Whats with this

[karl head]

Ok now I half way into my reassembly when I come across this new issue I have attached a few pictures to hopefully explain the problem . I reinstalled the timing chain following the manual, rotated it through all strokes while watching the piston and valves and everything looks good. however when I put the timing case cover back on the marks are no where near for TDC in facts you can't see the pulley marks at all. so I pulled it all again and started over and you guessed it still the same . So I'm thinking maybe the cover is incorrect, so pull out the spare cover (218)'s and sure enough the marks line up. as you can see from my pic's I put a new mark on my pulley to indicate TDC but you can also see how small the scale is on my pointer.

Has anyone run into this Issue before or is there something I'm missing.

[Don Coatney]

Is your engine actually at top dead center as in the number one piston all the way to the top of its stroke?

[karl head]

Yeah Don

I don't even have the head on, and used my dial indicator to find True dead center. I am about to post what I hope is a better picture to show the refrence marks on the pulley

[karl head]

as you can see from my other pictures #1 is TDC in compression/power:confused:

Oops I see you can't see that one sec.

Edited October 4, 2012 by karl head

[Dave72dt]

The correct cover for that pulley would be the one with the pointer. I've seen mismatches before and generally indicate one of the pieces has been replaced at some time. You can use either one now that you have TDC marked permanently on the pulley. I'd use the one I could read the best when the engine is installed. That would be a reason for using different locations for marks.

[karl head]

The correct cover for that pulley would be the one with the pointer. I've seen mismatches before and generally indicate one of the pieces has been replaced at some time. You can use either one now that you have TDC marked permanently on the pulley. I'd use the one I could read the best when the engine is installed. That would be a reason for using different locations for marks.

Thanks Don that's what I thought also, unfortunately the one I have with the pointer wont fit because the lower pulley is larger. I am considering pulling the pointer and welding it or glueing it to the one I have in place.

[Dave72dt]

Thanks Don that's what I thought also, unfortunately the one I have with the pointer wont fit because the lower pulley is larger. I am considering pulling the pointer and welding it or glueing it to the one I have in place.

Apparently it's not right pulley for that cover either if it won't clear the pointer. Typically you would use a a pulley with degree marks on it with a POINTER and and one with a TDC hash mark on the pulley with a cover that had the degrees marked on a tab.

[NiftyFifty]

I found the industrial 251's have the wrong pulley for an auto application but also no timing marks . My original flywheel had no markings even after I removed and cleaned up I could find nothing so I did the TDC and made my own mark.

[Guest dadsdream]

you probably already know this but just using an indicator alone can be difficult to find TDC. there is usually about 10 degrees, 5before and 5 after that the indicator will barely move if at all.

when i find tdc i put a degree wheel on the crank and roll the piston up till the indicator reads the highest point.

then zero the indicator.

roll the crank backwards about 1/4 turn.

roll the crank forwards till the indicator reads .050 before your zero mark.

make a note of what degree the pointer on the degree wheel is at.

roll the crank forward past zero(TDC) on the indicator till it is at .050 below again.

make a note of what degree pointer on the degree wheel is at.

add/ divide or somehow figure the middle point of the two readings on your degree wheel

roll the crank to that middle point. that is true TDC.

if you don't have a degree wheel you can also do it by making marks on your front pulley,then measuring the distance between them and finding the middle. just not as accurate but still pretty close.

Eric

[karl head]

Yes I did take this into account, using a similar method I narrowed down and marked it I am still considering mounting the pointer from my other cover, I would of changed covers however the pointer is to close to the pulley and I damaged the seal area removing the pulley on the original engine. the bolts I used were to long

Thanks Karl

[NiftyFifty]

Don't get too hung up on it, with these old engines your almost adjusting the distb blindly anyway. It's good to get the TDC roughly to start, but after that its set by ear and performance. I run a few degrees advanced but not so much as to affect hot start or pre detonation, but I set it just by how it runs... Near impossible to hover over that metal fan with a light and make slight adjustments.

[karl head]

I will try not too, did lots of tuning by ear when i was a lot younger so I'm far from a novice . right now just trying to get it setup before winter I have got the main engine back together working of the fuel pump and intake and exhaust mans and carb next hoping to fire it up after the long weekend.

Thanks Karl

[Jeff Balazs]

Hi Karl;

Ditto on what 4mula-dx said. Just needs to be close enough to get it to run.

