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-   -   781 bbc heads from auto? (https://www.offshoreonly.com/forums/general-q/316163-781-bbc-heads-auto.html)

dereknkathy 08-01-2014 07:20 PM

it would be difficult to get that compression with those 118 cc chambers. look for a set of alum heads with the chamber size you need.

Jonesyfxr 08-01-2014 07:25 PM

What current casting number do you have??

SB 08-01-2014 08:02 PM

There was a $2900 502 for sale this week. Prosystems carb and such.

Too bad.

GLENAMY 242SS 08-01-2014 08:12 PM

Current casting # 360 peanut heads not looking very useable trashed out and tired. Bottom redone 2 yrs ago. I am freshening-up the stock engine not buying any real performance parts, read alum heads, just putting the boat to good running order for 1-2 years.
I saw the 502 and the 509 and would like to have but i need to swap the alpha for bravo before adding any "real" power.
I found some recent rebuilt 781's for $250 my head shop said they would replace valves with stainless 2.25/1.88 and cc and machine heads for compression correction for around $400. I thought this to be a prudent direction.
Am i missing something? I am asking 'cause i really am no expert at this.
Thanks and as always any all sugestions welcome.

Jonesyfxr 08-01-2014 08:23 PM

Those 781's will blow your 360'sw out of the water and with a tad of machining they will hit your comp ratio. Do an RPM Airgap intake and go have fun. This will really wake up your engine.

GLENAMY 242SS 08-01-2014 09:07 PM

It has been sugested to use inconel exhaust valves. My question is what is different about them, when are they needed and why? Thanks again

Jonesyfxr 08-01-2014 09:42 PM

http://www.performanceboats.com/dyno...el-valves.html

GPM 08-02-2014 02:35 PM

If you cut the heads enough to raise the compression you will most likely have to cut the intake to match. The 2.25 valves may be a waste on that small bore motor and just cost you some low end torque. You might be better off with some closed chamber heads with 110 cc combustion chambers.

Jonesyfxr 08-02-2014 03:52 PM

We are running the 781 heads on a 461 BBC in an all steel Chevelle and the engine is a monster! It pulls like a freight train in the eighth and will be in the 6's with some tuning....all steel and full interior I might add.

781 heads are great, with a bit of work done to em.

GPM 08-02-2014 04:00 PM

What compression, what gears, what cam ? what have you compared them to ?


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