turbo SBC's... was RE: Thanks for the EFI! (off topic)

[Greg Hermann]

At 8:24 PM 12/14/01, elcamino73 wrote:
>Got a link to any info on them?
>What can you tell me about them Greg?
>
I'm aware of a cam profile for a mushroom tappet that will (roughly) do as
follows:

duration at .050" CAM lift = 207°
CAM lift = .370" (multiply by rocker ratio to get valve lift)
Lift rate = .011" CAM lift per CAM degree

Lifter requirement= 1.375" face diameter. Lifters like this are/were a
Sealed Power part--1.375" head, .625" body . Was used in the IHC RD series
404/450/501 cid I-6 truck engines.

I think a typical SBC flat tappet "high energy" type cam is lucky if it
gets .004 or .005" of cam lift per cam degree!!

A big advantage to mushrooms over rollers is that you don't get the big
side loads on the lifter bores in the block.

This size lifter may not fit into an SBC without having the OD of the
lifter face clip the lobes for valves on the other bank, but I am SURE
there's gotta be someone out there who knows what to do for putting
mushrooms in an SBC, somebody always does EVERYTHING for SBC's !! :-)

If I remember correctly, it was Charlie Reichard at Cam Dynamics (???) in
Maryland (???) that told me he had this cam lobe design. Charlie does a lot
of puller cams. If my rememberer is working right, they do have a web site.

Charlie also told me you can use MUCH shorter clearance ramps on a mushroom
cam than on a roller, thus keeping the "advertised" duration much closer to
the .050" duration.

Don't know if they are still doing it for a "cheat", but I know some NASCAR
guys were running mushrooms for a while. Rollers were against the rules,
and the tech check was to stick something down the pushrod hole to see if
the lifters would rotate. Mushrooms rotate ! :-)

Mushrooms are a PITA to assemble--they basically have got to be the first
thing into the block after the cam bearings. Then the cam, after the
lifters, then everything else.

Greg


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