38 replies to this topic

[Dusky]

The big yellow Vizard book describes the 28/36 DCD as a highly functional piece.

He also says there is nothing between it and an appropriate SU they had to do three power runs on each carb and average the results to get any difference. And don’t forget these were all done without having the bonnet in the way. To be able to run a half decent filter you will need a bulge or a cut out.

Like I said not worth it no real power gains bonnet needs modifying and then paint. For about 1 BHP but with less low to mid range torque.

For you. A lot of people find it a lot easier to tune one of these than file a needle. Life and car ownership is about more than squeezing every last horse out of an engine anyway.

[cal844]

Tuning a needle is for a rolling road and su (or carb) specialist... The latter is a hard thing to find.

Edited by cal844, 03 January 2021 - 10:21 PM.

[mini-auto]

I've removed some material from the underside of the inlet manifold about level depth with the pre existing scallop and the manifold is still a way off being flat with the head.

 

I don't think I'm going to be able to remove enough material.

 

In end view you can see that the inlet manifold falls away towards the exhaust.

 

Would it be possible to get an inlet manifold with less or no drop ??

 

I realise that this will lift the carb/air filter towards the bonnet but I'm thinking I'll buy a bonnet to mess with. (add bulge, etc)

 

I can see no reason why I shouldn't dink the exhaust but with the manifold I have I think the dink would have to be quite deep and really I'd rather not dink.

 

 

 

 

 

 

[Dusky]

Iirc mini mania used to sell a manifold that was straight.
How much space do you have between the manifold/carb and bulkhead?
Other option could be to space it away from the head. ( 10 minute 20£ job at a place that has a waterjet cutter to make up some spacers to put between the head and inlet manifold. Might need longer studs then though.
Depending on thickness you’ d then need to use stepped washers or machine (aka grind) a recess in the spacers.

[whistler]

I've removed some material from the underside of the inlet manifold about level depth with the pre existing scallop and the manifold is still a way off being flat with the head.

 

I don't think I'm going to be able to remove enough material.

 

In end view you can see that the inlet manifold falls away towards the exhaust.

 

Would it be possible to get an inlet manifold with less or no drop ??

 

I realise that this will lift the carb/air filter towards the bonnet but I'm thinking I'll buy a bonnet to mess with. (add bulge, etc)

 

I can see no reason why I shouldn't dink the exhaust but with the manifold I have I think the dink would have to be quite deep and really I'd rather not dink.

 

 

Read my post.

[Cooperman]

The choices seem to be to either put a fairly big dent in the ex. manifold centre pipe or change the ex. manifold to an original Cooper S 3-into-1 manifold.

[a lonely peanut]

Nice to see another user going against the grain and using this carb, It's great to see some variety in this area. I put one on my 1969 clubman seven years ago and it has been excellent. Used an ITG filter at first but then switched to a K&N pancake which was better, especially in terms of bonnet clearance.

 

There are other manifolds available but I had great difficulty finding them. I have a Gerrard Mk2, which is much straighter than those 90 degree manifolds and does not foul on the LCB as it remains mostly level, it doesn't have the coolant passage though and is closer to the bulkhead. Never found any information about this manifold though.

 

You could either source a different manifold or as others suggested put a ding in the exhaust manifold. 

[nicklouse]

Looks like the design of the manifold was done working on a cut standard exhaust manifold as of the years the exhaust manifold have  come out of the head straight for longer as they work better. If you are going to continue with this look to a different exhaust manifold.

[mini-auto]

I'm wondering if I could get a tubular manifold manufactured.

Pair of 90 deg pipe bends, maybe a bit of straight pipe between the bends, couple of laser or plasma profiled plates for the connections to the head, a flat rectangular plate profiled to mount the carb.

Possibly use one piece continuous formed bend instead of welding bends and straights. (no weld bead or penetration into pipe bore}

Manufactured from stainless.

Bit like the Janspeed on page 139 of the Vizard yellow book. but with the plate to mount the carb on the top instead of the side.

Fit a heat shield below the inlet manifold, between inlet and exhaust manifolds.

 

I'm sure for optimum flow there'll be some science involved in the positioning (height) of the plate that mounts the carb and the size/shape of the opening and bends, etc.

Edited by mini-auto, 06 January 2021 - 11:03 PM.

[Shooter63]

Put a photo up of how close you are now you've ground the inlet, I bet a bit of heat and a quick wack with a hammer on the central pipe would do it

Shooter

[stoneface]

You could always machine a degree or two off the mounting faces of the inlet manifold so the drop angle is lessened.

Even a 1 degree change would lift it approx 2.5mm at 6"

You might need to do the same to the carb mounting face to make it square/level

[GraemeC]

You might need to do the same to the carb mounting face to make it square/level

 

But then the mounting studs for the carb wouldn't be perpendicular to the face.

 

I'm sure Fusion Fabs could make you a nice tubular inlet manifold, what the cost would be though.....? Probably be cheaper to buy a second Maniflow manifold and modify it. 

Or speak to Maniflow and see if they can make you a centre pipe that bends more sharply at the flange?

Edited by GraemeC, 07 January 2021 - 09:09 AM.

[3VILC]

It looks like its now very close. I like the idea above could you get some spacer flanges made up to push the manifold back further from the head? It doesnt look like you would need much. You would of course also need to space the nut side of the exhaust flanges by the same amount to get the nuts to clamp both manifolds still

[nicklouse]

It looks like its now very close. I like the idea above could you get some spacer flanges made up to push the manifold back further from the head? It doesnt look like you would need much. You would of course also need to space the nut side of the exhaust flanges by the same amount to get the nuts to clamp both manifolds still

Bit then you may have issues with the scuttle panel.

[stoneface]

 

You might need to do the same to the carb mounting face to make it square/level

 

But then the mounting studs for the carb wouldn't be perpendicular to the face.

 

Easy enough to sort, remove old studs and re-drill for helicoils, the drill diameter for a helicoil will be big enough to remove the old thread even at 2 degrees change of angle over 1/2" depth; or drill tap for next size of thread and use stepped studs, or weld up and re-drill and tap.