Roadster LWB Marina 1.8 TC air filters and preventing carbs from over heating

[listerjp2]

Hi Adrian

1) Your engine is a 1275cc A series, not a 1798. B series.

2) Your engine is a single carb set up & not a twin carb set up.

The twin TR7 carbs being of larger size , according to Peter Burgess book give less low down torque on a standard 1798 B series engine than the twin 1. 1/2 SU's. It is for that reason they weren't usrd as standard on MGB's.

However if the cylinder head has tripple valve seats, been ported and gas flowed with a long cente branch manifold & a cam such as a piper 270 . Then the TR7 carbs will improve matters.

So my point is it really depends on whether the B series is standard spec or not.

I have rolling road tested many engines. Both the A series & B series engines gave between 2 & 5 hp with water injection.

The key thing here is to get as much cold air into the intake, being drawn from the front of the car, ideally with a large bell ram pipe on the grill end of the hose.

In the future instead of my current pancake filters. I plan to use an area on the offside to mount an airbox with filter, possibly using the cylinder head studs to attach some bespoke brackets. The cold intake from the front enters the airbox , which might be from a puma 1.7. then the large outlet goes to something similar to GGrum's stainless steel fabricated unit on his Alfa engine.

However the air feed to the air filter box (originally from the puma 1.7or Fiesta Mk4),will have to travel either over the engine or at the back of the engine between the cylinder head to bulkhead space and then feed into the carb fabricated air box at the rear or on the top of it. The limiting factor to the routing is that the Puma 1.7 intake hose diameter is very large and it therefore might not fit under the Bonnet/ Rocker cover space , as there needs to be some clearance also there too from the hot engine below it. It is therefore likely to need to have an air entry point into the fabricated carb box at the rear,rather than the top.

Point taken.

[listerjp2]

Thanks for the update. looks like an interesting option to consider.

I found this picture online and if yours is this close then I would plum for the tea strainer option for the left hand carb.

Adrian

[martinclan56]

Good find that as it shows the problem well.
I think you would have to use the tea strainer option for both carbs otherwise they would flow differently?
However it still doesn't really solve the problem of getting cold air into the carbs. I am seriously thinking of cutting the bonnet side panel to do that. Relatively easy in my case as I don't have louvers. But how to make it look aesthetically pleasing? Hmm....

[redmonty]

I found this picture online and if yours is this close then I would plum for the tea strainer option for the left hand carb.

Adrian

Many thanks for finding and uploading the picture, that is an option I had originally considered, but I would be interested to see what they had done to the bonnet edge to accommodate the ram pipe head? Also if only one ram pipe draws air from outside the bonnet and one is inside, will this affect air flow/air temperature onto one carb more than the other?

At the moment I will try to get it running before doing any mods. In the build manual it talks about cutting the insulating carb spacer blocks in half so they are 10mm thick, so I wonder if adding the boat bilge pump fan blowing cold air over the carbs combined with my aluminium heat shield will be enough to stop fuel vapourisation in the carbs when hot and stationary if I have reduced depth 10mm insulating carb spacer blocks? If so I may be able to gain a few precious mm.

I also found an interesting cobra head air pipe which, if they only did the right diameter, may have fitted a very stubby ram pipe and if the end of the hose was cut down a bit to reduce its depth, who knows?

https://www.speedingparts.co.uk/p/engine-tuning/silicone-hose-hose-clamps/cobra-head/cobra-head-25.html?_gl=1*1mcmd9q*_up*MQ..&gclid=CjwKCAjwyo60BhBiEiwAHmVLJVgjL5xPlGF_d1cqrDSL69C00lRqM-QZgaNoH16mQXw5wykLDqm0choCz2QQAvD_BwE

I found these stub stacks on Ebay which could be worth a punt at £9.99 for a pair? Just need to find out how deep they are.

https://www.ebay.co.uk/itm/200962949913?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CEznwNDXSmu&sssrc=2047675&ssuid=lTPTSxt5TUG&widget_ver=artemis&media=COPY

[listerjp2]

Many thanks for finding and uploading the picture, that is an option I had originally considered, but I would be interested to see what they had done to the bonnet edge to accommodate the ram pipe head? Also if only one ram pipe draws air from outside the bonnet and one is inside, will this affect air flow/air temperature onto one carb more than the other?

At the moment I will try to get it running before doing any mods. In the build manual it talks about cutting the insulating carb spacer blocks in half so they are 10mm thick, so I wonder if adding the boat bilge pump fan blowing cold air over the carbs combined with my aluminium heat shield will be enough to stop fuel vapourisation in the carbs when hot and stationary if I have reduced depth 10mm insulating carb spacer blocks? If so I may be able to gain a few precious mm.

I also found an interesting cobra head air pipe which, if they only did the right diameter, may have fitted a very stubby ram pipe and if the end of the hose was cut down a bit to reduce its depth, who knows?

https://www.speedingparts.co.uk/p/engine-tuning/silicone-hose-hose-clamps/cobra-head/cobra-head-25.html?_gl=1*1mcmd9q*_up*MQ..&gclid=CjwKCAjwyo60BhBiEiwAHmVLJVgjL5xPlGF_d1cqrDSL69C00lRqM-QZgaNoH16mQXw5wykLDqm0choCz2QQAvD_BwE

I found these stub stacks on Ebay which could be worth a punt at £9.99 for a pair? Just need to find out how deep they are.
https://www.ebay.co.uk/itm/200962949...mis&media=COPY

Try to keep the airflow the same so these could work. If all else fails just leave then without any cover.

Even if you have an electric fan for the rad make sure you still have the original fan as this keeps the hot air moving out of the under bonnet area. OK takes a few HP from the engine but stops any overheating.

With restricted space I still would go for tea strainer for both carbs.

Adrian

[redmonty]

Good news... it has been over 10 years since this car was last started and 20 years since it has been driven. After over 9 attempts today to get it started and replacing coil, condenser, cleaning points, checking circuits and cleaning up ignition related spade connectors, it started :-)

Next step sorting out clutch hydraulic cylinders and brake cylinders. Then fixing leaking fuel tank. Hopefully I will be able to get it on the road soon after waiting 20 years.

[rhysnolan]

Lovely looking front wings by the way! I sell a blower kit, everything included. Normally for race seats where cool air can be blown into the lumbar region.

[redmonty]

Lovely looking front wings by the way! I sell a blower kit, everything included. Normally for race seats where cool air can be blown into the lumbar region.

The wings were the work of the guy who originally built the kit. He made some small moulds for the front rounded edges and grafted them onto the wings. How much are the race seat blowers and do you have any pictures of the kit or website with details of what is included etc?

[rhysnolan]

The wings were the work of the guy who originally built the kit. He made some small moulds for the front rounded edges and grafted them onto the wings. How much are the race seat blowers and do you have any pictures of the kit or website with details of what is included etc?

If you got to our site Racetech Europe and use the phone number you will be speaking to me.

[redmonty]

If you got to our site Racetech Europe and use the phone number you will be speaking to me.

Apologies, just spotted your response Rhys. Will have a look once sorted the numerous other tasks to actually get the car to move and stop!