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10-12-2015, 07:28 AM | #1 |
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Flathead Cam Weber F7RS
Got this cam the other day. It is Weber F7RS. I never seen a flathead cam w/ this much duration. Can anybody tell me anything about the cam. Thanks again for all the help.
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10-12-2015, 07:35 AM | #2 |
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Re: Flathead Cam Weber F7RS
Let me do some research on this. I believe it is a radius lifter cam. They made a few of these types of grinds.
Here is some required reading for any flathead cam freak. Willie, look about 1/2 down. There is a timing card for this cam. It was called "The Giant". http://www.midstateantiquestockcarcl...at_heads4.html |
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10-12-2015, 07:37 AM | #3 |
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Re: Flathead Cam Weber F7RS
I believe that maybe a radius tappet cam.
Martin. |
10-12-2015, 08:53 AM | #4 |
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Re: Flathead Cam Weber F7RS
I don't have specs, but it was a radius lifter cam.
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10-12-2015, 06:34 PM | #5 |
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Re: Flathead Cam Weber F7RS
Thanks Tim for the info on cams. I'M going to add this to my library. Jack.
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10-12-2015, 09:12 PM | #6 |
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Re: Flathead Cam Weber F7RS
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10-12-2015, 10:33 PM | #7 |
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Re: Flathead Cam Weber F7RS
You can get radius lifters from Pete. But, That's not a street cam. Something for the track.
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10-13-2015, 12:19 AM | #8 |
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Re: Flathead Cam Weber F7RS
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10-13-2015, 01:45 AM | #9 |
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Re: Flathead Cam Weber F7RS
Micky,
I believe your correct on the 1" radius lifters. Martin. |
10-13-2015, 06:45 AM | #10 |
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Re: Flathead Cam Weber F7RS
I dn't know that, only ran the 404. Will have to think about that? Interesting.
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10-13-2015, 07:02 AM | #11 |
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Re: Flathead Cam Weber F7RS
Take a look at the bottom of the page in the link below regarding 2" v. 1" lifters.
http://www.midstateantiquestockcarcl...at_heads4.html Am I incorrect to assume that the 1" v. 2" refers more to the compound or bend of the radius v. the actual size of the lifter? I truly have no idea and I'm now very curious. Last edited by Tim Ayers; 10-13-2015 at 07:31 AM. |
10-13-2015, 07:08 AM | #12 |
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Re: Flathead Cam Weber F7RS
Tim you are correct
I bought a set of the 1inch ones at LARS years ago when i was hunting for a 2 inch set For my 404-A :-) Found it out after i got back home |
10-13-2015, 08:27 AM | #13 |
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Re: Flathead Cam Weber F7RS
According to the site, the idea behind the radius is to allow for a more radical opening and closing ramp. Does it also make the cam "bigger" by allowing the lifter to stay of the face of the lobe longer vs. a square making contact like a "stock" style lifter?
Cams are one of my favorite subjects and would love to know more. Also, not to start a side bar discussion, but Barney Navarro said he didn't like roller lifters for the roller would "pool" up the oil as it started to accelerate up the ramp and didn't do what it was designed to do (spin). Not sure about all that, but I'm curious on the rationale behind a radius lifter. |
10-13-2015, 09:35 AM | #14 | |
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Re: Flathead Cam Weber F7RS
Quote:
For example here are the velocity numbers for my favorite two Potvin grinds - can't really show area under the curve in 'text' : a) Potvin 3/8: maximum velocity of .008512 per degree of rotation happens at .1239 of intake ramp lift. b) Potvin 425: maximum velocity of .008519 per degree of rotation happens at .1925 of intake ramp lift. Now, the Isky 404-A: maximum velocity of .009738 per degree of rotation happens at .163 of intake ramp lift. Roller Lifters: I'm not going to dispute what Barney said - as I would have to know the context of his comments (cam, spring pressure, etc). What I will say is that roller cams tend to take more spring pressure to keep them tracking on the lobes . . . and "rolling/spinning" is a part of that. If roller cams didn't work, you wouldn't see them being used in just about every top-competition engine today. What is difficult with roller lifter profiles in flatheads is that we do not have the added benefit of a rocker arm and associated ratio and our base circles are very small. About the only way we can achieve high ramp velocities (to say match a radius) and increase the area under the curve is by using inverse radius/hollow flank profiles. You've probably seen a few cams like this - the lobes look more like "peanut shapes". A great example of this is the top race cams that Harley used on the KR flathead and also what Kenny Kloth had made for his record setting engines for Bonneville. One of the problems/issues with inverse radius cam profiles is that it takes SMALL cam grinding wheels to make the inverse profile with the small base circles of a stock flathead cam blank - and most of the cam grinders use bigger grinding wheels. Solution: If you bore out the cam bores of the block, use larger journals/bearings and increase the base circle diameter of a custom steel billet core, then we have a LOT more to work with. This is what most of the high-end Bonneville guys are doing - it is the only way to get the profiles and lift that they need. Enough of my babble . . . Dale |
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10-13-2015, 09:45 AM | #15 | |
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Re: Flathead Cam Weber F7RS
Quote:
Thanks for the info. Yes, I agree with what you said about rollers. There is a reason why top racing guys are using them without question. I still kick myself for about 25 years ago I was at a yard sale. There was a brand new box of Crower adjustable roller lifters with the jig to drill the lifter bores. The guy wanted $100 for the set and I declined. I sure wish I had those in my stash now. |
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10-13-2015, 03:40 PM | #16 |
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Re: Flathead Cam Weber F7RS
Too soon old, too late smart. The more I learn about camshafts, the less I know about camshafts. Back in the 60's we ran the 404 with the double spring package. Instolation was a bitch. and the engine ran OK for a while untill one of the lifters gave up and we switched to a 400jr. Which ran much better. However we eat up a few lifters here as well. We were running 85 lbs of spring pressure as reccomended by some expert?? after that fix dropping the installed spring pressure to 65 lbs the cam and lifters lasted several seasons untill we switch ed to a Sig Errson cam. Learned allot the hard way. Nut I still say, The air pressure in the right fron and a great driver is all you need on a short track.
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10-14-2015, 08:28 AM | #17 | |
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Re: Flathead Cam Weber F7RS
Quote:
The Crower roller lifters are quite heavy (just put a set in my 42 Merc engine), but they beat the hell out of making your own. If I was building a race engine for Bonneville, I would make my own - just as we did on our Flathead Cadillac engine. |
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10-14-2015, 08:31 AM | #18 | |
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Re: Flathead Cam Weber F7RS
Quote:
On a side note, FlatDog used to run the dual-spring Isky package and he and I talked a lot about it. He then switched over to the single 185-G springs on his .450 lift roller - used about 100 lbs on the seat and had no problems at all with his race engines. Man - he was a good dude . . . miss our bench racing conversations! |
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10-14-2015, 08:42 AM | #19 |
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Re: Flathead Cam Weber F7RS
"The air pressure in the right front and a great driver is all you need on a short track."
Ol' Ron, there is a lot of wisdom in those words.
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10-14-2015, 09:17 AM | #20 | |
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Re: Flathead Cam Weber F7RS
Quote:
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