The Stovebolt Site Forums The Shop Area Engine Shop Need Help Tuning 1961 235 Engine in my 1952 3100

Thought I would do a tune-up on the 1952 3100 that I purchased a few months ago.

The engine is a 1961 235 connected to a 4 speed trans. and was running pretty good but wasn’t sure of the age of the parts so thought I would replace them and start “fresh”.

Took the truck to a mechanic I’ve known for over 40 years and is familiar with the old GM 6 cylinder engines. He changed the plugs (R45 at .035" gap) and replaced the points (set at 0.19"), condenser, rotor and cap. He set the timing so the pointer lined up with the “U/C” mark on the flywheel. The engine was idling smooth after he finished so I headed home. I didn’t get far when I noticed the engine was surging and there was a dead spot where the engine speed didn’t increase when I pushed the accelerator. Once I got into 4th gear, it took about 3/4 mile to get up to 55 mph. Since it was closing time, I waited the next day to take the truck back to him. He just checked the work he had done the day before and everything looked okay. I told him that since it was surging, I suspected a fuel problem so I changed the glass bowl filter and also the one next to the fuel tank outlet. The previous owner had cut out a section of the hard fuel line and installed an inline filter.

Although it looked clear (a plastic see-through filter), I replaced it with a new one from NAPA. While I had the filter off, I opened up the shut off valve under the tank and there was a good flow of gas out of the tank so I was sure that the outlet hadn’t been clogged with debris from inside the tank.

After he finished checking everything, I took it for a test drive and found it was still surging. I asked him to drive it also and he agreed there was a problem.

He said that sometimes this could be from bad points so he removed the new ones and put in another set. The engine ran smoother but after another test drive, he said it was still surging. Since he was in the middle of another job when I showed up, he asked me to bring it back next week.

He is going to pull the top off the Carter YF carb and see if there is anything there that could be causing the problem. I told him I would post on Stovebolt.com and see if I could get some help from the members.

Would appreciate any help/information you can provide.

come on folks... I know someone in here has some tips and suggestions.

-W

Thans for the encouragement!!!

The truck was running pretty good before the tune up so the logical guess is that something got out of whack during the tune up. We did have a tough time setting the timing since the surface of the flywheel was rusty. I have since cleaned the flywheel ring and painted the bead so it will be much easier to see with the timing light.

I did talk with the previous owner who told me that he had a problem with replacement distributor caps not lining up properly with the rotor with the #1 cylinder set to TDC. He had to trim some of the plastic tabs so it aligned properly. Anyone else have this problem?

Basically, he said to set the dwell to 30 degrees, bump the engine until the pointer lined up with the bead, confirm #1 piston is at TDC, make sure rotor lines up with #1 contact on distributor cap, then check timing and confirm pointer aligns with bead.

Thoughts/opinions/anything???

Thanks

SC3100,

Sorry, but I have to ask: 6v or 12v? If 12v, do you have a ballast resistor?

It is possible that someone in the past has the distributor installed one tooth off and instead of finding that they have been modifying the distributor caps. I find it unlikely that very many replacement caps would have the aligning tabs wrong. It sounds like you're on the right track to go back to basics, confirm TDC, confirm the cam position that both intake & exhaust valves are 100% closed THEN make sure the distributor points at #1 on the cap. The only things left are compression, spark and fuel for a running engine.

Yay 'bolters...

Thanks for jumpin' in.

-W

Many thanks.

It's 12v and does have a ballast resistor.

The truck did run perfect when I bought it so whatever adjustments/modifications the previow owner did, they worked. He was a mechanic who owned his own shop and was very diligent about doing everything right.

Will just start again from square one and follow his instructions. He was sure it was the timing since the problem happended when you tried to accelerate and there was a load on the engine.

Thanks again

Was the vacuum advance properly hooked back up?

Chuck

You might need more base timing. I've had that particular problem myself, and spent way too much time chasing "feul" problems. I talked to my uncle, who used to race a 235 powered '49 Chevy sedan back in the '50s, about it, he said it needed the timing bumped up. I went 15 degrees, runs great now. Mine does not have a vacuum advance, so you might need to work with it a bit to see what yours really needs to run at.

Update:

Finally got a chance to take the truck back to the mechanic yesterday armed with what I thought would be the answers to my rough running engine. Following the instructions from the previous owner, set dwell to 30 and timed engine to line up pointer to bead (I had cleaned flywheel and painted bead bright yellow). Truck still ran awful. We then confirmed that rotor did not match up with contacts in cap so turned distributor. Long story short, truck would not even start. Unfortunately, the mechanic was backed up with some other work (wish he hadn't even started work on mine) so I told him just to get it where it would start again and I would bring the truck back next week. Did that but was barely able to get the truck back home (2 miles) since it was misfiring so bad.

I (and some Stovebolt members) have come to the conclusion that the distributor has been installed incorrectly and is a tooth off. This would explain why the PO had modified the cap so it would line up with the rotor.

That being said, will attempt to start from scratch. According to my 1952 manual I need to:

Put a mark on the distributor body where the #1 cap contact is located

Remove valve cover and turn engine until both valves on cylinder #1 are closed. Flywheel pointer should be at U/C mark.

Loosen screw and pull distributor out of engine. Put distributor back in engine making sure rotor lines up with mark on distributor. Will probably have to use long screwdiver to turn oil pump so distributor will drop in.

Set gap in points (0.019") per 1961 engine specs

Set timing so pointer lines up with bead

Sound about right?????

Many thanks

SC3100,

What you describe that you are going to do is OK but unnecessary. I think your conceptualization on how the distributor gets lined-up is a little off.

Once the distributor is in place, the rotor could actually point anywhere.

After rotating the engine and having the #1 cylinder at approximately TDC, many people try to install the distributor body so that #1 is at about 5 o'clock relative to block.

However, you could install the distributor in any convenient orientation (as long as the distributor body/clips/grease-cup clears the side of the block).

Then rotate the distributor body so that the rotor points to any lead on the cap. Clamp the distributor.

Then place the lead from that contact in the cap to the #1 spark plug.

Then place the other ignition wires CLOCKWISE on the cap in the following order from #1: 53624 (for a firing order of 1-5-3-6-2-4).

This will get you close to the correct timing setting.

If I am wrong or unclear, someone will correct/clarify.

Tim,

Many thanks for the information.

One of the things we tried yesterday was to turn the distributor body so the rotor would line up with the #1 cap contact with the engine at TDC. Problem is after doing this, engine would not start at all. With the vacuum advance link the position of the distributor body is pretty much set but I understand what you are saying about being able to set the #1 wire anywhere on the distributor.

If you turn the engine to TDC and drop in the distributor, I assumed the rotor needed to line up with the contact on the cap that you have designated as the #1 contact. It appears that in my case, the rotor does not line up. If you turn the distributor to line up, I guess it changes the timing so much that the engine won't start. The PO modified the cap and the truck ran fine but obviously didn't really fix the issue.

Thanks,

Ron

Ron,

Is there a possibility that you are a full rotation off of the #1 cylinder's compression stroke when you have the flywheel timing ball/mark lined up with the pointer on the bell housing? The crankshaft turns two full rotations to fire a cylinder.

How are you determining that you are on a #1 compression stroke when you have the flywheel timing ball/mark lined up with the pointer on the bell housing?

Tim,

So far, all of the timing adjustments have been made with the engine running. The next step would be to remove/install the distributor again after confirming that #1 is at TDC by observing the valves on #1 cylinder.

I've already been to the mechanic three times to get the truck running right so thinking now would be a good time for me to learn how to tune and time the truck myself. The mechanic has given up on ignition timing and now wants to take the carb apart. The previous owner was very specific about making sure that the rotor lines up with the cap when the cylinders fire and had modified the cap to fix. Fortunately, I kept the old cap and will put back on the truck this weekend and see if it makes any difference.

I'm just bummed that my "new" truck ran great and now I can't even drive it because it misfires and sounds like it's running on maybe 3 cylinders.

Thanks again for your input,

Ron

Perhaps you don't need to rely so much on that "bead" in the flywheel.

Pull out the number one spark plug. Have the distributor cap off so you can see where the rotor points. Have someone crank the engine while you hold your thumb over the spark plug hole. Watch the rotor, when the compression blows your thumb off the hole, mark where the rotor was at when that happened.

Place the number one lead in the hole on the cap that is closest to the mark.

Also, you know there is a screw on the vacuum advance that has to be loosened to move the distributor in the advance.

Doing this should get it close enough to fire up and you can time it by ear.

Sounds like the "bead" you're trying to set timing to may not be where it is supposed to be. So take it out of the picture for now.

Thanks Roy,

Will give that a try.

It's got to be something simple. The truck ran great when I got it. That's what I get for trying to fix something that isn't broke!

Ron

Ron,

At some point, if you cannot figure out what the problem is, you might have to start "from the beginning" by checking out each part and system in an orderly fashion.

