1962 c10 235 lack of power
 

I recently got my c10 on the road after 3+ years of ‘rebuilding’ it (mostly cutting/welding rust out. .

I expected it to not be a tire roasting fire breathing speed machine.
But it just lacks power.
*In second gear at about 35-45mph (speedo bounces) I can have it floored up a hill and gain zero speed.
I expected it to be similar to a jeep cj with 4.2 engine i had. Way less power.
This was my grandads truck.

It’s original engine, trans, etc. 63k miles on odometer.

So… it idles well, and compression is ok’ish at about 110 psi.
(I haven’t really checked compression since before first got it turning/running)

Coil, plugs, wires, points etc are new. New vac advance.
It has original intake and split Williams exhaust, original exhaust manifold was shot.

It smoked a lot until I got it real good and hot by driving it a good solid 30 miles.

Plugs always looked oily to me… or could be way too rich. But that got better when I lowered float level a tick.

Original Rochester b.
Timing set by most manifold vacuum then retarded a twitch. Ended up at about the third has mark from ball/circle.

What should I check next? Leak down test?
Or is a very underwhelming amount of power normal?

Re: 1962 c10 235 lack of power
 

These engines are certainly not known for performance - arriving at 60 in around 13 seconds. This is 3 seconds slower than my 2009 Honda CRV which is about 3 seconds slower than current CRV's. That said, it should not be so bad unloaded as you describe. 20 years ago when I learned to drive stick on my brothers - now my after his death at 19 in 1999 - C10. I remember it not to be lightning quick but also that I thought it quicker than my own first car, a 1986 Cutlass with a 307.

Running too rich would not affect power as much as you describe. I suspect a timing issue but would still do a leak down test to gather as much data as possible. Are you still running the original lead fuel only head or has it been hardened to run unleaded fuel? This was what happened to hasten the beginning of the end for the 235 in my C10. Head warped and coolant was lost. A new, hardened head was sourced and installed during the summer of 1997, but a light mixture of coolant was used and the block cracked sometime during the winter of 1998.

Re: 1962 c10 235 lack of power
 

When I drove my '61 home (before I restored it), on the original 235 and 4-speed, it took me quite a while to get comfortable driving it at the highway speed limit (60mph). Debris flying out the back and everything. We've come a LONG way from 1961.

Once I was ok doing 60mph, I figured I'd pan it and see what it was like for power. Oh. That was it. 60mph. Wheee. :|

Re: 1962 c10 235 lack of power
 

I would like it to do 0-60 in 13 seconds instead of minutes; downhill; tailwind.
I haven’t had it above 40 yet probably.
I have stayed on slow back roads so far. Only been legal on road for a week.

On my morning commute it dawned on me that I put an aftermarket air filter on it, and ever since it makes a sucking sound… I associated it with a drilled out air box on a honda or vw 4banger, but those were always a deep brawww sound. This is definitely a sucking sound. Maybe it’s restrictive. I will try it this weekend without air filter. If still no power I will do leak down.

I’m sure it does not have hardened valve seats. I will Google it, maybe I need to add zinc or something.
I do have a spare 235 that was supposedly rebuilt in the 90’s.

Re: 1962 c10 235 lack of power
 

Biggest lack o' power headscratcher i ever had was a 472 cu in Caddy that couldn't get out of its own way. I tried/changed everything obvious (except for the plugged up muffler.) Thankfully we still had good old school mechanics around back then and they figured it out.

Re: 1962 c10 235 lack of power
 

Was the Rochester removed, cleaned, and rebuilt? If not, I suggest starting there. Also, maybe take the points out, throw them as far as possible, and get an HEI. Finally, did you check for vacuum leaks? Good luck, let us know if you make progress.

Re: 1962 c10 235 lack of power
 

Carb rebuilt yes.

I had put an hei in, and it ran great for a mile or so, then engine ran terrible, then engine would not even start. Put points back in… no known issues with dizzy, fires up every time.

That HEI is now in my spare engine (that had a bad cap/rotor) after replacing the module, cap, rotor, coil from a tuneup kit. It seems to work now. My guess is the module died. (Good ole eBay)

I haven’t specifically tested for vacuum leaks, but it did have a strong manifold vacuum.

