Hot Rods AD_NAPCO's 39 GMC Rocket 324 Build

I think I still have some parts carbs in the shed if you cant find a spring.

 

Jeff, that's great... I'll let you know if I come up dry. Thanks!

 

Well... Nothing too exciting to report, other than I received my rebuild kit for the mechanical fuel pump from Then and Now Automotive, and so I spent the afternoon rebuilding the fuel pump.

I got it mounted just in time for the fiance to drive up and order me to the shower for some friday night "thing" we're doing with some friends...

I'd rather be here screwing around with the truck.

To be continued...

 

Ok... So, no apparent success yet, but here's what I think I know. Put a gauge on the fuel pump and cranked the motor over. Seems that I must have rebuilt it correctly. The pump is pulling about 3 lbs. of vacuum, and pushing about 4 lbs. of pressure. This according to the guage. It still doesn't seem to visually indicate that kind of pressure to me, and it doesn't seem to be pushing fuel up to the carb quite agressively enough. Maybe it is.

Still can't get the damn thing to idle. It'll fire and die immediately... So, back to the drawing board.

 

Does it die when you let go of the key in the start position? If so, check to see if you lose power to the coil in the run position.

 

if you have a remote starter i would try spraying some gas into the carb while your starting it to see if you can keep it running, just the right amount of fuel and it should just keep running.

 

power to the coil is good. I have been using a remote starter with the key in the run position.

I fiddled with the choke a bit, and finally got it run for about 20 seconds. Seems really hard starting. It may be a spark advance issue. I'm going to go back to square one with setting the initial timing. That might be the issue.

 

Seriously about to lose my mind. I posted a video on youtube of the motor firing and dying...

Take a look and see what you all think.

http://www.youtube.com/watch?v=mIYG2TQiAq8

 

If the motor has been sitting for a long time its not going to idle correctly right away,work the throttle until it warms up and then adjust the mixture screws and turn up the idle speed a little. If you dont have the radiator hooked up you need to do it now and let the motor warm up completely and let it run awhile.

 

Two things; one is I can hear low compression on at least one cyl, but that is not the problem.

Second, the choke seems to open too much when the vacuum pulls it open a bit.

Now, I see you are not fighting it to keep it going. You have to do that with a long dormant motor.

If you are handy with both hands, fire it up, but keep the choke from opening up that much, and also fight the throttle to keep the squirter going.

Yes, like said, heat is your friend. Get it warmed up before getting frustrated. I've been working for two collectors since spring, getting barn finds to run. I rarely have water in them in the beginning. I run them up warmer each time, fixing or adjusting things, then run again, until I get to where I think it's fairly hot. By then, things usually start to look better. Let it cool completely, then I add water. Even without a rad, if you can leave the water pump not spinning, but keep water in the entire block and heads, you can run it a while longer.

 

Will do... I do have the radiator hooked up.

I'll try to fight it to keep it going. I've just never had this much difficulty getting long dormant inline Chevy and GMC 6's to run and I've woken my fair share of them from decades of slumber.

Will report back when I've given it another round of trying. I will also look at the choke adjustment and see if I can figure out why it's opening too far. Perhaps I need to engage the choke spring a little tighter.

 

how many turns out are your idle mixture screws? i just checked two of my 4-jet carbs and they are out 2-1/2 turns, i have 4 4-jet carbs but two of them have the idle mixture screws stuck, also like the other guy said, keep it running by pumping it, it might run when it gets above the idle circuit.

 

It's hard for me to see just how far it opens when running. That opening is caused by the "vacuum break" AKA "choke pull-off". On that carb, I think it's an internal piston, If it was external vacuum can, then you bend the U link to set the gap to specs.

Adjusting the choke cover has no effect on the vauum pull off.

 

This one's off a '55. Should be the same as yours. and F&J's right, just a Y shaped piece of metal. About 3.25 inches long, just shy of 3 inches wide at the widest point, and just shy of an inch at the narrow end.

