Can anyone in UK drill a Stromberg CD175 Ported Vacuum

[Doddsy]

Short post. Does anyone know of a UK based entity who can drill the ported vacuum source on a Stromberg CD175?

Long post. My winter project is to (finally) install the Vacuum Advance unit that I purchased over a year ago from British Vacuum in US (great service by the way). I have decided to use a ported vacuum source having read the numerous posts on the subject (is this the most common thread?). Plan A was to use the spare CD175 which I purchased on ebay two years ago which has the ported vacuum source already drilled (at least I know what this is supposed look like). Today I removed one of the original carburettors to switch the body over. Fitting the vacuum advance module to the distributor was easy. However I have now found a major snag with the spare carb. The throttle shaft on the spare carb is thinner by about 1 mm. I need to install the original throttle shafts so everything joins up. I thought I could drill the spare carb body but the seal housings are also smaller so there won’t be any metal left to hold the seals in place.

It looks as if the only way forward is to send the original carb to the US to have it drilled. My reluctance is of course it getting lost en route and not British Vacuums capabilities. The obvious alternative is to stay with the (disconnected) vacuum retard whcih seems a step backwards….

[mgcjag]

Try Burlan..they may be able to help http://burlen.co.uk/?SID=jf7b9a7bjk54ef ... re=default Steve

[madjack4]

Hi im sure u can get any good engineering company to drill and fit a take off the guy at british vac co is very helpful he told me where to drill mine as it happened i fitted a set of new su carbs they had a ported vac fitted .And just leave the advance unit in the distributor it will work ok without vac pipe the advance vac unit has transformed my e type better performance and a good improvement on MPG (25% aprox)

Regards Rob

[Ole-xke1974]

I imagine anyone with a decent knowledge of tools and a drill press can do it. If you were in Annapolis, US I'd ask you to stop by.

[JJC]

If not needed to be done right away, why not send to Joe Curto in New York, US. He is the best in this area, and the only thing you have to deal with is the shipping time. Get cheapest rate to ship, and deal with the guy in America that everyone uses. A genius when it comes to SU's and Strombergs. Best of luck.

Happy New Year !

[MarekH]

Dear Nigel,

You could also just do it yourself. The carburettor body is very soft alloy. As you have a spare showing you how to do it, get a then piece of brass tubing and insert it into the spare so as to see the angle and position of the drilling. You can then partially then drill a very small pilot hole using a Dremel and check with another thin piece of brass tubing that it is at the right angle before proceeding all of the way. Finally, drill the topside with a thicker drill and press an appropriate piece of tubing into the topside. You can even practise on the spare - there is no downside unless you drill all the way through and chemical metal can seal the gap perfectly well if you get it wrong.

Given that ported vacuum is the same as manifold vacuum, but just much diminished or not present under certain circumstances, you could also consider using manifold vacuum but dump the signal if the throttle is closed. Philip posted a picture of one of the valves from an XJS which will achieve that for you.

Finally, if you get stuck, there is a company near me that can do this if you want to pop round sometime.

Happy new year.

kind regards
Marek

[Whitact]

Hi Nigel,
After Marek's post you probably have all the info you need but if you are interested Colin L posted full details (dimensions, angles etc) of exactly how he did his here: http://forum.etypeuk.com/viewtopic.php?p=97258#p97258.
FWIW I had mine done by British Vacuum without any problems at all.
Cheers

[lowact]

Yep, I drilled my own. Here is how it ended up:
The benchmark, what u r trying to achieve, is documented on page 31 of this Jaguar publication: https://1drv.ms/b/s!AiSPBKa26IcchJgz_vFYjJKROLFR9g
This was written for HE engines however is equally applicable to our lower comp engines (the only variation between different engine setups is the static advance).
The following graph is my comparison, of what I achieved compared to this benchmark:

