Help! High Throttle hesitation

Need a little refresher here, this is what a pro tec to distributor and Holley carb conversion.?

What's the condition of the carburetor?

I'd suspect the same and make a guess that when the secondaries are open that's when your problems start.

I think I'd take it apart for a clean/rebuild as a starting point

Hey, at least you're prepared

I'd just have a good manual/set of instructions but look closely at secondary related items especially, just as a hunch. Cleanliness is your friend.

Plenty of people here with Holley experience to help out with any questions

Don't know if you have a clutch headed screwdriver for the secondary metering plate, they're not real easy to find but you can "hack" your way through the job with a flat blade of the right size.

You made it this far, you're almost there

New cam or reused? Not sure this sounds like proper engine break in procedure.

TRBenj wrote: New cam or reused? Not sure this sounds like proper engine break in procedure.

New, Roller cam.    I was told by the engine builder that the first 20 minutes of run time were the important part, I followed their instructions for that break in period.   I know there are several schools of thought on engine break in, but I would be interested in hearing where you feel I am going wrong, and what to do differently.    I only want to do this engine replacement task once.     I am running Joe Gibbs break in oil, and have ~2-3 hours on the engine.   

Update on the carb situation:    I pulled it apart last night, and began the cleaning process.    I soaked all the parts in carb dip, and everything looked pretty clean.   I blew the orifices of the main body out with air, and a chunk of black goo came out of one of the secondary orifices, so good possibility that was the problem.    I did notice that many of the fasteners were barely finger tight, and that the main jets(?) on the primary side were loose.      Unfortunately one for the alignment pins on the primary metering block fell on the workbench when I took the plate off, so I am going to see if I can find a new metering block as a replacement.    

I also read up on power valves, there is a 2.5 in the carb kit, but from the way I understand it, I want to move to a 4 or 6.5 with my upgraded intake manifold?   I do not intend to go further with upgrades, but with the free'er intake I need a higher number valve, correct?   I appreciate fuel economy, so I am thinking the 4 is probably a good compromise with correct mixture at the higher throttle positions, but not changing the fuel mixture too early.

Roller cam, good. Post cam break in (not needed for roller- flat tappet only), you want to set the rings. You want to load/unload the engine pretty good right off the bat. Don't stay at any rpm for very long- avoid idle (once warm) and no prolonged wot. Constantly varying the throttle is good, but don't be trying to keep the rpm way low.

Fuel/cooling/timing needs basic sorting before you begin, of course.

Kris,
I would use the proven method of Holley power Valve selection!!! The starting point is to check manifold vacuum at idle on a warmed up engine. Divide this number in half.
ex. 13 hg.'s at idle divided by 2= 6.5.
A 4.0 hg. power valve will slam shut at 4.1 hg.'s and begin to lean out the fuel mix as the engine recovers vacuum and RPMs at WOT.
Recommend putting in the 6.0 or 6.5 hg. Power valve that comes in the 4160 Holley marine Kit.
I don't believe you will find a marine based Carb Kit for a 4160 Holley that comes with a 2.5 hg. power valve
Compared to the street version the Power valve, Main Jet sizes and the J Tubes are the main difference in the Marine Carburetor,.Keep us informed!!!!

1980nautique wrote: I don't believe you will find a marine based Carb Kit for a 4160 Holley that comes with a 2.5 hg. Power valve the main difference in the Kit selection,besides the J Tubes, is the power valve selection. Keep us informed!!!!

I don't believe you're right

It's hard to find a later model 600 cfm marine Holley 4160 with something other than a 2.5 PV as the original PV.

Earlier ones a 6.5 was common

You should clean your !!!!! key too by the way

Tim - thanks for advice.   I did set timing etc, and will check it again once I reinstall the carb, and will also dial in the carb with a vacuum guage once it is re-set.   Cooling is working well, all systems were normal during my lake run on Monday.
I have followed the school of thought that rings need seating at all ranges of RPM, when new, so I'll adjust my speed expectations and run a little faster to make sure we set the rings correctly, but will not baby it so to speak.

1980 - sounds like good advice... no Idea where my vacuum numbers are right now, so I guess that you are suggesting I install the 2.5 that came in my kit and replace once I have accurate vacuum numbers?    

Kris, cut and paste this address: "http://documents.holley.com/techlibrary_carb_numerical_listing.pd" into your browser. and use your LIST # and verify required Power Valve.
Does the Carb have "J" tubes on the bowl vents?

1980nautique wrote: Kris, cut and paste this address: "http://documents.holley.com/techlibrary_carb_numerical_listing.pd" into your browser. and use your LIST # and verify required Power Valve. Does the Carb have "J" tubes on the bowl vents?

Hey thanks for the chart   

I've got 7 marine 600 cfm 4160's either on boats or on the shelf   You might call me a hoarder or maybe somebody who likes spare parts

First one is a 6576 list number not on the Holley chart, it's old (from 1976) it's always had a 6.5 PV since it was new

Continuing on list number 50419-1 (have 2 of them) 2.5PV

List 9392 2.5 PV

List 7163 2.5 PV

List 80319-1   2.5 PV

and last but not least a list 75009 with a 6.5 PV

And all those PV numbers are from the Holley chart

When I talked to Holley's tech line a few years ago they told me they purged alot of the older carb info when they computerized

The whole 2.5 pv never made sense to me when they made that switch, especially to old list rebuild kits that used to come with a 5.5 or 6.5.

To have to wait til the vacuum is less than 2.5" before the carb switches from lean cruise to high load, only induces a distinct dull flat spot when you mash it.

Alright,   
There 3 sets of numbers on the horn of the carb, they are:

FIJL-CA
50469-1
3492

I believe the list # is the 3492, but not too sure at this point.    I may try and start assembling tonight, likely going to be tomorrow evening.

So I re-assembled the carb last night and just spent a couple of hours putting everything back together.    I reset the timing at 11°BTDC at 600 RPM.   then adjusted the carb idle needles for 16.5-17" vacuum (600 rpm).    I'll have to wait until tomorrow to throw the boat in the water, but it is running on the hose.    I hope all is well on the top end now, it does start good, and seems to idle nicely.   I did check the idle mixture screws, and they will make the engine die if I get them too far in, so we're running on the idle circuit at idle.    

One more fun fact for Ken The secondary plate seems to have a 59 stamped on it.   the five is pretty lightly stamped, but I think that was the correct number.