HEAT RISER UPDATE.

TOM-WA-

Will someone with an operating heat riser on their step down do me a favor?

With the car cold and not running can you grab the weight on the left side of the manifold and tell me what direction you turn it to manually operate the riser.

Do you turn it down towards the ground or up towards the block?


THANKS A BUNCH

TwinH

Well I hope I'm not muddying the thread anymore but I just checked my spare
Twin-H manifolds and viewing from the counterweight end (rear)counterclockwise
is "open" and clockwise is "carb heat". Oh,and by the way my spring must be
installed backwards because its holding the flap "open" sitting on the shelf...

RonS

Twin-h, Disconnect the spring or, better yet, pull the carter pin and remove it. The shaft should have free movement. The weight should, by gravity, drop, opening the valve. Replace the spring so that some tension is against the pin/stud. The spring end should be in a cupped up angle against and below the stud. Tom,looking from the firewall to the front, mine has the weight at 12 oclock when closed and 9oclock when open, NO Spring it will fall to 9 oclock. check the pictures posted by 39

TOM-WA-

Ron:

Are you and twin H saying the same thing... I must be really stupid but it seems to me that you are both saying just the opposite?

onerare39

Tom, they are both saying the same thing.

Spring tension is holding weight up (12 o'clock position)
baffle is closed, exhaust heat to carburetor.



Screwdriver is pushing weight down (9 o'clock position) baffle is open, exhaust heat to exhaust pipe.

TOM-WA-

THANKS SO MUCH...

They say a picture is worth 1000 Words....For the past 2 years I have had
my Heat Riser in the wrong position..no wonder I was cooking the Gas.

Amazing that such a small item can cause so much trouble...

Also its amazing how the written word can also be so confusing.. I think that the
responses I received were equally split..About half were WRONG!!!

TOM-WA-

NOW WHAT?

I positioned the Heat Riser in the OPEN POSITION per your photos and I thought that would solve the problem.....Well it didn't.

Makes no difference either open or closed..The Carb is still getting to hot and
all the gas is vaporizing..


Back to the drawing board

Unknown

Tom

Using your words... a picture is worth a thousand words... posting a picture of your carburetor installation from side, front and opposite side might provide clues to others in their attempts to assist you in diagnosing your problem? :unsure:

Good Luck

RonS

Tom, what carb are you running? have you checked fuel pump pressure? what type of fuel pump. What are the air temps that you are driving in? Does it idle well, or starve for fuel under load or just cruising at steady speed. You may want to hook up a long rubber fuel line hooked to a tee and pull it inside on the seat. Observe what and when the pressure drops. If it drops just before the starvation, you may have a blockage in the fuel line, tank, or gas cap. Fuel pump may not have enough PSI or volumn. I read that these big 308s require 3pints in 30 seconds. Does anyone know for sure? Can the exhaust manifold be at fault? like deposits blocking exhaust exit or Glowing like embers? Is engine water temp OK? Compression check to see if exhaust gases are leaking into the cylinders or intake.

tigermoth

you could just make a blanking plate for the manifold. regards, tom

TwinH

Ignition timing? Retarded timing will really increase the exhaust temps.
Please disregard if your comfortable on where the timing is at,I'm just throwing this out there as a possibility...

brumac

The muffler could also be plugged or the exhaust too restrictive.

Bruce