Dr.Jeff
True Classic
Cliff, it would depend on how much material is taken off the head, cam box, block, and possibly what cam is installed, so sort of hard to tell if you might need one or not.
Camshaft timing
- Thread starter B0b
- Start date
CnC79X19
True Classic
Thanks Doc
TonyK
True Classic
Bob Martin's Black Dallara had a Midwest Bayless ported head and camshaft. Bob purchased a variable timing pulley from another vendor for the camshaft and had his son put it together on his car. The car never really ran right and was difficult to start hot or cold. He had the car up here at my place and we took a look at it. The timing marks were off on the camshaft pulley as it was timed to #1 cylinder but also it was off about 2 teeth as well. I put the pistons at 90 degrees and we released the timing belt and rotated the camshaft to #4 and then did our best guess at #4 lobes pointing straight up. I put a paint marker on the camshaft pulley for reference and we cranked the engine, it started right up without issue. We then ran the car up and down the road and each run adjusted the camshaft pulley a little bit. Two runs we were gaining on how the engine ran, 3rd run it was dropping off, so we adjusted back a bit and I took a file and marked the camshaft pully to the pointer. He ran that way a couple of years until we did the Abarth engine swap.
TonyK.
Grimsby Ontario Canada.
Last edited:
B0b
Daily Driver
. The timing marks were off on the camshaft pulley as it was timed to #1 cylinder but also it was off about 2 teeth as well
In my case, the crank and cam sprocket marks line up with #1 cylinder ready to fire, not #4. Not sure why, but also not sure that it matters - I'll just set the ignition timing to #1,
Make sense?
In my case, the crank and cam sprocket marks line up with #1 cylinder ready to fire, not #4. Not sure why, but also not sure that it matters - I'll just set the ignition timing to #1,
Make sense?
B0b
Daily Driver
I have a euro (4331512) cam and an aluminum cam sprocket (aftermarket) .
I ignored all the marks, and established crank TDC. Then I set the cam exhaust lobe center position. Used dial indicator for both the crank TDC and the cam lobe, plus checked the crank with a dead stop. Installed and tensioned the belt, and rechecked both the exhaust and intake lobe centers, using #1 cylinder.
Then noticed that with the crank at TDC between the compression and power strokes (both valves closed) that the mark on the cam sprocket was at or near the pointer on the cover bracket.
According to what I read, the valves should have been open ( at TDC between exhaust and intake strokes) when the cam sprocket mark is aligned.
I ignored all the marks, and established crank TDC. Then I set the cam exhaust lobe center position. Used dial indicator for both the crank TDC and the cam lobe, plus checked the crank with a dead stop. Installed and tensioned the belt, and rechecked both the exhaust and intake lobe centers, using #1 cylinder.
Then noticed that with the crank at TDC between the compression and power strokes (both valves closed) that the mark on the cam sprocket was at or near the pointer on the cover bracket.
According to what I read, the valves should have been open ( at TDC between exhaust and intake strokes) when the cam sprocket mark is aligned.
MikeHynes
True Classic
For a cam with symmetrical lobes - You can set the valve lift of both of the valves, on the #1 cylinder, to equal amounts when #1 piston is at TDC. That's split overlap, no advance or retard. That's how the stock timing marks are set - split overlap on the #1 cylinder.
At #1 TDC - More lift on the intake valve = advanced cam timing, more lift on the exhaust valve = retarded cam timing. A degree wheel will tell you just how many degrees advanced or retarded the cam timing is.
The engine will run when the cam timing advanced, or retarded, way too much. You have to have it pretty far off to prevent the engine from running. It will run A LOT better when the cam timing is set "right". (What's "right" is a topic for a more detailed thread, but split overlap is a very good place to start.)
At #1 TDC - More lift on the intake valve = advanced cam timing, more lift on the exhaust valve = retarded cam timing. A degree wheel will tell you just how many degrees advanced or retarded the cam timing is.