 

Thanks for the pics, Canuck... I should have a stock clamp on the way from a guy that was parting a 324.

Flames shot out of the carb this morning. That was disturbing.

Double checked and all my plug wires are routed correctly.

My points have now burned, so I'll need a new set of those, and a condensor.

One thing I just noticed when I took the rotor off is that i have one spring on the mechanical advance weights that is badly stretched. I'm wondering if that could be a big part of my problem seeing as the centrifuge is basically lopsided.

I have been searching all morning online and have come up with zero sources for a distributor advance kit for a 56 Olds distributor.

Anyone got a source? Can anyone tell me of another application that they know will work? The local parts robots can't seem to help much.

 

I've had that on hot wired engines before. Either use a ballast or a internal resisted coil while test running. If the points are really messed up, it can cause it to misfire and flame up.

If it is a real 56 dist, it should be close to the SBC design as they both have the window to adjust the points. The springs may be the same or close enough. It would not suprise me if the pull rates were slightly different on the chevy springs, but I think a recurve kit would have several?

 

I'm using a ballast resistor and a coil intended for external resistor. I spoke with Jim Lindor "GMC BUBBA" on this board and he said that the basic recurve kit for an SBC or even later 50's or 60's olds will work so I ordered a kit that was actually listed for later 50's Olds from Summit along with a few other bits I'd been needing.

I'm wondering if I should even attempt anything further until I get the mechanical advance at least properly sprung. Jim did say that the stretched spring would make it really hard to set the timing right, and I did check with a dwell meter last night, and noticed pretty erratic needle movement between 29 and 32 degrees, so I'm thinking I should leave well enough alone until that part of it is figured out.

Also, if any of you have need of fuel pump rebuild kits, or a pump rebuilt, I highly recommend Then and Now Automotive. They have excellent, high quality, complete kits and their tech support guy, Mike, is really knowledgeable and very helpful.

All their kits are specific to the number on your pump's mounting flange so that eliminates a lot of room for error. I have gotten a couple kits from them now and
they have been perfect fits.

http://www.maritimedragracing.com/antique_auto_parts_cellar.htm

 

Pictures are the least I can do, I've been following this thread intently myself, learning all I can about these old Rockets, so I'm happy to contribute. And I'm glad to hear that you tracked down a stock clamp. Would have offered to ship you my spare otherwise.

Don't lose hope on getting her fired up and running. Once you do, the victory will be that much sweeter.

 

Here is a 56 dist and the earlier 49-55.


Not sure if you can see the crazy looking circular ballast on top of the coil on pic #2.

 

I don't want to hijack the thread, but since we're on the subject of distributors, I have a stupid question I'd like to ask. (Rather be safe than sorry.) On the 55 distributor, just above the drive gear, the shaft thickens. This wider section is stopping me from sliding the distributor out of the block, as there seems to be a collar or ring in the block making the block hole too narrow. (Make sense?) It looks like this ring is removable, but was pushed in on an angle. Is there something I'm overlooking, or am I going about removing the distributor in the wrong way?

 

I have a clean low mile (41K) 1955 here and the dist came right out fine. I am thinking you have a higher mile motor with a lot of sludge causing a tight fit?

 

From my previous experience, I thought it should just slide out, no problem. But then I thought what you're thinking, that there is some sludge, but some prodding with a flathead screwdriver says there is something in the hole. And when I give the distributor a yank upwards, it's definitely hitting something. If I was at home, I'd take a picture to show you.

Worst comes to worst, I'll just cut the shaft on the distributor. It's pretty beat up anyways. I'll have to try some more next weekend when I'm home and report back.

 

Frank, based on your pics mine is definitely the 56 distributor with the big rotor, thanks for verifying that for me... That ballast resistor on the earlier dist is indeed crazy!

