Tim R
Silver Level Sponsor
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1725 Camshaft Question
- Thread starter Tim R
- Start date
husky drvr
Platinum Level Sponsor
Tim,
This information is on page 16 of the general data section of WSM 145.
This partial chart is from the "Alpine Marque," issue #7, page 30, which can be found at a link on this site's "Home" page.
Hope this helps,
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Tim R
Silver Level Sponsor
Don,
That is great. Thank you. I have been having problems with low compression (100-120 across all four cylinders) of the 1592cc engine in our Series IV. The car starts and drives but has little power and limited top speed.
The valves have been professionally pressure tested when the cylinder head was on the bench and all seal perfectly. After re-fitting the cylinder head with a new copper gasket I then did a leak down test and all four cylinders scored top marks. The only leak with 100psi pumped into each cylinder when set to TDC was the expected hiss through the ring gaps audible from the top of the engine.
This has made me suspect that the camshaft which I know has been re-ground in the past to be wrong. It is in a 1592 engine but I was told that the cam had been ground to "1725 spec"as this was 'sportier'.
I have measured it with a DTI set up on the valve cap with the tappet gap set to 20 thou exactly as shown in the WSM. and it appears to have the following readings:
Inlet opens 25* (BTDC) should be 29* BTDC
Inlet vale closes 65* (ABDC) should be 63* ABDC
Neither of those readings appear to be that far out and I doubt that this is causing the problem, however......
Exhaust valve opens at 40* (BBDC) should be 69* BBDC
Exhaust valves closes at 50* (ATDC) should be 23* ATDC
These readings appear to be way out and I am assuming that it is starting to exhaust before it has built full compression?
Is there anyone here who has expertise on camshafts and can interpret these figures and tell me if this is what is causing the problem.
Tim R
That is great. Thank you. I have been having problems with low compression (100-120 across all four cylinders) of the 1592cc engine in our Series IV. The car starts and drives but has little power and limited top speed.
The valves have been professionally pressure tested when the cylinder head was on the bench and all seal perfectly. After re-fitting the cylinder head with a new copper gasket I then did a leak down test and all four cylinders scored top marks. The only leak with 100psi pumped into each cylinder when set to TDC was the expected hiss through the ring gaps audible from the top of the engine.
This has made me suspect that the camshaft which I know has been re-ground in the past to be wrong. It is in a 1592 engine but I was told that the cam had been ground to "1725 spec"as this was 'sportier'.
I have measured it with a DTI set up on the valve cap with the tappet gap set to 20 thou exactly as shown in the WSM. and it appears to have the following readings:
Inlet opens 25* (BTDC) should be 29* BTDC
Inlet vale closes 65* (ABDC) should be 63* ABDC
Neither of those readings appear to be that far out and I doubt that this is causing the problem, however......
Exhaust valve opens at 40* (BBDC) should be 69* BBDC
Exhaust valves closes at 50* (ATDC) should be 23* ATDC
These readings appear to be way out and I am assuming that it is starting to exhaust before it has built full compression?
Is there anyone here who has expertise on camshafts and can interpret these figures and tell me if this is what is causing the problem.
Tim R
Barry
Diamond Level Sponsor
A "standard" S-V camshaft with 29/63 intake timing and 63/29 exhaust timing CALCULATES to be installed "straight up" (aka, no advance or retard), to have equal intake and exhaust duration of 272 degrees at tappet lift or about 222 degrees at 0.050" valve lift, to have a lobe separation angle of 107 degrees and to have 58 degrees of overlap. In other words, a fairly typical "sporty", but certainly not "hot" camshaft.
Your camshaft as installed with 25/65 intake timing and 40/50 exhaust timing CALCULATES to be installed 11 degrees retarded, to have almost equal duration of 272 degrees intake and 270 degrees exhaust, to have a lobe separation angle of 96 degrees and to have overlap of 79 degrees. In summary, a camshaft with normal S-V lobe profiles, but with the exhaust lobes retarded by almost 30 degrees.
The extremely small lobe separation angle and extremely large overlap suggest to me that someone either had a completely different idea about camshaft design than the rest of the world or (more likely) simply made a mistake when setting up the camshaft grinding equipment.
Your camshaft as installed with 25/65 intake timing and 40/50 exhaust timing CALCULATES to be installed 11 degrees retarded, to have almost equal duration of 272 degrees intake and 270 degrees exhaust, to have a lobe separation angle of 96 degrees and to have overlap of 79 degrees. In summary, a camshaft with normal S-V lobe profiles, but with the exhaust lobes retarded by almost 30 degrees.
The extremely small lobe separation angle and extremely large overlap suggest to me that someone either had a completely different idea about camshaft design than the rest of the world or (more likely) simply made a mistake when setting up the camshaft grinding equipment.
spmdr
Diamond Level Sponsor
Tim, WOW that cam is OUT there!
