89Force235

Well, I can say that the cross section area of the B&M 174 intake was not as large as as the square port gasket I used...And, I did port match my head to a large oval intake and gasket before installing the blower so, although it is miss matched the actual area of and location of the two different ports wasn't that far off. I honestly wasn't too worried about the difference between the two after seeing how it fit together. Here's a pic of my heads after i finished the port matching.


Like I said before, my interest in changing heads is really related to loosing weight. The port miss match, increased flow i.e. potential for more hp/torque, and reduced likely hood of detonation due to aluminum's heat transfer characteristics are all added bonuses.

SB

iTrader: (1)

The 781 heads aren't too bad weight wise. Pick up a Dart or Merlin cast iron BBC. Wholly schit !

You going to install the metal block off plate that came with the intake gaskets for the exhaust crossover port ?

How about a lifter valley tray ?

Both are cheap mods to keep some heat out of the intake.

89Force235

As far as the weight of the heads go, I had them on a bathroom scale when i was checking my valve spring seat pressures with the drill press. Yes, checking spring seat pressures with a bathroom scale and a drill press that's how us poor guys do it . Anyhow, I think they were like 76 lbs each assembled. I remember thinking it was ridiculously heavy but now I don't feel do bad.

Concerning the heat in the in intake those are good comments.

There's no crossover port in a B&M 174 intake so it's "blocked" as is. Actually I don't think Ive ever see a blower intake with a cross over port but I could be dreaming....

I never thought of installing a lifter valley tray, that's a good idea.

SB

iTrader: (1)

Yes, the intake does not have the crossover port. Your 781 heads do. What's stopping the exhaust and it's heat going thru that port ? The intake ! The heat, the heat...repeat after me, the heat, the heat. LOL.

The steel plate will help block some from hitting the intake. If you wanna be trick, coat the steel block off.

Another cooling trick for the heads. Run coolant lines from rear of intake up to the t-stat housing.

Don't be a fraid to run a 120*F thermostat if you are running a t-stat.

89Force235

OK, now I'm picking up what you're dropping off here. Those little plates will give a little more protection. My neighbor whos a drag boat and fast lake boat guy suggested the lines from the rear of the intake to the thermostat housing too.

I'm not running a thermostat. Think I'll see much benefit from plumbing the rear of the intake to the thermostat housing?

SB

iTrader: (1)

You mentioned aluminum heads transfering heat better. I'm giving you ways of removing heat much better from intake and all heads on the BBC.

BTW: poor mans coating the exhaust heat block's off's is finger paint ultra black to intake manifold side of metal block off's. Remember to use the solid block off's, not the one's with holes in them.

ICDEDPPL

iTrader: (1)

7.5#`s of boost?!
174 blower?

ouch.

ezstriper

nope, did it several years ago, made great power, used a comp blower cam, along with a 4.25 crank...had in a 251 checkmate, ran low 80's, but did not have Hyd steering and figured out quick that with my sons driving it was not a good idea and replaced it with a 500hp..

89Force235

That's a nice set up! As much as I'd like to see my turd of a boat get into the 80's, I'd honestly be thrilled at this point to break 60.

Care to share how much boost the 177 make on a 496?

Also, as long as you are sharing, cam specs and WOT rpm?

Thank you!

89Force235

I know, I know, I know, the general consensus here is:
174 = junk,
177 = ok.

But please give me the benefit of a doubt, there is only whopping ~1.6% difference in overall displacement between the two blowers. If I'm seeing excess heat with the 7.5 pulley I'll dial back the boost. The pulley I have is what I got with the blower when I bought it.