Runs but no power and spits

[Rob123]

I’ve got a 1976 project car that I got riding and can drive around the neighborhood. Before that the car hasn’t run in over a year. PO resealed the engine but put everything in wrong (fuel lines and vacuum lines switched, spark plug wires in wrong order, so many things…)
Cams and crank are in time and spark is at 8 degrees BTDC on a warm engine, I’m getting just over 100 PSI on all 4 cylinder.
The issue: I have very little power and the intake spits when the second carb barrel opens.
Any ideas? I’ve heard exhaust could be clogged but I don’t have a cat. I thought maybe the intake valves aren’t closing completely but then I wouldn’t get ok cylinder compression.

[18Fiatsandcounting]

Is the ignition timing advancing as it should when you rev the engine? I know it's hard to gauge since the timing marks usually only go to 10 degrees BTDC, but the timing should advance to around 35 degrees BTDC at 3500 rpm or so.

100 psi is very low but not a complete disaster. How about the other cylinders?

-Bryan

[Nut124]

Is the ignition timing 8deg BTDC with or without a vacuum connection to the dizzy? Should be w vac if any, disconnected.

100psig is low indeed. This was with throttle wide open, right? If all 4 cyls are the same then I'd suspect a systemic cause rather than bore wear. Cams not timed right would be the cause.

[Rob123]

Good idea on the spark advance! I just checked: the timing moves up when I rev the engine. I don’t have an advance light but it does look like roughly 30 degrees when around 2500-3000 RPM range.

Compression ranged between 105 and 120 on all cylinders.. with a 20 year old cheap pressure gauge which I don’t trust.

I suspect I may be feeding it way too much fuel or possibly an exhaust leak. Any other ideas?

It’s quite stable at idle and revs well without load.

[18Fiatsandcounting]

At this point, I'd say your ignition is likely good enough for now. If that's the case, the likely cause of low power when driving is lack of fuel (or way too much). Do you have an electrical fuel pump or mechanical? Either could be starting to fail, or there could be a filter that is plugged up, or even a fuel line or hose that's restricted. 105 to 120 psi compression isn't great, but if all else on the engine is fine, it should run OK but not stellar. Another possibility is a vacuum leak in the intake.

Can you describe more about the low power when driving? Does it just not rev very well, or it doesn't pull well under load, or can't go up hills, or starts faltering at higher rpms, or ???

How do the spark plugs look? Clean, or carbon or oil fouled?

-Bryan

[Rob123]

Nut- I’ll have to look closer into the timing, the marks line up but I’ve been suspicious about the cams.

Bryan- I’ll look closer for intake leaks.
As for the power: If I rev slowly it’s no problem, if I blip the throttle it hesitates.
When driving around my block before the engine heats up I can barely drive up my driveway. Under heavy load the engine just about stalls with no power and lots of smoke out the exhaust.
When the engine warms up I don’t get the stalling but definitely not getting the right power.
If I go full throttle (causing the second barrel to open) the engine will usually spit.
Fuel: the pump was shot so I replaced with a new pump and replaced both filters. New pump is slightly higher PSI.

I haven’t really messed with the carb yet, other than dialing back the idle fuel screw.
Could be too much fuel?

The spark plugs are new.

Thanks for all the support thus far!

[18Fiatsandcounting]

Fuel: the pump was shot so I replaced with a new pump and replaced both filters. New pump is slightly higher PSI.

It was really starting to sound like a carburetor problem, and then I saw this. How much higher PSI? The float bowl valve needle is designed for 3 to 5 psi, so if your fuel pump is much more than that, it can overcome the needle valve and flood the engine with gas. Which would pretty much explain all of your symptoms.

Another question: When you say you see smoke out of the tailpipe, what color? Sooty black, steamy white, or oily bluish? This diagnostic, along with the spark plug color, will tell you a lot.

-Bryan

[Nut124]

Rob123, you state that you do not have a timing light. How can you make any assessment about timing w/o a light? Get a light w adjustable advance and check the timing and advance.

[Rob123]

I have a normal timing light without andjustable advance, so I estimate based on the timing markers on the belt cover.
Then new pump is in the 3-5psi range, it’s printed on the label but I can’t remember what it was. I remember it being 1 psi more than my last pump.
Smoke: black. As this leads to gas in the exhaust, I wonder if my fuel rate or a spark issue could cause it.

So, seems I definitely need to learn about this carb! I was planning to hold off as I wanted to switch to megasquirt but seems I need to lesrn about this carb.

Thanks again for all the support!!

[18Fiatsandcounting]

Yes, black smoke would be running way rich, and that could cause many of your symptoms. In addition to the ignition timing advice suggested by Nut, I'd take a look at the carburetor.

Do you know which carb you have? If stock, I believe it is a 32ADFA, which is, shall we say, OK but not great. Prone to various issues, and by the mid 1970s, loaded down with all sorts of emissions control stuff that rarely works any more the way it should.

So, a carb rebuild might be in your future. But, back to ignition, you might also check plugs wires and distributor cap/rotor as these can cause misfires if bad.

-Bryan

[Rob123]

Thanks Bryan!
Yes, it’s a 32ADFA. The PO has remnants of a rebuild kit. I’ll check the plugs then dive into the carb… or pull the trigger on getting megasquirt setup!

As for the spark side: looks to be new-ish wires, cap and rotor. I plan to switch that over to megasquirt as well after I get the fuel going.

[Rob123]

Spark plugs are dark and sooty. They have very little time on them (and less than 1 mile!).
So, certainly running rich!

I took the top part of the carb off to check the bowl, clean the internals and check the jet sizes.
All looks good, everything looked proper and jet sizes all matched the specs (primary main 1.25, secondary main 1.40, primary air 1.85, secondary air 1.70).

I’ll keep looking around the carb for anything suspicious. I also may put it back together and idle it again to check for any differences.

[Nut124]

Have you tried to adjust idle mixture?

[Rob123]

The idle mixture screw was 2.5 turns out, so I played with that a bit and set it at about 1 turn out. I confirmed when closing it the whole way the engine almost stalled.

I took the car for a couple laps around the neighborhood, noticeably better!! I still think I’m running rich though, or maybe still an intake cam issue. The engine spits a little when the second barrel opens.

Thank you so much for the feedback!

[Rob123]

Quick update:
I’ve put about 35 miles on the car and it’s been running well! No more spitting and I get normal power on cold starts.

Thanks again for the help.