Torque & HP Open Discussion

M3Fan wrote: What's the logic in using the HM manifolds? Are they proven to flow better?

Cool factor Joel Pure speculation on my part but they are 3" outlets, the Donzi guy's want them and Reid has them on the worlds fasest Mustang.

I agree they are cool, they polish up pretty, they are loud and they do save weight maybe not the best flowing but certainly close enough.

Thats a pretty wide port, not a whole lot of material between the mounting holes and the port to seal. However they are the same width as my current heads though and I have had more problems getting them to seal on the bottom than on the sides.    

81nautique wrote: Joe, I am concerned with sealing them up. Have you ever had any luck with the copper permatex hightemp sealant.

Alan,
I'd like to comment on the copper high temp. It's a silicone and I'm not a big fan of any silicones! They have very poor adhesive qualities and really don't "wet out" on the surface. They only work when you have a large surface areas. I'd go with the "tried and true" Permatex non hardening (no. 2) Form-a-gasket. It's good for 400F.

eric lavine wrote: Joe, I think as you are running, the wind over the windshield creates a vacuum, so i dont think it would help with the cover up or down. I was more on the lines thinking of forced fresh air from the front of the boat...it just seems the little venting they have now doesnt matter

Eric, I disagree- Ive skied on enough cold mornings to know that the windshield doesnt protect much beyond where the driver sits. The engine gets more fresh air than it could possibly use with the motorbox off. Ive driven mine plenty with it off and saw no difference in performance either- though it is louder and looks pretty cool. The venting from the factory must be sufficient, at least on most of our boats.

I do see your point, though- my buddy has a pretty fast MC that picks up a good 2mph with the engine cover off- it must be starving for air with it on.

Alan, cant wait to see everything bolted up!

81nautique wrote: Not to mention the PCM manifolds don't allow for taller valve covers without adding a spacer to move them outboard, which ofcourse doesn't exist so more backyard enginering required.

Have you considered a set of header flanges? I know some people who make them in Addison. How thick of a spacer would you need?

Victory Header Flanges

Andy wrote: 81nautique wrote: Not to mention the PCM manifolds don't allow for taller valve covers without adding a spacer to move them outboard, which ofcourse doesn't exist so more backyard enginering required. Have you considered a set of header flanges? I know some people who make them in Addison. How thick of a spacer would you need? Victory Header Flanges

Andy, yes I was actually going to go that route until I stumbled onto the HM manifolds. I wouldn't think I'd need much but would have to test fit with some spacers to figure it out. I will keep you in mind if I don't like the HM's I may just do the spacers. Last time I talked to waterdog he mentioned making a set up for his boat.

Thanks for the heads up.

For reference I did run the pcm manifolds with Ford Racing tall valve covers for a year, the fit was tight. On one side I could fit a piece of paper through without drag but not much more, on the other the paper would drag. Any spacer width would have made it enough to keep paint on both parts.

Thats what I was thinking, but I wasnt using stock heads so its possible there is a little difference and tolerance stack up to take into account and some may be a little tighter.

In regards to additional air flow, I also thought that these boats could benefit, but I've tried the same tests w/o the box and didn't see improvements. Then later, I observed this on our Classic with the scoop on the box, which is open to the engine: early on prior to rebuilding the engine, it had an enormous amount of blow-by coming from the vent tube. When running the boat it would actually blow the smoke OUT of the scoop meaning to me that there was more air/pressure coming out than going in the engine compartment, which really surprised me. This does not contradict what Eric is saying I don't think, as he is speaking more of forced induction and the scoop on the Classic is not sealed to the carb, but is open to the engine compartment.      

Reid, that's what I was thinking, at 40 mph with straight induction and cool air it may p/u some performance...hell I always try to think of the ratio's ....dollar per HP or MPH.
I keep thinking of the Mythbusters to where the truck with the tailgate down got worse mileage than the truck with the gate up, completely opposite of what was thought

Just like a golf ball, the resistance of air-air is less than air-pickup bed (not to mention the greater area/length to travel).

Sanity - Do I get anything back when I contribute positively to the forums?

Hollywood, did you ever see the wizard of oz when the wizard put the ribbon on the scarecrow? he goes on to start rappin the square root of an isosolize triangle....you always had it in you lol

Did anyone ever cut open a PCM exhaust riser?

wakeboardin2k4 wrote: 81Nautique- I'm loving the motor build. What's your expected HP? are you going to re-prop? When changing to the CC heads do you need to change pistons to shape to the new heads or are you running stock pistons? I'm assuming from what you said about the heads being available in aluminum that you went with iron? What advantages does sticking with iron have over going with aluminum for boats? Thanks

Expected HP is 380 but that's optimistic and only a simulated number. Prop question can't be answered until the boat is in the water, I have several to play with and will try them all once the motor is dialed in.

You don't "need" to change pistons when going with a smaller CC head but with any type of change like new cam or shaved heads/deck you have to check for piston to valve clearance. I do not have stock pistons and we think I'll be fine but will check clearance and relief them if I have to.

The iron heads are certainly cheaper than aluminum and I was concerned about consistant engine temps in an open cooling system. If it was a closed system and had more consistant engine temps they would be an option to consider but without that you could be looking at issues that I didn't want to deal with.

I understand aluminum heads can withstand high compression ratios because they dissipate heat better but at 10:1 the irons are fine.

Also, Seems this thread has become more about my motor than was intended so if anyone wants to add to the conversation please jump in. It was meant to be just a general engine hop up thread, not about me.

Someone else will have to help with your 454 question

Another question I have is can anyone clear this question up for me?

I was told by a teacher that PCMs 454 had a cam gear/crank gear instead of a timing chain. Which would mean although its a counter rotation motor it has a std rotation cam?

Which would mean having a custom cam made to follow the bizarre pcm firing order and crank setup wouldn't be that hard to achieve?

Just trying to learn from the masters of boat hp building