Spitfire Help, Lack power on spitfire 1300 engine

My spitfire was running great till a couple weeks ago. It would run great and give good power when I would leave in the morning. But when I took it at lunch or later in the day the car wouldn't give me power and felt sluggish. The idle also I noticed started to idle very low like 4-5 rpms vs the 7 - 8.

I have changed the fuel filter, checked the timing and gap.

I don't seem to have power when I am going down the road and put my foot down.

What should I look for next?

Thanks

tomgt6 said:

My spitfire was running great till a couple weeks ago. It would run great and give good power when I would leave in the morning. But when I took it at lunch or later in the day the car wouldn't give me power and felt sluggish. The idle also I noticed started to idle very low like 4-5 rpms vs the 7 - 8.

I have changed the fuel filter, checked the timing and gap.

I don't seem to have power when I am going down the road and put my foot down.

What should I look for next?

Thanks

Click to expand...

You need to use a systematic approach.
Actually the diagnostic chart in your average Bentley Manual is very good.
Try to recall, was there anything you did just prior to the lack of power? Did you fill up at the gas pump? Maybe picked up some trash in the gas. I'm thinking fuel, fuel filter clog.

That is what I thought that is why replaced the fuel filter.

I know 95% of fuel system problems are electrical, but I've a gut feeling there's still a fuel problem. How is the fuel delivery to the carburetors? How do the float bowls and needle valves look -- clean, or possibly choked with sediment? Are both carbs functioning (i.e., could linkage to one have loosened up)?

Just some thinking out loud here....

Hi, was the old filter clear, could you see any thing, like rust, in it?

How's your fuel pressure? SUs like 2-2.5 Lbs at the carb, no more. Are the slides free in side? Remove the air cleaners and look inside, are both slides at the same level to start with? With the engine off, do the slides move freely up and back down with your finger in the carb?

SU tuning and troubleshooting links
https://www.nicoclub.com/archives/2-write-ups-on-tuning-su-carbs.html

https://www.classiccarhub.co.uk/articles/guide_to_setting_up_tuning_su_carburettors.html


I just re read the original post, " it runs good in the morning" Your choke could be stuck on. Assuming you have the dual SU setup, the choke cable pushes the two jet assemblies away from the body of the carb, effectively eliminating the first few steps of the needles, making the mixture rich. That's fine when it's cold, not do good when it'd warm.

Look at the choke cable and make sure it's not binding when you push it back in. If the cable doesn't retract all the way you may need to replace the cable or at least grease (silicone spray up the end works too) and adjust the travel.

mike h

OK no luck.
I have done the following
1. replaced fuel filter
2. Check points gap
3. Checked timing
4. Check valve clearances
5. Pulled the plugs and the number 1 plug is fouled black with gas
6. 2-4 plugs look great
7. Swapped number 4 and 1 plug. Also checked to make sure number 1 plug is getting a spark.
8. Swapped the number 2 and 1 plug wires
9. Pull the number 1 plug wire and idle doesn't change so number 1 cylinder isn't firing
10. Replaced the distro cap
11. Did a compression test on number 1. Got 147psi.
Forgot to add that I went through the carbs and everything look good.

Still no power and number 1 still not firing correctly. If I rev engine up to about 4000 rpms I get a misfire.

What do you guys think? What am I missing.

The only thing I can think may be that the timing chain jumped but then wouldn't all the cylinders be an issue?

Have you checked the fuel pump?

tomgt6 said:

The only thing I can think may be that the timing chain jumped but then wouldn't all the cylinders be an issue?

Click to expand...

Yup, chain jumping would affect all cylinders equally.

Have you looked to see if maybe there is a broken valve spring on #1 or #2? The remaining spring may be enough to close the valve during the compression test, but not enough to close it with the engine running.

When you swapped the plugs around, did #1 foul again?

How about a vacuum leak on the #1 intake runner?

Might also be worth watching the #1 intake and exhaust valves with the valve cover off and the engine running to make sure they are opening and closing OK - no bent pushrods or broken springs....?

Before walking away from ignition problems as a possibility....

You moved plugs and plug wires yet the problems stayed at #1. The compression value for #1 looks good to me. So... how about checking and/or replacing the dizzy cap and rotor? Also, have you checked for wear/play in the dizzy shaft?

Had a prob with higher rpm misfire and a lack of power on my 73 Spit. Wound up being the condenser in the dizzy. It was only a year old...

Maybe change the rotor and cap,

I had an issue on my TR6 with a bad (New) cap, causing a misfire

Hondo

Just a thought but if it's missing at higher RPM it could be a weak valve spring causing the valve to float a little, kind of a built in rev limiter.