|12-29-2011 04:44 PM|
|72chevyBuild||I like the 260H, i had one on my 283 SB with 305 HO heads and a holley intake and that motor ran strong. But i am running camel hump heads and a stock intake, i just want a good cam to run with that.|
|12-29-2011 03:34 PM|
|BigEd36||The 260H, with shorter duration, will have better torque and responsiveness at take-off and low speed driving with a stock torque converter and hiway gearing. Comp Cams shows an RPM operating range of 1200-5200 rpm for the 260H and 1500-5500 rpm for the 268H, so the 260H brings on the bottom end at a lower rpm, basically right off of a fast idle speed.|
|12-28-2011 10:55 PM|
|72chevyBuild||Why? Cause of the duration difference?|
|12-28-2011 10:53 PM|
|12-28-2011 07:01 PM|
|72chevyBuild||thanks for the info i feel better with using the 268H cam without changing my converter.|
|12-28-2011 06:57 PM|
|12-28-2011 12:02 PM|
|72chevyBuild||Since my compression will be close to 10:1 do I need to change my converter?|
|12-28-2011 09:34 AM|
|72chevyBuild||No I am not going to do any more bore to it. But the casting numbers on the block are infact a 307 from 1969. But I am still deciding to use the 260H cam or the 268H cam still undecided.|
|12-28-2011 12:26 AM|
Cobalt327 made a good suggestion to run the compression ratio figures. I ran the compression ratio using 4" bore, 3.25" stroke, 5.7" rod, standard .025" deck height, a .015" thick by 4.1" bore head gasket (Fel Pro #1094), 7cc for piston dish (flat top with 4 valve reliefs), and 64cc heads (the double hump heads). I got a static compression ratio of 9.43. Using the specs for a Comp Cams 260H I got a dynamic CR of 7.99 so your build is well within range for pump gas use.
|12-27-2011 06:30 PM|
|72chevyBuild||the cam i have is like a 204 to 208 duration not a 210 or 212.|
|12-27-2011 09:12 AM|
|72chevyBuild||Yeah I think my cr would be around 9.5 or 9.75 to 1 but I also have a 260h cam I am thinking about using? What do you think?|
|12-26-2011 11:42 PM|
Makes sense- the 740P is a 327 SBC slug. So your 307 is now a 327.
Nothing wrong w/that cam duration and cylinder head- keep the quench tight, the CR might be a bit low, but w/a short cam that's OK. Might want to run the dynamic CR numbers just to be sure you're in pump gas territory.
Long tube 1-5/8" headers, a dual plane intake and a Q-jet would make a pretty sweet street engine.
|12-26-2011 04:59 PM|
|72chevyBuild||Just found out my 307 is bored to a standard size 327. Planning on running camel hump heads and a small mild cam around a 210 or 212 duration. Anyone got some opinions on that? I would like more help on my build|
|12-21-2011 10:57 PM|
|72chevyBuild||Yeah the 307 has the stroke of a 327 but the bore of a 283. But I'm just wondering what size it is, I am thinking probably .060 over. Thanks for the info|
|12-21-2011 10:25 PM|
The do share the same bore, but not the same stroke. The 283 stroke is 3.00", the 307 is 3.25".
I'll give you a start in your search, the 740P piston was manufactured by Ohio Piston & Pin, now out of business, and sold under the brand names Nytel and Ertel. They were once associated with Dynagear, but not sure in what capacity.
Maybe some here from back in the day can shed more light.
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