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Discussion Starter · #1 ·
since I always have heard ppl say 400 heads are garbage, I was wondering would the heads off my 68 307 be better? I would of course have them upgraded ported,springs, valves. would they be better than the 400 head I have now which has also been ported springs valve job.
the motor hasn't been swapped in yet.
I believe there are 2 versions off the sbc 400. an early 70-73 block and a 74-80 as indicated by some casting #'s. I have the earlier 70-73 block which may or may not be different in some way 2 the later years. something from the EMISSIONS or epa type shidd is calling out. So when ppl talk of the heads being garbage they may be indicating tht of the later blocks maybe. . so. ?
but would my current 307's heads be better on the motor.I have stock dished piston on the rebuild. -22 cc
 

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All the money you spend on old heads would be better spend on a good aftermarket set.

Heads that go on 400 blocks required steam holes. Steam holes can be drilled in non-400 heads and must be done if driven on the street.

What compression ratio are you trying to make? 64cc heads on a 400cid engine with 22 cc dishes will get you around 9.3:1 cr.
 

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Discussion Starter · #4 ·
I'm not sure about what compression ratio I'm runnin. don't understand tht cr stuff 2 much yet. and thts a good point about the old heads. ive seen a few aluminum heads on ebay 4 right around 400 so those are in my ball park.
I want a compression ratio that will possible get my car into the high 12's low 13's @ the track but still let me use 91 or 93 octane for cruising the highways. I was thinkin maybe a 68cc head but not 2 sure
 

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If you piece meal junk and or used random parts then your performance will be exactly that,,,random at best.

do you want to use the 400 you have?
How fast exactly do you want to go?

This is what I used for a super low budget 400 for a friend that want good mileage and power
car ran 14.1s and got 20 mpg on the rare occasions he kept his foot out of it(on street tires)
we did the engine including buying a core and freshened the turbo 350 with a rebuilt stock converter.this car also had 2.73 gears,1986 Monte Carlo
engine stock rebuilder short block with the deck resurfaced,no measurements taken,installed a sig erson TQ-20 cam. Engine was assembled by Rory McNeil from Bond mechanical Vancouver BC. The heads were stock 400 heads with a decent stock valve job,GM off road valve springs...Intake was a holley street dominator,625 carter afb,small tube headers,.
If you want to go 13s,make a few improvements
If you want to go 12s you need posi/gears/tires and 80-100 more horses
 

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I'm not sure about what compression ratio I'm runnin. don't understand tht cr stuff 2 much yet. and thts a good point about the old heads. ive seen a few aluminum heads on ebay 4 right around 400 so those are in my ball park.
I want a compression ratio that will possible get my car into the high 12's low 13's @ the track but still let me use 91 or 93 octane for cruising the highways. I was thinkin maybe a 68cc head but not 2 sure
Buying used heads on eBay is NOT a good plan.
 

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Discussion Starter · #7 ·
na I wouldn't even go tht route 4 some used aluminum heads unless they were 200 o something.
these are the heads I was speaking of Chevy 350 383 400 Aluminum Cylinder Heads Straight Plug 327 283 SBC Bowtie New | eBay . the posi is something id like 2 get next but with my 8.2 rear I wanna at least go 8.5.

2 vinnie. that's a nice build and are yu serious tht a 400 got 20mpg on 2.73 gears? because thts the same gears I believe I am working with. although my speedometer is off 12mph. says 60 on dash gps says 72. so I'm not sure if its different gear or what tht issue is all about.
 

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You really should invest in a book or two so that you can get an idea of how to plan an engine build. Just go on amazon and search for "hot rod chevy" or something similar, several titles will come up for you to choose from. Authors like David Vizard and Graham Hanson have their detracters but you won't go very wrong with their advice.
 

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You really should invest in a book or two so that you can get an idea of how to plan an engine build. Just go on amazon and search for "hot rod chevy" or something similar, several titles will come up for you to choose from. Authors like David Vizard and Graham Hanson have their detracters but you won't go very wrong with their advice.
 
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