Ah yes, I understand. The head was the same "casting" as the TR4A head, but
have machining for the exhaust valve stem and intake port that match the
earlier high port heads.
Thanks, Dave H.
> On November 30, 2018 at 6:04 AM Randall <TR3driver@ca.rr.com> wrote:
>
>
> > Does anyone have anything to add about the information I
> > provided about a what looks like a 5th casting for 4 cylinder
> > TRs? I hope the message came through with the attached photos.
> > Dave H.
> >
>
> Perhaps I am confused. The information you supplied seems to match the
> information TeriAnn has listed for (some?) TR3B through CT21470E TR4. P/N
> 511084 is listed in the SPC as being a cylinder head (less valves and
> springs) for TR4 through CT21470E. It takes the same exhaust valves as
> earlier TRs, with the 3/8" stem rather than the 5/16" stem used later on.
> The SPC I have is not explicit about the change from triple exhaust springs
> to double; but it's my belief that it happened around the same time as the
> change in exhaust stem diameter.
>
> The book says the later double springs can be fitted, but is somewhat
> confusing on the topic of "collars", since the same term is used both for
> the spacer that goes under the triple springs, and for what I call the
> "retainer" that goes above the spring. I believe the sets with double
> exhaust springs take a different retainer (142137 vs 105083) for both intake
> and exhaust; and should be used without the spacer (108242). Both inner and
> outer springs have different part numbers between the two sets, and I
> believe the dimensions are different.
>
> It also mentions the "conversion" guides to use the 5/16" exhaust valves in
> the earlier heads. The earlier heads actually have a larger hole for the
> exhaust guide, so these conversion guides are thicker to fill the larger
> hole.
>
> -- Randall
> 56 TR3 TS13571L once and future daily driver
> 71 Stag LE1473 - awaiting engine rebuild
> 71-2-3 Stag - awaiting gearbox rebuild
>
>
>
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