Now that I am getting closer to assembly of the car I have been thinking of my issue with clearance of my carbs under the bonnet.
Its taken a bit longer then anticipated to finish the frame since we left our house in the Boston area and went back to Wisconsin during Covid.
I have rebuilt the motor with the increased bore (30 thou over, 9.5 to 1 instead of 8.75 to 1) high compression pistons, hotter cam and head rebuild with new valves, guides and seals. This should increase the HP well north of the original 78HP.
I have the original HIF carbs (in rough shape) a set of HS6 carbs that were used on an old MGB race car with a ported MGB SU intake and adaptors (very thick) as well as a Cannon intake adapted to EFI with a custom box and Toyota throttle body.
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IMG_0718.JPG
Note the HS6 carbs have had extensive work- intake port blended. TB bore smoothed, and the intake manifold ported and smoothed.
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Cannon EFI intake- front view.jpg
The motor now sits below the top of the scuttle but the SU style systems are too wide which will place the intakes to the carbs thru the side of the bonnet. Great for cool air intake. Not good for driving in the rain!
The Cannon EFI system I purchased has an unusual config and I have no feedback as to how or if it ran. I think the adaptor box and TB are not smooth transitions. The stock Weber DVG carb which is the usual conversion for the MGB is a poor substitute for the SUs, typically rougher running and result in a drop in performance.
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Cannon EFI 1.JPG
The DVG style throttle body will set on top of the Cannon intake in place of the custom box and is actually shorter than the DVG carb! I would have to place a 90 degree boot on top to route air thru a filter box.
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IMG_0745.JPG
Note the thick phenolic adapters. Those flat washers at the manifold mounts are temp for staging- too thin for use.
My problem and the reason to ponder these choices is the HIF and HS6 systems will protrude thru the bonnet. I can swap out the complete SU intake manifold to a race style SU HS6 manifold and stock thickness phenolic adaptors. It would pull in the HS^ carbs almost 2", but it would still leave no room for the air cleaners. And some of the MG folks say the HS6 SU carbs are too much for even my motor running on the street. Others on the site say they are a bit much but should work.
As configured, the Cannon would protrude as well. But after some research I discovered I can replace the custom box and throttle body with early VW GTI DVG style throttle body (straight bolt on) and it will fit under the bonnet. Plus I will have the enhanced running of EFI. All MGB motors will benefit from adding EFI- that's a given. But the cost vs benefit for this application is in question.
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VW DVG TB.jpg
My request for feedback here is:
Have any of you any experience with converting to EFI on an MGB?
Any one used HS6 on a modified MGB motor?
What have most of you been running for the ECUs on custom systems?
I am thinking of the Microsquirt system. Anyone have experience with programming this unit?
Thoughts?