If the yard dries enough to get the truck out of the backyard/shop, I will test on it some today with/without air filter.

Re: 1962 c10 235 lack of power
 

Pics attempt:

Re: 1962 c10 235 lack of power
 

I'm throwing this out there because it happens way more often than can imagined... have you re-re-rechecked the firing order of the spark plug wires. If yes, have you confirmed the engine is getting spark at each plug? An addition, is the carb definitely getting enough gas? As a side, HEIs are great until the coil craps out, which can be surprisingly quicker than you expect.

Re: 1962 c10 235 lack of power
 

Checked and confirmed firing order. Also pulled each boot from plug one at a time and got a noticeable miss without each.

Gas…. I assume so. I’m not certain how I would verify. New gas tank, new fuel line, new fuel pump etc. . Not that New = Good.

I am not totally against popping the hei in there again. Though I would like to get a small-top external coil (I don’t like how the big-top fits in there).





———
Today I took the air cleaner off. No noticeable change.
While in there I figured I would tinker with timing, I touched the dizzy to ‘check the vac advance’ and the dizzy spun without moving the vac advance. Tightened that up and set the timing again (seems rather advanced base timing). Idles best at the triangle, I moved it back to the second hash mark where I had it before. I thought for sure no vac advance would have been a problem. Took it for a drive and had a little more power. (Now I noticed that when I was expecting more power; I was getting loads of smoke out the tail pipe… bluish I think) (Btw the Glass-packs are annoying I will find some actual mufflers). Got home and set up for the leak down test…. Well the Amazon leak down test is not compatible with my air compressor connections… (I have the male end female connector that would work, but need a female) (always something).
So I did the next best thing and just blew some air into cylinder 1 Tsc compression stroke. Lots of air (all of the air) coming out of the downdraft tube, and a smidge from the head oil drain…. RINGS is my guess.
Makes sense for a 63 year old engine that hasn’t been used since 1991. Maybe now I know why my grandad abandoned it.

Re: 1962 c10 235 lack of power
 

Plugs. 1 on left, 6 on right.
3 looks either not getting all oily, or lean. Rest look oiled up to me.

Re: 1962 c10 235 lack of power
 

Attempt3

Re: 1962 c10 235 lack of power
 

Did you know any distributor will slowly rotate if not secured and the timing will be retarded.
Exactly what happened with your hei.
What did you use for a hold down clamp?

Re: 1962 c10 235 lack of power
 

Those plugs are in bad shape. If it's carbon, the engine is way too rich, if it's oil, that's beyond my skill set. Here's a link to a good Rochester B trouble shooting page, 2/3rds down is a section on black & sooty spark plugs.

Re: 1962 c10 235 lack of power
 

Plugs are oily. Sure likely to be a little carbon also, wasn’t too many miles ago we were dumping marvel mystery oil and straight oil and all sorts of things to get it lubed and spinning and running.

This morning I did the same air pressure test, and the spare engine holds. The air pressure and does not blow it all out the crank case.

I also forgot to mention that yesterday I got home from about 20 miles drive…
And the oil pressure light was flickering at idle.
Think this engine is done and needs a backyard rebuild, or more.

I will probably change the oil and put some 40/50 weight oil in it and drive it a bit more.

Also I am waiting to get the right air chucks I need to do leak down test. I have never done that and I want to try it. I will do that before pulling the engine.

Re: 1962 c10 235 lack of power
 

It looks like the plug w/ no discoloration isn't firing. Check for spark.
I'd check for working advance as well.

Re: 1962 c10 235 lack of power
 

Might be on to something.

Split exhaust… 4,5,6 is noticeably cooler and 1,2,3 (especially hand test at exhaust outlet). Like 1 or 2 of pistons 4,5,6 are not doing much work.

Leak down test not very good: 1-38%, 2-39, 3-33, 4-35, 5-30, 6-30%

I only did piston 1 on my spare engine so far… 40% (cold and not run for a few weeks). I was hoping for better on the spare.