Any older engine can vary quite a bit on what the optimum settings may be. Things like the condition of the timing chain and valve train....camshaft wear....distributor wear.....and the overall condition of the fuel and exhaust system all come into play.

But don't sweat it ....... you will find the proper settings easy enough. Your ear and a bit of road testing will tell you pretty much all you need to know. Old workhorse engines left in a "soft" state of tune are a thing of beauty all unto themselves. All you have to do is take care of their basic requirements and let them do what they do best.

Jeff

[Fernando Mendes]

as you can see from my other pictures #1 is TDC in compression/power:confused:

Oops I see you can't see that one sec.

No.According your pic number 38886 the number 1 cylinder is not in compression stroke.It is in exhaust stroke.

[Don Coatney]

No.According your pic number 38886 the number 1 cylinder is not in compression stroke.It is in exhaust stroke.

Does not matter. Top dead center is in refrence to the piston being at the uppermost top of its travel.

[Plymouthy Adams]

when setting TDC so to place/relocate a timing tab or make a new mark on a damper....one should do this with a degreeing wheel and say .050 down on either side of TDC..the movement is so slight as the piston approaches and passes TDC bit of travel a guess is just a bit hard to make by eye..with the head off using a piston stop dead center of the piston to take piston slap out of the equation..rotate clockwise till it stops..record the number on the degree wheel and rotate counter clockwise and note that number when the piston stops..Count the degrees between the two recorded marks, divide this number in half and remove the piston stop..rotate crank till you reach the 50%mark as this is now TDC and mark your damper or mount your tab whatever the case may be..with the degree wheel stillin place yu can also mark you damper in 2 degeee increment for timing also if you remarking the damper..

[Fernando Mendes]

Does not matter. Top dead center is in refrence to the piston being at the uppermost top of its travel.

Don,"but" the number 1 piston is at the top for the firing(compression) stroke with both valves CLOSED ,in this same time number 6 piston is in the end of the exhaust stroke,with exhaust valve just closing.

[Plymouthy Adams]

Don is only stating that the TDC mark is the same be it compression or 180 out..the 4 stroke engine takes 720 degrees of rotation per cycle..so anytime the crank is 360 degrees from X mark it will return to same mark one rotation regardless of the stroke you may be on..this is only relevant when setting the distributor to electrically time the firing to the correct stroke..

[Don Coatney]

Don,"but" the number 1 piston is at the top for the firing(compression) stroke with both valves CLOSED ,in this same time number 6 piston is in the end of the exhaust stroke,with exhaust valve just closing.

Top dead center is the same on number 1 and number 6. For the purpose of pointer alignment it does not matter what the valve position is nor what stroke the number one cylinder is on. The procedure that Tim mentioned for finding top dead center is the best although few will follow it.

[Fernando Mendes]

Then,since today,all my GMC 1944 and Jeep 1942 WWII manuals(and Dodge trucks driver's manual too,in page 39) are wrong.Then,why and for what timing marks???

Dodge trucks driver's manual says in page 39 "........With Nº 6 piston at the top of the EXHAUST stroke,Nº 1 piston will be at the top for FIRING stroke".

[Fernando Mendes]

See this drawing.

[NiftyFifty]

Fern only the timing chain marks are what matter for what stroke your in, that you want to be sure you are in the TDC #1 compression stroke. The only other time this matters is when you drop the distributor in, there again you must be on the proper stroke, but in all cases the balancer will show 0 degrees

[Don Coatney]

Dodge trucks driver's manual says in page 39 "........With Nº 6 piston at the top of the EXHAUST stroke,Nº 1 piston will be at the top for FIRING stroke".

That is correct but the timing pointer should align with the TDC mark on the balancer no matter what stroke either cylinder #1 or #6 is in when at top dead center.

[Fernando Mendes]

Ok guys,I gave up now.

What is the correct degrees(before or after) TDC for pilothouse B3-B engine?I saw in the driver's manual and can not see.

[Dave72dt]

Correct ignition timing is TDC for your truck as found in the truck repair manual.

All you're doing with finding TDC is creating a reference point that's repeatable. The crankshaft itself does not determine compression or exhaust stokes. It just goes around and around and the piston will reach the top at the same point in rotation every time it does. The camshaft determines whether it's compression or exhaust stroke. You could, if you really wanted to, find TDC without a camshaft or valves in the engine.

TDC is a reference point commonly used for cam timing and ignition timing.