SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: H20Nut21Bahner on December 13, 2016, 11:20:52 AM
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Hey guys, I'm trying to figure out if the set of heads I have are worth having done. Not looking for anything spectacular, maybe a mild budget build.
The casting number is 3993820, which shows to be from 71-74 chevelle/camaro? The little bit of info I have found his far, shows that they're just about the same as the 781 and 049 heads.
Any truth to that?
Would these be worth having them done?
Any insight is appreciated
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Don't have an answer for that but I do have a set of 990s off my BBC going up for sale
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Hey guys, I'm trying to figure out if the set of heads I have are worth having done. Not looking for anything spectacular, maybe a mild budget build.
The casting number is 3993820, which shows to be from 71-74 chevelle/camaro? The little bit of info I have found his far, shows that they're just about the same as the 781 and 049 heads.
Any truth to that?
Would these be worth having them done?
Any insight is appreciated
Considering "Peanut port" heads easily yield 450 hp, (And I've seen more) The question usually returns to budget.
Whats it gonna take to 'build' them in your area? How far gone are they? The consensus seems to be 112 to 113cc chambers. Slightly better than 781's, but verify that by cc'ing the chambers.
Compare that to a set of fully set up aluminum heads. Are they worth it? I don't know.
thats all I got.
Dan'l
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I looked this number up in our ProSIS software and chamber sizes can vary all the way up to 122cc. You'll need a big dome to make compression with those... not my favorite way to do it. Closed chambers with flat tops make around 9.5:1. IMHO if you can pick up some closed chambers for a couple hundred bucks you'll be ahead.
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I am not a big fan of OEM big block heads. Here is the reason, they are 60's technology, and they are heavy. You would likely be much happier in the end with a decent set of aftermarket aluminum heads, they will make more power, they are lighter, and generally they allow more flexibility with cam choices.
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If you've got the coin to pony up for a $2000+ set of heads, aftermarkets are the way to go. Closed chamber oval ports can make 500+ hp which is enough for most people and cost a fraction of aftermarkets... probably less than 1/2. That $1000+ difference can determine whether some people are on the water next month vs. next year. Can't build every motor to the exact perfect spec with perfect parts. Sometimes you need to know when it's "good enough" for the owner's needs.
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H2O,
Could you share more about your horsepower goals and intended use?
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H2O,
Could you share more about your horsepower goals and intended use?
Not looking for anything spectacular at all Joe. The way it sits as of now, is how I picked it up. Block, crank and cam(was told Melling RV). #1 piston was melted, from what I was told, too much timing, too low octane fuel and possibly too much compression? Still has 6 pistons in it(pop ups), not sure yet of brand or possible part number stamped in them. I'll have to find a set of pistons and rods. I'm going to put it on the stand this weekend and have some more specifics.
As for what I'm looking for/expecting, not much at all. Just figured I'd piece it back together little by little and have a back up runner, or if I came across another hull at a decent price then I'd have something to drop in and toy with.
Needless to say, expectations are at the bottom of the barrel
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I looked this number up in our ProSIS software and chamber sizes can vary all the way up to 122cc. You'll need a big dome to make compression with those... not my favorite way to do it. Closed chambers with flat tops make around 9.5:1. IMHO if you can pick up some closed chambers for a couple hundred bucks you'll be ahead.
Thanks for the info, I've got a contact for a couple of different sets of heads at a fair price for known runners. Looking to basically have a back up runner.
Will posting casting numbers of the other sets in the morning ..
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Don't have an answer for that but I do have a set of 990s off my BBC going up for sale
Sent from my iPhone using SoCal Jet Boats
what kinda info can you give on those 990's and price? Those are good heads...
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Not looking for anything spectacular at all Joe. The way it sits as of now, is how I picked it up. Block, crank and cam(was told Melling RV). #1 piston was melted, from what I was told, too much timing, too low octane fuel and possibly too much compression? Still has 6 pistons in it(pop ups), not sure yet of brand or possible part number stamped in them. I'll have to find a set of pistons and rods. I'm going to put it on the stand this weekend and have some more specifics.
As for what I'm looking for/expecting, not much at all. Just figured I'd piece it back together little by little and have a back up runner, or if I came across another hull at a decent price then I'd have something to drop in and toy with.
Needless to say, expectations are at the bottom of the barrel
More questions.
I'm assuming this will be a .030 or .060 over 454?
What RPM do you want it to turn? Weight and size/type of hull will influence the impeller size which, with your horsepower, will define your RPM.
Cubic inch and RPM determine airflow demand. To keep port velocity high, select the smallest port size that supports the required airflow demand.
What exhaust? Logs vs headers will require different cam timing events (less duration and/or overlap).
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They came off my 496 I'm not sure of valve size but there were played with and set up for a flat tappet solid lift cam they have 3 seasons on them came off running motor I just put dart heads on asking 600
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More questions.
I'm assuming this will be a .030 or .060 over 454?
What RPM do you want it to turn? Weight and size/type of hull will influence the impeller size which, with your horsepower, will define your RPM.
Cubic inch and RPM determine airflow demand. To keep port velocity high, select the smallest port size that supports the required airflow demand.
What exhaust? Logs vs headers will require different cam timing events (less duration and/or overlap).
It's a .060 over 396 block. Not real sure what it will go into yet, may just sit on the stand for a while as a back up motor.
I have an offer open to me on a couple different sets of heads:
14092360, or 346236 casting numbers.
I have a basically stock 454 in my tank(cruiser), same as Dennis's. More or less "throwing" this back together as a spare