The engine will run when the cam timing advanced, or retarded, way too much. You have to have it pretty far off to prevent the engine from running. It will run A LOT better when the cam timing is set "right". (What's "right" is a topic for a more detailed thread, but split overlap is a very good place to start.)
B0b
Daily Driver
I didn't use a split overlap - the cam isn't symmetrical. I set it to intake at 112 ATDC and exhaust 108 BTDC, reflecting the 24/68 64/28 timing of the cam. A diagram was thoughtfullly provided earlier in this thread, which my measurements of the cam confirmed.
Who knows whether the aftermarket sprocket has marks for a stock NA cam, a stock euro cam or ??
My post yesterday was just to mention that for some reason I got the timing without an adjustable pulley.
And to ask about the #4 vs #1 ignition timing
Who knows whether the aftermarket sprocket has marks for a stock NA cam, a stock euro cam or ??
My post yesterday was just to mention that for some reason I got the timing without an adjustable pulley.
And to ask about the #4 vs #1 ignition timing
TonyK
True Classic
Well that is the issue. ( 2 belt teeth) Plus Bob's son a mechanic at the time for Lexus thought all engines time to #1 cylinder and the rest goes south from there. I have a 1979 X purchased new in 1979 with original paint. I shaved the head a lot which now changes the timing of the cam shaft timing and I played with the 40-80 camshaft by moving it a tooth advanced and retarded. Advanced I had a poor idle with no real bottom end retarded a tooth and the bottom end and idle were a lot better. With that amount of overlap on the camshaft it is possible to play the camshaft timing a tooth one way or the other and still get what you want for driveability and performance. One tooth retarded worked better for me than advanced. Now remember I took .160" off of the head, so the timing shifts quite a bit as well due to that modification.
TonyK.
Grimsby Ontario Canada.
Dr.Jeff
True Classic
This issue with aftermarket cam gears having incorrect timing marks is interesting. I realize the 1300 and 1500 have different cam timing marks and some aftermarket gears may be made for one or the other, or even have both marks. But those two marks are almost 180 degrees off one another, so no way that is the reason.
As for the possibility of the gear being made for a different cam profile. For the moment let's assume a setup with a stock cam gear (i.e. correct timing mark), and various cams - stock US, stock Euro, and all manor of aftermarket. Wouldn't the stock timing mark still be correct for all of those cams? Because the cam and cam gear are indexed by a dowel pin, so all of the cams are made to be fitted at that position relative to the cam gear. If a aftermarket cam maker wants to incorporate some extra advance into the design of a particular cam profile, then it would be done relative to the dowel pin, and the timing mark on the cam gear is still "correct". Therefore I don't think the cam matters, and if the timing mark is incorrect on the cam gear then it is a faulty cam gear....not one designed for some other cam.
However another question might be if all stock Fiat cam gears have the same timing mark? For example what if the Euro market got cam gears with a little more advance built into them (i.e. altered timing mark) for better performance on the Autobahn. Then I suppose the aftermarket cam gear could have been patterned after one of those 'alternative' factory gears' specs. But I seriously doubt there are any factory cam gears that are as far off (different) as reported earlier. So it would seem to go back to being a faulty gear design.
Can anyone think of any other reasons for the mark to be so far off on a aftermarket gear?
As for the possibility of the gear being made for a different cam profile. For the moment let's assume a setup with a stock cam gear (i.e. correct timing mark), and various cams - stock US, stock Euro, and all manor of aftermarket. Wouldn't the stock timing mark still be correct for all of those cams? Because the cam and cam gear are indexed by a dowel pin, so all of the cams are made to be fitted at that position relative to the cam gear. If a aftermarket cam maker wants to incorporate some extra advance into the design of a particular cam profile, then it would be done relative to the dowel pin, and the timing mark on the cam gear is still "correct". Therefore I don't think the cam matters, and if the timing mark is incorrect on the cam gear then it is a faulty cam gear....not one designed for some other cam.
However another question might be if all stock Fiat cam gears have the same timing mark? For example what if the Euro market got cam gears with a little more advance built into them (i.e. altered timing mark) for better performance on the Autobahn. Then I suppose the aftermarket cam gear could have been patterned after one of those 'alternative' factory gears' specs. But I seriously doubt there are any factory cam gears that are as far off (different) as reported earlier. So it would seem to go back to being a faulty gear design.
Can anyone think of any other reasons for the mark to be so far off on a aftermarket gear?
carl
True Classic
There was chat in ancient times on MIRA about cam wheels for Euro twin cam motors having different locating dowel holes and giving different cam timing over the US spider motors. I don't think it was ever resolved that that was the case. As was the X, the Euro spiders had different cams than US cams. Why would a manufacturer make different cam wheels when the cams themselves were different and you could accommodate any difference in timing by having the cam itself have a different dowel locating hole?
Dr.Jeff
True Classic
Exactly. I have no idea if Fiat made different cam gears for any of the X's, but that was my point - it would not be necessary when the cam could incorporate the intended timing difference (if there was any) directly in it. So to me it seems any aftermarket cam gear with incorrect timing marks is a fault in the design/quality and not an intended change. If I understood the earlier description of the item in question, it sounded like the same one as others found fitment issues on. If that is so, then I suppose it would not be impossible for it to have multiple problems.
B0b
Daily Driver
I think I figured it out, at least for my situation.
The cam timing is set with the #1 intake lobe at 112 BTDC. The timing belt fit the sprockets well, and after adjusting the tension I confirmed the 112 degrees held.
In this picture, the crankshaft is at TDC between the compression and power strokes ( both valves closed).
There are two marks on the sprocket - 1.3 and 1.5. The 1.3 mark is about 1 1/2 teeth beyond the pointer.
But note that the 1.5 mark is exactly 180 degrees from the pointer.
So if I had set the cam timing to #4 cylinder, the 1.5 mark would have lined up with the pointer, and all would look great.
Didn't occur to me to do that because
Now I have to decide whether to take it apart and reset it to cylinder 4, At the moment, the distributor rotor is pointing at #1 on the cap, so it will work fine.
The cam timing is set with the #1 intake lobe at 112 BTDC. The timing belt fit the sprockets well, and after adjusting the tension I confirmed the 112 degrees held.
In this picture, the crankshaft is at TDC between the compression and power strokes ( both valves closed).
There are two marks on the sprocket - 1.3 and 1.5. The 1.3 mark is about 1 1/2 teeth beyond the pointer.
But note that the 1.5 mark is exactly 180 degrees from the pointer.
So if I had set the cam timing to #4 cylinder, the 1.5 mark would have lined up with the pointer, and all would look great.
Didn't occur to me to do that because
- it is a 1.3 engine
- I didn't see anything in the factory manual about using #4 instead of #1
- the 4331512 cam was, I thought, from a 1300.
Now I have to decide whether to take it apart and reset it to cylinder 4, At the moment, the distributor rotor is pointing at #1 on the cap, so it will work fine.
Dr.Jeff
True Classic
I'm with this comment:
So not sure what you (Bob) are saying is quite right. #4 won't be 180 degrees out from #1. Unless I'm misunderstanding what was said.
B0b
Daily Driver
at the cam, it will be 180 degrees. In other words, in the photo, if the cam sprocket was turned 180 degrees, the #4 valves would be open, rather than #1.
Then the 1.5 marks would line up.
The #1/#4 timing comment you refer to is OK as far as adjusting the ignition timing, but doesn't apply to where the rotor is positioned to start with.
The rotor needs to point at whichever cylinder is used for the cam timing.
Then the 1.5 marks would line up.
The #1/#4 timing comment you refer to is OK as far as adjusting the ignition timing, but doesn't apply to where the rotor is positioned to start with.
The rotor needs to point at whichever cylinder is used for the cam timing.
Actually they won't quite line up - put the 1.3 cam marks on the 1.5 pointer (or vice versa) and the cam won't be exactly one-half turn off. It will be close enough that the motor will run if you set the distributor to fire #1 instead of #4, but still far enough off that it won't run well.
(Ask me how I know)