[DeTomaso] Great new brakes, but stalling when braking

[Will Kooiman]

That's exactly what happened to me.

New Holleys come with the flute, but not the jet extensions.

I hit the brakes hard with the air filter off and watched a bunch of gas
come pouring out the boosters - not the vents tubes.

It helped a lot to lower the float level.

It completely went away when I leveled the carburetor.  I did it with
redneck engineering.  I bought a plastic 2" carburetor spacer and sanded it
with a belt sander until it had the right angle.  I kept checking with a
level until I was happy that everything was okay.

A better solution is to mill the carburetor pad on the intake.  I didn't
want to do that because I had a fairly rare intake.

You don't have to bend the carburetor studs or redrill the manifold.  You
can keep them at the original slanted angle.  You can redrill to be
perfectly perpendicular if it bugs you, but the slant isn't so bad that you
can't keep the original holes.  I know - more redneck, but it works.

-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of Mikael
Sent: Monday, May 28, 2012 10:41 AM
To: detomaso at realbig.com
Subject: Re: [DeTomaso] Great new brakes, but stalling when braking

Thanks for input everybody

Today's progress:
Tried a rubber hose from one vent to the other, hole up in the middle, no
difference. That made me quite sure it was a primary lean issue more than a
secondary rich (from fuel dripping) issue. But just when I made that
conclusion and did another test downhill, I noticed a black cloud when
restarting. Apparently not from the vent tube flowing over, but...? So drove
home, took the carb off, held it at a 45 degree angle, and yes, fuel dripped
out the rear venturis. Took the carb apart now that I had it off, because I
was thinking about adding jet tubes and flute to the secondary, but it was
already installed. Guess some previous owner had the same issue? I also
remember now that when I got the car and checked the floats it was way off
(but so was the timing and the rest of the carb), maybe the rear float was
lowered to avoid this issue.

One way to find out. Lowered the rear float one turn, and testing. And it's
much better. I can still stall it if I try, but it needs a long emergency
stop to get it to stall.

So it was too high float, combined with Holley's fundamentally flawed design
(A Rochester has the fuel bowl in the middle, and even then it has a plastic
insert that prevents the fuel from slushing around!). Since the jet tubes
and flute are already installed, I guess the only remedy is lowered float
level or angling the intake manifold. On the first, there's a reason the
float level should be up to the hole, but when I tested 5-6000 rpm in 2nd
gear with the new lowered float, it ran fine. On the second remedy,
currently the carb tilts a little forward, maybe I should get the intake
grinded next winter. Not now.

And Mike if you're reading this, yes I know you told me secondary float
height from the start :-)


Mikael



-----Oprindelig meddelelse-----
Fra: bill gaino [mailto:gaino at earthlink.net] 
Sendt: 27. maj 2012 15:02
Til: Mikael; detomaso at realbig.com
Emne: Re: [DeTomaso] Great new brakes, but stalling when braking

Mikael, have you tried a "slosh tube"?  Cut a piece of fuel line and stick
it on each vent tube.  Some carbs have longer vent tubes, always keep an eye
out for them and aquire when you find them.This will form an arch over the
carb. Now cut a hole in the top of the tube to let air in. The idea is that
the fuel will slosh to the front bowl rather than dump into the carb opening
and flood. We used this simple setup drag racing.  Try that.  Bill 1362

-----Original Message-----
>From: Mikael <mikael_hass at mail.tele.dk>
>Sent: May 27, 2012 5:03 AM
>To: detomaso at realbig.com
>Subject: [DeTomaso] Great new brakes, but stalling when braking
>
>First, let me explain why I know I have this problem. I've installed 
>Dennis Quella Willwood brakes this winter, and they definitely work. So 
>I've probably made more hard stops than ever. Great brakes.
>
>But the engine stalls when under hard and long braking. I've read the 
>forums about this, and suggestions include:
>Too lean, richen idle
>Front float too low, raise
>Rear float too high, lower
>Ignition too retarded, advance
>Brake booster vacuum leak
>Other vacuum leaks
>
>I've tried most of the above with no luck. It should be said that with 
>my cam profile from hell, it only sees 10 inches of vacuum at a nice 
>steady four corner idle around 900 rpm.
>
>In the end I tested something a bit scary, going very fast in reverse 
>and hard braking. And then it doesn't stall! That to me says that this 
>is indeed a fuel gravity issue, but I have no idea how to fix it. 
>Somebody wrote about jet extension (since those idiots at Holley put 
>the jets on a wall instead of on the floor like a Rochester or Summit 
>carb), but others were against it because then I might get fuel 
>starvation when accelerating hard, a much bigger problem.
>
>Any ideas?
>
>Mikael
>
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