carb blowing out fuel/air mix

[ed53-+]

just got the 48 ready to fire, have spark, have fuel, timing ? close enough i think. problem is when i kickstart theirs a vacuum
and then there's equal blow out. making me think i have a bad manifold leak or theres leaky valves , before i put the motor together i poured gasoline in the heads and had no leaks. compression feels acceptable , i certain that im gear timed correctly
bendix carb i rebuilt. any suggestions ? out there. thanks for the help

[kitabel]

Compression test results?

[ed53-+]

yup,thats happening tomorrow alonmg with a manifold vacuum test

[58flh]

You want the Manifold leak test!,Vacuum is another entity.--After your tests,check valves for correct movement,also which Bendix do you have & was it a straight-up rebuild?----You probably checked,but lokk down the throat of the carb. & make sure the pump-shooter is streaming down the center of the manifold.I have seen them faced the wrong way & with a Aircleaner on you cant see anything until it spills back out!--Also the 3/8-hole on the top front of the Bendix MUST NOT be blocked by a custom cover!--If it is blocked by the numerous custom aircovers out there -Just drill it & fire away.Just something to check!-I have seen this blocked-off a lot of times over the yrs.--Respectfully---RICHIE

[Cotten]

ed53-+!

You meant "pressure test" and not "vacuum test" the manifold, right?

....Cotten

[steve_wood]

Ed53-+

The manifold pressure test the guys have mentioned is definitely important.

That being said, I seem to recall that my pan did the same thing when it was kicked through. But it fires up just fine. Something to do with the fuel/air flow behaving very differently at slow speeds.

Have you tried actually firing her up? Couldn't hurt to try.....

[old.wrench]

Ed 53,
I wonder if what you are experiencing is just what normally happens when the timing is off a little (advanced too much?). If your timing is off you will get some blowback through the carb when you attempt to kick the motor over. It sounds like this is happening during your first attempts to start the motor after putting every thing back together. If you are setting your timing with a test light, after you set your your point gap and then bring your timing mark into the hole with the front piston coming up after the intake valve closes and set your timer with the light, try rotating the motor through a few cycles while observing the test light and valve and piston position to verify that you've got it just right. First start ups on a new rebuild can be a little tricky. Good Luck!

Geo.

[rrhawg]

It sounds like it's possibly a leaky intake valve. A compression test or better yet would be a leak-down test. You can put pressure to the spark plug hole and see if air comes out the carb, the valves must be closed. You can put it to top-dead center and hold the brake on or taking the pushrods out works also. It could be that a pushrod is to tight or the cam timing is off also.
Rich

[ed53-+]

well i did a cylinder compression, and intake leak test. bad news, 30 psi at cylinders, no leaks in manifold, also i discovered that i hadnt torqued several of the head bolts, ( forgot to finish up after pre-torque sequence) . so i pulled the heads today
poured gas into the valve ports had some minor leakage in the intake, and theirs cracks in the sparkplug c.bore area.
so being an inside machinist of 20+ years , i should be able to deal with this, a friend does the valve jobs, and ill make sure
the surfaces head/cylinders are flat. thanks for all of your input
ed