45 btdc ??? on a GT
06-17-2003, 01:25 PM
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45 btdc ??? on a GT
Guys,
I'm currently rebuilding my engine and I have a question regarding the timing setup. I have read loads of stuff on this but I have yet to find anything that clearly defines how I get from a previously un-marked cam and crank setup to a correctly fitted belt. I suppose the biggest issue is that I see lots of references to 45 BTDC and I only have a 45 degree mark after TDC.
My crank is currently on the 45 after mark with the heads fitted and the belt new and in the box,,,, how do I safely get the belt on from this position on the basis that it looks like I'll have to turn the engine thru at the least - 90 degrees????
Please help if you can
Regards.
I'm currently rebuilding my engine and I have a question regarding the timing setup. I have read loads of stuff on this but I have yet to find anything that clearly defines how I get from a previously un-marked cam and crank setup to a correctly fitted belt. I suppose the biggest issue is that I see lots of references to 45 BTDC and I only have a 45 degree mark after TDC.
My crank is currently on the 45 after mark with the heads fitted and the belt new and in the box,,,, how do I safely get the belt on from this position on the basis that it looks like I'll have to turn the engine thru at the least - 90 degrees????
Please help if you can
Regards.
06-17-2003, 03:52 PM
#3
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There is not usually a 45 deg ADTC mark on the dampener. There should be a 45 deg BTDC mark. Makr sure that the numbers and letters on the dampener read correctly as you stand in front of the car.
You will have some difficulty in installing the belt at the 45 deg BTDC mark if you didn't mark the cam sprockets - there is no mark on the cam sprockets at this position.
Here are two possible ways to install the timing belt:
Set the crank at 45 deg BTDC.
Set both cam sprockets on the timing marks.
Turn the crank to TDC and install the belt.
Set the crank at 45 deg BTDC.
Set both cam sprockets three teeth ahead of the timing marks.
Install the timing belt.
In either case, snug the belt with the tensioner, then check the timing at TDC. When it is correct, set the tension, turn the crank two full turns to TDC and recheck the tension.
This is a grossly over-simplified description of a critical operation.
If you screw this up, it could cost a LOT of money!
You will have some difficulty in installing the belt at the 45 deg BTDC mark if you didn't mark the cam sprockets - there is no mark on the cam sprockets at this position.
Here are two possible ways to install the timing belt:
Set the crank at 45 deg BTDC.
Set both cam sprockets on the timing marks.
Turn the crank to TDC and install the belt.
Set the crank at 45 deg BTDC.
Set both cam sprockets three teeth ahead of the timing marks.
Install the timing belt.
In either case, snug the belt with the tensioner, then check the timing at TDC. When it is correct, set the tension, turn the crank two full turns to TDC and recheck the tension.
This is a grossly over-simplified description of a critical operation.
If you screw this up, it could cost a LOT of money!
06-18-2003, 08:18 AM
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Guys,
First of all,,, thankyou for spotting a mistake that would have cost me time and probably money. The vibration damper is on the wrong way round,,,, How I did this I'll never know,,, I looked back at the pictures for that engine (I'm build one good engine from two GT lumps) and it was so obvious I could weep!! good call about the numbers being readable from the front of the engine.
Secondly,,,, Wally, your brief description is all I needed to set me on the right track. What I needed to know was that I could turn from 45btdc to tdc without the belt fitted.
What about this??? assuming the vibration damper is on the wrong way round,,,, and that I only have the left head fitted with the cams in place with the cast points pointing directly away from the head as in the manual,,,,, is it safe to refit the damper correctly and turn the engine clockwise to the correct 45btdc position (or tdc) so I can fit the belt????
My other option I guess is to watch the piston tops on the right side and turn the cams on the left to match valves seated and piston up on the left,,,,,, it would just be easier to know it's safe if it is???
I have the other belt info from you Wally,,,, cool from another site or thread.
Thanks Guys.
First of all,,, thankyou for spotting a mistake that would have cost me time and probably money. The vibration damper is on the wrong way round,,,, How I did this I'll never know,,, I looked back at the pictures for that engine (I'm build one good engine from two GT lumps) and it was so obvious I could weep!! good call about the numbers being readable from the front of the engine.
Secondly,,,, Wally, your brief description is all I needed to set me on the right track. What I needed to know was that I could turn from 45btdc to tdc without the belt fitted.
What about this??? assuming the vibration damper is on the wrong way round,,,, and that I only have the left head fitted with the cams in place with the cast points pointing directly away from the head as in the manual,,,,, is it safe to refit the damper correctly and turn the engine clockwise to the correct 45btdc position (or tdc) so I can fit the belt????
My other option I guess is to watch the piston tops on the right side and turn the cams on the left to match valves seated and piston up on the left,,,,,, it would just be easier to know it's safe if it is???
I have the other belt info from you Wally,,,, cool from another site or thread.
Thanks Guys.
