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Old 07-14-2008, 06:19 PM
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Double hump heads

Hi,

I've over bored my '66 283 .030 and installed a pair of '67 Camaro SS 350 double hump heads with 1.94" intake valves. I've turned the engine by hand to set the lifters and the intake valves don't hit the block deck nor cylinder bores. So far, so good, but Im having the uneasy sensation that maybe I'll have a low compression ratio. Any of you guys have an idea of what kind of C.I my 283 will have? The pistons are flat top. Thanks.
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Old 07-14-2008, 06:28 PM
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Around 8.7:1 depending on gasket used and if your blocked been decked or not.

Thats 64cc heads, 30 over 283, 21 thou headgasket and 16 thou in the hole.

Sell those heads on ebay for a couple hundred and buy some aftermarkets. Very cheap, a lot more power, and cooler.
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Old 07-14-2008, 06:41 PM
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Shipping heads from Brazil to the states rules out eBay and of course importing heads from the states can be costly too. He probably will be happy with what he has.

Trees
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Old 07-14-2008, 06:41 PM
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Quote:
Originally Posted by Nsomnia
Around 8.7:1 depending on gasket used and if your blocked been decked or not.

Thats 64cc heads, 30 over 283, 21 thou headgasket and 16 thou in the hole.

Sell those heads on ebay for a couple hundred and buy some aftermarkets. Very cheap, a lot more power, and cooler.
Well, it's an engine just to go around the town without hi perf intentions. I thought that it would be worse. Something like 8.5:1 is not that bad. I had a 55 Chevy with a 8.0:1 265" two barrel and was a nice driver. Thanks for the info. Now I have were to start. I have a pair of 283" power packs that I can rebuild and use in the near future.
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Old 07-14-2008, 06:46 PM
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Quote:
Originally Posted by trees
Shipping heads from Brazil to the states rules out eBay and of course importing heads from the states can be costly too. He probably will be happy with what he has.

Trees
A pair of Edelbrock aluminum heads here will cost you around US 3,000. The import taxes are pretty steep. The American rodders don't know how lucky they are...
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Old 07-14-2008, 07:25 PM
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The humps will work great on your 283 actually a little to much head for that size engine.They will flow all that little puppy will need in fact they work well in a tunnel ram dual 4bbl in this case . any aftermarket head exept maybe a stock vortec would be overkill(runners way to big for the little small block).If you can get the fuel to support it flat mill em .040 and use a steel shim gasket ,do not increase the valve size. Also if you can find em a set of 305 heads 416 casting I think would also work very well on this engine. You need to think small cam and all.A cam advertised for 1500 to 4500 in a 350 might very well not start pulling till 3000 and stop at6500 in the "83.
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Old 07-14-2008, 07:45 PM
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Quote:
Originally Posted by barnym17
The humps will work great on your 283 actually a little to much head for that size engine.They will flow all that little puppy will need in fact they work well in a tunnel ram dual 4bbl in this case . any aftermarket head exept maybe a stock vortec would be overkill(runners way to big for the little small block).If you can get the fuel to support it flat mill em .040 and use a steel shim gasket ,do not increase the valve size. Also if you can find em a set of 305 heads 416 casting I think would also work very well on this engine. You need to think small cam and all.A cam advertised for 1500 to 4500 in a 350 might very well not start pulling till 3000 and stop at6500 in the "83.
Well, a .030 overbore makes it a little bigger than the original 283. The fuel here is good enough for my 396 Chevelle with 10.25:1 because it has some alcohol mixed to it. Well, I rather not mill the heads cause they're kind of "historic". The cam I'm using is the '67 SS 350 cam. I guess that a C.I of 8.5:1 is not that bad, at least for a while. I'm going to use a 600 CFM Holley vacuum secondaries or a Edelbrock Performer. Thanks for the information.
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Old 07-15-2008, 07:46 AM
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That will probably be a good cruiser, good mileage and fair power.
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Old 07-15-2008, 08:04 AM
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Quote:
Originally Posted by barnym17
That will probably be a good cruiser, good mileage and fair power.
I hope so...
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Old 07-15-2008, 08:40 AM
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Quote:
Originally Posted by Luiz
Well, a .030 overbore makes it a little bigger than the original 283. The fuel here is good enough for my 396 Chevelle with 10.25:1 because it has some alcohol mixed to it. Well, I rather not mill the heads cause they're kind of "historic". The cam I'm using is the '67 SS 350 cam. I guess that a C.I of 8.5:1 is not that bad, at least for a while. I'm going to use a 600 CFM Holley vacuum secondaries or a Edelbrock Performer. Thanks for the information.

Sounds like its going to be a fun engine, streetable, economic, and piece of history.
I likey lets ee some pics.
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Old 07-15-2008, 09:36 AM
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Quote:
Originally Posted by n-gin
Sounds like its going to be a fun engine, streetable, economic, and piece of history.
I likey lets ee some pics.
Well, piece of history a 283 really is. Compared to the last generation of the V-8 Chevy engine it looks like the piece of bone used by the "2001 A Space Odyssey" monkey... Simple and effective.
Do you know how to post pics here? Thanks.
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Old 07-16-2008, 04:57 AM
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When you reply to a tread there is a manage attachments button. Click on it and it will brouse your computer for pictures, or you my have to select a pic. Click to edit the picture to make sure it is not too big. Resize it so it can fit the screen or pixle size. After saved exit the screen for editing and double click the new saved pic. It will save it to a separate miniscreen and then just click the upload button. Then submit a reply.
If you still have trouble there is a place on here with step by step instructions. Good luck.
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Old 07-16-2008, 05:26 AM
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Quote:
Originally Posted by n-gin
When you reply to a tread there is a manage attachments button. Click on it and it will brouse your computer for pictures, or you my have to select a pic. Click to edit the picture to make sure it is not too big. Resize it so it can fit the screen or pixle size. After saved exit the screen for editing and double click the new saved pic. It will save it to a separate miniscreen and then just click the upload button. Then submit a reply.
If you still have trouble there is a place on here with step by step instructions. Good luck.
Thanks. Your explanation is good enough.
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Old 07-18-2008, 08:30 PM
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Just a test to see if I'm able to attach the 283 pic with double hump heads...
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Old 07-20-2008, 06:03 PM
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I took off the double humps. I bought a pair of newly rebuilt 283 power pack heads (9.25:1). The ones with a cast triangle atop of a cast rectangle. I've put a double hump side to side with a power pack and I could see how much bigger the DH combustion chambers are compared to the PP one. I guess that a 283 with dome pistons and double hump heads would make a nice engine...
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