 

I would not cut it. There is an upper and lower boss on the dist body that goes into the motor. Then 2 bores, upper and lower, in the block to fit those two bosses. They are the same diameter. So, you need to pull the dist straight up to guide the lower dist boss through the upper bore. If you've ever slid a cam out of all it's journals, it's the same deal; you have to line it up perfect.

Depending on casting shifts, the top edge of the lower boss on the dist body could have been exposed to varnish and sludge, so when it gets lifted to reach the top bore, that varnish could make it seem too big to come up. Spray carb cleaner and twist the dist to try to get it started in the top bore.

 

Thanks for the advice Frank. I'm planning to be home this weekend, so I'll give it another try.

 

Alright! Got my mechanical advance springs and weights. I started with the heaviest springs in the kit, which were probably less than half the tension of the springs that were in there. Put new points, condensor and cap on just to be safe and regapped the points.
I still had to rotate the distributor some while cranking to get it to start to fire.
I then primed the carb and while hand choking, with the key in run position I used the remote starter to attempt to fire it up... Well, it fired and ran, and I got it to run for a good 45 or so seconds and tried to ease off the choke a bit and it wanted to die. It's really really racing right now so I need to fiddle with the idle and mixture a bit and hopefully get it to idle slower.

Water pump is definitely toast. I had water spraying all over me from the fan right at the end there.

All in all, a good outcome, I just hope I didn't get it too hot too fast. Had a lot of old grease burning off pretty quick after I got it running.

 

your engine should idle on its own with the choke wired open in about 30 seconds of starting, you should just have to keep it running by pumping the throttle a little every time it starts to stall.

 

Thanks Budd... hopefully I'll be able to get it there. I fired it up this morning again, but quickly decided to wait on anymore tuning, because the water pump is spraying so bad. Supposed to have a rebuilt unit at the parts store in the AM to pick up so I can cure that particular problem.

So, while I'm thinking about it, I wanna talk cooling.

That said, I think that maybe what I need is a radiator out of a 39-40 big truck.
I think the core support itself is basically the same all the way from AC100 (1/2 ton) to AC450 (3 1/2 ton) because the grille is the same and the Master Parts book shows the part number to be the same up to AC300 (1 1/2 ton), but my bet is that the radiator itself from a 450 would bolt up to a 100 support.

The mopar radiator doesn't bolt up correctly anyway, and I really doubt the stock radiator for the 1/2 ton 228 6 cylinder would come close to cooling the Rocket 324.
I don't want to put an aluminum radiator in there because I don't like the streetrod look.

My owners manual only goes up to 300 series for cooling system capacity. 100 series shows 15.5 quarts, and 300 series shows 17 quarts. I'm wondering if a 450 would have even more capacity, and if so, if its more cores? The stock 324 cooling system, without a heater is 20.5 quarts. The way the 39 GMC core support is built, it looks like there's room for a much deeper radiator, the only thing I can see that would have to change is the lower baffle.

What would you guys do? Look for a big truck radiator and see if there is an appreciable difference or try to find a radiator from a different application that works better than the existing MoPar unit?

I like the idea of using the big truck radiator because it'd be clean. Above all, I want this build to be clean, which is something that the PO obviously didn't care too much about.

 

i think your rad support is the same as my 45 gmc, i installed a rad out of a 66 chevelle 6 cylinder, a V8 rad might be the same size with more cores, the chevelle rad now sits infront of the rad supports held in by a couple of 20ga Z-bends i made up.

 

I spoke with US Radiator this morning. They're about a 90 minute drive from here. They said I could bring my stock GMC radiator in and they can use it as a pattern and build a radiator to work with the 324 with the inlet, outlet where I want them and the tank style I pick.. Price ranged from $476-$678 depending on which level of cooling ability I want, but I guess they are all 4 row, which I would think even at the base level should be plenty sufficient.

If I were to go that route, and they can build in a transmission cooler, should I bother? Would the dual range hydra-matic even have provision to use a cooler?