Just for reference, a link to more cam info:
forum.sunbeamalpine.org
I can't wait to see what that cam casting number is. My guess is some version of a Holbay cam.
A 1592 version of a H120 cam??? Hmmmm
DW
Just for reference, a link to more cam info:
Camshaft identification
This is supposed to be a Holbay camshaft. Any opinion? Lift:7,9 mm. 981186 C MC24794
I can't wait to see what that cam casting number is. My guess is some version of a Holbay cam.
A 1592 version of a H120 cam??? Hmmmm
DW
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Jay Laifman
Donation Time
Here is a thread where we talked a bunch about cam options: https://forum.sunbeamalpine.org/index.php?threads/holbay-camshaft.19609/page-2
spmdr
Diamond Level Sponsor
Tim, I confess to NOT being up on the early Alpine cams.
But if I were a gambling guy, I'd bet it's not a
common stock 1592 cam that was just ground incorrectly,
And "incorrect" is a matter of opinion.
The bad news is there is a very good chance all the factory
ID may well be ground off your cam.
So I'm not holding my breath.
What do you know about the history of that cam?
DW
But if I were a gambling guy, I'd bet it's not a
common stock 1592 cam that was just ground incorrectly,
And "incorrect" is a matter of opinion.
The bad news is there is a very good chance all the factory
ID may well be ground off your cam.
So I'm not holding my breath.
What do you know about the history of that cam?
DW
Tim R
Silver Level Sponsor
spmdr
We've had the car 20+ years. It was surprisingly fast for an Automatic and we were often asked what engine we had in it to make it go like it did.
In 2015 the bottom end was rumbling so we pulled the engine to fit new mains etc. While we were at it we treated the car to a rebore, new pistons etc. The guy that supplied the engine parts told us that the camshaft was now 1725 spec as this was 'sportier'.
When we rebuilt the engine it started and ran fine at low speeds while we ran it in. The car was used most days but was based in London so was always at 30 or 40mph. On the odd time it went on faster roads we found that it was gutless and ran out of power at 60mph.
We lived with it like this but when my son moved out of London and needed the car to drive normally we decided to find out what was wrong and do something about it. The compression was low on all four cylinders (100-120). We suspected a valve or ring problem. We replaced the rings and ran the car in again and checked the head and it held pressure with no problem. When the engine was rebuilt was did a 'leak down test' and all four cylinders scored top marks when filled to 100psi. Compression however was still 100-120 across all cylinders.
This only left either the camshaft or the timing wheels as possible culprits. I contacted the supplier and asked if he had supplied a 1725 cam and oil pump or if he had re-ground the original 1592 cam to a 1725 profile but it was over 8 years ago and he couldn't remember.
I measured the cam lift with a DTI and they were all close to what you would expect. When I used a DTI to measure when the valves were opening I got the results shown above which was quite a surprise for me.
When I get a chance to get it out I will know more. I have a nearly new 1725 cam and followers to replace it with.
Tim R
We've had the car 20+ years. It was surprisingly fast for an Automatic and we were often asked what engine we had in it to make it go like it did.
In 2015 the bottom end was rumbling so we pulled the engine to fit new mains etc. While we were at it we treated the car to a rebore, new pistons etc. The guy that supplied the engine parts told us that the camshaft was now 1725 spec as this was 'sportier'.
When we rebuilt the engine it started and ran fine at low speeds while we ran it in. The car was used most days but was based in London so was always at 30 or 40mph. On the odd time it went on faster roads we found that it was gutless and ran out of power at 60mph.
We lived with it like this but when my son moved out of London and needed the car to drive normally we decided to find out what was wrong and do something about it. The compression was low on all four cylinders (100-120). We suspected a valve or ring problem. We replaced the rings and ran the car in again and checked the head and it held pressure with no problem. When the engine was rebuilt was did a 'leak down test' and all four cylinders scored top marks when filled to 100psi. Compression however was still 100-120 across all cylinders.
This only left either the camshaft or the timing wheels as possible culprits. I contacted the supplier and asked if he had supplied a 1725 cam and oil pump or if he had re-ground the original 1592 cam to a 1725 profile but it was over 8 years ago and he couldn't remember.
I measured the cam lift with a DTI and they were all close to what you would expect. When I used a DTI to measure when the valves were opening I got the results shown above which was quite a surprise for me.
When I get a chance to get it out I will know more. I have a nearly new 1725 cam and followers to replace it with.
Tim R
husky drvr
Platinum Level Sponsor
Tim,
This is copied and pasted from an earlier discussion.
1725 uses 11 teeth and three main engines use 12.
Swapping the oil pump drive gears is relatively simple. Installing a 1725 pump in a three main block - not so much.
The first challenge is the 1725 pump's oil delivery line is a size larger than the hole into the three main block's oil gallery to the oil filter. It gets worse from there.
