What carb mods are required with .030 over and cam?

[sam60]

I had my 454 bored .030 over and changed the (marine mild Rv?) camshaft. I have nothing to compare it too as the boat was seized at purchase. It would modulate the rpm upon throttle on the only trip out and I wonder if the stock Holley 750 should have the jets upsized for the changes.

When running in the driveway, I get a big sucking sound when it is dyeing as I throttle up. The ignition is a new upgrade to the Delco Voyager.

 

[Black as]

Re: What carb mods are required with .030 over and cam?

I had my 454 bored .030 over and changed the (marine mild Rv?) camshaft. I have nothing to compare it too as the boat was seized at purchase. It would modulate the rpm upon throttle on the only trip out and I wonder if the stock Holley 750 should have the jets upsized for the changes.

When running in the driveway, I get a big sucking sound when it is dyeing as I throttle up. The ignition is a new upgrade to the Delco Voyager.

When was the last time you overhauled your carburettor ?

The thing is with boats and carby's its best to check the colour of your spark plugs black is rich white is lean and brown is o.k.

 

[sam60]

Re: What carb mods are required with .030 over and cam?

When was the last time you overhauled your carburettor ?

The thing is with boats and carby's its best to check the colour of your spark plugs black is rich white is lean and brown is o.k.

It's all either rebuilt or new. Rebuilt carb, engine, new plugs along with completely new ignition. I think it's down to jetting of the carb. It was in storage with water in the cylinders and bad gas for 4 years. Went through all of it, except jet size change if required.

Holley 4160.

 

[wtsgems]

Re: What carb mods are required with .030 over and cam?

A 750 cfm Holley should be able to keep up with a 454 even with a different cam and .30 over. not being a critic. but how sure are you everything is set right with your valves. are you able to idle long enough. to warm up your engine. Holley. carbs are cold blooded. Tend to load up
I would do a compression check and retime before. switching carbs are you or have you had some backfires when timing last time if so you could have bent a metering rod.
backfires and Holley carbs don't get along at all. check and make sure your carb linkages are set right maybe your opening your back barrels to soon flooding if your running real rough. and can't seem to smooth out no matter we're you move the distributor you might be 180 out.

 

[sam60]

Re: What carb mods are required with .030 over and cam?

A 750 cfm Holley should be able to keep up with a 454 even with a different cam and .30 over. not being a critic. but how sure are you everything is set right with your valves. are you able to idle long enough. to warm up your engine. Holley. carbs are cold blooded. Tend to load up
I would do a compression check and retime before. switching carbs are you or have you had some backfires when timing last time if so you could have bent a metering rod.
backfires and Holley carbs don't get along at all. check and make sure your carb linkages are set right maybe your opening your back barrels to soon flooding if your running real rough. and can't seem to smooth out no matter we're you move the distributor you might be 180 out.

It idles smooth and hesitates on throttle up.

 

[Bondo]

Re: What carb mods are required with .030 over and cam?

It idles smooth and hesitates on throttle up.

Ayuh,.... That's usually a lean condition....

accelerator pump,..??

 

[wtsgems]

Re: What carb mods are required with .030 over and cam?

Could be
This is the hardest part of a engine rebuild tracking all the little bugs I am not a master mechanic more of a shade tree learn from mistakes one.
But I have found that sometimes you need to back up and go back to the basics
You don't want to be throwing parts at it and hope one sticks.
I don't know your experience or how much you played a part in rebuilding the engine so please don't think I am talking down to you. I think this part of the rebuild can be the most difficult tracking down the little bugs.
Going by what you have said you here then engine sucking air when the throttle up and it dies.
The first thing are you using the remote to throttle or directly unhook the remote and move the throttle directly ( just don't have your face over the carb) The next thing i would ask is are you letting the engine warm up completely and I would hope you have installed a thermostat? shoot the thermostat housing with a laser temp gun.
Back to the basics check the timing and timing advance. Reset and adjust the carb to factory specs check the needles make sure the o-rings are good and the needle isn't buggerd. Check and measure you linkages and linkage timing. Those back barrels shouldn't be opening that fast. It has been a while but if I remember correctly part of the choke system actually blocks use till the engine warms up.
You could have your float adjustment wrong Holley carbs have two bowls primary and secondary the primary is your normal operating bowl secondary is for when you open the back barrels.
When you say your throttling up are you going to full throttle or is it cutting out at even a gentle throttle?
I would check out these links also http://holley.com/TechService/Instructions.asp
I have another question was your rebuild kit a Holley kit or an after market?
Check this site too
http://www.bob2000.com/carb.htm

 

[sam60]

Re: What carb mods are required with .030 over and cam?

