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Old 06-04-2007, 11:17 AM
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Switching Heads???

I have a 1966 283 and the heads are pretty much pooched. I have a 78 350 and the heads are good as far as I know. Can I put 350 heads on a 283??? Both carberated motors. The valve guides are bad and if the 350 heads are in better shape I'd like to use them on the 283. Thanks

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Old 06-04-2007, 11:43 AM
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Yes, they will fit. BUT, you need to make sure the combustion chambers are the same size. If the 350 heads are larger, the compression will drop, or smaller, will go up. Do you have the numbers off both sets of heads? If so, you can ck the CC size at http://www.mortec.com

Mark
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Old 06-04-2007, 12:05 PM
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Well the 283 heads are 60cc chambers and the 350 heads are 74 cc chambers. I think I'll have the 283 heads fixed and get new valve guides inserted. Also while they are doing that they can put in hardened seats too. Thanks Mark you have been a great help!!
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Old 06-04-2007, 12:28 PM
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You could probably get by with a different head gasket (thinner) and use the 350 heads. Maybe someone with a calculator will join in and figure it out.

Mark
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Old 06-04-2007, 01:20 PM
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I'm with Jmark, I think you're probably best going with getting your heads rebuilt (the 283 ones). The valves and combustion chamber size are probably much more appropriate for that motor. The 350 heads might will lower your compression roughly 1.5 points and may over-flow at low RPM. For that reason the motor may be gutless and very soggy below 2500 RPM.

K
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Old 06-04-2007, 02:48 PM
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For a 283 a set of 305 heads should be cheap and available and will work as well as the stockers, already have hardened seats etc.
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Old 06-04-2007, 05:02 PM
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Quote:
Originally Posted by Jmark
You could probably get by with a different head gasket (thinner) and use the 350 heads. Maybe someone with a calculator will join in and figure it out.

Mark
An 0.039"/0.040" gasket is about 8 cc's. An 0.015" steel shim gasket is about 3 cc's. So, the 5 cc's difference in the gaskets would never make up the 14 cc's difference in chamber volume.
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Old 06-05-2007, 12:07 AM
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Head vol.-
Comp. ratio
55cc -9.5
58cc - 9.1
62cc - 8.7
64cc - 8.5

This is from the KB catalog for a 283, .030" over, .040" quench clearance, and +6cc flat-top pistons (stock equivalent). I'd guess CR in the mid-7's for the 350 heads. 305 heads run ~64cc, HO 305 heads (416's) are ~58cc.
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Old 06-05-2007, 10:23 PM
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As mentioned above a 305 head like the common "416" casting would be a good way to replace the heads on your 283. If you want to improve the power of your 283, port the 305 heads and install larger 1.94" intake valves. These heads respond very well to porting. These modern heads already have hardened ex seats for unleaded gas and have the bolt holes for post 1969 engine accessories. they have a 58cc chamber volume.
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Old 06-07-2007, 01:45 PM
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I guess I better start looking for some 305 HO heads. WE have a swap meet coming up near by, I'll have to take a cruise over and see if I can score a pair. Thanks guys your info has been greatly appreciated!!
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Old 06-07-2007, 06:20 PM
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Quote:
Originally Posted by budthespud
I guess I better start looking for some 305 HO heads. WE have a swap meet coming up near by, I'll have to take a cruise over and see if I can score a pair. Thanks guys your info has been greatly appreciated!!
I'd be carefull of buying heads from a swap meet. Usually either unusable junk or if they are good they are way overpriced.
You can buy a whole running 305 with the 416 heads for under $100. many will give a 305 motor to ya. All you need to do is pick it up.
Check your local buy and sell rag, online classifieds junk yard or even the local automotive machine shop for usable castings.
Do not mention "HO" or any reference to high performance. ya just want a usable set of "416" casting 305 heads.
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Old 06-07-2007, 06:59 PM
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Well I guess I'm doing a total switch here. I just got in from the garage and I was checking the 350 motor I got out of a van 7 years ago. The guy told me it had a blown head gasket and it ran like crap. The reason I pulled it was that it had been rebuilt 1 yr earlier. Tonight I pulled the sucker apart and to my surprise it has a 4 bolt mains. Never nude that!! So sitting there having a few brew-skis I though the heck with the 283, 350 more torque, more HP and better shape overall. It don't take a rocket scientist to figure that one out. I actually thought the 283 was in better shape but I was wrong after taking a look at the 350.
Now as for the heads I'll see about a 305 engine F-BIRD'88 in the area and if I don't I'll work the 350 heads with some P & P and go from there. Hey I have a 74 Formula 400 that I restored 3 yrs ago. She's my rubber burning baby!! Have a good one all, Thanks!!!
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Old 06-07-2007, 10:15 PM
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With the way the price of gas is going you might want to stay with the good old 283. It can give you very good performance when modified properly.
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Old 06-11-2007, 05:23 AM
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Yea you are right about the gas mileage F-BIRD but it's a money thing. The 350 with save me a lot of $$$ by using it than practically rebuilding the 283. Further inspection has shown me that the heads have been done too on the 350. They just need some P & P. Hey and money saved can go to other stuff that I'm sure I'll be purchasing in the future. Thanks!!
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