GM 186 Head questions
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Burning Brakes
Joined: Oct 2000
Posts: 792
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From: Palatine
GM 186 Head questions
got some freebee heads
462624.....75-86...350/400......76cc chamber, 1.72/1.5, 1.94/1.5 or 2.02/1.6 valves.
and also
3927186....69-70...302/350......Camel hump,64cc chambers,accessory holes
forum members said I should practice porting on the 624's, and port and use the 186's.
My 77 is stock, this summer I'll be putting in a 268Hcam , and performer mani. Will the 186's work well with the 268H cam when and if I do put them on? Im a begginer, were can I learn how to port correctly? And what tools should I invest in? Thanks, Paul
Also how much better are the 186's than stock heads? How much HP can I expect with a heathy top end (setup with heads and cam), and stock bottom end?
462624.....75-86...350/400......76cc chamber, 1.72/1.5, 1.94/1.5 or 2.02/1.6 valves.
and also
3927186....69-70...302/350......Camel hump,64cc chambers,accessory holes
forum members said I should practice porting on the 624's, and port and use the 186's.
My 77 is stock, this summer I'll be putting in a 268Hcam , and performer mani. Will the 186's work well with the 268H cam when and if I do put them on? Im a begginer, were can I learn how to port correctly? And what tools should I invest in? Thanks, Paul
Also how much better are the 186's than stock heads? How much HP can I expect with a heathy top end (setup with heads and cam), and stock bottom end?
Drifting
Joined: Dec 1999
Posts: 1,462
Likes: 1
From: Reno nevada
Re: GM 186 Head questions (Blues77)
186 were among top of the line for their day. They were @ 165cc intake volume and could be ported to the mid 170 cc size. It's what I use. Mine are fully ported and the chambers polished and unshrouded. Summit Racing sells some books on porting. Without some guide you can actually ruin the flow. Mine were done with 1204 Felpro intake match and a D port template for the exhaust.
I preferr a die grinder like the Makita. I have friends that like air tools. I use metal bits for taking the metal out fast and then switch to finer stone shapes to smooth.
I preferr a die grinder like the Makita. I have friends that like air tools. I use metal bits for taking the metal out fast and then switch to finer stone shapes to smooth.
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Re: GM 186 Head questions (Lt1er)
the 624 heads are basically what you have on your engine now.. They , I think are stock on vettes in 78 and 79.... I'd use the 186's for two reasons: they are not better than the 624 smog heads and the chamber is smaller which will boost compression a bit... Just make sure you check to see if the 186's have hardened valve seats or not. You might want to get them upgraded to hardened valve seats if they are not.