I suggest buying the following parts and change them one at a time. It will not be a waste buying these parts because you should probably have them (and carry them as spares):

Spark Plugs
Spark Plug (Ignition) Wires
Points
Rotor Condenser
Distributor Cap
Fuel Filter(s)

Then, in order of increasing expensiveness:
Coil
Fuel Pump
Distributor
Carburetor

I carry all of the above items (plus other items that might break but would not cause your problem, such as a fan belt). The only one of those parts I have needed over the last 8,000 miles is the fuel pump (twice a few years ago - perhaps alcohol in gas affecting the seals?).

Also, double/triple check all your electrical connections (and wires) in the ignition system, and check all you ground cables and connections.

Keep at it, and good luck.

The only other off the wall thing I can think of is if the plate the points mount on is installed wrong. (Not sure you can do this) If so, this would be the only reason I can think of that the cap would have to be modified to line up correctly.

Otherwise you should be able to put Number one plug wire wherever it lines up when the thumb is blown off the hole.

Make sure the wires are in the correct order.

Roy,

You are right about the need to "modify" the distributer being an oddity.

It's too bad that Ron does not have someone near him with a truck with a similar distributor. A quick swap and start-up would eliminate concern over an oddball distributor being the culprit.

All,

Thanks again for your help.

I woke up yesterday morning with the plan to finally get the truck fixed and running smoothly again. It was my goal for the entire day.
The first thing I did was put a mark on the side of the distrubutor that lined up with the #1 cap connector. I then removed the cap and put the truck in high gear. By rocking the truck I was able to get the pointer on the U/C mark on the flywheel and get the points open at the #1 cylinder location. I then looked at the end of the rotor and it was about 1/2" from the previous mark (the cap location of the #1 connector). I put another mark on the side of the distributor for the rotor location. Obviously, something is wrong. A friend who was helping me said to loosen the distributor, pull it up, and move the rotor to the right location. I didn't think it wasn't quite that simple so I said "let's put the original distributor cap back on and see how it runs first". So I removed the new NAPA cap and put on the old one that came on the truck when I bought it and had been modified by the PO (the aligning tab had been ground off). I connected the ignition wires, set the cap on so the #1 wire would line up with the actual rotor location. The truck stared immediately and after warming up idled smoothly. I took it for a short drive and there was no misfire, surging or bucking like before. In order words, it ran great like it did before I decided to do the tune up! LOL!
Long story short, I decided just to leave it like it is. The truck is running great although there is some type of rotor alignment issue for lack of a better description. If it was just a matter of pulling the distributor and reinstalling, I asked myself why didn't the PO and the mechanic I took it to do this??
Regardless, the truck is running great and I can drive it again.

Any ideas???

Thanks again for your feedback.

Ron

How does the cap stay on? Isn't it held down by two clips? If so, when it is moved out of place, how is it held on?

Also, you wouldn't "have" to pull the distributor and reposition the rotor. Simply loosen the clamp at the bottom of the distributor and turn it to match the mark you made and see if it runs there. I can't think of a reason at all the plate inside the distributor would be off in any way to have to modify the cap.

The clamp bolt is right at the block level on the vacuum advance. Slotted screw driver will loosen it. Then turn the distributor a little to line it up with the mark. Try not to push down or pull up on the distributor while you turn it.

Roy,

The cap isn't turned too much. The two spring clamps still hold the cap down, the clamps just fit to one side of the molded "shoulders" The PO ground down the small ridge on the side of the shoulders.

When I had the truck at the shop last week, we saw that the rotor was out of alignment so he turned the distributor to line up with the rotor but then the truck would not crank.

Could the cam be installed incorrectly or even the flywheel? Certainly is a mystery.

The cam would be correct if it runs good with it fixed as it is. The only reason I can think of that you would have to grind the tab and move the cap out of place is if the point plate inside the distributor is not mounted correctly.

This would make the points out of sync with the holes on the cap.

Sounds like someone has had the distributor apart and didn't put the plate back in right. I'm not sure how they could pull that off.

I have an old distributor in the shop. I'll have to look at it now to see if that plate can be installed wrong.

Thanks again Roy.

Regardless of how odd it sounds to grind off the locating tab on the distributor cap, it works. Drove the truck yesterday and it ran great.

Please correct me if I'm wrong, but with everything at TDC on #1 (flywheel on U/C and points open), if the distributor body is moved to line up the rotor with the cap contact, the timing is then too far off and prevents the engine from starting. As several member have stated, the distributor body can be in iny orientation (without interfering with the block of course).

Thanks again for your help. I'm still puzzled but at least I can drive again.

Ron

What I don't understand is having to modify the cap. Cutting the tab and turning the cap on the distributor tells me the cap hole is slightly out of sync with the point plate. And I just can't understand how that could happen.

If the plate were correct, then modifying the cap would put it out of sync instead of correcting the problem.

I haven't had a chance to look at my old distributor yet.

I agree with Roy, your distributor is an enigma. If you are going to keep and use the truck, you might want to consider getting a $65-$80 remanufactured one (or, even a used one).

I stopped by the garage yesterday to tell the mechanic I had the truck running again. I told him I got #1 cylinder on TDC and put the old modified cap on and aligned it with the rotor.

He commented that the only thing he could think of was that an incorrect distributor plate had been installed so that is looking like the best solution. So, how do I tell if the plate is wrong and how do I get the correct one? Would it just be easier to buy a rebuilt distributor? What supplier do you recommend??

Since it's running great and I will probably drive it less than 1,000 miles a year, will not rush to "fix" it again but would be nice to be able to do a normal tune up in the future.

Thanks again for all of your help. Much appreciated.

Ron

Best bet is to get another complete distributor.

There is a Delco number stamped in the plate. Post it and I can tell you what it is meant to fit.

Thanks Dave,

The number on the distributor body is 1112353 923.

Any way to tell what points plate is supposed to go with this distributor?

Any recommended source for a rebuilt distributor. I will check with the local NAPA store today.

Ron

Discovered that the distributor on my 235 is from a 48-50 engine (most likely a 216). All of the tune up parts I installed were for a 61 235 engine (confirmed year of engine by block cast number). Not really sure if there is any big difference but did order new points, cap, rotor and condenser for the distributor (not the engine). Will see if there is any differences that would explain why the rotor doesn't line up with the #1 cap contact when the #1 cylinder is at TDC. Maybe the locating tab on the distributor cap is different on the earlier year distributor. Worth a shot.

Thanks again,

Ron

Something else to look at, the cam to distributor gears. I'm not certain but seems like there may be a difference in materials used in the distributor drive gears between those engines. Could cause premature wear if that is the case.

It is not a good idea to use a 216 distributor in a 235 unless you use a 235 gear on it as Roy mentioned, I have done this when the customers wanted the stock look.
The points will fit 216 and 235, but the shaft for the rotor is to short for the 235 rotor lineup key to lock on properly, so you must use a 216 cap and rotor.

Isn't the height of the distributor cap and maybe the rotor different between 216 (and early 235) distributors and later distributors in 235s and 261s?

And, didn't the cam gear difference take place between 1953 and 1954, depending on the use/style of the engine? Maybe low-pressure 216 and the earlier 235s vs truck high-pressure 235/261 in '54 and car-235-Powerglide in '53?

I have been following this topic and have been looking at my distributer. It was out to replace the vac adv and I wrote down the numbers Delco Remy model 1112403 sn 8h14. Is there a referance to find if this is correct for my truck ,a 59 with a 1957 235 block.

The parts book calls for your 403 number to fit 1955-62 all 235 & 261.

All,

Again, thanks for your help and information. Looks like distributor 1112403 is the correct unit for my engine (60-61 235 per block cast number).

Although I have the wrong distributor, the truck is running great. I checked with the previous owner and he didn't change the distributor so it's been that way for about 15 years and +35K miles. I will keep a modified distributor cap in the truck just in case. Have made a permanent mark on the distributor where the rotor lines up at #1 TDC so easy to get cap lined up.

Picked up new cap, rotor, points and condenser for the distributor yesterday. Shorter cap and rotor but will still be out of alignment with the rotor at #1 TDC so I have plenty of spares.

Will look for a 1112403 distrubutor in the future and get it prepped/rebuilt and just keep "just in case".

Still, it would be nice to figure out why the rotor is out of alignment.

You guys are great!!!

Ron

Thanks for the dist info. one thing less to work on.

All,

First, let me again thank everyone for their information and feedback. Much appreciated.

It's clear that I have the incorrect distributor in the 61 235 engine in my 52 3100 truck although I'm still not sure if this is what is causing my rotor to be out of alignment with the distributor cap when the #1 cylinder is at TDC.

It was mentioned in a post or two that if you use the early distributor (I have a 48-50 unit from a 216 engine) that you must use the later distributor gear. I haven't pulled the distributor in my truck and if I did, not sure I could tell if it was the older gear or not. Regardless, would this explain why the rotor is out of alignment or is the later model distributor gear requirement just because of metal differences?

In the process of looking for a 1112403 distributor to have on hand just-in case.

Many thanks,

Ron