engine guys,,,build 468 won't run out
 

I built a 468, gen 4 with the following;
wiseco 9.5 forged pistons, crane 731 roller cam, full roller motor, dart alum heads, correct isky springs, 325 runners, 121 chambers, dui dist.single plane intake, holley 850 double pump,, rex aluminum exhaust manifolds. ,,,runs good, idles good, runs cool at 150 degrees, 60 psi oil pressure, 4,ooo rpm at 3/4 throttle, but no change applying full throttle. last year 21p prop turned 4700 with stock 454 mag.
Thought it was fuel pump, installed new holley electric, shows 7 psi.. At wot , fuel flow shows 23 gph,,,,,could the heads be too big for a 468 ?? yes the throttle is fully opened, ect. Same boat, same prop, 1988 265 Force. Would appreciate opinions from knowledgeable engine guys. Thanks,
Dale

Whats the full advance on the timing and @ what rpm........I ran AFR 305's on 540's

Same prop ?
What is your fuel pressure at Wide Open and top rpm ?
Also, as asked, total timing ?

36 degrees,,,full in at 2500 I believe

mid range seems good

will check fuel pressure at both tomorrow,,,,,,,,36 degrees timing

I had two 509's with the 741 cam and I thought they could use a little more cam.
You might be running out of cam, that and the heads are a little big. I am running AFR 357's on a 598 solid roller.

plug gap is .055 as dui recommended, ( I thought it was big ) ran stock wire from ignition to trip a 35 amp relay , #12 direct from the battery to the relay then #12 to the dist
Same prop, 21p bravo 3 blade
I should have consolidated the answers,,,,,sorry,,,,,,

Id bet its starving for fuel.

Which holley pump?

325cc heads are the same size ports a 365hp 454 mag had. Its not the heads holding it back.

Curious, did you degree the cam in, if so to what

Baja, I have !" spacers between the heads and exhaust manifolds, because without them, the exhaust curves in, and hit the valve covers, which in turn, I had to make a special socket to get at the plugs. It changed the access angle enough the make that simple task big ones. But, after I check the fuel pressure as the other guys suggested, I will do the boat yoga, and pull the plugs,,,
I appreciate the suggestions guys, I spent alot of time and money to go slower.

I agree on the spark plug gap.

Personally, I don't care what DUI says. Even if it could fire that large gap, the cap/rotor/and wires will be taxed tremendously.

I recommend No more than .040" on the gap. No less than .035" .

No reason to reinvent the wheel here.

Fuel psi alone isnt the end all. Ive rebuilt carbs that have had crap stuck in the needle and seats, and showed good fuel pressure on the gauge.

I had issues last year where my secondary had stuff in it and wouldn't let me spin one engine. (fell on face at 4200) Went through all of the Ignition, plugs and stuff. Funny thing is the AFR was reading good even at WOT, so I never payed much attention to fuel.

How do you figure that? My fuel pressure is the same 9 PSI at idle or WOT. A regulator is used to maintain a pressure.

Well, I thought I found it, secondary accelerator pump not fully pressed at wot. Still had a a big squirt left. Adjusted the nut, went back out, same thing, 4000 rpm at 3/4 throttle, no grain at full. Called dui dist. got a guy that knew nothing and had to go ask someone each question. They said " doesn't sound like a dist. problem." Gee, thanks DUI. Next will regap the plugs, although starting to think maybe a carb problem. Holley marine 850 double pumper. Carb worked fine on last engine. Only difference on the carb is I removed the choke.

did you check float levels both front&rear?

Only a suggestion, with boating season almost over... maybe pull engine and run on dyno?

Accelerator pump shot has zero to do with engine hp/performance. All it does is quirt fuel in when the airflow change is faster than the carb;s resultant added fuel flow. This keeps engine from lean pop backfire when accelerating.

You probably fuk'd the accelerator pump spec's. You are supposed to have some arm movement left when at WOT as you don't want to bottom it out. Search net for Holley Accelerator Pump Lever Adjustment so you put it back to stock.

So you changed heads cam compression exhaust and ignition and reused carb. Did you tune the carb to the new motor on a dyno,? Checked afrs? Plug chops at various rpms and loads ? I keyed in when you said the arb worked great on old motor, this motor is a completely different anima

Did you remove the choke blade completely or just disconnect the linkage? They have been known to "fly" closed if the linkage was disconnected and blade still installed.

And if you are going to remove the choke blade you might as well go all the way and mill the choke tower off. Then tune.

yes, checked and set them both

it had a spring at the end of travel, so it doesn't bottom out, but you could be right about I made ot out of spec.

I didn't do any of those things,,,,,,,but why would it peak at 4000, with 1/4 throttle to go,,,,,,,carb is set up with the standard jets and power valves that come with the holley 850 marine dp,,,,,,,,flow meter says around 23 gph at wot,

removed choke complete

not a carb guy, I took it apart, and blew out everything, maybe I can borrow another carb to try,,,,,,,what would be a next step to try with this carb ? great power from 3 to 4k, then its like on a rev limiter,,,,,,,with 1/4 throttle left

no rev limiter

??

Ok, found the deal yesterday.
My son and I put it in, beautiful day, calm Lake Erie for a change. We drove around, topping at 4k, 3/4 throttle. Started checking everything. Fuel pressure, throttle, ect. ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,rewind,, ,,,,,,,,,,,
Back in the spring My buddy climbed in to set the timing , I told him 36 degrees. He is the most careful , ocd , accurate person in the world, so I never doubted it was correct. Yesterday, I climbed my fat self under there to check it, and guess what ? It was at 24 degrees full advance. So, I reset it, off we went, and it went to 4700, rpm ,,,I'm holding it there, playing around with the trim,,,,,,thinking about prop pitch,,,,and,,,,,,rattle rattle, power loss, pulled it back, clanking at idle,,,,still had oil pressure,,,,shut it down. Hello Boat US ? Lesson learned, do your checks yourself,,,,,will advise after I pull it if something broke, or my engine building skills. were lacking, or my machine shop failed me. It should run 4700 all day, all forged crank, dimple rods, wiseco forged pistons, ,,,,,,,,,,,,,,,,,

double