Ser II secondary throttle

Hi Stew, I referred to your previous post on this forum in a discussion on Jag lovers Etype forum. An e type guy was sceptical about the fact that the later cams on the SII were in fact modified to improve emissions, and suggested that there were some changes made , but they were directed at a reduction in cam noise with no loss of performance .He asked me about the specs for the cams ( presumably before and after ). Since i am certainly no expert here i fel somewhat in the middle on this one . Could I prevail upon you to maybe give us some guidance on this matter. Thanks,John M Holmes 1970 S II OTS project, Ontario.

John,
The Series 2, variation 3 engine, identified by the black sheetmetal crossover and notches for same on the center of the cam covers, was detuned to meet emmissions regulations by use of a different cam and distributor. By replacing these items with those found in the earlier variations 1 or 2, a significant difference in performance can be achieved.

Stew Cleave
JOCO Chief Judge
'69 E-Type 2+2
and other LBC's

George, i wondered why you make the suggestions re replacement of distributor and cams. what is the logic behind it . Just a little of the background would be useful for me to understand where you are coming from . I have a 1970 OTS project on the go , and i will be into engine and ancillary rebuild probabley this winter. All this discussion is apparently quite relevant to me . thanks, John M Holmes

Mallory Unilite is a solid state distributor, not a dual point. Mine has cranked away for many years without maintenance. The advantage of the Mallory in Steve's situation is that he can easily set them up for whatever advance his engine demands. He's pretty much committed to buying a new distributor, anyway, as his may be a retard unit, or may have no vacuum mechanism at all.

I thought the S2 cams had the same lift & duration as the S1 cams, the only difference being a softer ramp for quieter operation.

Mike Frank

A mallory is a waste of $$$$. Dual points are only worth the $$ for revs where you get point bounce. In your car that is in excess of 6500. Your valves will float before then. Change the dist to a Mk2 or "S" with auto box and put in a electronic unit if you wish and save the $$$$. I could get 7000-7500 in my XK140 with this. You can too with better cams. 6000 is the witching rev. Get past it in both directions and you will not break a crank. Good luck.
George Camp

George,

Good point, and well taken. Terry and I talked about that. He said the same thing. I'm considering changing the distributor/ignition anyway, over to a Mallory Unilite. The cam, well, I guess I'll do that when I have a few spare samolians. As you know, I do a lot of work on my cars myself, but that's one I'd probably let Terry to, to be sure it is done right.

But of course, with that extra power I'll need to upgrade the brakes, upgrade the suspension, get better wheels and tires.... Is this called the Domino Effect, or Shipwrights Disease? :-)

Steve Weinstein

Steve your mech. is correct on performance but low speed and idle will be affected. When you go to three carbs you need to change the dist. and cams to get the full benefit. Your 70 has a retard dist (not advance) and the cams are for a sedan (XJ6). Just changing the carbs and manifold will not give you the punch.
George Camp

John,

I have a '70 XKE FHC, manual, with dual Strombergs. Terry Lippincott, a well known Jaguar mechanic in Pennsylvania, did some work on the car before I picked it up. One of the things he did was wire the secondary butterflies open, as an interim measure. I will eventually change over to triple SU's but for now, this gives better performance.

Terry told me that the secondaries are really not needed and impede performance. Now with them wide open, the carbs are essentially straight through and the car performs nicely. Can't wait to feel the kick that the three SU's will give it.

Steve Weinstein, JTC-NJ
JCNA Slalom Committee Chairman
JTC Slalom Chair
'72 E-type 2+2
'70 XKE FHC

I left mine unchanged except for removing the butterflies. I figured that since it is now a straight line into the head it would bypass the cross-over anyway. I am no expert on the "duplex" manifold system though.

Well, David, that is a very nice solution. I wish I had seen it earlier, but I did my own fix...I undid the secondary linkage and springs and safety wired the butterflies open. Yours is better, because the system looks right.

My next problem is should I block the secondary plumbing at the crossover point?

I removed the secondary set of throttle butterflys on my '68 FHC by removing the carbs. as a set and then just removing the 2 screws that attach each to the shaft. I then rotated the shaft to the open position and drew them out of the shaft through the intake opening and reinstalled the carbs. I left all the linkage intact so it still operates the secondary shaft. The throttle response on mine is dramatically better with them removed and I am much happier now with the car's acceleration. Obviously though since everything is still intact except the butterflys if yours has a linkage or bushing problem this will not solve that. FYI my engine is the type that has the cross over pipe from the intake to the exhaust manifold at the rear of the engine. I am not sure if there are differences on later series II type engines.

My car is a manual FHC. The problem is not with spacers or linkage. When I try to manually operate the secondary throttle linkage (disconnected from the primary linkage) I can feel the butterfly sticking. It sometimes takes great force to break it free if the car has been unused for a long time.

OTS FHC or 2+2? Automatic or Manual? There are slight differences between the 2+2's and the others. Check the thickness of the spacers while we wait for George, he may be racing. George told me not to try to overcome the secondary throttles when I asked him if I could eliminate them. Also check and lube the linkage shaft from the fire wall forward (under the duplex manifold). Check the condition of the bushing on the bracket that mounts to the firewall. On a 2+2, this bracket has a lot of adjustment potential and was a big part of my problem. Check the adjustable link between the before mentioned linkage shaft and the primary throttle shafts to see that it is getting the proper mechanical advantage (not pulling in a straight line) how are your primary throttle shafts - any play? I still think the problem will be found in the spacer thickness. George?
Stew Cleave
JOCO Chief Judge
'69 E-Type 2+2
and other LBC's

The primary butterflies work as they should...they open and then as the throttle shaft continues to rotate the secondaries come into play. The secondary butterflies stick in the closed position. I make sure before starting on a drive that I have broken the secondaries loose, but, even after warming up, there is a point in foot pedal movement where I feel the secondary butterflies sticking. With added pressure I can break them and continue acceleration. However, I always run the risk that the throttle shaft couplers between the two carbs will slip, giving me one oipen throttle and one closed...kinda scary.

George Camp is the expert on these and will probably respond. While we are waiting for George (he may be resting): I just went through my intire linkage because I was not getting full primary throttle and, in addition, found that the spacers between the carbs and the intake manifold compress with time and affect the secondary linkage travel. New spacers (about 1/4" thick) solved the problem. Do your secondary butterfly's stick when disconnected from the primary throttle shaft? Can you tell whether its the butterflys, shaft, or lingage that stick? When they stick, I assume that the primary's get stuck with them. If so that can be a dangerous condition (hate to state the obvious). George?

Stew Cleave
JOCO Chief Judge
'69 E-Type 2+2
and other LBC's