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MG Midget and Sprite Technical - Inlet manifold. How hot?

OK, this one might be fun.

It is a manifold I'm making for this Morris Minor sidevalve project. Before I get playing too much with the electronic ignition device I've got to have fabricated the manifolds and hung the carbs to ensure they fit within the bodywork. I've made the exhaust system from the manifold off a 'dropped' motorbike plus a laser-cut flange. The inlet is a midget one cut apart and the sleeved from 1 1/4 to 1 1/8 inch by virtue of lathed sleeves that are then hammer-formed (smacked into place) to make the correct shape to the flange. The problem is that the carb end needs to have the sleeve made a bit more airtight and rigid. To do this I need a material that is fuel resistant, rigid without the risk of cracking and also heat resistant. Soooooo...how hot does an inlet manifold get??? Will 250 degree C silicone do the job?

Pic shows half finished exhaust.


rob thomas

...and a pair of carbs but on an unsuitable manifold.
As you can see, the carbs are quite small in comparison to Midget ones and these steel inlet manifolds are too long, leaving the filters too close to the shock. The Midget manifold will bring the float chambers up by virtue of the angle of the intake.


(PS Forget lumiweld. I can't get enough heat into the existing manifold.)



rob thomas

Rob,
Any silicone I've ever seen says not for use in cintact with fuel. Tried to fix the air intake hose on my BMW and there was enough vapor coming back to dissolve the silicone sealer. I'd try to see about an O-ring setup.
Tim Michnay

JB Weld?
David Lieb

1st.

I doubt the intake gets vary hot, esp. if you make a heat shield out of aluminum ally or stainless....most likely warm to mild hot to the touch without serious burns to the hand

2nd I dont understand the question...where are you putting sealicone ...is it between the carb and the intake manifold at the connection of where the clamp is at?

If so Id think just some cork gasket or black compound gasket material will do fine. to seal it from leaking ...just check the flanges with a straight edge for straightness and have resurfaced if need be.


Prop
Prop

David. JB weld might be a good option. Does it really live up to the hype of being good enough for a diesel engine block?

The manifold is bolted straight onto the exhaust mounting flange with a thin gasket so there may still be a lot of heat exchanged, especially after the engine is switched off and the airflow stops. The silicone was an option to go between the inlet manifold body and the sleeve. The inlet manifold 'opens out' quite a bit where it approaches the carb end and this is the area where the sleeve would otherwise be able to move. I've 'mocked up' one in this picture so you have to imagine the 1 1/8 bore tube being flush with the mounting face.

The only other option I have is to find a Frogeye manifold which is already narrowed down to take 1 1/8 H1 carbs.


rob thomas

....and the other end....


rob thomas

This thread was discussed between 21/02/2010 and 22/02/2010

MG Midget and Sprite Technical index

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