WMH carbs, running too hot in the midrange? What do I do?

[RUNWME]

The Carbs are WMH and there is the number 2 nearby the WMH but not inline with the rest of the part number.
Carb part number is 3311-821687C

Have them on a Ported 2.5 with 125 psi compression.
They had 66 main jets and engine would go over 1250 when wide open. I drilled out to 76 drill hole and EGT at wide open throttle is 1100 degrees (ok)

The problem is these carbs bury the temp gauge 1300 at cruising RPMS.

They have jets in coming in the front. (air bleed?) I noticed that the velocity stacks patially cover the lip leading to the airbleed jets (see picture)

What can I do to these carbs to get cooler midrange temps?

ANY help is appreciated ! I want to get it cooler by the weekend :)

Thank you
David

Also I need a cam and rod for these carbs. The old carbs cam pushed up. These the cam needs to push down. I have it rigged right now where it works. Getting full throttle and full timing.

[XTB21]

What size are your progression jets?

[RUNWME]

Which are the Progression jets? Are they the ones coming in the front I was calling airbleed jets?

I can pull them out and look tonight. If it effects midrange, would I need to enlarge or put smaller jets in place to cool down midrange?

THANK YOU
David

[RUNWME]

You know what sucks about this problem is that it wasn't a problem before I added EGTs gauges.

Sometimes Ignorance is BLISS !! This engine runs beautiful, no lean surge, and if I didnt have EGT telling me there was a problem, I would never worry about it!

[Dave S]

Drill a hole where the jet is covered.:)

[RUNWME]

Thankyou for the responce Dave. I ran the carbs with the velocity stacks off and still no real change.

WOT temps are fine. Midrange is still too hot. :(

This weekend is first nice weekend on forecast in 12 weeks!!

I really hope someone has an answer I can put into effect today!

Thanx,
David

[XTB21]

Did you find out what size your progression jets were?

they maybe too big!

[RUNWME]

The jets going into the front of the carb They are the jets visible in my picture (are these progression jets?) They are size .040

Will buying smaller ones richen up mid? if so what size do you
recommend?

Thank you!
David

[235spd liner]

you may not have the mid timing up retarted timing will show high egt.............. just a gess good luck

[RUNWME]

That could be something to check. I didnt have the correct cam to run factory linkage so I rigged it where the throttle opens linear with the throttle cable. (can see alittle bit of it in picture)

At what RPM should you have max timing?

[XTB21]

I run pretty much the same setup 245hp with wmh 1's the book says that the progression jets take over off idle my jets are 66's, the air jets are reversed from the fuel jets though bigger = leaner
smaller = fatter

[RUNWME]

My main jets are drilled to .76 (were 66) and this took care of wide open throttle range.

I wonder if putting larger progression and larger fuel jets would be the answer, or if smaller progression and smaller mains would help.

Or would I be simply keeping same curves with no real net effect.

I am going up to the house to check timing now....

[RUNWME]

Originally posted by 235spd liner
you may not have the mid timing up retarted timing will show high egt.............. just a gess good luck

Looks like a good geuss! I took hood cover off STV and opened the throttle. I noticed it went full timing BEFORE throttle blades started opening.

Then I went to Cougar and opened throttle. The timing advanced at same rate as the throttle and it was 1/2 throttle before full advance. At cruising it would have only had approx 15-17 degrees of timing.

If low timing causes high EGTs, then I think you have found my problem. I will drop it in the water tonight (weather permitting) and test it with timing locked at 25 degrees :)

Thank you
David

Are the EGTS high because unburned fuel going out of engine?

[XTB21]

Sorry bout the mix up i meant my progression jets were 66's mains are 68 which is standard from the book for a 93 245

[235spd liner]

no it would not be unburned it will be burning still on the way out = high egts some of my nos power cars we run the egts at 1500
bc the timing is pulled back like at 15 but that is with a lot juice like 500 hp................. good luck

[Talon2.5]

heres the off idle circuit if ya need it............

[Markus]

I have no experience with Merc. carburators, so I cannot tell you what jet sizes you need. However, I can tell you how carbs work and what you can to do:

Air jets (or air bleeds) have more effect compared to fuel jets the higher the flow, because of the properties of gases versus liquids.

Therefore, your air jets will have comparatively more impact than your main jets on higher RPMs.

Consequently, one solution to your problem is to put in larger main jets as well as larger air jets. That would give you more fuel in the mid-range from the larger mains, whereas the larger air jets would lean out the engine on the top.

I do not know what throttle openings you use in the mid-range, but if you have a small throttle opening, another solution is to put in smaller air jets for the off-idle circuit

A final remark, though: Before going through the hazzle of re-jetting, read your pistons and/or plugs to make sure that you really are lean in the mid-range.

There have been a number of posts here over the years about how to read pistons. For reading plugs, check out the excellent article by Gordon Jennings on my links page (see below). However, you need to put in fresh plugs right before you start testing to be able to read them.

[RUNWME]

Thanx guys.. I am sneaking up on it and getting pretty close to acceptable! Now its fine tuning. :)

David