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Lifters [Tappets] and MSX Head
- Thread starter iceben
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Hap Waldrop
Yoda
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Same as would go with a normal MGB head, it depends on your engine, the early blocks had the long lifter and the shorter pushrod, the later engines all used the short lifter and long pushrod. If you are starting from scratch, I recommend a billet cam, APT would be a good choice and also thier lifter, which are 60 Rockwell C hardened short lifters which would use the later pushrods. When I build a early long lifter street motor I always use APT lifters, which are the short ones and convert if needed to the longer pushrod. I rencently build a customer motor using the Harland Sharp 1.5 roller rocker and this combination would not work with the MSX head, pushrod holes were too samll, I could have fixed the problem for extra labor by boring the pushrod bigger in the head, but the customer elected to go back with stock rockers and pushrod and save money. Hope this helps.
D
Deleted member 3577
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[ QUOTE ]
I recently build a customer motor using the Harland Sharp 1.5 roller rocker
[/ QUOTE ]
Hap,
Do you know what weight those things are?
I have heard that roller rockers are much heaver than standard rockers.
But.....Standard rockers are anywhere between 1.30 & 1.45 ratio.
(The inconsistency in stock rockers bothers me a bit)
That means w/ a fast road cam from APT the overall lift could be anywhere from.
0.293 x 1.30 = 0.380 -or- 0.293 x 1.45 = 0.425 (or for 1.5 roller-rockers) 0.293 x 1.5 = 0.440
(all figures - valve lash = about .016)
That is a huge difference!
I like the idea of titanium push rods & spring retainers in order to get the weight down.
What are your feelings on this?
BTW....I don't have to adhere to any rules for building my engine.
(so carbon fibre push rods are something I'm doing research on also)
I recently build a customer motor using the Harland Sharp 1.5 roller rocker
[/ QUOTE ]
Hap,
Do you know what weight those things are?
I have heard that roller rockers are much heaver than standard rockers.
But.....Standard rockers are anywhere between 1.30 & 1.45 ratio.
(The inconsistency in stock rockers bothers me a bit)
That means w/ a fast road cam from APT the overall lift could be anywhere from.
0.293 x 1.30 = 0.380 -or- 0.293 x 1.45 = 0.425 (or for 1.5 roller-rockers) 0.293 x 1.5 = 0.440
(all figures - valve lash = about .016)
That is a huge difference!
I like the idea of titanium push rods & spring retainers in order to get the weight down.
What are your feelings on this?
BTW....I don't have to adhere to any rules for building my engine.
(so carbon fibre push rods are something I'm doing research on also)
Offline
[ QUOTE ]
But.....Standard rockers are anywhere between 1.30 & 1.45 ratio.
(The inconsistency in stock rockers bothers me a bit)
[/ QUOTE ]
Not just stock rockers, but all rockers. Since the rocker tip is moving in an arc & the valve stem is moving in a straight line, the effective rocker arm ratio varies as the valve stem moves up & down.
When a straight line through both end rocker contact points & rocker pivot center is at 90 degrees to the valve stem, the effective rocker ratio might be 1.45. As the rocker to valve contact point moves through the rocker end's arc, it's valve contact end effectively moves closer to the rocker pivot & reduces the actual ratio to something like 1.3. The valve contact point of the rocker moves closer to & further away from the pivot throughout the cycle. Exactly how much change there is depends on the rocker arm geometry, height of the rocker pivot in relation to the valve stem, etc.
This effective ratio change still happens with a roller tip, but the tip to valve stem is more of a rolling contact rather than a sliding contact.
D
But.....Standard rockers are anywhere between 1.30 & 1.45 ratio.
(The inconsistency in stock rockers bothers me a bit)
[/ QUOTE ]
Not just stock rockers, but all rockers. Since the rocker tip is moving in an arc & the valve stem is moving in a straight line, the effective rocker arm ratio varies as the valve stem moves up & down.
When a straight line through both end rocker contact points & rocker pivot center is at 90 degrees to the valve stem, the effective rocker ratio might be 1.45. As the rocker to valve contact point moves through the rocker end's arc, it's valve contact end effectively moves closer to the rocker pivot & reduces the actual ratio to something like 1.3. The valve contact point of the rocker moves closer to & further away from the pivot throughout the cycle. Exactly how much change there is depends on the rocker arm geometry, height of the rocker pivot in relation to the valve stem, etc.
This effective ratio change still happens with a roller tip, but the tip to valve stem is more of a rolling contact rather than a sliding contact.
