Solid Lifters - Team Camaro Tech
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post #1 of 4 (permalink) Old May 6th, 01, 03:10 PM Thread Starter
 
Join Date: Feb 2000
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Question

I recently purchased a basket case 68 Camaro that came with many extra parts. One of those parts is a set of solid lifters. I located a reference to these in a book, and they were called Mushroom Tappets. They have an extremely large base to them, and the rest looks like a normal lifter.

Does anybody know what these were used for? Has anybody here ever used them? Final question, how were these installed?

I have no use for them, and I have had a few guys ask me questions, but I don't know the answers.
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post #2 of 4 (permalink) Old May 6th, 01, 04:31 PM
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Bill
 
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rod,
Mushroom tappets are used mostly in circle track motors that require the use of a non-roller camshaft in particular classes. They allow the use of much more aggresive cam profiles than a regualr solid lifter. They require some special machining on the block. They are rarely used any more, I dont even think Comp Cams has a mushroom tappet cam in thier catalog any more. They are probably best used as paperweights.

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post #3 of 4 (permalink) Old May 6th, 01, 04:41 PM
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If the base of the lifter is a larger diameter than the rest of the lifter body, then you have a mushroom tappet. It can be either solid or hydraulic. They are installed thru the bottom of the lifter bores...so in otherwords if you ever need to replace one, you have to go in thru the oil pan. The reason for mushroom lifters is because chevys use a smaller diameter lifter than fords and chryslers...I dont remember exact sizes off the top of my head but its something like a 1/8-1/4" difference. Because of the larger diameter of the non-chevy lifters, cam grinders can grind a lobe with a more aggressive lift curve. This more aggressive, or faster acting, lobe would dig in to a chevy sized lifter and destroy it in short order. The mushroom tappet is somewhere between a standard lifter and a roller lifter...roller lifters give better performance because you can get so much more lift with the same .050 duration. For example...for a 230 @.050 cam, you wont see many flat tappet cams (solid or hydraulic) with much over .480 lift...the same [email protected] can easily get you .525-.550 lift with a roller, and about .505-.510 with a mushroom tappet. Mushroom tappets came about during the early nascar days when it was felt that non-chevys had an advantage on the track due to the larger lifts available because of the larger diameter lifters...they were used to equalize things at the track. You wont see many mushroom tappets on the street...they are just too much of a pain for a real street car, but in any circle track series where rollers arent allowed, you will still find a lot of mushrooms being run.
As a side note, you will notice that most cam companys use a standard lobe for all engines...compare similar grinds between chryslers and chevys and fords...heck, even between big and small block chevys...all of the lobe lifts are the same...the valve lift is only different if there is a difference in rocker ratio. Very few cam companys have capitalized on this lifter size advantage for non chevy engines...hughes (a major aftermarket chrysler supplier) is one of the very few that do this. If you are interested in a streetable mushroom grind, crower has a large selection.

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post #4 of 4 (permalink) Old May 6th, 01, 04:42 PM
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Bill, you posted as I was typing! You are right...some mushrooms require block machining, but not all...like I said, there was a lot of them that installed thru the bottom of the motor.

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375hp 78 Chevy truck
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