popping at speed?
 

at certain throttle positions I can hear my motor making a popping sound.....

is this from being to lean or to rich?

to much advance or to much retard???????

when it does pop it slows down and then goes again...

anyone have a clue?

now that I have my water problem solved its time to work on this......

its not that bad, but it is surely annoying....
I dont like to hear popping sounds.....

im running a 75ocfm carb on a 351w

I have a jetting kit too...anyone got any ideas?

heres some visualization for ya...

If it is a Merc Alpha 1 or an OMC That uses the intermittent kill switch (momentarily cuts juice to the ignition to allow for smoother shifting) I would start there. I had an OMC with this problem once. Sometimes it just needs to be adjusted - in my case the torque of the engine was bending the switch bracket slightly against the lower shift cable, allowing the switch to make momentary contact at high speeds. Another thing to check is your ignition timing. I have seen engines pop throught the exhaust or carb when the timing is too far retarded.

ya I think its the timing too...

my sig says the drive I have....my motor does sort of rev up fast in neutral, but when its in gear and I do it it POPS loudly through the carb....

so if its in gear and i hit the throttle abruptly i hear PAP!
I was lead to believe this was form to much advance?

I guess its form to much retard?
I guess im a retard :p

ill play with the timign a bit, but my motor is already hitting 5300 rpms

I really dont want to advance it mroe so I can hit 5500-5700 rpms and maybe get a couple MPH out of it :cool: ;)

heh, I better be careful with my stock ford valvetrain....

If the igntion all checks out ok , do a compression check. Burned intake valve can cause this. Also worn or wiped exhaust lobe on your cam. Compression test should show something different . I wiped an exhaust lobe and had the same indication:(

you know, I didnt want to think abotu that but my motor does sound a bit weird on the port side......

how do you burn a intake valve?

and how do you wipe out an exhaust lobe?

thanks for any info in advance

Only problem is....its a FORD:D :D :rolleyes: :rolleyes:

thanks for pointing out my problem....:rolleyes:

I beleive this is the technical Q&A forum not the BADGER FORUM:p ;)

If you open the throttle quickly in gear, and you get a pop (backfire) thru the carb, I would suspect the accelerator pump. But if you are getting similar symptoms while running, I would look for a vacuum leak. Do a compression test/leakdown test to make you don't have a cam lobe going away or a broken/ bent pushrod. Are your heads older style or newer style rocker arm studs? Your distibutor cap looks automotive. Check for corrosion at the terminals.
What carb? 750 may be a bit big for that motor.
I looked at your pics closely and see you have an AFB (Edelbrock). Is the secondary air valve working correctly? Where is the hose from the rear of the carb going? Do you have a PCV valve in the valve cover or a wide open fitting with no orifice? Your fuel line and inline filter may be undersized or restricted.
OK I'm getting a headache from thinking too much!

That hose is from the top of the holley fuel pump and goes into the intake(incase the fuel pump blows),

I have a pcv valve on my valve cover with a ball...

the heads are 1975 rebuilt heads??-is tthere some sort of a difference? I think there older style, the block is a 1975 as well.

the carb doesnt have vaccum secondaries it is a manual secondary......I gained 1 mph buy using the 750 cfm carb....from a 600cfm

here are some more symptoms....

after a nice ride on plane when I slow down(FOR A NO WAKE ZONE) the rpms go down and then back up to the regular rpm's it does this for a couple minutes then goes back to normal idling.

and then theres the abrupt throttle causes that PAP noise I said before....

and the high rpm pop........

timing??????

I dont think its my carbI hope its not a burned intake valve....

how do you burn a intake valve?

by the way this motor is fairly new, 46 hours on her....

david, there are 3 separate articulation spots for the accelorator pump,
are you thinking its pumpiing to much gas in the motor, and thats why I get that PAP sound?

what about the poping sound when im on plane?

it does it when I keep the throttle in the same position for a long period of time...

anyone else have suggestions?

I know the carb is mech secondaries. There is an air valve similar to the air valve in a Quadra-Jet in the secondary bores that restricts air flow if you open the throttle fast at low rpm's. It functions (opens) when airflow increases sufficiently to pull fuel from the nozzles. There is no accelerator pump in the secondaries, and if you modify the air valve function, you will get a flat spot (bog) or backfire when you open the throttle fast under load.
The rear hose attachment on the carb is for a power brake booster. You are correct about the small line on the fuel pump. It is possible that with your fuel pump vent hose attached to a vacuum source, it may be causing the fuel pump to not work to full capacity and cause low fuel pressure, resulting in a low fuel level in the carb, which can causes a lean mixture, which could cause backfiring thru the carb.
Some of the early Ford small block heads had adjustable rockers vs. non-adjustable. Cam changes (smaller base circles) can create adjustment problems with fixed adj. rockers.

beerock,
If your motor sounds a little funky on the port side , check for a loose or broken rocker or bent pushrod on an exhaust valve. If the exhaust can't get out it will cause a popping on the intake side. Been there , done that:rolleyes: more than once:( . Once was a rocker starting to split and was actually bending back from the split. Another time it was a bent pushrod.
Sometimes there is no other reason but Gremlins in the motor causing these things to happen:rolleyes: .

