Track Tac

Lets step back in time for A moment

N

NAPA28

New member
Just A what if, for some bench racing.
What if the flathead cams 20 check rule was never changed and the slapper cams never came around. Motors would of lived longer and rods would of been lasting longer IMO. What do you all think? The animal would still of came around regardless but would the flathead dyed so fast in karting. It was close to 8yrs after this rule was changed 98-01 I think.
 
IKF never had a .020 check. The 95-3 was designed as an IKF cam.
WKA's drop of the .020 check came about when Dyno Cams told WKA they were releasing the cam, and that it was a game changer.
 
I believe Charlie sox was one, maybe
actually I have always wondered, when I was young I always had to take a good tiller cam out and cut the shaft.lol
 
The drop of the .020 checks allowed us to open the valves later and close sooner, or later, as preferred. Changing the profile prior to .050 lift, other than opening and closing points make little difference. What really made it work was the spring rule change, allowing an exhaust spring to be ran on the intake. You now could "toss" the valve over the nose and get enough valve lift to hit the head and catch the lifter at the right time on the backside to ease it down on the lobe without bouncing badly. Next thing you know everyone starts breaking lifters, so the billet lifters were allowed along with chamfered lifter bores and backfacing of spring pockets. Next came the billet rod and 7000+ rpm. None of this would have happened if the spring rule change did not happen, without it the motor had a built in rev limiter.
 
In hindsight, It would of made more since to put A 10 and A 20 check rule in place then allowing the springs, lifters and so on. Kind of the reason for my post was just A reaffirmation on this hunch I've had since them days. Even after seeing it was going in the wrong direction, instead of adding things to add, Take away the one thing and make it illegal (the cam). Yet still allow the other stuff since its not going to help you afterward. Now im not saying there wouldn't of been another reason the $$$ would of spiked in the motor, But don't you guys think this would of helped?
 
T&T Speedshop said:
The drop of the .020 checks allowed us to open the valves later and close sooner, or later, as preferred. Changing the profile prior to .050 lift, other than opening and closing points make little difference. What really made it work was the spring rule change, allowing an exhaust spring to be ran on the intake. You now could "toss" the valve over the nose and get enough valve lift to hit the head and catch the lifter at the right time on the backside to ease it down on the lobe without bouncing badly. Next thing you know everyone starts breaking lifters, so the billet lifters were allowed along with chamfered lifter bores and backfacing of spring pockets. Next came the billet rod and 7000+ rpm. None of this would have happened if the spring rule change did not happen, without it the motor had a built in rev limiter.
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I disagree with some of this. Not so much the results, but the "why".
The .020 check was the big thing because it allowed you to grind the face of the cam flat all the way from the base circle to the part of the cam nose that gave you the .050 point.
Putting a 95-3 in would bump your rpm from 5900 or so to 62 or 6300 with no other change.
What allowed the rpm to go to 6900 or 7000 was the Raptor 2 (?) piston. The old style round barrel piston had a lot of drag and held the rpm down to about 6400, unless you squeezed the piston on the sides to make it cam shaped, even then the rpm gain was limited. The new style piston was more like a limited modified piston and had far less drag and far less skirt allowing the rpm to climb dramatically.
For special one or two race motors, I used to turn them 7000 using the old intake spring. They were fast for a while, but instead of valve float I guess you would call it valve ricochet because the intake would hit the head so hard it would cut a pretty deep relief, and WKA came out with a rule preventing it.
 
Bob Evans said:
I disagree with some of this. Not so much the results, but the "why".
The .020 check was the big thing because it allowed you to grind the face of the cam flat all the way from the base circle to the part of the cam nose that gave you the .050 point.
Putting a 95-3 in would bump your rpm from 5900 or so to 62 or 6300 with no other change.
What allowed the rpm to go to 6900 or 7000 was the Raptor 2 (?) piston. The old style round barrel piston had a lot of drag and held the rpm down to about 6400, unless you squeezed the piston on the sides to make it cam shaped, even then the rpm gain was limited. The new style piston was more like a limited modified piston and had far less drag and far less skirt allowing the rpm to climb dramatically.
For special one or two race motors, I used to turn them 7000 using the old intake spring. They were fast for a while, but instead of valve float I guess you would call it valve ricochet because the intake would hit the head so hard it would cut a pretty deep relief, and WKA came out with a rule preventing it.
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That's right Bob. By removing the .020 check the "clearance ramp" could be removed. In .005 the lifter would be at the .050 check and slap the valve.
We had some of Mike's (Dyno) 95- cams in early 94. If you remember a few had longer timing under .020. Then it was realized lofting the valve offered more benefit.
IMHO what killed the Flathead was the fact Briggs stopped building them.
Best, WP
 
Bob, on second thought,,,,,, NAPA28 has a great idea. May have to start another thread by Mike @ Dyno Cams. Mike's an advertiser here, give him a call and see if he would share what actually happened in 1994 to develope the 95-3 flathead cam.

From my old memory,,,, in 94 my contact at Dyno Cams was John Johnson, great guy. He told me they worked day and night on the new WKA 20 check rule. We were privileged to be "in the loop / conversation" so he sent us a few cams to try. We did not do any R&D just got to try out what they had developed for the next year.

Ever notice there's not a 95-1 or 2,,, or any other -1 or -2 after 94. The third iteration of the 95 series cam was the winner, so Mike decided to never use the -1 or -2 designation after that. Now get Mike to tell the story, I do not want to be inaccurate even on the smallest detail, because this can be a great story. Similar to "The Beast", story of 1994 Indy engine for Penske.

Best, WP
 
"IMHO what killed the Flathead was the fact Briggs stopped building them."
Agreed, that and those crumby Chinese parts that Briggs started selling before they discontinued the flathead.
I thought that Briggs switched to the overhead valve configuration in order to be able to build engines that met EPA emissions standards.
 
NAPA28 said:
Motors would of lived longer and rods would of been lasting longer IMO.
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We will never know now, but I have a hunch that the "chinese" rods would have popped even if the cam rules hadn't been changed. That bad batch (or batches) ruined a lot of engines.
 
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