[Jack Gifford]

Since it's only roller lifters which create enough side-load to break lifter bores, let's discuss flat-tappet options. The move to roller lifters in motorsports was primarily to allow lobes to have more aggressive profiles. Mushroom tappets provide almost as much lobe design freedom as roller lifters. If you weren't messing with engines when OHV V8s started to take over ('49 Olds, etc.) you probably don't remember the popularity of mushroom lifters- not just in flathead V8s, but also for a decade or so in overheads.

Label this an academic exercise; I don't expect anyone to convert their Pontiac to mushroom tappets. Just food for thought...

[hurryinhoosier62]

Jack, does anyone still manufacture Lee-Wilcox type lifter for any engine other than the flathead Ford? We used them in the majority of Lycoming aircraft engines but even NASCAR stopped using them decades ago.

[mechanickeith]

Jack, I have A Tempest 4 banger with an Isky solid cam in it with mushroom lifters!

[Stan Weiss]

Jack,
In away that technology is still being used in modern engines. The lobe profile should be no different than is used with a OHC running on a large diameter bucket.

Stan

[242177P]

UD Harold said that there was power to be had with larger lifters.

[avman]

Originally Posted by 242177P

UD Harold said that there was power to be had with larger lifters.

Being a Pontiac AND Mopar big block family, I have read about the advantages of the larger diameter lifters in Mopar and AMC many times. It allows for a more aggressive ramp on the lobes amongst other advantages, as long as the cam lobes are also wider to match.
I also heeded the warning not to wind up with Chevy lifters in our Pontiac.
We are using Comp Cams hydraulic roller lifters and cam in the 421 now.

[mechanickeith]

Just have to remember T G I F !!!

[Dragncar]

Originally Posted by avman

Being a Pontiac AND Mopar big block family, I have read about the advantages of the larger diameter lifters in Mopar and AMC many times. It allows for a more aggressive ramp on the lobes amongst other advantages, as long as the cam lobes are also wider to match.
I also heeded the warning not to wind up with Chevy lifters in our Pontiac.
We are using Comp Cams hydraulic roller lifters and cam in the 421 now.

I have been kicking around the idea of a 55mm custom steel billet solid flat tappet cam with the 4-7 lobe swap for the 540 I am doing. The block is set up for the 55mm babbit and .904 bushed lifter bores.
I have never even heard of anyone doing it. But I do not see why it could not be done. Solid .904s are cheap compared to high end solid rollers. I would think all I would have to do is get the custom cam and standard Mopar lifters and the right length pushrods.
I bet you could end up with a sft with the big lobe that is not far off in performance as a std core solid roller.
I would not have to worry about needle bearing failure. The steel cam would be very tough. I just bracket race the car.
I have not bought a 55mm cam yet and have a nice set of Jessel .904 lifters for the wide ports.
BUT, I don't think a flat tappet cam can work on wide ports since they have the offset lifters. Everything has to be centered as the flat tappet lifter rotates. So I would have to use my std High Ports. Easy to get them to flow like my E heads, or close to it and just use my Norris rockers and stud girdle.

Will it work ? Crazy ? Heard of anyone doing it ?

[Jack Gifford]

Keith- I'd like to see a picture of a mushroom tappet of your four. Any photos or catalog pictures?

[mechanickeith]

Originally Posted by Jack Gifford

Keith- I'd like to see a picture of a mushroom tappet of your four. Any photos or catalog pictures?

The only picture I currently have.

[mechanickeith]

Originally Posted by Jack Gifford

Keith- I'd like to see a picture of a mushroom tappet of your four. Any photos or catalog pictures?

Jack, I will try & get you better pictures. You want dimensions also??

[Jack Gifford]

No, I don't care about dimensions. Thanks for the photo. Are they about as light as any other flat hydraulic tappet?

[mechanickeith]

Don't have a scale but feels about the same. Nothing noticeable.

[Half-Inch Stud]

Wide/mushroom lifter idea is good to run to ground. Wondered as such when studing cam time events, and equalizing the loads on Flat HYD lifter faces, bore side loads.

Wiped-cam lobes Problem always been an On-ramp to peak lift issue. never really seen the lobe fail on the closing event due to valve bounce, but maybe the lifter face gets damaged enough to grind out the On-ramp. Always wondered why "rev-kits" didnt stick around to keep the lifters weight on the cam lobe with RPM

[RAIV55]

Originally Posted by Half-Inch Stud

Always wondered why "rev-kits" didnt stick around to keep the lifters weight on the cam lobe with RPM

Don't think I ever seen a rev-kit on a flat tappet cam. Do you know of any?
On rollers they do help keeping the cam looking good but in my opinion they are an installation and maintenance nightmare.

[Half-Inch Stud]

Originally Posted by RAIV55

Don't think I ever seen a rev-kit on a flat tappet cam. Do you know of any?
On rollers they do help keeping the cam looking good but in my opinion they are an installation and maintenance nightmare.

Brfore my time, i found ISKY had such rev-kits for the Valley area. But were not for sale when i was looking to buy.

[Stan Weiss]

I dug out my '79 Isky catalog. It still lists for sale Mushroom lifters and the Installation tool. .995" Diameter mushrooms.

Stan