Put 305 heads on a 327?

Bill Stone

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I just picked up a 1969 327 Im gunna drop in a 55 Im buidin,its got feulie heads on it,I abandoned a 305 I was gunna use so its still kickin around.A circle track racer told me he had a 327 with 305 heads on it & it was a hot motor.I know the combustion chamber is smaller on the 305 heads so it ups your compression,but how about the valve sizes? Wouldnt that limit the power your engine can make? Im not goin racing with it,I want a reliable motor to go long distances with.Would it make any sense to put those heads on or would it be a foolish move?
 

racecar68

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Circle track guys do this cause the rules specify iron heads, or stock heads. The normal performance heads are 64cc and 2.02 intake and 1.6 exhaust. the 305 head has 58cc and smaller intake 1.94 and exhaust 1.5 . For a street eng. that has flat top pistons this is a great combo at about 10 to 1 compression ratio. The smaller valves dont hurt at rpm below 5,000and even help low end torque. So you get good compression, can run on pump gas and the price is good.
 

Bill Stone

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Hmmm...thats sounds pretty tempting then.Im not going Drag Racing with it,I just want a dependable smooth running motor that I can go far with.The motors going in a 55 Chevy.Another added bonus would be the accessory holes to set up the alternator & power steering if that what I end up with.So those valve sizes are the same as the smaller fuelie heads?-Bill-
 

racecar68

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The 1.94 intake and 1.5 or 1.6 exhaust are the generic small block sizes. this should be a good combo for the street and would also work with a mild cam.
 

hurst01

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Bill,

This is doable, but would not be my favorite. Some of the early 305 heads were prone to cracking. If you put them on, check the head gasket for the 327 and compare it to the 305 heads. Under no circumstances put a 305 head gasket on the engine. The bore of the 327 is about 1/4" larger than the 305. If you use the 305 head gaskets the piston could possibly hit the head gasket. The smaller valves in the 305 will be great for low performance driving, dependability, and get better torque and economy.
If you are looking for performance, keep looking. Although the 305 heads have 58cc, which will give a better compression ratio, the smaller valves will hinder the performance. It all depends on what you are expecting the engine to do.
Once the heads are mounted and buttoned up, no one will know the difference. The 327 has the same bore as the 350, but the 327 has a stroke of 3.25" whereas the 350 has a 3.48" stroke. The 305 heads do not have the same size valve as the older fuelie heads.
 

flagmanmike

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327 maybe, 350- probably not. we had a customer at the machine shop where I worked, do this inadvertently/accidentally & they had trouble w/blowing the starter nose cones off of that motor- assumeably from the added compression. Sure took awhile to figure out! Other than that- I agree w/ Hurst01 ESPECIALLY about the cracking prevalence of the "improved cooling" style heads- more water passage/less casting. Gasket info too- the "fire ring" that seals the combustion chamber would be hanging inside the cylinder, if you used 305 style. Hope this helps, I'm a 55' guy myself, should be one in every garage!! :cool:
 

hurst01

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The best thing about the small block Chevy's is that just about anything will fit anything. Now, the later mid-90s 305 heads are more dependable. Actually considered Vortec heads and have excellent flow rates that will produce excellent low end torque. I have never heard of breaking the starter nose off in a situation caused by changing the heads, but what the heck? It all depends on the price you are going to have to pay for the engine.
What are you running in your 55 mike?
 

flagmanmike

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I put an 11 1/2 :1 .030 283 in my 55' about 25 yrs. ago got the thing broken in, then got some bad conversion parts/ advice while doing the front disc brake conversion. Then as happens, it got back-burnered, then I had a hostile take over in the compound where my shop was (in the city) so, I traded my 68'Camaro for the down payment on 5 acres in the stix. Have just lately re-prioritized this project, now that my shop is built & outfitted properly. Decided that some less worthy projects will have to make the Supreme sacrifice-be sold to fund this one, I've had this one 27 years & never gotten to drive it- I have WAY too many projects for one guy. Will be 4-wheel disc, possi, 69', high nickel block 350, & 350 turbo this time around! loved your formula for 383 stroker motor will try that after things settle down around here Thanks-FlagmanMike!
 

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