DeTomaso Mailing List: February 98, Message #39
     



From: 	"Mary Taphorn" <marytaphorn@email.msn.com>

Subject: Fw: Fw: Fw: FPP 4145 update

Date: 	Sun, 1 Feb 1998 20:24:07 +0000





-----Original Message-----

From: JDeRyke@aol.com <JDeRyke@aol.com>

To: marytaphorn@email.msn.com <marytaphorn@email.msn.com>;

detomaso@realbig.com <detomaso@realbig.com>

Date: Sunday, February 01, 1998 3:28 PM

Subject: Re: Fw: Fw: FPP 4145 update





>John, either Snap-On or Craftsman makes a "professional" air-powered valve

>spring compressor at an outrageous price (as I remember--can't find either

>catalogue right now) that will handle any spring. Your seated pressure

seems

>very high, even for a 7000 rpm roller cam set for drag-racing. Jack Roush

told

>me that with SVO alloy heads, seated pressure should not exceed 145lbs

@1.900"

>height or the seats would recede into the heads from the pounding. The SVO

>catalogue verifies this. How long do your other valvetrain components last?

I

>assume you're running iron 4V heads? J DeRyke



>> Thanks for everyone's feedback on the spring compressor. I suppose they

work with the heads on the engine so long as care is exercised to prevent

the valve from falling into the cylinder.

>>Jack, I've only got ~ 3,000 miles on the engine so perhaps it is to early

to talk about durability.  I must admit, however, many of those miles were

earned at Pocono, Road Atlanta, Texas World Speedway, several autocrosses

and airport circuits.

I took the precaution of installing both hardened valve seats on intakes and

exhaust as well as hardened spacers between the head and the spring; I

experienced the problem of rotating springs cutting into the heads on

another engine.  I am using an iron 4V quench head.  Initially, I had a

problem with the Dorman's HPX 8740 Chromemoly rocker arm studs breaking at

the base of the adjusting nut.  I surmise the cam's opening ramp was

generating an acceleration rate for the rocker arm that was greater than the

stud could handle as the lash went to zero and the roller rocker slammed

into the adjusting nut .  Replacements offered by Dorman were not a solution

as the problem persisted. A change to ARP rocker arm studs cured the

problem.



John T