1275s over heating since rolling road tune

[underkut]

hello all
I recently treated my rally modified(although only road used) 1965 1275 S to a trip to the rolling road as i wanted things to be right as i intended to clock up some miles this year.
I took it to a recommended and very good tuners on the dorset border.
while there they treated it to timing adjustment and reground the H4 needles (by hand , a real pleasure to watch).
The car peaked on the rolling road at 87bhp so i was very pleased.
Since then the car has constantly run hot , although it does cool down (just above normal) when cruising with no traffic.
I have tried a fuel additive and octane booster as recommended by the tuners, both together and seperatly .i have tried a drop in the tank catalyste as advertised on ebay, still no luck.
I dont really want to start playing with the timing as the car runs well and pulls very niceley (as the torque curve showed on the rolling road).
I am now thinking of changing plugs from a 6 to a 7 heat range .
Has anyone else got any ideas. I wont go down the line of an electric fan as everything else has period gear fitted and i dont want to loose that.
regards
Mark

[Rusty old S]

Mmmm . mixture to weak , timing retarded, head gasket problem, as you know when on rollers this will get it realy hot and will find a weakness if thre is one ,many a good engine has given up whilst on the dyno. I would take it to another rolling road not mentioning you have previouly paid for a tune just get a report and compare . Hand filing needles ok in the sixties to get that 1 extra BHP to beat the rest but nowadays for weekend mature road use bit of a guru style smokescreen , sounds if it better left like it was before the tune up

[underkut]

The mixture is fine, i have checked the plugs and have a perfect colour, the car does not use any water so i am ruling out the head gasket, timing is a possibilty but as mentioned the car does pull very well with no hesitation, any further ideas, i have removed the stat and flushed out the rad neither made any difference.

[foxy52]

Mmmm . mixture to weak , timing retarded, head gasket problem, as you know when on rollers this will get it realy hot and will find a weakness if thre is one ,many a good engine has given up whilst on the dyno. I would take it to another rolling road not mentioning you have previouly paid for a tune just get a report and compare . Hand filing needles ok in the sixties to get that 1 extra BHP to beat the rest but nowadays for weekend mature road use bit of a guru style smokescreen , sounds if it better left like it was before the tune up

...i would rec peter baldwins rolling road as he tuned mine and got 98bhp..!!! as u say its a worry putting yr engine under the max possible strain as many a good engine would give out !!! i am not tech versed to adv further ..give him a bell at his royston premises at the wilshers garage..?! if anyone can adv peter can...ps my engine only gets hot in heavy slow traffic but the rad water is fine ,my only gripe with a seriously modified head,bigger carbs etc.is higher oil use !!. ,my guess is most get very very hot and i try to avoid busy roads with slow traffic for that reason ...

[gr4h4m]

Sounds to me if the car runs ok at speed is must be an air flow problem at idle. Check the simple things before everything else, like the fan is on the correct wy around and the fan bel is tight. You could try a fan that gives more air flow.

As the weak /lean your only going to know for sure with something like a wide band. Maybe the timing is too advanced at idle? Or you are pushing the Cooling capabilities of your rad.... I guess its not a 2 core..

[andy1071]

I have found that after a rolling road session, I need to retard the ignition 1 degree or so, and tweak the mixture 1 or 2 flats.
-Mind you, this is on 'steady-state' rollers, rather than the modern 'transient' types.

Never trust the temperature gauge! Even the capilliary type are not that accurate.
Get some temp strips on the thermostat housing or rad top tank by the upper hose.
-Or check with one of those infra-red thermometers (not so easy, as you have to stop, and get the bonnet open before the engine starts to 'heat'soak)

I wouldn't change the plug type. Modern plugs are more tolerant than they used to be, so have a wider heat range.