Even though the VW only uses a 1.25 rocker ratio, wouldn't that it's OHV make a difference in the design of the lobe?Not sure if we answered Jack's original post or not but since the lifter diameter on the ford was .999 to 1.00 wouldn't some of the V.W. masters work?
Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
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Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Jack Vines
Studebaker-Packard V8 Limited
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Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Can't answer that for sure Jack; don't remember the actual foot diameter of the v.w tappet( just remember that it was close). If the inch per degree of lift did not exceed that of the Ford it might be possible. With the .25 multiplication at the rocker the v.w. could conceivably be less than the ford. Aren't the Champion tappets 1.25 base diameter? If they are you could be on to something.
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Here is some info from my notes: Flathead ford with stock lifter = .0087 lift per degree, 1.250 foot diameter tappet =.0109 lift per degree. There may be a more current formula for this; Mike would know. As mentioned the 8cm is 110/ 110, the 1cm is 109 icl/111 lsa, eab (53 only) is 112.5 icl/115.5 lsa, the 37-48 (78-6250 core) is 112/111.5, the 49-52(8ba-6250) core is 109.5/111. The 32 core was a machined billet and the only year for this. I don't have info on the 32 to 34 cores but believe they were slightly different than the 37-48.
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
H-D work in the '60s indicated that there is substantial flow over the top of the valve at full lift, needs as much as .125" vertical clearance to the relief pocket. There is also flow leaving the rear of the seat (away from the bore) and passing forward, the method is a shallow concave pocket above the gasket surface.
If you sink the valves remember this may reduce the short turn radius. The valve must present a curtain toward the bore immediately it cracks open.
I'm beginning to suspect that there is more relationship between the deck's relief contour and the head's chamber above it, similar to 2-stroke development. The deepest reliefs don't appear to do much, since the flow is already arcing upward.
Once H-D discovered this, every race cam 1940-69 had 65 degree intake valve closure regardless of the other 3 positions (with static CR between 5.5 and 6.0:1). Capturing cylinder pressure is more valuable than inertia fill ABDC.
Since the .440" lift H-D cams still used 30 degree intake seats I would guess that the cross-over to 45 occurs at higher lift?
If you sink the valves remember this may reduce the short turn radius. The valve must present a curtain toward the bore immediately it cracks open.
I'm beginning to suspect that there is more relationship between the deck's relief contour and the head's chamber above it, similar to 2-stroke development. The deepest reliefs don't appear to do much, since the flow is already arcing upward.
Once H-D discovered this, every race cam 1940-69 had 65 degree intake valve closure regardless of the other 3 positions (with static CR between 5.5 and 6.0:1). Capturing cylinder pressure is more valuable than inertia fill ABDC.
Since the .440" lift H-D cams still used 30 degree intake seats I would guess that the cross-over to 45 occurs at higher lift?
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Thanks, Panic. Do you have H-D KR cam specs for what would be considered their torque cam?every race cam 1940-69 had 65 degree intake valve closure regardless of the other 3 positions (with static CR between 5.5 and 6.0:1).
What was the highest C.R. H-D ever used on the KR? (Yes, flatheads always have the tradeoff between more flow and more C.R., but what did H-D consider the sweet spot; the 5.5 - 6.0 you referenced?)
Jack Vines
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Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
There is a guy here locally who has some of that old HD KR flat head racing stuff. I might be able to borrow a cam and see what they were running. Supposedly they were the most developed flathead engines of their era.
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
The KR had lots of R&D spent on it, but they started with a huge handicap: the original cylinder-cam location.
The intake and exhaust cams have the same (nominal, not actual*) separation distance between base circles and lobes as the intake and exhaust stems for each cylinder. However, this only makes the stems parallel to each other, not to the bore axis (22.5° from vertical, rear tilted back + front tilted forward). The tappet positions were not where they wanted the valve seats, but angled fore & aft by 4.5°. This created a pocket in which the seat is recessed (and shrouded) similar to the relief pocket in the Ford V8 and others, but pointed 90° away from helpful!
In addition, for cooling the seats were located outboard of the outer cylinder wall, which made the chamber wider left to right and added volume (meaning lower CR). These are all mistakes inherited from the original 1929 Model "D" engine.
Indian made no such mistakes, the seats are exactly where they wanted them and closer to the bore, the cam gear misalignment was handled by rocker arms to put the stems in the right places and parallel to the bore axis so the seats are flush with the deck. The result: the 648 ("big base") Scout out-powered the KR until the H-D got both new 1/4-speed pump and breather timing and the huge 1-1/2" pin and rod set by 1955.
The KR is not a good model for chamber design because so many relationships don't translate. A Scout with its "better" bore-to-stroke ratio (2.875" X 3.500" vs. 2.745" X 3.8125") should have had a lower optimum static CR, but because of the superior chamber design it was higher, over 6:1.
In a water cooled engine even less info is useful.
The street KR had 6.5:1, but they got more power every time they removed metal from the chamber, so the final ratio was more like 5.5:1. For more details go here to see the original 1965 Cycle World interview: http://www.beautyofspeed.com/data/doc_c ... /index.htm
An engine with higher bore to stroke ratio like the UH (3.422" X 4.28") can't get the same optimum CR as it's opponent Chief (3.25" X 4.8125"), it's about 1 point lower (and the Chief has the same valve gear advantage).
On the back burner is my booklet on the flathead L6 engine (Chrysler 237, 251, 265 Ply-Do 218, 230, Pontiac 239, Hudson 308, Ford 223) using much information from my (almost done) Chevy Stovebolt booklet (shameless self-promotion: http://victorylibrary.com/235BK.htm)
The intake and exhaust cams have the same (nominal, not actual*) separation distance between base circles and lobes as the intake and exhaust stems for each cylinder. However, this only makes the stems parallel to each other, not to the bore axis (22.5° from vertical, rear tilted back + front tilted forward). The tappet positions were not where they wanted the valve seats, but angled fore & aft by 4.5°. This created a pocket in which the seat is recessed (and shrouded) similar to the relief pocket in the Ford V8 and others, but pointed 90° away from helpful!
In addition, for cooling the seats were located outboard of the outer cylinder wall, which made the chamber wider left to right and added volume (meaning lower CR). These are all mistakes inherited from the original 1929 Model "D" engine.
Indian made no such mistakes, the seats are exactly where they wanted them and closer to the bore, the cam gear misalignment was handled by rocker arms to put the stems in the right places and parallel to the bore axis so the seats are flush with the deck. The result: the 648 ("big base") Scout out-powered the KR until the H-D got both new 1/4-speed pump and breather timing and the huge 1-1/2" pin and rod set by 1955.
The KR is not a good model for chamber design because so many relationships don't translate. A Scout with its "better" bore-to-stroke ratio (2.875" X 3.500" vs. 2.745" X 3.8125") should have had a lower optimum static CR, but because of the superior chamber design it was higher, over 6:1.
In a water cooled engine even less info is useful.
The street KR had 6.5:1, but they got more power every time they removed metal from the chamber, so the final ratio was more like 5.5:1. For more details go here to see the original 1965 Cycle World interview: http://www.beautyofspeed.com/data/doc_c ... /index.htm
An engine with higher bore to stroke ratio like the UH (3.422" X 4.28") can't get the same optimum CR as it's opponent Chief (3.25" X 4.8125"), it's about 1 point lower (and the Chief has the same valve gear advantage).
On the back burner is my booklet on the flathead L6 engine (Chrysler 237, 251, 265 Ply-Do 218, 230, Pontiac 239, Hudson 308, Ford 223) using much information from my (almost done) Chevy Stovebolt booklet (shameless self-promotion: http://victorylibrary.com/235BK.htm)
Last edited by panic on Sat Sep 02, 2017 12:33 am, edited 1 time in total.
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
* the intake and exhaust cams are gear-driven in train at the same speed, each with 28 teeth (in a small 4-cam engine, 32 in the big engines), but obviously in opposite directions. The #2 rear intake has an extra row to be driven off the pinion gear at 1/2 speed.
These engines (and all H-D until 2000) followed a well-known engineering principle WRT roller tappets: the lobe's side thrust against the roller in the opening phase is very severe and limits maximum values. To alleviate this, they advanced the entire valve train (above the lobe: tappet block, tappet, valve and in OHV pushrod) 1/8" ahead (to the left for CW rotating cams #1 & 3, to the right for CCW cams #2 & 4) of the base circle. This spaces the tappets 1/4" farther apart (1/8" away for each tappet) than the cams, which is the actual stem separation distance.
Now, the rising lobe is directly under the roller, and maximum acceleration and thrust angle can be safely increased. On the closing side the angle is worse, but it's only spring tension, not a mechanical load, and far less important.
This advantage could be added to any pushrod engine using large tappets by bushing them eccentrically down to a conventional size like .842". In a V8 the bushing offset is not mirror image left and right bank but follows engine rotation: both in the same direction.
