Valve timing question
Discussion
Have adjustable sprockets at 2.5 to 10 degree advance or retard at multiples of 2.5. The sprocket has 19 sections so 18.95 per tooth. Currently at 50 thou lift intake opens at 3.8 ATDC (should be 12 ATDC) and close at 38 ABDC (should be ABDC). Exhaust opens 16.7 BBDC (should be 47 BBDC) and close 12.5 ATDC (should be 9 BTDC). Do I need to advance or retard the cams? So nearest I get is 7.5 for the intake so either position 4 or position C for the exhaust closed can get is move it one tooth and then last postion on sprocket for 10 degrees. Just cannot get it straight in my head which direction clockwise or anticlockwise for each cam. The sprockets are made by Jim Wolf for nissan ka24de it states position 1 to 5 will advance cam by 2.5, 5, 7.5 and 10 crankshaft degrees and A to D will retard cam by 2.5 to 10 degrees. Just cannot get it straight in my head. Note car is FI giving 430hp with bad valve timing. Tks a lot
scoobydo123 said:
intake opens at 3.8 ATDC (should be 12 ATDC) <<< need to retard by 8.2 degrees
close at 38 ABDC (should be ABDC). <<< is there a number missing here?
Exhaust opens 16.7 BBDC (should be 47 BBDC) <<< need to advance by 30.1 degrees
close 12.5 ATDC (should be 9 BTDC) <<< need to advance by 21.5 degrees
If you adjust the cam timing it will alter the opening and closing timing by the same amount. You seem to be trying to alter the opening and closing timing by different amounts so I don't see how you can achieve that timing with that cam. Am I missing something?close at 38 ABDC (should be ABDC). <<< is there a number missing here?
Exhaust opens 16.7 BBDC (should be 47 BBDC) <<< need to advance by 30.1 degrees
close 12.5 ATDC (should be 9 BTDC) <<< need to advance by 21.5 degrees
I would be more concerned as to why they are so far out to begin with ?
New grinds should be pretty much bang on these days. 8deg is bad, but 30deg is utterly ridiculous. So either whoever installed them initially was a muppet, whoever is measuring them is a muppet, or whoever ground the cams is a muppet lol
So why are they so badly wrong ?
New grinds should be pretty much bang on these days. 8deg is bad, but 30deg is utterly ridiculous. So either whoever installed them initially was a muppet, whoever is measuring them is a muppet, or whoever ground the cams is a muppet lol
So why are they so badly wrong ?
scoobydo123 said:
No I appreciate that I just cannot get it in my head which direction I need to go. Seems so simple until I read the instructions on the adjustable sprockets. Tks
The pictures show you how to do it. Moving the gear clockwise on the cam by one bolt position (and two sprocket teeth) retards the cam timing by 2.5 degrees. It works because the degrees per bolt is not an exact multiple of the degrees per sprocket tooth.But you need to know what timing you're trying to achieve, because I don't think the timing you said you wanted is achievable with that cam based on the figures you quoted.
Muppet who installed set up with default valve lash and also spent the money on the sprockets and set them up on the default slot on the sprocket. Head has been skimmed due to same muppet hiding a problem with mechanic in a bottle solution. The lash was up to 8 thou out from what the cam card calls and each thou is around 1 degree the list goes on :-( HG now ok but just struggling get head round which direction I need to go which is rather embarassing.
@GreenV8S I see how the sprockets work but tying myself in knots with which direction I need to go respectively to get much closer to the cam card.
With the adjustment I have then 3.8 with the 7.5 gives 11.3 for the intake should be 12 I can live with that :-)and the exhaust 16.7 with the 18.95 plus the 10 on the sprocket will give me 45.65 so near enough to the 47. But which way do I need to go, this is doing my head in :-)
With the adjustment I have then 3.8 with the 7.5 gives 11.3 for the intake should be 12 I can live with that :-)and the exhaust 16.7 with the 18.95 plus the 10 on the sprocket will give me 45.65 so near enough to the 47. But which way do I need to go, this is doing my head in :-)
In my mind I have that on the intake when the valve has travelled 1.27mm the crank has not rotated enough so I need to retard the camshaft so move it to position C so the crank will move further to get to 1.27mm of lift? For the exhaust we want it to happen earlier so clockwise looking from the front 1 tooth and position 5 but brain cell is exploding going round in circles like a fly with one wing.
Write down the actual timing you have now. Make sure there are not any typos in it.
Write down the timing you are aiming for. Make sure this is consistent with what you are starting from. You can't change the cam duration - if you alter the opening timing you alter the closing timing by the same amount.
Write down the timing you are aiming for. Make sure this is consistent with what you are starting from. You can't change the cam duration - if you alter the opening timing you alter the closing timing by the same amount.
Yes I have done that
figures in brackets are what the cam card says should be set up as
Intake opens 3.8 ATDC (12 ATDC)
Closes 38 ABDC (50 ABDC)
Exhaust opens 16.7 BBDC (47 BBDC)
Exhaust closes 12.5 ATDC (9 BTDC)
Here is the cam card
http://www.briancrower.com/makes/nissan/cam_card/b...
Just cannot get it straight in my head which direction ie for intake am I to go for (4 or C) and the exhaust which direction for one tooth and then (5 or D)
Tks
figures in brackets are what the cam card says should be set up as
Intake opens 3.8 ATDC (12 ATDC)
Closes 38 ABDC (50 ABDC)
Exhaust opens 16.7 BBDC (47 BBDC)
Exhaust closes 12.5 ATDC (9 BTDC)
Here is the cam card
http://www.briancrower.com/makes/nissan/cam_card/b...
Just cannot get it straight in my head which direction ie for intake am I to go for (4 or C) and the exhaust which direction for one tooth and then (5 or D)
Tks
You've said what the cam spec is not what your target is. Since the cam spec would require you to adjust the opening and closing by different amounts, obviously it's not possible to achieve that.
I'll assume you want to split the difference and retard the inlet by 10 degrees. To do that you would turn the cam gear clockwise by four bolt positions and eight teeth on the sprocket, while keeping the cam and chain in approximately the same position. That should retard the cam by 10 degrees.
The exhaust is a million miles out. Assuming your numbers are correct you want to advance it by about 31 degrees. To do that I'd move the chain one whole tooth on the sprocket to give to 19 deg ish advance and then rotate the cam gear anticlockwise by five bolt positions and ten teeth on the sprocket, while keeping the cam and chain in approximately the same position. That should advance the cam by 31.45 degrees.
Mark everything up before you start because it would be incredibly easy to get confused or lose track of how far you have changed it. And measure the current timing another couple of times to make sure you are not starting from duff measurements, because that timing is crazy. And measure what you end up with before you seal it up.
I'll assume you want to split the difference and retard the inlet by 10 degrees. To do that you would turn the cam gear clockwise by four bolt positions and eight teeth on the sprocket, while keeping the cam and chain in approximately the same position. That should retard the cam by 10 degrees.
The exhaust is a million miles out. Assuming your numbers are correct you want to advance it by about 31 degrees. To do that I'd move the chain one whole tooth on the sprocket to give to 19 deg ish advance and then rotate the cam gear anticlockwise by five bolt positions and ten teeth on the sprocket, while keeping the cam and chain in approximately the same position. That should advance the cam by 31.45 degrees.
Mark everything up before you start because it would be incredibly easy to get confused or lose track of how far you have changed it. And measure the current timing another couple of times to make sure you are not starting from duff measurements, because that timing is crazy. And measure what you end up with before you seal it up.
DVandrews said:
Am I missing something here, according to the figures, there is *no* overlap? Or are the figures with a nominal lift value?
normally I would expect to see the inlet cam open prior to TDC and the exhaust close after TDC..
Dave
A lot of cams will quote the figures he seems to be using at 1mm or 50thou lift. 50thou more typical for US engines, 1mm more common for JDM etc.normally I would expect to see the inlet cam open prior to TDC and the exhaust close after TDC..