Oh, also the vacuum advance has a LOt of slop and barely turning the dizzy…. Looking into that.

Re: 1962 c10 235 lack of power
 

Put a timing light on each plug wire to check for spark, or test each with the plug out.
Advance is 3 parts, initial, mechanical and vacuum. Why check one and not the others?

Re: 1962 c10 235 lack of power
 

Yes I was doing the timing light thing.

Wire to 6 was very sporadic and seemed to depend on how I held plug wire. 5 was also a bit erratic. 2 seemed twice as fast as all the others. 1 was most consistent…. Overall erratic.

I swapped the hei dizzy back in.
Got the timing set and had it running etc.
then it was time to call it a day.

Will drive it and test on it after I get the 12v ignition/start source figured out.

Re: 1962 c10 235 lack of power
 

Open the hood w/ the engine running after it gets dark. I'll bet there's a lightshow... :)
I'd guess you need new plug wires and maybe a cap and rotor.

Re: 1962 c10 235 lack of power
 

Already replaced the points ignition system with HEI.

Re: 1962 c10 235 lack of power
 

Ran an ignition wire for the hei (my dad did the original hei install, he might have run it off of original wiring… which may have lead to the hei failing when voltage dropped, will never know).

The header for 4,5,6 got good and hot eventually. Turned out that my inductance timing light doesn’t always pick up the spark signal for whatever reason. I wasn’t getting spark per timing light on 4,5,6, so I switched to the spark in a window inline spark tester and it was fine (and timing light wouldn’t pick it up).

I also checked compression, rear are better than front cylinders… just like leak down.

At first the rear cylinders still weren’t doing work, but after some time, something ‘popped’ and all of a sudden the pistons were firing, or at least some of them.


I think…. (Hope)
The plugs were still gapped to .045 for hei, and perhaps the points ignition wasn’t jumping the gap, especially with fouled plugs and most likely a good bit of blow by. And then it took a while for the hei to fire through the fouling, but then it did, made a pop sound, and started working.

Cannot guarantee all cylinders firing (common exhaust port for 4,5). But I am pretty sure more cylinders are partying now than before.

Of course I got it ready, and it started pouring down rain. So whenever the yard dries and I have time I will take it for a drive and see how it is now.

Re: 1962 c10 235 lack of power
 

How's your valve adjustment?
Valves set to tight can cause low power and lower compression numbers.

Re: 1962 c10 235 lack of power
 

Valves are adjusted and okay.


Drove it today.
Does a tad bit more power.
Definitely runs smoother.
The air/sucking noise lessened but still there, but better.
I figure I still have a piston not doing much work.

Also…. Between 2nd and 3rd gear is quite a ratio jump. Might get a 4 speed or t5 and try that. I want 1st gear synchros anyway (I will eventually figure out how to shove it in first without completely stopping).

Re: 1962 c10 235 lack of power
 

Does the vacuum advance work? It should hold when pumped down. Is it hooked up to the correct vacuum port on the carb?

Re: 1962 c10 235 lack of power
 

As big of a fan of original, untouched trucks as I am I don't like the 235 and don't plan to keep anything I find with one that way. My honest recommendation is swap to V8 and be done with it. These 235's are only fun if you don't really daily drive or drive often. Now if thats the case, and you want to stay #'s matching then a rebuild of the engine or carb, petronix ignition better plug wires etc may help but if you intend to drive this thing frequently in modern traffic, I say ditch it

Re: 1962 c10 235 lack of power
 

I was somewhat tempted by the "cool factor" of keeping my original drivetrain, but with an LS you get triple the power on half the gas with zero oil leaks.

Re: 1962 c10 235 lack of power
 

Swapped 3 speed to 4 speed.
*Switched engine out.

Has Way more power,,,, drives like a regular truck now. Can get to 55 without trying. Hills not a problem.

Turns out my spare engine smokes quite a bit, but that is what I expect of a free engine.

Time to rebuild the original engine.

(Not interested in v8, nor modern engines).

Re: 1962 c10 235 lack of power
 

Check to see if your balancer has spun. The pulley has the timing mark, sometimes the rubber gives out and spins giving you a false reading.