Could be
This is the hardest part of a engine rebuild tracking all the little bugs I am not a master mechanic more of a shade tree learn from mistakes one.
But I have found that sometimes you need to back up and go back to the basics
You don't want to be throwing parts at it and hope one sticks.
I don't know your experience or how much you played a part in rebuilding the engine so please don't think I am talking down to you. I think this part of the rebuild can be the most difficult tracking down the little bugs.
Going by what you have said you here then engine sucking air when the throttle up and it dies.
The first thing are you using the remote to throttle or directly unhook the remote and move the throttle directly ( just don't have your face over the carb) The next thing i would ask is are you letting the engine warm up completely and I would hope you have installed a thermostat? shoot the thermostat housing with a laser temp gun.
Back to the basics check the timing and timing advance. Reset and adjust the carb to factory specs check the needles make sure the o-rings are good and the needle isn't buggerd. Check and measure you linkages and linkage timing. Those back barrels shouldn't be opening that fast. It has been a while but if I remember correctly part of the choke system actually blocks use till the engine warms up.
You could have your float adjustment wrong Holley carbs have two bowls primary and secondary the primary is your normal operating bowl secondary is for when you open the back barrels.
When you say your throttling up are you going to full throttle or is it cutting out at even a gentle throttle?
I would check out these links also http://holley.com/TechService/Instructions.asp
I have another question was your rebuild kit a Holley kit or an after market?
Check this site too
http://www.bob2000.com/carb.htm

The engine was seized with pitted cylinders, carb was full of varnish, electric fuel pump was non-functional, spark plug gap was .0RUST" and ignition change was to eliminate obsolete spitfire module, so most parts were thrown at it out of necessity (no offense taken). It was a factory Holley rebuild kit. We had it out once before winter and it ran fine at idle (Warmed up as much as the 140* stat allows) and mid-top rpm. Warm or not it would surge when throttling up.

Distributor is installed with cylinder 1 at TDC on the compression stroke. Timing is to spec.

I Will go back through the carb. and check everything, thanks.

Bondo-I will check the air/fuel for a lean condition as well.

 

[wtsgems]

Re: What carb mods are required with .030 over and cam?

Lol didn't mean you were only that you didn't want to start.
Holley. does have a marine 750 cfm for 450 not sure of your linkage setup
online specs showed a 750 to 800 cfm specs for the 454 my dads dodge. challenger only had an 800
I actually was talking to him this evening and he suggested watching your fuel pressure drops below 4 Psion and that could be your. problem

 

[carguy5068]

Re: What carb mods are required with .030 over and cam?

Im not much on omc outdrives but have run holley carbs for years and it sounds like power valve. located in metering plate. one good backfire will wipe one out is your carb vacuum secondary or double pump? choke adjustment is very critical on a holley also. especially if electric. with engine warmed up loosen the three screws holding electric choke down with motor running and choke wire connected rotate round black plastic till it runs the best. from there move to your float level adjustment remove float bowl plug or sight plug and adjust float level till fuel barely flows out site hole. on both ends of carb. adjust 4 corner idle circuits but not if idles smooth already. as far as jets go im pretty sure i ran 74s on the primary side and 76s on the secondary but mine was double pump with 4 corner idle circuits. on an engine built much like yours and ran perfect in a heavy chevelle with automatic. the edelbrock rpm 850 cfm quadrajet model 1910 would be perfect on your boat if you were thinking of swapping carb out. the smaller primarys make them economical for cruising and the huge secondarys give them a broader powerband

 

[sam60]

Re: What carb mods are required with .030 over and cam?

Was able to get back to it this weekend and it was just the accelerator pump lever was not in position properly.:facepalm:

Runs great on muffs, no more hesitation or sucking air sound. We'll see next week how it is on the lake.