Don’t read too much into the rpm scale, this test is with the car stationary (no engine load) so throttle openings are only a fraction of what would be if u were driving at these speeds. If u did this test while driving the plots would all be compressed into the LHS, below ~2000 rpmish (in theory).
The yellow trace, “CEI manif” is the manifold vacuum from the above publication. Compared to this, my “manifold” pressure is down a bit, I attribute this to engine wear.
My distributor “advance” vacuum is delayed a bit compared to the “CEI distrib’r” vacuum (from the above publication). I attribute this to the positioning of my drilled tapping. The throttle plate is 1.6 mm thick. When closed the inner face/edge is the seal. The plate is slightly angled so only the inner edge seals, there is triangular gap under the edge of the throttle plate when it is closed. I chose to have my drilled tapping immediately outside the outer face. I imagine that if I had drilled closer to the inner face, to be more under the exposed edge of the angled throttle plate, my vacuum would not be delayed, relative to the benchmark.
One possible benefit of the above delay, the surge when the vacuum comes on is more gradual, less abrupt, which reportedly can make it difficult to creep along at idle, only if u have manual car. If this is a problem u could fit a delay valve, part # EAC4025. Despite the differences to the benchmark, my vacuum advance provided a seemingly livelier feel and improved fuel economy, not atm as I have reverted to Opus, my advance distributor is back with my HE engine under development …
Note that the benchmark “CEI distrib’r” still sees ~10” Hg vacuum at idle. This is because it is a regulated manifold vacuum, not a throttle-edge vacuum, ref page 21 of the above publication. This is the last vacuum advance system developed by Jaguar, designed to provide the best of both, the idle/low speed efficiency of a manifold vacuum supply (to the distributor vacuum module), together with the idling stability of a throttle edge tapping supply. May not be easily retrofitted to an E, if the throttle body tapping used to fire the dump valve needs to be in a different position compared to what is provided on our CD175’s.

[Doddsy]

Just a quick update. Thanks all the replies which were really helpful. After much deliberation I have sent my original Carburettor body off to British Vacuum for the drilling of ported vacuum port. I sent the body and thrilled shaft/butterfly only. I will report back on how this turns out as well as how I perceive the difference the vacuum advance makes.

[Doddsy]

Thanks again all for your advice regarding Vacuum Advance and Ported Vacuum on a Series 3. I just want to let everyone know how this has worked out for me. There are a lot of differing opinions on this excellent site concerning Vacuum Advance. This is just to add my tuppence worth and I don’t think of my self as an expert although I have owned my car for 37 years now.

I received the carburettor body back from British Vacuum (in US) which they had drilled and installed the ported vacuum port. Their service and communications were faultless and I cannot recommend them highly enough. I had shipped just the carb body with the throttle plate installed. My concerns regarding customs and duty were unfounded.

The drilled carburettor was quickly rebuilt and replaced. I was able to use the original steel vacuum tube with a vertical bend to connect the new port to the Vacuum Advance module. The Vacuum Advance Model was an easy swap for the original Vacuum Retard Unit. I took the opportunity to replace the choke cables as these were frayed at the carb ends so time for new inners. Not the easiest of jobs but doable with the dash top removed. I also have rebuilt and recalibrated my speedo hence the dash top removal .

I rebalanced the carbs and reset the static timing then rebalanced again and again. I have the Reopus Electronic ignition system. Installing the Vacuum Advance Unit did move the pick up quite a bit which I hadn’t expected. This was easily sorted although my distributor is now on its adjustment limit. I have also now disabled the bypass valves. One was sticking open for too a long time. I replaced the gaskets with blank gaskets and plugged all vacuum connections. I still have the temperature controlled valves in place.

Then it was time for a test run. There was one small issue with the new choke cables fouling and staying stuck on one bank. This was quickly resolved by cutting the excess off the cable inner. You do need special cutters to do this without just recreating the original frayed ends. I have since done a number of runs in the car on a mixture of smaller road, motorways and around towns. In summary I am very pleased with the result. The engine pick up does seem to be a lot smoother in all gears. This could of course be wishful thinking. I have yet to to see if economy is improved however for me that is secondary.

In summary my car is going really well and I would recommend anyone thinking of installing Vacuum Advance to do so. I chose ported Vacuum and this has worked out well for me.