The Stovebolt Site Forums The Shop Area Engine Shop 2 of 6 cylinders are not firing - what 1st?

After a long 3 hour ride in my 1953 truck, I noticed the engine was miss-firing.

My first thought was that it was an electrical problem so I replaced the Plugs, Plug wire-set, Distributor (cap, rotor, condenser, & points) BUT the missing was still present.

While the engine was running, I disconnected spark plug wires one at a time to learn that the #1 and #2 cylinders are not firing at all. I was amazed the darn thing was running and driving as smoothly as it was being so bad off

1st check completed: Spark was confirmed at both the non-working cylinders.

So my question is... What should I check next?

I was thinking cylinder compression and if good then I'd try my hand at adjusting the rockers on the valves.

I'm just a rookie so I really appreciate all your advice, thanks!

replace the spark plugs or swap with a firng cylinder to see if the problem moves.

Double check the spark plug wire routing then check compression.

Joe

Make sure you're getting spark to the plugs. A cheap spark tester is invaluable here.
if spark, pull the valve cover and observe/check the pushrods,rockers and valve actions. Are they opeing & cosing?
#1 & #2 share the same intake manifold port, could be a blown gasket , loose intakes, cracked intake. While running a squirt of carb cleaner around the gasket surfaces can pin point this.
Good luck & let us know.
Dave

Eyell, Good thought since there was 2 down - but no I tried this and I trouble checked the firing order

I have tested the compression and here are the results:
1: 60
2: 0
3:110
4:110
5:115
6:120

So something definitely going on there. I think I should try my had at adjusting the lifters - does anyone know where I can get a good procedure for that? Otherwise, it looks like I just warm the motor then loosen the lock nut and turn them down. I can remember my dad saying slowly tighten until the ticking sound is gone then back-off until it's just back again.

Bad head gasket between 1 & 2? Maybe?

Valve lash adjustment procedure.

Head gasket or burnt valves are my top two things to look at, on second thought remove your valve cover and check the valve train for broken springs/push rods, or bent push rods, crank eng over and watch rocker arm travel .lots can go wrong valve adjustment wont fix no compression unless the adjusres magicaly backed themselves off!!

A quick check would be to introduce air into the spark plug hole when at top dead center and listen for where the air comes out. It will come out through the carb (bad intake valve), or the tailpipe (bad exhaust valve), or the neighboring cylinder (blown head gasket), or into the crankcase (bad/stuck rings). A lower portion of a two-part compression tester with the quick disconnect that fits your air compressor works good for this. Turn down the pressure on the regulator of your compressor or put a regulator in line if your compressor doesn't have one.

First, thanks to everyone for your advice I really appreciate it.

Been playing around with the valve adjusters. Making the push rods as loose as I could (but still seating)then re-tested the compression and here are the results:
1: 70
2: 65
3:100
4:105
5:110
6:115

I double checked and definitely have a strong spark on all.

Next, I'm gonna try Carl's idea and put some 5-10 psi of air into the cylinder using the lower portion of the compression tester and we'll see where it leaks out from. I'll let you know

I'll bet you have some valve problems or like Tim mentioned, head gasket between 1 and 2. Pull the head and let us know.

If you were driving with the valves tight enough to have no compression, start it and run it for a few minutes. Let the valves and seats scuff in and clean themselves. Then take the compression again.

If there is anything on the valves or seats the air test could give you a false positive.

On my truck I had a run issue last Friday, and I ended up not having compression on #1, and it was a broken valve spring. Make sure you check everything else too!

Running it now won't hurt it. And it might help it. Look for a bad spring with the valve cover off. Run it for a while and you just might get those valves to seal. That would qualify as a "free fix" in my book. Let us know what you get.

Here's the latest, I put some compressed air into #1 and it came immediately out #2. So all of you who have been guessing bad head gasket you win

So my new question is... since I'm going to be removing the head to replace the gasket; should I have it professionally rebuilt including valves, valve seats? Do people send those out for service? Also, if I get the valves replaced, do they sell valves that would make my truck compatible for unleaded fuel?

Thanks all!

Since you have a blown head gasket, you need to assess if any damage has been done to the head in that area as well as the cylinders before you go any further. My opinion on hardened valve seats is that it depends on the condition of your seats. If they are recessed from excessive wear or multiple valve jobs in the past, than I would go with hardened seats, especially on the exhaust. I would not recommend replacing serviceable valves/valve seats for fear of unleaded gas, but if you have to replace the seats from too much recess, might as well go with the hardened ones.

If it was mine I would also have the head magnafluxed to check for cracks. Sometimes its easier to find a serviceable head than to put a bunch of money into rebuilding a head with severe damage.

A good machine shop should be able to take care of all of the above... Keep us posted.

If you have a valve that isn't sealing in #1 the air would come out of #2 because it would have at least 1 valve open.

It won't cost you anything to run the engine for a while, recheck the valve clearances, and then take the compression again.

The fact that compression came back up in both cylinders when you adjusted the valves indicates they did have a problem.

Eliminate 1 problem at a time.

I recently had the head on my 216 refurbished. For $300 I had the head magnafluxed, a couple cracks welded, new valves, guides, seats, springs and the head was acid dipped and cleaned.

In my case I had 3 cylinders that wouldn't pump up over 20 psi and it didn't even run when I purchased it.
Ends up all the exhaust valves were burnt and the seats were highly pitted. The rebuilder indicated he would have had to taken too much off inorder to have cleaned the seats and valves up.
Course I had to pull the head inorder to find these problems....
$$$'s well spent in MHO

Good luck
Dave

I found a mechanic who tells me that after adding oil to the cylinders he saw a 40 pound increase in compression. Because of this he is telling me that I really need Rings too, and therefore may as well do a complete engine rebuild. I don't have the skill-set to do a rebuild so I'm fine with paying for the work.

He can do the work for $4000 with parts and labor. OR, he tells me he has a 235 that was rebuilt in his warehouse and he'll install it and give me a 1 year warranty for $2800.

Does $2800 sound like a good deal to you guys?

I had a professional take a look. He says that because the compression increases when he puts oil in the cylinder that means that the truck also would need Rings. His estimate for rebuilding my motor is $4000-$4500.

Or, he is offering up a rebuilt 235 which he will install and warranty for $2800. Does that sound like a good deal to you guys?

ever wonder why the difference in price? Since he is doing the work on YOUR engine, and (I am assuming here) he also did the work on the other rebuilt engine. The cost should be the same. Something doesn't sound right, what didn't get done on the other engine?

I noticed that too - good quesiton. He said it was completely rebuilt - rings, valves, valve seats, sent to the machine shop. He said it has 2000 miles on it and it's been in storage recently. He said he stands by the quality of the engine which is why he is offering the 1 year warranty

the answer to that question is he has an engine that's been gathering dust for years and he sees one last chance to sell something he thought he never would

2,800 is ballpark for a rebuild, he's quoting 4-4,500 to do yours because he doesn't want to, rather cut his losses on the one in the corner

Bill

Hmmm looks like I'll be driving it home today so I can take my time and shop around some.

Call Jasper Engines & Transmissions. They might list a price on their website.

Maybe someone has had experience with this company/service?

Just a quick follow-up to the above thread. I opted to go ahead with the 235 engine swap. My hot-rod shop gave me assurances that the 235 they were proposing was a high quality rebuild that they would back it up with a 1 yr warranty.

Everything went well and the new 235 seems really solid. I put about 200 miles on it over the weekend

I still have my old motor which I may still restore for the experience of it.

Take care all and see you on the highways