These engines (and all H-D until 2000) followed a well-known engineering principle WRT roller tappets: the lobe's side thrust against the roller in the opening phase is very severe and limits maximum values. To alleviate this, they advanced the entire valve train (above the lobe: tappet block, tappet, valve and in OHV pushrod) 1/8" ahead (to the left for CW rotating cams #1 & 3, to the right for CCW cams #2 & 4) of the base circle. This spaces the tappets 1/4" farther apart (1/8" away for each tappet) than the cams, which is the actual stem separation distance.
Now, the rising lobe is directly under the roller, and maximum acceleration and thrust angle can be safely increased. On the closing side the angle is worse, but it's only spring tension, not a mechanical load, and far less important.
This advantage could be added to any pushrod engine using large tappets by bushing them eccentrically down to a conventional size like .842". In a V8 the bushing offset is not mirror image left and right bank but follows engine rotation: both in the same direction.
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Wouldn't the limiting factor be the resultant pressure angle, regardless of whether it's achieved by lifter offset or a concave opening flank?
Felix, qui potuit rerum cognscere causas.
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Happy is he who can discover the cause of things.
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Victory Tech papers has a lot of KR camshaft specs
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Here are some photo's of Harley KR parts to support what Panic is talking about. Also a comparison of a KR "J" and an XR "E" cam at the lifter then a comparison those two cams at the valve. The flat head race cam's always look so radical to over head cams.
Ron
Ron
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
We were just agreeing OHC bucket tappets and flatheads with similar diameter tappets could use the same cam profile. What am I missing from the above where the H-D has quite a bit more lobe lift and quite a bit less valve lift than the Jag XJ?
Jack Vines
Studebaker-Packard V8 Limited
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Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
You guys are going overboard on this.
Designing flat head cams are as easy as any other cam.
You're limited by the tappet diameter and the valve to head lift.
Not really any different then designing a SBC cam for a circle track class, where the rules limit the lift.
A couple of years ago, I had to do the same for an overhead valve engine that was limited by rules to .500" lobe lift. It won the 24 hours of Daytona.
I didn't really do anything different then I do for a ,390"/.410" lift rule SBC.
Designing flat head cams are as easy as any other cam.
You're limited by the tappet diameter and the valve to head lift.
Not really any different then designing a SBC cam for a circle track class, where the rules limit the lift.
A couple of years ago, I had to do the same for an overhead valve engine that was limited by rules to .500" lobe lift. It won the 24 hours of Daytona.
I didn't really do anything different then I do for a ,390"/.410" lift rule SBC.
Mike Jones
Jones Cam Designs
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Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
Wasn't that one of those 'low lash' deals?CamKing wrote:You guys are going overboard on this.
Designing flat head cams are as easy as any other cam.
You're limited by the tappet diameter and the valve to head lift.
Not really any different then designing a SBC cam for a circle track class, where the rules limit the lift.
A couple of years ago, I had to do the same for an overhead valve engine that was limited by rules to .500" lobe lift. It won the 24 hours of Daytona.
I didn't really do anything different then I do for a ,390"/.410" lift rule SBC.
-Bob
Re: Flathead - who's got a new tech cam grind? Anything in the OHC world applicable?
All of the 1953-69 KR lobes are "kidney"-shaped with concave opening flank and normal convex closing flank. Yes, the duration needed for area pushes a lot into OL. Much of the tweaking for gearing, track conditions is in the choice of exhaust which are 30+ degrees shorter. Here's my chart of KR grinds:
http://www.victorylibrary.com/tech/KR-cam-c.htm
The cams can be switched (any intakes with any exhausts), but not re-clocked without surgery.
Caution: the 1929-83 H-D roller tappet uses a non-std. .855" roller, and will respond IDK to a concave profile designed for a .750" roller.
I'm trying to suss the effect of a VW Type I tappet which is 19mm (.748") body and 31mm (1.22") "foot", so max vel is huge by the usual formula (where .040" is an acceptable safety margin to prevent edge contact): V-MAX = (tappet diameter - .040”) ÷ 114.6, or .0103" per degree. This is 45% greater than max vel for a common .842" tappet.
http://www.victorylibrary.com/tech/KR-cam-c.htm
The cams can be switched (any intakes with any exhausts), but not re-clocked without surgery.
Caution: the 1929-83 H-D roller tappet uses a non-std. .855" roller, and will respond IDK to a concave profile designed for a .750" roller.
I'm trying to suss the effect of a VW Type I tappet which is 19mm (.748") body and 31mm (1.22") "foot", so max vel is huge by the usual formula (where .040" is an acceptable safety margin to prevent edge contact): V-MAX = (tappet diameter - .040”) ÷ 114.6, or .0103" per degree. This is 45% greater than max vel for a common .842" tappet.