#21  
Old 11-15-2020, 02:28 AM
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i4abuygto i4abuygto is offline
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I also found locally a set of big block Oldsmobile "G" 442 cylinder heads from 1971 which I believe are a 80 CC head. Which of my options would give me the best compression ratio and performance value?

  #22  
Old 11-15-2020, 03:03 AM
Aus78Formula Aus78Formula is offline
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It depends on the condition of the 403 block. If it is already running and fairly healthy, bolt the 350 heads on and go. If the 403 needs a rebuild with a rebore, then consider the KB pistons that are a match for the 403 heads as they also suit the odd size of .024 and .039 overbore.

  #23  
Old 11-15-2020, 10:37 AM
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prostreet64 prostreet64 is offline
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The small block heads you referenced are 69cc according to Joe Mondello's Tech Guide. I believe the chambers are to small for your intended purpose. On the 403 I think the c.r. would be around 10:1 or higher. The big block heads are 455 heads and at 80cc should work well with the 403. I am not that familiar with the Olds heads in general so I am not sure what changes might be required to make them 'work' with the 403. At least the big block heads already have the 2.00/1.62 valves and that is good thing.

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  #24  
Old 11-15-2020, 03:42 PM
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i4abuygto i4abuygto is offline
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The Stock 403 was freshly rebuilt and is still in the car- photos are in an earlier thread. The 403 runs strong and the short block is in good shape. I made a mistake shortly after purchasing the car which created a hydra lock and took out one of the head gaskets. The short block is fine and in good shape and I will not be pulling the engine.
My options are to bolt on the stock 4A heads that have new valves in them- I am going to have a machine shop check the heads for valve seating and trueness before I bolt them back on.
I thought, I would add compression at this time by changing the head configuration, if at all possible.
I am a rookie as far as head configuration possibilities but I want to increase the performance by making whatever head changes I can make at a moderate cost.
I heard that the 350 heads will take the larger valves and add compression with the smaller chamber.
Then I found a lead on the 442 heads - at 80 cc will they bring up the compression over the stock 4A heads.
Or maybe just bolt on the stock 4A heads and call it good.
It did run pretty good.
I am not sure what it might cost me to get the 350 heads ready to bolt on with machining and placing the larger valves to work.

  #25  
Old 11-15-2020, 09:57 PM
Aus78Formula Aus78Formula is offline
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The compression increase will be minimal, especially if the 4A's have been given a lick or two. Be aware the BB heads will require the RPM intake to match.

  #26  
Old 11-16-2020, 12:06 AM
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i4abuygto i4abuygto is offline
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Thank you Aus78Formula for your advice. So my aftermarket aluminum intake would need to change with the BB heads, and then, likely I would need to change the shaker hood or it would not probably even work.
And the SB heads will give minimal compression change for the investment in installing larger valves and machining work.
So, to just have the stock 4A heads checked for valve sealing and for trueness would probably be my best bang for the buck. Just bolt them back on and go.

  #27  
Old 11-16-2020, 12:30 AM
Aus78Formula Aus78Formula is offline
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Yes, if it's a TA with a shaker and all original aircleaner and A/C etc, then best to stick to small block heads that work with the low-profile intakes of the stock Olds 350/403 #16 intake or Edelbrock Performer (not RPM) or Olds 307 A4 intakes, that way everything fits as it should. If you couldn't decide about which heads etc to go with then the hassle of making a shaker work might help!

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