Dave
They would also quote centrelines for both intake and exhaust. Depends which method the user deems they are less likely to screw up I guess.
At 30 deg difference...something isnt just screwed up, it's f
ked up.scoobydo123 said:
Yes I have done that
figures in brackets are what the cam card says should be set up as
Intake opens 3.8 ATDC (12 ATDC)
Closes 38 ABDC (50 ABDC)
Exhaust opens 16.7 BBDC (47 BBDC)
Exhaust closes 12.5 ATDC (9 BTDC)
Here is the cam card
http://www.briancrower.com/makes/nissan/cam_card/b...
Just cannot get it straight in my head which direction ie for intake am I to go for (4 or C) and the exhaust which direction for one tooth and then (5 or D)
Tks
If I am correct, you are missing something here.figures in brackets are what the cam card says should be set up as
Intake opens 3.8 ATDC (12 ATDC)
Closes 38 ABDC (50 ABDC)
Exhaust opens 16.7 BBDC (47 BBDC)
Exhaust closes 12.5 ATDC (9 BTDC)
Here is the cam card
http://www.briancrower.com/makes/nissan/cam_card/b...
Just cannot get it straight in my head which direction ie for intake am I to go for (4 or C) and the exhaust which direction for one tooth and then (5 or D)
Tks
The measurement on the card is the cam position at 0.050" of valve lift. You are measuring the cam position as the valve is opening (i.e. 0.000" of valve lift)
That aside, the important measurement for timing the inlet cam is 121°.
Only rotate the crank forward - you do this to make sure that all the slack is taken out of the chains/belts.
Securely attach a protractor to the crank.
Zero the protractor to TDC on #1 cylinder.
The max lift of #1 inlet valve should occur at 121° on the crank protractor.
If you think everything is OK and just want to check, rotate the crank until the inlet valve has been opened by 0.050" and measure the crank angle. It should be 12° ATDC.
This is why I always set to xx valve lift at TDC, as long as you know whether it's with or without clearance you can't go wrong.
Advancing the inlet cam means the valve opens earlier, retarding it the opposite, you tend to find the more performance orientated engines have both valves open at TDC and lesser ones or street and emission friendly have both just closed at TDC.
The pulleys sound a bit w@nky if they only have 2.5 degree increments....
Advancing the inlet cam means the valve opens earlier, retarding it the opposite, you tend to find the more performance orientated engines have both valves open at TDC and lesser ones or street and emission friendly have both just closed at TDC.
The pulleys sound a bit w@nky if they only have 2.5 degree increments....
pingu393 said:
If I am correct, you are missing something here.
The measurement on the card is the cam position at 0.050" of valve lift. You are measuring the cam position as the valve is opening (i.e. 0.000" of valve lift)
That aside, the important measurement for timing the inlet cam is 121°.
Only rotate the crank forward - you do this to make sure that all the slack is taken out of the chains/belts.
Securely attach a protractor to the crank.
Zero the protractor to TDC on #1 cylinder.
The max lift of #1 inlet valve should occur at 121° on the crank protractor.
If you think everything is OK and just want to check, rotate the crank until the inlet valve has been opened by 0.050" and measure the crank angle. It should be 12° ATDC.
he did state 50thou in the first post.The measurement on the card is the cam position at 0.050" of valve lift. You are measuring the cam position as the valve is opening (i.e. 0.000" of valve lift)
That aside, the important measurement for timing the inlet cam is 121°.
Only rotate the crank forward - you do this to make sure that all the slack is taken out of the chains/belts.
Securely attach a protractor to the crank.
Zero the protractor to TDC on #1 cylinder.
The max lift of #1 inlet valve should occur at 121° on the crank protractor.
If you think everything is OK and just want to check, rotate the crank until the inlet valve has been opened by 0.050" and measure the crank angle. It should be 12° ATDC.
Either way, all numbers need checked and verified. That way it would.....should be impossible to get it wrong.
And I still want to know how TF it's 30deg out with any dots or markings lining up correctly....I would see that as impossible.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff