hello,
We have problem with our engine, we thought it was small heads, stuffed carby, we were wrong
we are now leaning to believing the camshaft timing is wrong.
the engine has good torque outside of its supposed cam range, inside its cam range there's no powerband, just revs out, it revs to 7000 easily just no powerband, its almost as if the secondaries not working(they are).
shitty little 6 cylinders stay with us and its fraken annoying
the cam is a federal mogel copy of the 286 crane, we are tending to believe its camshaft timing because when you line up the dizzy after working on her she wont start, takes moving the dizzy about a quarter of a turn advanced to get her to run,
this happened on points dizzy when motor was first put together, we changed to electronic and same thing.
at the moment its a process of elimination, but is there anyway we can confirm camshaft timing without pulling the camshaft out?
Getting camshaft timing wrong?
Started by
_waratah_
, Jul 08 2008 08:20 AM
23 replies to this topic
#2
_ChevLX_77_
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Posted 08 July 2008 - 11:34 AM
Its a very high possibility that its your problem. a 1/4 just to start it is a lot
#3
TerrA LX
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Posted 08 July 2008 - 10:14 PM
What sort of vacuum reading are you getting??
#4
_waratah_
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Posted 09 July 2008 - 06:27 AM
we havnt got that far into investigating yetWhat sort of vacuum reading are you getting??
what would be a sign being a tooth or two out?
#5
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Posted 09 July 2008 - 05:12 PM
#6
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Posted 09 July 2008 - 07:12 PM
A quick and easy way to check valve/cam timing on 308's with a single pattern cam is to get the engine to TDC on the overlap of No. 1 (or if you prefer TDC when the rotor points to No. 4). Rip off the drivers side valve cover and check the lift on the intake and exhaust valves on No. 1. The intake will be just starting to open, the exhaust will be just about closed but they both should have the same lift (between 0.050" and 0.150" depending on cam size). The quickest way to check is to put a straight edge across the two valves, if the cam timing is wrong the straight edge will be on an angle. If your careful you can also measure how far advanced or retarded the cam is by reading off the degrees before or after TDC on the balancer when the lift is equal.
This is not so accurate on dual pattern cams or those with wildly unsymmetrical lobes. It will tell you though if the timing is within a few degrees of correct or not.
Good luck
This is not so accurate on dual pattern cams or those with wildly unsymmetrical lobes. It will tell you though if the timing is within a few degrees of correct or not.
Good luck
#7
_Yella SLuR_
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Posted 09 July 2008 - 07:35 PM
^ agree, take it back to basics. Check mechanical relationships first, do dizzy timing last.
#9
rodomo
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Posted 09 July 2008 - 08:10 PM
I had a mechanical relationship once, her name was RobotaCheck mechanical relationships first,
#10
_Yella SLuR_
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Posted 09 July 2008 - 08:18 PM
Too much information. Some people I know have only had mechanical relationships, think they are called wankers.
^ quick fix. Present company excluded of course!!!!
^ quick fix. Present company excluded of course!!!!
Edited by Yella SLuR, 09 July 2008 - 08:19 PM.
#11
_The Stig_
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Posted 11 July 2008 - 08:59 PM
I'd be interested to hear the end result of this thread. I built a 253 once, with a stage 3 heatseeker cam (Can't remember specific grind and don't know what it would equate to nowadays), couldn't get it to run at anything under about 25 degrees ignition timing. Cam was dialled in properly with degree wheel, dial gauge, etc. (And yes, I have done plenty of them and know how to do it), dizzy was fully rebuilt and balancer was new and showed accurate timing settings. Engine screamed, didn't detonate, owner was happy with it, so I just left it as it was. I still quite often wonder what the story was....20 odd years later!
How did you line up the timing marks? 9 links?
How did you line up the timing marks? 9 links?
#12
_waratah_
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Posted 13 July 2008 - 10:53 PM
ours doesn't scream hey, it revs high but no power.
probably wont be to next meeting before we find out .
was talking to a well noted drag racer around my parts, he agrees everything points to being 1 tooth out, however he threw in a scenario that i have stuff all knowledge about.
we run a crank out of a hz all the rest of the timing gear/cam is out of a hj pre pollution engine, is this likely to impact on getting cam timing right?
probably wont be to next meeting before we find out .
was talking to a well noted drag racer around my parts, he agrees everything points to being 1 tooth out, however he threw in a scenario that i have stuff all knowledge about.
we run a crank out of a hz all the rest of the timing gear/cam is out of a hj pre pollution engine, is this likely to impact on getting cam timing right?
#13
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Posted 13 July 2008 - 11:13 PM
Cranks are the same, cam gear has the hole retarded a bit on HZ for pollution reasons so theoretically, (if you could notice the 2 or so degrees it is), if you had a cam ground spot on to run in a HQ and stuck a HZ gear on the cam then yes it would be slightly retarded, but not by a tooth, which would be very noticeable.
#14
_Yella SLuR_
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Posted 13 July 2008 - 11:31 PM
I did calculate it once, one tooth is something like 12 degrees advance/retardation, hence why you use variable timing gear sets and not teeth (too coarse).
I set up an engine one tooth out by using that damn Max Ellery Book (V8 pics show timing chain one tooth out). It didn't run right so we took the cam back out and set it right. I never heard it run, so can't tell you what it did/didn't do.
I set up an engine one tooth out by using that damn Max Ellery Book (V8 pics show timing chain one tooth out). It didn't run right so we took the cam back out and set it right. I never heard it run, so can't tell you what it did/didn't do.
#15
_The Stig_
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Posted 14 July 2008 - 08:26 AM
I've dialled in quite a few cams over the years, nearly all of them Holden V8's. Quite often I've found that if you put in an aftermarket cam and just line the dots (Or count off the 9 links with the Holden V8's), then check against the cam card you will find the timing won't be exactly where it's meant to be. I used to use the rollmaster sets with a whole heap of keyways cut into them, with "+" and "-" and the number of degrees stamped into them. I spoke about it one day to my local machine shop owner, he told me if I ever needed to change the timing on one, without having to buy the rollmaster sets, bring in the std cam gear and let him know how far I wanted to move the timing, and in what direction, and he could redrill the camshaft dowell in another spot and put a new timing mark in. I did a couple that way too, and it worked well.
I'd definately recommend buying a degree wheel, a dial gauge and an old solid lifter, and checking the timing that way. I found the easiest way was to check off the degrees at 0.050" lift (From memory). Also, don't rely on the timing marks on the harmonic balancer. Work off TRUE TDC (Use a positive stop. An old spark plug with a length of nylon screwed up the end is a good way). That way you don't have to worry about what engine the crank or cam is out of. You KNOW the cam timing is correct.
I'd definately recommend buying a degree wheel, a dial gauge and an old solid lifter, and checking the timing that way. I found the easiest way was to check off the degrees at 0.050" lift (From memory). Also, don't rely on the timing marks on the harmonic balancer. Work off TRUE TDC (Use a positive stop. An old spark plug with a length of nylon screwed up the end is a good way). That way you don't have to worry about what engine the crank or cam is out of. You KNOW the cam timing is correct.
#16
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Posted 14 July 2008 - 07:11 PM
^ just to add, if you want the timing spot on with this method then keep winding the motor in the correct direction of rotation. Do not wind it back onto the stop.
#17
_waratah_
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Posted 22 July 2008 - 11:36 PM
did this tonightA quick and easy way to check valve/cam timing on 308's with a single pattern cam is to get the engine to TDC on the overlap of No. 1 (or if you prefer TDC when the rotor points to No. 4). Rip off the drivers side valve cover and check the lift on the intake and exhaust valves on No. 1. The intake will be just starting to open, the exhaust will be just about closed but they both should have the same lift (between 0.050" and 0.150" depending on cam size). The quickest way to check is to put a straight edge across the two valves, if the cam timing is wrong the straight edge will be on an angle. If your careful you can also measure how far advanced or retarded the cam is by reading off the degrees before or after TDC on the balancer when the lift is equal.
This is not so accurate on dual pattern cams or those with wildly unsymmetrical lobes. It will tell you though if the timing is within a few degrees of correct or not.
Good luck
6 degrees advanced is the conclusion we came too.
#18
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Posted 23 July 2008 - 12:59 AM
Are we talking 253 or 308, Waratah?
Here is some more info to consider:
I have about 5 different stock holden cam gears here ranging from HJ HX HZ & Blue VC.
I lined them all up a long time ago to compare and I can tell you that they are all different with respect to mechanical timing. We all know why , compliance to pollution regulations. The biggest variation I saw was an whole tooth(which is about 7.5deg) with respect to the dowel pin so the fact you got 6deg doesnt really surprise me.
Here is some more info to consider:
I have about 5 different stock holden cam gears here ranging from HJ HX HZ & Blue VC.
I lined them all up a long time ago to compare and I can tell you that they are all different with respect to mechanical timing. We all know why , compliance to pollution regulations. The biggest variation I saw was an whole tooth(which is about 7.5deg) with respect to the dowel pin so the fact you got 6deg doesnt really surprise me.
#19
_waratah_
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Posted 23 July 2008 - 10:33 AM
its 308.
but everything but the crank was on the old motor.
however the book used as reference was vb/vc commodore book, where as when the the old motor was built the hq/hj book was used.
we have no idea if that would lead to a problem?
but everything but the crank was on the old motor.
however the book used as reference was vb/vc commodore book, where as when the the old motor was built the hq/hj book was used.
we have no idea if that would lead to a problem?
#20
fuzzypumper
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Posted 23 July 2008 - 08:40 PM
Well AFAIK the cranks are all the same, even the crank timing gears are all the same.
The only difference I know is the CAM gears are all very different.
Sure you dont have a compression ratio issue(too low)?
Its not too hard to loose at least 0.5 to 1 comp ratio or even 1.0 to 1 for 253's by a compatible
but incorrect head gasket. With a stock cam the effect isnt too noticeable but with a performance cam
the effect is more prodominant.
The only difference I know is the CAM gears are all very different.
Sure you dont have a compression ratio issue(too low)?
Its not too hard to loose at least 0.5 to 1 comp ratio or even 1.0 to 1 for 253's by a compatible
but incorrect head gasket. With a stock cam the effect isnt too noticeable but with a performance cam
the effect is more prodominant.
#21
_draglc_
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Posted 23 July 2008 - 09:05 PM
i did the same thing on a 6, cam was one tooth out on the gears.. started, but ran like a dog just like you described.
#22
_waratah_
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Posted 03 August 2008 - 08:35 PM
end result!!!!!!!!!!!!!!!I'd be interested to hear the end result of this thread. I built a 253 once, with a stage 3 heatseeker cam (Can't remember specific grind and don't know what it would equate to nowadays), couldn't get it to run at anything under about 25 degrees ignition timing. Cam was dialled in properly with degree wheel, dial gauge, etc. (And yes, I have done plenty of them and know how to do it), dizzy was fully rebuilt and balancer was new and showed accurate timing settings. Engine screamed, didn't detonate, owner was happy with it, so I just left it as it was. I still quite often wonder what the story was....20 odd years later!
?
dizzy still turned a quarter of a turn more than it should, cam timing is now confirmed to be correct.
the fraken thing screams now, revs effortlessly to 7500 and extremly quickly and with plenty of g forces.
around 3000rpm all hell breaks loose until way over 7000.
#23
_The Stig_
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Posted 04 August 2008 - 06:05 PM
So what was the problem? Just ignition timing?
#24
_waratah_
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Posted 05 August 2008 - 12:26 AM
just re did camshaft timing , we got our powerband back.
car wont run still with dizzy lined up, but around a quarter of a turn and she's fine, .
but its just thrown up more problems, with the amount of revs we are getting and how quickly we are going to break rockers and possibly lifters so ....................
roller rockers here we come.
car wont run still with dizzy lined up, but around a quarter of a turn and she's fine, .
but its just thrown up more problems, with the amount of revs we are getting and how quickly we are going to break rockers and possibly lifters so ....................
roller rockers here we come.
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