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Triumph Spitfire - Spitfire Mk3 Tuning Help Required.
|I have a 1968 Mk3 Spitfire of which I am having considerable trouble in tuning. The car is of original spec in every way of which ill give some info below;|
Distributor D200 7953460
Vac Unit 7953461 (New unit)
New reconditioned pair of HS2 Carbs.
The car has just been fitted with a Unleaded Head and this is really a initial tune as the car has only done approx 100 miles since a complete restoration.
Ive set the timing to 8' BTDC (Also tried 6' BTDC as someone suggested this works well with unleaded), tho I have experimented with settings of approx 10-12' BTDC which seems to give more power but I dont think its to healthy for the engine at that.
The carbs were set using the "color Tune" method of richening the mixture to produce a "yellow" flame then Leaning it out to "Bunsen Blue". This was repeated for both carbs.
My problem is this, the car has absolutly NO power, In the Manual it states a 0-60 time of approx 16 seconds, Ill be lucky to get to 30 in that.
My main question is regards mixture setting, even tho ive color tuned it, using the alternate "lifting Pin" method I have to richen the carbs so much to obtain the correct engine responce, so which is correct?
Any Help/Info greatly appreciated.
|Try setting the carbs with the lifting pins, then drive the car. I think you will find it much better.|
As far as the timing, as long as it doesnt spark knock at the higher advance, run it like that.
|OK, Ive tried the lifting pin method and I can get the front carb to respond but the rear has to be richened to the point of flooding before i get the same responce.|
Ive gone back and colourtuned the carbs and have now retimed to 6'BTDC with the vacuum ADVANCE disconnected.
What im unsure about now is the amount of advance given when reving the engine is the same weather the vac advance unit is connected or not. The Advance unit is brand new and is functioning when removed from the distributor and connected to the vac hose.
Are we now talking a badly worn distributor? as there is some play in the spindle.
Theres got to be a simple explanation to this as ive never encountered such a flat engine condition before.
1)Set the timing to 10 deg. BTDC
2)Points to .014" - .016"
3)balence the carbs.
4)set to color tune.
Now you are at the standard set up point, you can now start to investigate the issue, remember never change more than one thing at a time, always return to std. befor trying another stage.
Start by rocking the dist, shaft at the cam end & check for sideways movement- no more than .002/.003" if its any more - change the dist.
Second stage- increase the advance in increments of 1 deg. - road test at each change until you can hear the engine pinking under hard excl. then back off 1deg.
Your problem may just be the timing marks on the pully are out of possition (not uncommon).
It could also be that the timing chain is set one tooth out or has jumped due to ware. You can check this by removing the spark plugs & measuring the relationship of the piston to the lift of the rocker arm - I do not have the details but if you have a mate who has a simular car you could measure his.
Best of look
|Ok guys, got it sorted.|
Very embarrasing but ill tell you. Ive had this car for 10 years now, and it has only been on the road for the last 1.5 years and done approx 160 miles. When I first purchased it the first thing I did was rebuild the engine, then set about the rest of the car over the next 8 years, taking this time due to lack of funds or just having a break from it.
Anyways, basically It appears I screwed up with the cam timing. I put "new" timing gears + chain on and they didnt have the same marks as the original. So in effect yesterday when I dismantled and checked the cam, the inlet valves, instead of opening 25'BTDC were infact opening at approx 20'ATDC. Im surprised the thing ran at all.
So today I set it up right, redone timing/carbs and hey presto! it goes like a rocket.
So thanks for everyones input, it wasnt wasted as such info will be usefull to others, and ill just go hide my face for a year or two :op
This thread was discussed between 05/08/2000 and 16/08/2000
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