D
Guys, I think that the point being made was that there are inconsistencies in the basic rocker itself, due to manufacturing tolerances and stackup. Roller rocker tolerances are generally more tightly controlled, and have far greater accuracy than the stock items.
Just my couple of pence.
Jeff
Just my couple of pence.
Jeff
Offline
Yes. I think it would make sense. Most rocker sellers don't state average lift though. They advertise the maximum ratio. Also, the actual effective ratio will vary with valve stem, pushrod, & rocker shaft height of the particular installation. This means tha the "average" is also a variable. The seller has no control over these variables.
The only way to know for sure is to measure your particular engine.
D
The only way to know for sure is to measure your particular engine.
D
D
Deleted member 3577
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I have messed w/ these things a bit by just mixing & matching out of a bucket full of em.
From the push rod end they are fairly consistant.
(1" from center of shaft to center of ball)
From the other end, I've seen variances of half a tenth.
(from 1st wear mark to center)
Offline
[ QUOTE ]
I have messed w/ these things a bit by just mixing & matching out of a bucket full of em.
From the push rod end they are fairly consistant.
(1" from center of shaft to center of ball)
From the other end, I've seen variances of half a tenth.
(from 1st wear mark to center)
[/ QUOTE ]
While having matched rocker arms is certainly important, there are a couple of other items which are just as important to the big picture. Namely, valve stem heights, rocker pivot height, rocker tip radius, & sometimes pushrod length, if the adjusters happen to be on the valve end of the rockers. I think Jeff knows - considering he spent 8 hours for setup.
D
I have messed w/ these things a bit by just mixing & matching out of a bucket full of em.
From the push rod end they are fairly consistant.
(1" from center of shaft to center of ball)
From the other end, I've seen variances of half a tenth.
(from 1st wear mark to center)
[/ QUOTE ]
While having matched rocker arms is certainly important, there are a couple of other items which are just as important to the big picture. Namely, valve stem heights, rocker pivot height, rocker tip radius, & sometimes pushrod length, if the adjusters happen to be on the valve end of the rockers. I think Jeff knows - considering he spent 8 hours for setup.
D
Hap Waldrop
Yoda
Offline
[ QUOTE ]
[ QUOTE ]
I recently build a customer motor using the Harland Sharp 1.5 roller rocker
[/ QUOTE ]
Hap,
Do you know what weight those things are?
I have heard that roller rockers are much heaver than standard rockers.
But.....Standard rockers are anywhere between 1.30 & 1.45 ratio.
(The inconsistency in stock rockers bothers me a bit)
That means w/ a fast road cam from APT the overall lift could be anywhere from.
0.293 x 1.30 = 0.380 -or- 0.293 x 1.45 = 0.425 (or for 1.5 roller-rockers) 0.293 x 1.5 = 0.440
(all figures - valve lash = about .016)
That is a huge difference!
I like the idea of titanium push rods & spring retainers in order to get the weight down.
What are your feelings on this?
BTW....I don't have to adhere to any rules for building my engine.
(so carbon fibre push rods are something I'm doing research on also)
[/ QUOTE ]
I never weighted them for a difference. I thin k the biggest thing with the 1.5s in the stock pedestal is is plays with valve geomentry and moves the pushrod too close to the inboard side of the pushrod hole in the head, so I like either getting pedestal made with the right shaft pivot hole or I've seen folks make a oversized shaft bushing in the stock pedestal so thay could move the shaft hole to the right side, or you can just spend more money and get the Titans and they come with new correct pedestals.
A for titanium pushrods and retainers, I've used titanium retianers, have them on my SCCA HP car right now, but I never used titanium pushrods.
[ QUOTE ]
I recently build a customer motor using the Harland Sharp 1.5 roller rocker
[/ QUOTE ]
Hap,
Do you know what weight those things are?
I have heard that roller rockers are much heaver than standard rockers.
But.....Standard rockers are anywhere between 1.30 & 1.45 ratio.
(The inconsistency in stock rockers bothers me a bit)
That means w/ a fast road cam from APT the overall lift could be anywhere from.
0.293 x 1.30 = 0.380 -or- 0.293 x 1.45 = 0.425 (or for 1.5 roller-rockers) 0.293 x 1.5 = 0.440
(all figures - valve lash = about .016)
That is a huge difference!
I like the idea of titanium push rods & spring retainers in order to get the weight down.
What are your feelings on this?
