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.

Be nice to know the cam specs, lift, duration, LSA.

If you have the heads off Bore notch the block while you are at it.

I'll see if I can find the cam specs.

Bore notch? Not sure what that is? Boring the block for valve clearance?

bore notch is basically opening up the bore a little right where the intake airstream goes past valve and runs into the cyl wall. DON"T cut down anywhere near the top ring...stainless valves are not inconel, but should hold up to marine use. they are a little heavy, but few people rev much past 6k.

Grinding out the block to unshroud the valves. You can use the head gasket as the template. Also do not go to deep.

I see. Thanks

How fast is your current set up with pp heads?
On my 781 heads i didnt increase valve size. I changed so many diff things i gained 10mph but i changed heads,cam, intake manifold, domed pistons, who the hell knows. if im in dead calm water i can push the 24 pantera to 70 with 23plus rpm approx 5100
I never dynoed motor but ppl have guessed approx 420ish

* I had to put stiffer sprigs in 781 heads bc i changed cam to approx .6 lift and bob mandera recommend it plus i got morel lifters, with the 781 you have to change to adjustable rockers, you cant use gm non adjust setup

70 sounds good. As for my speed I'm not sure as I don't have a gps in te boat. Had a little hand held once and saw low 60's. I have a 23 mirage plus that I'm seeing a bit over 5000 rpm's. I just ordered a 25p mirage plus today because I was told not to spin over 4800 with my bottom end.

I did get a set of crane gold roller rockers to go with the 781 heads.

I'm hoping for a nice improvement. We'll see...

Nice good luck with the build I have stock bottom end

Bring up and old thread here but how did it turn out? I am looking at putting a set of 781's on my 454 this winter along with a new cam and intake. Did you go with larger valves?

I ported, gasket matched the heads and intake, high rise intake, 850 Holley and a mild cam. The boat is a bit over propped with a 25p mirage plus and I'm only getting 4600-4700 rpms. But did gain 500-550 rpms and about 4-5 mph.

I also put 2.19 intake and 1.88 exhaust valves with avoid bit of bowl work.

if you hafta buy heads and pay for the work, it would be a better idea to go square port or alum heads. the OP had access to free heads and port work, or at least favors from a bud. once you find a $350-400 set of ebay heads and the same for port work, you are approaching the used price of good heads.

Derek is right. I had the heads and machines to do the work. If I would have had to pay for all the work it would have been a good bit of money and would not have been worth it at all. If you were to follow the same style head build you could get a set of used alum heads for what it would have cost and gain a lot more power with a good cam over what I gained using them. But in my case I had everything and the machines to do it so it was only time.

I just recently (this last Monday) bought a 280 velocity with a 502 may. It has the 088 square ports. I'm going to start a new engine build like before, but have a 600 hp goal since I'm starting with good internals. I think I'm going the aluminum head route this time if I can find a deal on a set.

Do you know the cam specs? I would like to get a set of 088 heads but the 781's supposedly are capable of making more hp then I am after. Plus the 781's are cheaper and more readily available around here. I am hoping to make 450hp. Right now I and spinning a 23 mirage plus at 4800 WOT and reading 60 on the GPS. I have a labbed 25 mirage plus sitting my garage that I ran once. It dropped me down to 4400 at WOT. So basically my goal is to run the 25. Right now my plan is to get either set of heads, performer rpm air gap intake, and have a custom cam ground. What are your opinions? I want to stick with iron heads due to not having fresh water cooling and being in the salt water.

I don't remember the cam specs exactly but it was around 500-510 lift with a 224ish duration on a 115.5 grind. The cam was very mild because I have stock exhaust on that boat and from what I understand they have bad reversion issues with much cam. If you had better exhaust the power gaining potential goes up a good bit (as I understand it) because of much more cam possibilities.


I did all the work myself and was happy with overall low investment, but it i had to pay to have it all done I may have a different view on the gains I got.

I will be doing most of the work myself. I will only have to have any machine work done that I decide to do. After doing more research it seems like the biggest problem is the low compression of the motor. It seems to really limit the selection of cams. I am going to go talk to a machine shop/builder tonight that I have used before. Hopefully I can get some good info about pricing for the heads and cam selection.

I'm not sure what motor you are starting with but if its cast internals that's a limiting factor as well because you can only spin them up to 5000 RPMs so I've been told.

ok, you have a set of 088's, are buying alum, and have a very nice set of 781's that are done up the way monster wants and you don't have a ton of money in. sounds like mebbe you should discuss selling the 781's to monster...

The 781's are on my 235 Baja that I'm selling. That boat is complete and ready to run. I don't have any heads sitting around. The 280 velocity I just bought has a 502 with 088's that I'm either going to work over or get a set of alum heads. Probably use the 088's as I'm starting to realize that they will get me to my hp goal.

it was a thought. anyway, monster, you are talking custom cam grind. two words-Bob Madera. you don't need to know anybody's cam specs-lift profile-none of that. all you hafta know is those two words and you will get the cam that you and your motor like best...hi is gonna lean on you to convert to roller lifters though-but then all cam guys will...