781 or 063 head swap on 454
 

Hello everyone,

Last year I built a 454 to put into my new to me 235 baja. The boat has been great and we have really enjoyed it. Something has caused the valve stems seals to start to leak. I think its because the motor got hot a couple times when we first got it running before finding out my b1 was corroded and wasn't allowing enough water to pass through. It now has a low water pickup and everything has been fine. I'm going to pull the motor to fix the heads. While I have it out a good friend of mine owns a machine shop and has a set of 781's and 063's that he said I can have (we are doing some trading). From the research I've done the 781's will be better as I build the motor with a blower at a later date.

I currently have peanut ports with a high rise intake and a cam motion custom grind cam (don't remember the specs) and flat top pistons.


Am I on the right track going with the 781's? Either set of heads will get gasket matched and bowl blending. My buddy has a set of bigger valves and said he would put them in. Should I go ahead and install the bigger valves? Will it be beneficial? As of now the intake I have doesn't match up with the small peanut ports at all, but I needed an intake and had plans of upgrading the engine at a later time.

I have to pull the heads anyway so I'm hoping it will gain a little bit due to the better flowing heads.

Thanks for the advise!

Cp

Let me know how you do i have 781 heads on my motor, had to put in way stiffer springs and put the valves from my old pp heads in. im turning the motor to 5000 rpm not what are you getting out of your old motor.

i wonder if you will have to change push rod length...

With the peanut port heads it will go over 5000 if I let it with a 23 mirage plus. I'm actually in the process of buying a 25p mirage plus so I can let it go WOT with out it pushing beyond 5000. Why did you have to go with stiffer springs going from the pp heads to the 781? Do you have stock size valves (2.06 I think)?

Did you notice any difference changing to the 781's?

We are going to check the push rod length when we assemble the motor. Also going with crane gold roller rockers. Got a good deal on them so they can't hurt.

781's would be an excellant choice over the peanuts. Put in 2.19/1.88 valves. I assume your intake will match the large ovals? Is it a dual plane and what carb? Be needing to upgrade the exhaust also depending on how far you go with it.

Yes, its a dual plane. I will work on going with the larger valves. As of now I have a quadrajet on it, but I plan on changing it with this new round of upgrades. Any suggestions on what carb? I've been leaning towards a 750 or 850 holley.

Your right, I do need to address the exhaust as I know its not helping. Its just stock manifold with 4" thru hull's. I will be looking for a nice used exhaust after this set of upgrades are done.

750 Holley double pumper for 454 inch.

you have the wrong intake for the peanut heads. you already know this. that half inch ledge sticking into the intake air stream is worse than having peanut size intake passages. i assume it is a large oval-not rectangle port intake. the 781's are the best of the stock oval heads. and much closer to rect heads than peanuts. your bud has valves. marine, or hot rod? ALL boats see some reversion. you don't want SS396 exhaust valves. yes, pushrod length is same.

He has stainless valves for it so I assume they will work?

Thanks for the help everyone. I'm going to go with the 781's.

With gasket matching the heads and intake, some bowl blending, bigger valves, crane roller rockers and a Holley carb I hope to pick up a little power and that's always a good thing. Hope to has it done by the end of next week.