[camachinist]

It would be interesting to hear from the rest of the group who have TFS heads on this subject...

I think it has to do with the rotated polyangle valving arrangement they've come up with to get their airflow numbers....

Most aftermarket heads use bronze or bronze sleeve valve guides which have an excellent service record in the rebuilding insdustry...I did have some difficulties early on with valve guides I made myself because they were of the wrong alloy and had poor wear characteristics against hard chromed valve stems....I would only get one season or so out of them before replacement.

Do those TFS heads by any chance use a 1.7 rocker? If so, that may also be contributing....it magnifies any error in the machining angle of the rocker stud or bolt boss and threading...doing stuff like this, when departing from the OEM design, can be tricky even if all the numbers sound right...

As much as I think the TFS heads are cool (and, in 1995, when they were a new design, I felt the same way), I'll continue to recommend the more pedestrian heads like the Edelbrocks I have on the race car because of their proven design and reliability. You should get at least the OEM lifespan out of a set of aftermarket heads if they're to be considered for street use....

I had considered getting TFS heads for the race car at some point but will have to do more research on their maintenance requirements under racing conditions before justifying the cost vs performance improvements...

I hope everything works out ok for you....keep us posted..

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG

 

[camachinist]

I'd be curious to know what they did use on the early heads for valve guides....

When I bought my Edelbrocks in '95, TFS (I think Summit owns a chunk of them) had just come out with the Twisted Wedge heads and they were backordered....I coulda sworn from the catalog description that they had stellite seats, bronze guides, screw-in studs and guide plates from the factory on the bare heads.....

Those catalogs are long-gone so I have no way of verifying that...

I've been doing machine work for a long time now and the only viable alternative I've seen to either stock cast iron guides or solid bronze guides has been a bronze sleeve guide (thin wall) which installs within the stock cast guide or existing bronze guide with a special ream and installation tool...

If there's some new technology out there that someone knows about in this area, I'd love to hear about it....

FWIW, my ca. '95 Performer RPM's came with solid bronze guides...exemplary service received...

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG

 

[camachinist]

As I surmised, the root cause of the TFS problems was their departure from OEM valvetrain geometry...

Although this article, if entirely accurate, would contradict my assertion about the original TFS heads having bronze guides, I wonder why they, in contradiction to every established norm for the performance industry at the time, would install iron guides in an aluminum performance head...
There are a number of issues with this marriage and I am nonplussed as to why they didn't sort them through in pre-production.....

Thanks for setting the record straight on this products history.....

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG