781 bbc heads from auto?
07-31-2014, 01:16 PM
#1
781 bbc heads from auto?
What do i need to do to a fresh set of 781 heads built for automotive application?
Going on stock 454/330 with upgraded intake (edelbrock performen 2.0) and exhaust (stainless marine)
i am trying not to get burned by my lack of knowledge.
Thank you in advance.
Gary
Going on stock 454/330 with upgraded intake (edelbrock performen 2.0) and exhaust (stainless marine)
i am trying not to get burned by my lack of knowledge.
Thank you in advance.
Gary
07-31-2014, 01:19 PM
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Those are a great head to start with for an auto application. I would imagine they're good for a boat too. I'd do a mild port cleanup on the runners to clean up the casting flash, rebuild them and go to town.
I'm sure somebody with more knowledge marine knowledge will chime in and give you more insight.
I'm sure somebody with more knowledge marine knowledge will chime in and give you more insight.
07-31-2014, 08:29 PM
#5
What are your intentions with the boat? If you are planning to lean on it, a set of inconel exhaust valves would be a good investment. Downside is the cost - $350 - $400 for 8 of them. If just pleasure boating, you may be able to get away with a very good set of stainless exhaust valves. Ferrea makes some nice stuff. I would look to them for both intake and exhaust.
What cam are you running? Depending on lift, you don't want to skimp on the valvetrain. Good springs, retainers, keepers, pushrods, rockers and lifters are all needed to control harmonics in the valvetrain. I considered the GM heads, but when I added up the cost for the new parts and machine work, I was well north of $1100. For another grand I was able to go with a set of AFR 265 ovals, which far outflow the GM heads, especially on the exhaust side. This included the upgrade to inconel exhaust valves. Something to consider. Brodix, Dart, etc., also make some good heads that will make real power.
What cam are you running? Depending on lift, you don't want to skimp on the valvetrain. Good springs, retainers, keepers, pushrods, rockers and lifters are all needed to control harmonics in the valvetrain. I considered the GM heads, but when I added up the cost for the new parts and machine work, I was well north of $1100. For another grand I was able to go with a set of AFR 265 ovals, which far outflow the GM heads, especially on the exhaust side. This included the upgrade to inconel exhaust valves. Something to consider. Brodix, Dart, etc., also make some good heads that will make real power.
07-31-2014, 08:44 PM
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781 or 049 castings are the sought after oval portsn the drag racing world. I just got my brother in laws all steel 72 Chevelle with a 461 BBC doing 7.23 at 95 mph in the 1/8 and I've still gotta dial in the suspension. This motor has a set of 781's that I bowl ported and that car hauls the mail!!
07-31-2014, 09:23 PM
#7
Think i am going to look at a set of 781's this weekend already upgraded to 2.25 / 1.88 stainless valves. Used take-offs (car) but pics look to be good condition. I am taking some barsol and check for leaky valves. If all looks ok i will probably buy. Found on craigslist for asking $600 will try for $500. Take them to machinest for final checking and surfacing. Need to decide how much material to remove.
Like i said have stock 454/330 strock cams & 8.5:1 compression flat top pistons and would like to remove enough to get to about 9.75:1. Any ideas what the chamber cc's required for this?
Not trying to make race engine just adding some spunk and freshness to engine.
Like i said have stock 454/330 strock cams & 8.5:1 compression flat top pistons and would like to remove enough to get to about 9.75:1. Any ideas what the chamber cc's required for this?
Not trying to make race engine just adding some spunk and freshness to engine.
08-01-2014, 12:01 PM
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781's and 049's are good heads with a lot of potential. That being said, it is very expensive to reap that potential. You stated you are putting them on a 330hp 454, please keep in mind that motor has crappy cast pistons, a crappy cast crank, and crappy cast rods. If you aren't upgrading the cam, or plan on upgrading the cam, you may actually lose a fair amount of torque as well. The stock peanut ports that were typically on the 330's had excellent torque with the small cam that they came equipped with. To sum up my rant: Yes, they are good heads. Yes, they work well in marine applications, but you need to take care of the cam as well to see any benefit or you may very well see a loss. Another quick note, CC your existing chambers, then CC the replacements. 781's are open chamber and usually end up around 122 +/1 CC. It will probably drop your compression, which will get even worse with a better cam......
08-01-2014, 12:13 PM
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I've been in your position b4. I think it's a waist of money to buy those heads. You will see little to no performance gain. If you have heads get them freshened along with the bottom end and call it a day. Otherwise if you are really wanting to change the horsepower of the motor and see a difference on the speedo you are gonna have to break out the wallet and hide the bank statements from the wife if you are married...