BTW....I don't have to adhere to any rules for building my engine.
(so carbon fibre push rods are something I'm doing research on also)
[/ QUOTE ]
I never weighted them for a difference. I thin k the biggest thing with the 1.5s in the stock pedestal is is plays with valve geomentry and moves the pushrod too close to the inboard side of the pushrod hole in the head, so I like either getting pedestal made with the right shaft pivot hole or I've seen folks make a oversized shaft bushing in the stock pedestal so thay could move the shaft hole to the right side, or you can just spend more money and get the Titans and they come with new correct pedestals.
A for titanium pushrods and retainers, I've used titanium retianers, have them on my SCCA HP car right now, but I never used titanium pushrods.
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Dave--
What are you using the Carmex for?
On a different note how much total timing advance do you recommend?
What are you using the Carmex for?
On a different note how much total timing advance do you recommend?
D
Deleted member 3577
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Guest
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[ QUOTE ]
Dave--
What are you using the Carmex for?
[/ QUOTE ]
Well....I usually don't put the Elva away until it becomes painfully cold.
(Made it to Dec. 1st this year. /ubbthreads/images/graemlins/grin.gif)
So far as sparks go....
13 Static
20 at tick-over
36 full in (3500 RPMs)
Anything over 40 could be injurious
(97 octane & 9.5-1 compression)
Do they still have blue crabs in Baltimore around December?
(Might be on a parts run next week)
Dave--
What are you using the Carmex for?
[/ QUOTE ]
Well....I usually don't put the Elva away until it becomes painfully cold.
(Made it to Dec. 1st this year. /ubbthreads/images/graemlins/grin.gif)
So far as sparks go....
13 Static
20 at tick-over
36 full in (3500 RPMs)
Anything over 40 could be injurious
(97 octane & 9.5-1 compression)
Do they still have blue crabs in Baltimore around December?
(Might be on a parts run next week)
Offline
"Do they still have blue crabs in Baltimore around December?"
The crabs bury up in the bay bottom during cold months but what with the slim pickings we have been getting crabs from SC, FL, etc. for years and they are probably available. December is an oyster month.
If you're over that cold sore why don't you let me know when you are coming. There's a guy with a salvage yard very near where I live who has a field of dreams--LBC and others. Come down to Southern Maryland and I'll make you some of my famous oyster chowder.
Best--Michael
The crabs bury up in the bay bottom during cold months but what with the slim pickings we have been getting crabs from SC, FL, etc. for years and they are probably available. December is an oyster month.
If you're over that cold sore why don't you let me know when you are coming. There's a guy with a salvage yard very near where I live who has a field of dreams--LBC and others. Come down to Southern Maryland and I'll make you some of my famous oyster chowder.
Best--Michael
tony barnhill
Great Pumpkin - R.I.P
Offline
[ QUOTE ]
Do you know what weight those things are?
I have heard that roller rockers are much heaver than standard rockers.
[/ QUOTE ]
Another guy who thinks like me!
Can you compare their weights, Hap?
Do you know what weight those things are?
I have heard that roller rockers are much heaver than standard rockers.
[/ QUOTE ]
Another guy who thinks like me!
Can you compare their weights, Hap?
D
Deleted member 3577
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Guest
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I have heard that the lightest roller rockers are within 5 grams of standard ones.
The biggest difference then becomes where the weight is distributed.
Rollers have a much higher moment of inertia on account of having most of their mass toward the outer edge.
While all rockers describe an arc......The arc is so small that a properly faced one probably has little effect on ratio. IMNSHO
So far as side load goes.........Is this really significant?.....I'm thinking not.
The question then becomes.... How or where can I have my rockers "blueprinted"
So far as tappets having to move further on "bumpier" cams argument goes.
(Where someone claims it requires more force to move them further)
F=MV Squared would seem to suggest that the opposite is true
The biggest difference then becomes where the weight is distributed.
Rollers have a much higher moment of inertia on account of having most of their mass toward the outer edge.
While all rockers describe an arc......The arc is so small that a properly faced one probably has little effect on ratio. IMNSHO
So far as side load goes.........Is this really significant?.....I'm thinking not.
The question then becomes.... How or where can I have my rockers "blueprinted"
So far as tappets having to move further on "bumpier" cams argument goes.
(Where someone claims it requires more force to move them further)
F=MV Squared would seem to suggest that the opposite is true
jlaird
Great Pumpkin
Offline
https://www.rockerarms.com/ These guys might be able to help. They do MGs.