Engine Overheating

[gagvanman]

My 1776 has been suffering with overheating for a while. I have added an external oil cooler but this has not really helped.
Engine is running twin ICT34's with the following jetting:
idle jet 57
Main jet 160
Air corrector 180
Emulsion tube f6
Float jet 150

The spark plugs (NGK DE7A) tips are white indicating lean running which would explain the over heating, but the exhaust tip is black which would indicate lean running. I had considered going to a 155 main jet before I took out the plugs. I am confused.
Should I go to a hotter spark plug such as a NGK DE6A. Or a larger main jet (or both)?

Any other suggestions gratefully accepted.
Thanks

 

[K@rlos]

A 160 main jet is very big! I’ve only got 155’s in the 48’s on my 2276! An oil cooler will not help head or cylinder temps. What’s the timing set at? What’s the compression ratio? DE7A’s should be fine. Is the tinware all there and fitted correctly?

 

[sparkywig]

I've never fitted anything larger than a 150 main jet to ICTs, the air corrector seems a little large as well.

idle jet 55
main jet 150
air corrector jet 170
emulsion tubes F3/F6
needle valve 125-140

 

[gagvanman]

Timing is set to 29 deg BTDC.
Compression ratio is 7.5
Tinware is all fitted
The Air Corrector is set to what someone on this forum recommended. I changed the Idle Jet to 57 as the engine was hunting at 30mph in 4th gear.

K@rlos, you say you have 155 main jets in your 48's, but aren't those twin barrel carbs and therefore have a main jet for each port, the ICT's main jet is feeding 2 ports. (excuse me if I am wrong).

Thanks for all comments, still confused lol...

 

[K@rlos]

Timing is set to 29 deg BTDC.
Compression ratio is 7.5
Tinware is all fitted
The Air Corrector is set to what someone on this forum recommended. I changed the Idle Jet to 57 as the engine was hunting at 30mph in 4th gear.

K@rlos, you say you have 155 main jets in your 48's, but aren't those twin barrel carbs and therefore have a main jet for each port, the ICT's main jet is feeding 2 ports. (excuse me if I am wrong).

Thanks for all comments, still confused lol...

Is that’s 29 BTDC at what? idle? Full advance?

That is correct regarding carbs but the jet is still far too big. The calculation for getting ict jets ball park is Venturi size x 5 so that’s 29x5 = 145 then + 20 for the air corrector. Work from there with a wideband or rolling road. However that’s another matter, not the cause of your overheating.

 

[gagvanman]

K@rlos, I apologise I looked at a diagram of a 48 and there is only 1 main jet.

 

[gagvanman]

K@rlos, I don't mean to be disparaging but I don't think an engine would run very well with 29 BTDC at idle (i'm sure that was a typo) Yes 29 BTDC at 3000 revs.

Today I took out all the spark plugs (no mean feat with twin carbs). No fowling of any of them and all whitish, so still baffled by the exhaust being black. Tomorrow will re-check the timing and maybe set it to 28 deg BTDC at full advance, then tune the carbs using the snail gauge.

 

[67panel]

Could be a high HC (unburnt fuel) , what is your advance curve like i.e. ign timing at idle.

 

[K@rlos]

K@rlos, I apologise I looked at a diagram of a 48 and there is only 1 main jet.

I don’t know what you looked at but an ida has 2 main jets….

 

[K@rlos]

K@rlos, I don't mean to be disparaging but I don't think an engine would run very well with 29 BTDC at idle (i'm sure that was a typo) Yes 29 BTDC at 3000 revs.

Today I took out all the spark plugs (no mean feat with twin carbs). No fowling of any of them and all whitish, so still baffled by the exhaust being black. Tomorrow will re-check the timing and maybe set it to 28 deg BTDC at full advance, then tune the carbs using the snail gauge.

No it wasn’t a typo, You didn’t specify how your timing was set so how was I suppose to know? I’ve witnessed people do all sorts of stupid and wonderful things to engines over the years and yes I’ve seen an engine run with extreme advance at idle because some dick head garage didn’t know what they were doing

I’m assuming it’s the oil temps that are too high? If so need more details, What oil? What size oil pump? Oil pressure? how is the full flow system set up? What are the bearing clearances?

 

[mike202]

My 1776 has been suffering with overheating for a while. I have added an external oil cooler but this has not really helped.
Engine is running twin ICT34's with the following jetting:
idle jet 57
Main jet 160
Air corrector 180
Emulsion tube f6
Float jet 150

The spark plugs (NGK DE7A) tips are white indicating lean running which would explain the over heating, but the exhaust tip is black which would indicate lean running. I had considered going to a 155 main jet before I took out the plugs. I am confused.
Should I go to a hotter spark plug such as a NGK DE6A. Or a larger main jet (or both)?

Any other suggestions gratefully accepted.
Thanks

If it’s if any help my 2007cc with twin ICTs that have 150 mains and 55 idle jets. The white spark plugs being white doesn’t sound good so something seems wrong. Is your oil temp gauge telling you it’s over heating? Has it done this for some time, if so has anything changed?
I don’t have an external oil cooler just full flow oil system and don’t over heat.

 

[gagvanman]

I think I have finally fixed the overheating issue. After much trial and error, finally come up with a combination of timing and ICT adjustments that seem to suit my 1776.
Took the bus out for an extended run in 28 deg heat yesterday and the temp got to just a smidge over 100.
Really hoping this is cured. Thanks for all the advice on the forum.

PS now got to replace a knackered leisure battery then we can hit the road again...

 

[pierrox]

I'd be curious what you did to it in the end, in detail. Bigger jets? Did you go for a colder plug too?

 

[gagvanman]

pierrox, went back to basics. Checked what the static timing was with the vacuum advance blocked off, seems to be around 5 deg but not worried about what it was, just curious. Set the max advance to 28 deg. Took carbs off, set the idle screw to 1+1/2 turns in. Set the mixture screw all the way in, then 2 turns out, done with the vacuum tube, carbs balance pipe all blocked. Checked each carb with the snail gauge, left one at 9 / 10, right one at 7 / 8. starting with the left carb slowly turned the mixture screw in until engine started to falter then back out until the best running. Same for the right carb. Then adjusted idle using the snail gauge on each carb. Connected everything back up and ran for a while to monitor. Took no 2 and 4 plugs out, nice tan colour now. (didn't do 1 and 3, hard to get at). Took van for an extended run and temp around 100 deg.
Took the van out again for an even longer run, temp never got over 100. Happy days...