ..... how good are they?????
"Damaged holes in tapped threads necessitate replacement of cylinder head" I guess this was before Heli-Coils or TIme-Serts, eh? I've also fixed stripped threads in old metal things by brazing in a new layer and tapping that out . There are a number of old steel bicycles in my area that are running with brazed and retooled derailleur hanger threads-versus throwing the frame away or <gag> making into a hipster single speed. Sometimes I have to fabricate the whole derailleur hanger.. whether old cars or bikes, sometimes we have to make it ourselves :-)