Hey bee,
It's me again, I was just studying yuor picture.:confused: What kind of exhaust manifolds are they?? Can't say I've ever seen anything like that in a boat. (and I once owned a Ford too).

there glenwood lceramic coated og style headers

I have been told they restrict HP- about 30-40HP but the only company to make bassanet type headers is CMI and they cost 5000 :eek:

the glenwoods look really sharp though

Hey mopower- friend of mine lives in Pitman -Myrtle street

here another pic of the headers.

ok dave and I were chatting on aol

check this out....
the guys I bought the holley marine fuel pump form toldme I could run the fuel overflow hose to the intake.....

dave says the vaccum woudl cause the motor to fall on its ass being that the fuel pump would not be working correctly....


see the line going into the intake?

well thats form the fuel overflow on the fuel pump....

I hope thats the problem.......

Dave, I live on Spruce ave. a few blocks from Myrtle:cool: .

I'll have to look you up next time I'm over that way. BTW- did you see the "24' Scarab" for sale on 322 near the 7-11 a while back? Turns out to be a Nova with no windshield.

Just look for the 272 SR1 in the driveway along side the house.White with black,teal,and magenta stripes. Missed the "Scarab", I don't get over in that direction too often. Traffic on 322 can be a pain in the @$$:mad:

I'm thinking that hose isn't the problem, then again... I'm more inline with Mopower's suggestion of valve related problems especially since you said it does the popping at steady throttle. Timing and carb usually go with accelleration. Popping anytime often comes from burnt or bent valves OR broken/weak valve springs which are easy to check and replace.

Note the threads on Merc HP-500 carb motor's valve springs. Very similar and I've personally changed some in a friend's HP that wasn't revving right/popping. Make sure your springs match your cam requirements. What did the shop that rebuilt them put in?

Keep us informed with your findings.

Scott

Try unhooking that vent line going to the intake first. The suction on the back of your (fuel pump) diaphram is a problem. It should go to the air cleaner.
JB

Do you have ignition points?

BT :cool:

I say cam lobe. Mine did the same thing. It will get worse and then you will know. Check for milky oil. Mine leaked at the riser and washed the cam with water/oil, Took the lobe right off.

I never thought of checking the valve springs...

the springs work with the cam I have.....

I didint get a chance to play with the vent line this weekend...

Ive had my eyes on a set of gt-4o cast iron heads for it that go for 500+ I luv ford racings stuff.....

are there any heads that are better then the CAST IRON gt-40 heads? and for a nice price around, 500+?

I have a extra set of ford heads that I could get worked on but I would only work them if it was economically viable, you know bang for my buck kinda thing....

the ignition is all electronic(MSD 6t with rev control box) with a msd distributor/mechanical advance...
and a accel coil.

I'm hoping its the fuel overflow hose.....
and a bit of a timing issue....

I know its not suppose to pop if i hit the gas abruptly and ive been told its a sign of to much retard...:p hehe I think im just being retarded.....

had a nice weekend......
went out in 4-6 foot rollling swells......

I get my 24pitch prop this week....

Cant wait to try a nice new prop .....

my aluminum prop is so freakin shot out.......
gouges and one of my blades is bent from heating the blade up ....to much from cavitation....

I should be in 55+ range hopefully close to 60 MPh then ill get the pitch turned up to 25 or 26 ....... woohoooo;)

Ever find the issue?

Fuel pump vent hose should go ABOVE the throttle plates into the carb. That way, if you rupture a diaphragm, the gasoline goes into the motor - not into the bilge. But you cannot run that hose to a vacuum source or it will suck the diaphragms closed on the pump. If you have a marine carb, then you have the correct fitting on the carb to connect the hose to. If you do not, you can run a piece of hard brake line into your flame arrestor and have it aimed into the carb primary throat and hook the hose to that.

You can easily check to see if you are collapsing the pump diaphragms by disconnecting the hose from the intake - plugging the intake source that you were using, and running the boat with the hose not hooked to anything for a few minutes to see if that fixes it.

If that doesn't fix it, check your water separators for water (fuel filters..).

MC