Need help with my carbed fiat

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Nick_rp

I=V/R
Military
Joined
Jun 21, 2018
Posts
676
Reaction score
674
Location
puyallup, wa
Ram Year
2012 1500
Engine
5.7 Sport
Any suggestions appreciated. Fiat forum for my model is dead so im seeking even generic level advice as my experience with classics is minimal.

Details:
72 fiat 850 spyder
Water cooled 0.9L 4 cylinder rear engine, points distributor, 2 barrel carb, mechanical fuel pump

The problem:
10 secs after starting the engine, my header basically starts to melt off. The factory paint dosnt just smoke, its bubbling and dripping off ( font stuck on bold?)

My gut says it's extremely lean but ive never experienced this before. That amount of heat so quickly has me fearing to run it at all to put the evidence on the new plugs. I got 1000 extra parts with this car but an extra head wasnt one of them.

Carb was soaked for 3 days in a berrymans bath, jets gone through thoroughly, all gaskets and diaphragms replaced, float height set etc. Tested for vac leaks and found none, has fresh quality gas in it.

My carb experience is 99% from motorcycles so either im missing something or the more complicated design of car vs bike carb has me hyper focused on it

What do you guys think?
 
Last edited:

British Bulldog

Senior Member
Military
Joined
Sep 14, 2016
Posts
2,033
Reaction score
720
Location
Jacksonville NC
Ram Year
2021
Engine
Hemi 5.7 etorque
Assuming you using fuel suitable for that type head, you can only be looking at lack of coolant through head/manifold.
but you say this happens instantly?
The plugs tell you it is lean, or you can’t run enough to check their colour.
I hope you get it quickly, burning valve seats and valves would not help. Do you have an airlock in the cooling system?
I once saw a manifold gasket that had some cooling holes not punched out properly and the mechanic didn’t notice till vehicle overheated after a head gasket replacement.
How hot is the coolant when this happens?
 
OP
OP
Nick_rp

Nick_rp

I=V/R
Military
Joined
Jun 21, 2018
Posts
676
Reaction score
674
Location
puyallup, wa
Ram Year
2012 1500
Engine
5.7 Sport
Assuming you using fuel suitable for that type head, you can only be looking at lack of coolant through head/manifold.
but you say this happens instantly?
The plugs tell you it is lean, or you can’t run enough to check their colour.
I hope you get it quickly, burning valve seats and valves would not help. Do you have an airlock in the cooling system?
I once saw a manifold gasket that had some cooling holes not punched out properly and the mechanic didn’t notice till vehicle overheated after a head gasket replacement.
How hot is the coolant when this happens?
After how vilolent that initial startup was ( it actually was my very first startup for this car) i checked the plugs but the runtime was to quick for the spark plug to collect any evidence and i wasnt about to start it again. Parts for this car are scarce and really expensive, didnt want to risk a melt down. I posted on another forum im on and by there suggestion i pulled off the fuel intel hose to the carb and cranked the engine. Fuel pressure was about as much as a leaky faucet. Definitely a culprit for turning her lean. Ill check the fuel pick up screen and get rid of the mechanical pump for electric. After that ill have a little more confidence to turn the key again
 

pacofortacos

Senior Member
Joined
Apr 18, 2017
Posts
3,564
Reaction score
4,341
Ram Year
2016
Engine
5.7
Lean isn't the only thing that will make the exhaust hot. Fuel burning in the exhaust will do the same thing is your timing and camshaft timing correctly set? Dwell set correctly? Does it miss at all?
 
OP
OP
Nick_rp

Nick_rp

I=V/R
Military
Joined
Jun 21, 2018
Posts
676
Reaction score
674
Location
puyallup, wa
Ram Year
2012 1500
Engine
5.7 Sport
Lean isn't the only thing that will make the exhaust hot. Fuel burning in the exhaust will do the same thing is your timing and camshaft timing correctly set? Dwell set correctly? Does it miss at all?
Wouldnt that produce back fire though? But yea i went back realizing the mech pump dosnt drive itself. This thing has me scatter brained. I found a method to set timing to near the standard without the engine running. That way i can verify the pump and if its good i can start it up and fine tune with timing light. Unless of course the original issue persists
 

British Bulldog

Senior Member
Military
Joined
Sep 14, 2016
Posts
2,033
Reaction score
720
Location
Jacksonville NC
Ram Year
2021
Engine
Hemi 5.7 etorque
No, that’s correct for timing. You set distributor so points just opening , set timing marks then you can set timing with light once running ( and dwell angle)
You can also set points/distributor with just a 12v test lamp.
I think I am telling you stuff you already know as it HAS started lol. If timing was out a little it would still start, probably backfire as you said.
good luck!
I wish I didn’t live the other side of country ( Wisconsin)I’d visit!
 
OP
OP
Nick_rp

Nick_rp

I=V/R
Military
Joined
Jun 21, 2018
Posts
676
Reaction score
674
Location
puyallup, wa
Ram Year
2012 1500
Engine
5.7 Sport
No, that’s correct for timing. You set distributor so points just opening , set timing marks then you can set timing with light once running ( and dwell angle)
You can also set points/distributor with just a 12v test lamp.
I think I am telling you stuff you already know as it HAS started lol. If timing was out a little it would still start, probably backfire as you said.
good luck!
I wish I didn’t live the other side of country ( Wisconsin)I’d visit!
Actually the whole points system is new to me. Always heard/read about it but just now experiencing it. Its safe to say i didnt retain any of that sweet juicy knowledge when ever it came up. Ill get it though thanks man
 

pacofortacos

Senior Member
Joined
Apr 18, 2017
Posts
3,564
Reaction score
4,341
Ram Year
2016
Engine
5.7
It will backfire through the carb if the fire is going past the intake valve.

But if it is dumping fuel past the exhaust valve, the fuel can burn in the header and exhaust port.

Honestly, unless you want to keep the points/condenser for resto purposes, you can use the points to fire a MSD5 or 6 and not have to deal with dwell or a bad condenser - a condenser going out can do really strange ignition issues.
Most of the times they won't start with a bad condenser but, I won a race with one failing in my Cuda with a bunch of popping going on. Was enough to take down the 396 Chevelle SS though.
 

pacofortacos

Senior Member
Joined
Apr 18, 2017
Posts
3,564
Reaction score
4,341
Ram Year
2016
Engine
5.7
I don't know the specifics about that engine, but if it has adjustable rockers on it and the exhaust is adjusted on the tight side, what you are describing will happen also.
 

Latest posts

Staff online

Members online

Forum statistics

Threads
194,926
Posts
2,864,176
Members
155,296
Latest member
VLG6963
Top