Originally Posted by DMOORE (Post 4429976)

only thing i might want to change is:

#11 id switch to a single plane I have just had better performance with a single plane due to where boats seem to live RPM wise

Originally Posted by Persuader261 (Post 4429907)

Hey guys,

Im hoping some of the engine genuises on this site can verify a rebuilt engine build sheet. The guy who built the engine is an old timer who seems to know his stuff. When I looked at the engine the gaskets were fresh, everything was clean, and it ran on the stand. He claimed this is a reliable build for ~400hp that he has been doing for a while. The specifics are:

Any input or confirmation of the above build and what power it should produce would be very helpful.

Thanks,

Mike

Originally Posted by SB (Post 4430269)

A few people on OSO have proven the vic jr beats the air gap rpm in even 400hp 454's.

Yup, would have never believed it either. Bunch of tests where run in the boats before and after.....Wideband's to tune each set uo and etc, etc.

Dyno won't agree...but apparently this is where the saying "We don't race dyno's" come from.

I'll see if I can get one of the guys to chime in here.

Originally Posted by Sonic30ss (Post 4430278)

Interested in this- debating/researching this choice now

Originally Posted by apollard (Post 606641)

That would be me. I don't consider 51-5200 high rpm. Engine is a 0.030 over 454, iron 781 heads with some mild work (valves and removed the hump that is in half the runners. that's it - not even port matched). Off the shelf ISKY cam 221/231 @0.050, .565 lift, 114 LSA, 114 ICL. Mercruiser 496 exhaust and risers. Stock HP 500 carb (holley 800 dp).

Hardly what anyone would call great heads, excellent cam or good exhaust. What i would call a good budget build, nothing above average but better than stock Merc (except exhaust).

I've run and tuned both the Air Gap and the Victor Jr. No dyno sheets, but more in boat data than you can shake a stick at - AFRs on both banks, vac, fuel pressure differential (from which I can calculate fuel flow), RPM, advance all mapped.

The Victor Jr was faster by 2 MPH - and I saw none of the poor throttle response, etc you state. Planing time is exactly the same (I timed it). And I think there is more there with some fine tuning. 30 lb-ft in a boat is nothing, under acceleration your prop slip is covering for any loss (think high stall converter). Under steady state cruise, the lb-ft is the same at the same rpm - then, fuel flow tells the story as to which is better.

I was able to go down in jet size (primary & secondary) when i put the Vic Jr on due to improved fuel distribution. Fuel flow is lower at 3, 4, and 5000 rpm. So, more efficient due to all cylinders being equal afr - which almost always equals more power. So, I doubt I am losing 30 lb-ft at 3500.

Search here if you want the details of the poor distribution I experienced with the air gap - both in other threads and earlier in this one.

I'm not saying dual planes won't work, but saying they will only work well above 5000 and with above average parts is not correct IME. Your experience is different. That's fine. But don't tell the OP there is no other way. There is.

Originally Posted by apollard (Post 4430420)

Yep, that would be me - again. :D

Basically the info on the Performer Air Gap RPM to the Victor Jr is in the post above. Victor has much better fuel distribution than the RPM in my experience. I want to make clear I am talking boats here. I've used the Performer RPM on other engines on the street with no issues. But, they are not 100% loaded all the time. This was my intro into "Boat Engines ARE Different".

The entire reason for trying the Victor was HUGE problem getting the fuel distribution right with the Performer RPM- I had some cylinders sooting the plugs badly yet other plugs on the same banks were looking lean. On the widebands, the AFR would do weird things from cruise to WOT. I tried spacers, staggered jets, different carb, changed O2 sensors (thinking it was BS data), etc, etc. I found one other discussion about this on another forum, he even had it on the dyno and saw the same thing on the EGTs.

Then I put the Victor Jr on and it evened out AFR side to side and cylinder to cylinder. I changed nothing other than the intake and the carb jets. Both the plugs and the widebands agree the Victor is better in my boat.

More to the point, the GPS agrees it is faster - on a build that turns 5200.

SB is also correct, I pull almost 2" (depends on load) below the HP 500 carb. I never see less than 1.75" vacuum under it at WOT. I see less than 5 inches of water above the carb, so it isn't a restriction in the flame arrestor. I could use a bigger carb, but this isn't an all out build, so a $1000 carb for a couple of MPH isn't worth it.