Thought this might help with your planning,
Tim R
Silver Level Sponsor
Today I started to strip the engine down. I haven't got the camshaft out yet but I can see that the oil pump drive wheel has 12 teeth. Therefore it is a 1592 pump. I have a nearly new 1725 camshaft and followers that I want to fit and that will require an 11 tooth drive wheel so it will be a bit more difficult than I hoped. I also measured the pushrods. The ones on this engine are the later solid type, not the earlier hollow ones. These later ones are 3mm shorter. I am assuming that this is not an issue as the tappet adjusters will take up and length difference, am I correct or is there something I am missing?
Tim R
Tim R
Barry
Diamond Level Sponsor
The factory tappets in Series Alpine engines are not adjustable. Valve clearance (measured between the rocker arm "foot" (rocker arm "tip" on this side of the pond) and the end of the valve stem) is adjusted on the pushrod side of the rocker arm.
I have no idea if the available adjustment can compensate for a 3 mm difference in pushrod length, reduced cam lobe base circle diameters with reground camshafts or rocker arm tips that have been reground / refaced.
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Tim R
Silver Level Sponsor
I have been working on the car today. I dropped the bottom of the engine and removed the oil pump and can confirm it has a 12 tooth (1592cc) drive wheel.
I am amazed to find that I can't get the camshaft out of the engine with it in-situ. Obviously the camshaft has to be pulled out straight to pass through the bearings in the block and it then hits dead centre of the valance lip. I am going to have to lift the engine up (possibly take it out completely, just to get the cam out! Being an automatic with a gearbox oil cooler fitted it is even more complicated because the cooler sits behind the grill, totally in the way.
There is one number stamped into the cam in the engine and no number 'cast' into it. It is stamped MC22539 N.
The 1725 camshaft that I have has two number stamped into it 1989094 and MG24424, neither of which match the part number shown in the parts book and no number 'cast' into it.
Tim R
I am amazed to find that I can't get the camshaft out of the engine with it in-situ. Obviously the camshaft has to be pulled out straight to pass through the bearings in the block and it then hits dead centre of the valance lip. I am going to have to lift the engine up (possibly take it out completely, just to get the cam out! Being an automatic with a gearbox oil cooler fitted it is even more complicated because the cooler sits behind the grill, totally in the way.
There is one number stamped into the cam in the engine and no number 'cast' into it. It is stamped MC22539 N.
The 1725 camshaft that I have has two number stamped into it 1989094 and MG24424, neither of which match the part number shown in the parts book and no number 'cast' into it.
Tim R
Tim R
Silver Level Sponsor
Update:
By removing the gearbox oil cooler, undoing the engine mounts and jacking from underneath I was able to get the camshaft out. Hurrah.
To an untrained eye like mine when you look at the two camshafts both appear the same, there is nothing to show that the camshaft timing is significantly out.
I then set about measuring the cam lobes with a vernier gauge.
On the standard 1725 cam the lobes all measures 29mm across and 36.2mm high.
On the one that has been causing me trouble the lobes measure 26.8mm across and 34mm high.
Tim R
By removing the gearbox oil cooler, undoing the engine mounts and jacking from underneath I was able to get the camshaft out. Hurrah.
To an untrained eye like mine when you look at the two camshafts both appear the same, there is nothing to show that the camshaft timing is significantly out.
I then set about measuring the cam lobes with a vernier gauge.
On the standard 1725 cam the lobes all measures 29mm across and 36.2mm high.
On the one that has been causing me trouble the lobes measure 26.8mm across and 34mm high.
Tim R
Tim R
Silver Level Sponsor
Update:
I took the cam to a local specialist. He said that it looked much more rounded at the peaks than he would expect. The nearly new 1725 cam had more wear on the lobes that I thought so I have ordered a new 1592cc camshaft and followers and it will (hopefully) be as standard once I fit the parts.
Tim R
I took the cam to a local specialist. He said that it looked much more rounded at the peaks than he would expect. The nearly new 1725 cam had more wear on the lobes that I thought so I have ordered a new 1592cc camshaft and followers and it will (hopefully) be as standard once I fit the parts.
Tim R
spmdr
Diamond Level Sponsor
Tim, around here, NEW = never used.
Do you have a source for never used 1592 cams?
...Or would it be Renewed aka reground?
...Just wondering what cam timing you will end up with...
AND, those 1725 cam numbers stamped or what ever, are new to me. Hmmmmm....
Any chance you could snap a picture(s) of that removed cam?
DW
Do you have a source for never used 1592 cams?
...Or would it be Renewed aka reground?
...Just wondering what cam timing you will end up with...
AND, those 1725 cam numbers stamped or what ever, are new to me. Hmmmmm....
Any chance you could snap a picture(s) of that removed cam?
DW
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