Differences in HD8 carbs?
- Thread starter 302Rover
- Start date
christopher storey
Member
They are of a totally different type, with those on the E type having a shoe ( attached to the jet mechanism ) at the base of the carb which operates a brass rod of substantial diameter which goes vertically through the cast body of the carb, and then has a "tappet" on the top which operates the fast idle lever
here is a picture of the underside of E 4.2 carburetters
here is a picture of the underside of E 4.2 carburetters
302Rover
Member
christopher storey said:They are of a totally different type, with those on the E type having a shoe ( attached to the jet mechanism ) at the base of the carb which operates a brass rod of substantial diameter which goes vertically through the cast body of the carb, and then has a "tappet" on the top which operates the fast idle lever
here is a picture of the underside of E 4.2 carburetters
Hi Christopher,
thank you for the photo and information. What I"m trying to do is decidedly non-Rover and perhaps a bit off topic for this Forum. I am converting my E-Type to triple SUs from the dual Stromberg setup but trying to do it as cheaply as possible. To that end I am using a stock E-Type triple manifold but the HD8 carbs that I have were salvaged from a Jaguar saloon car, I think a Mk X. Those carbs don't have a choke mechanism, rather they used an auxiliary enrichment device. So I need to fit some sort of choke mechanism and it occurred to me that the Rover HD8 chokes perhaps could be fitted to the Jag HD8 carbs.
Unfortunately I got rid of all my Rover engine stuff, including the carbs, after I converted the Rover to a Ford V8 powered machine. Now I'm kicking myself for having done that. But I did see an ad for a pair of Rover HD8s being sold rather cheaply so am thinking about buying them if there is a chance I could fit the choke setup. I do know that both Rover and Jag used the same 'rod and foot' device but don't know anything about the jet body. is it the same size? Could I install it in the Jag HD8?
Once again, any help is greatly appreciated.
Cheers,
Tom
christopher storey
Member
Tom : I have two sets of 2000TC carbs somewhere in storage so I'll have a look to see what the choke arrangements are. I am a bit doubtful because my recollection is that the TC used HS8 carbs rather than HD. I'll also go through my SU catalogue and see what i can get out of that .
If you are using Mark X carbs, you are best having a word with Peter Crespin on either Jaglovers bulletin board ( US ) or on the Etype Forum ( UK ) because he has done conversions from time to time and almost certainly will know what to do
These are the carbs on my current late series 1 2000TC
If you are using Mark X carbs, you are best having a word with Peter Crespin on either Jaglovers bulletin board ( US ) or on the Etype Forum ( UK ) because he has done conversions from time to time and almost certainly will know what to do
These are the carbs on my current late series 1 2000TC
j_radcliffe
Active Member
Early TC's used HD8 carbs, then in about 68 I think, they changed to HS8's.
I may end up with a pair of HD8's to sell when/ if I get around to doing my HIF 6 conversion. I will let you know if I end up with some surplus carbs.
James.
I may end up with a pair of HD8's to sell when/ if I get around to doing my HIF 6 conversion. I will let you know if I end up with some surplus carbs.
James.
Vern Klukas
Active Member
TC HD8s have the same arrangement for the choke, however the choke lever is attached forward of the jet body, not between the jet body and the choke operating "pillar" as on the Jag carbs picture shown.
A bigger question in my mind would be if the Jag carbs have a separate idle circuit, which was a feature of the HD carbs but is absent on the TC HD8s for some reason.
Yours
Vern
Added a picture
A bigger question in my mind would be if the Jag carbs have a separate idle circuit, which was a feature of the HD carbs but is absent on the TC HD8s for some reason.
Yours
Vern
Added a picture
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christopher storey
Member
Tom ( and Vern )
having looked in my SU catalogue, HD8 were listed ONLY for 1966, and after that all twin carburetter cars had HS8, so your chances of finding HD are rather limited. In any event, the E type and mark X carbs do indeed have the separate idle circuit referred to by Vern . It is the big screw about 1/4 inch diameter on the top of the body . The effect of this is that the butterflies have to be completely shut at idle , and the air is admitted purely through the bleed circuits governed by the screws . If the Rovers HD8s do not have this then I think it would impossible to use the carbs as a whole ( although it might be possible to canibalise them for the brass rods, shoes etc )
having looked in my SU catalogue, HD8 were listed ONLY for 1966, and after that all twin carburetter cars had HS8, so your chances of finding HD are rather limited. In any event, the E type and mark X carbs do indeed have the separate idle circuit referred to by Vern . It is the big screw about 1/4 inch diameter on the top of the body . The effect of this is that the butterflies have to be completely shut at idle , and the air is admitted purely through the bleed circuits governed by the screws . If the Rovers HD8s do not have this then I think it would impossible to use the carbs as a whole ( although it might be possible to canibalise them for the brass rods, shoes etc )
Vern Klukas
Active Member
christopher storey said:
In actual fact, HD8s came on TC cars until late 1967 production. The service newsletter in January 1968 introduced the change to the dealers, apparently starting with C suffix engines. For NADA cars, it is a good way to tell the difference between 67 or earlier from 68 and later cars. As for why no idle circuit, I suspect the engine was impossible to tune with the circuit active, given it is way over-carbed in terms of airflow.
Yours
Vern
Vern Klukas
Active Member
TimBC said:
It should have HD8s, at least according to the service department. As far as the rest of the engine systems, the only difference between HD & HS is the double choke cable and different fuel inlet fitting on the HS carbs. I'm a little vague on whether the fuel return line and stronger fuel pump was fitted to all HS engines or whether that was just something on NADA cars to solve the vapour lock issues they had in hot weather, but that may be the third difference.
Yours
Vern
christopher storey
Member
No fuel return line on UK and Euro HS cars, nor are there any on HD8s used on E types
Vern Klukas
Active Member
christopher storey said:
I should of been clearer—the fuel return was introduced with the HS carbs in NADA cars. HD cars never had one.
At the same time, rudimentary emission control was added (crankcase vented to the carbs, thermo disk on the main jet, spring biased needle, the fringed brass plate behind the throttle disk to promote turbulence and the pop off vent in the throttle disks themselves).
As usual, NADA cars were ahead of the pack, with engines 85900001B and up affected for the TCs and 85800001H for the Automatics. Which means I guess the C suffix info applies only to production outside of the NADA cars.
This was also when dual servos appeared and the ignition coil moved over to the battery side of the engine compartment, along with a bunch of other refinements and steps back.
Yours
Vern