BBC compatibility...Grump?

[Mike C]

Hey Grumpy, know much about big block chevy's? I have a 427 for my truck to replace the 402. It is a 512 casting block, 69 or 70 2 bolt Mark IV. The heads are 290 castings and I find conflicting info. Are they 100.7 cc (REALLY closed chamber) or 109 cc chambers? I'm pretty sure 101 and the 291 casting is 109. My real question, will the 100 cc Mark VI Vortec heads work on a Mark IV block? I know the Mark V heads will not. If so, I'm going to get a set for my 433 buildup. I have heard they do for big-blocks what the SBC Vortecs do for small blocks and will save me from having to have hardened seats put in my 290s. Thanks in advance...

[grumpyvette]

heres info you can use, btw I build more BBC than SBC engines ,those #290 heads make nice hot street heads on a 427 if they get the larger valves and minor port work done to them,but theres no way that they can compete with a good set of aftermarket heads, now if you install the bigger valves (2,19/1.88) and do the port work those 290 heads should get you easily in the 10s with a well built 427 if you put it in your (Z) instead of the truck

These oval port cylinder head will fit all 1965-1996 Mark IV and Gen V or VI 396 thorough 502 cubic inch big block Chevrolet engines. They are fully machined with semi-finished Bronze Alloy guides and semi-finished valve seats that use 2.19/1.88" valves. These high velocity "290cc intake runners enhance mid range throttle response and torque. The exhaust runner volume is 110cc., the 110cc semi open combustion chamber design will make a very streetable compression ratio. Spring DIA is 1.55", with 7/16" rocker stud holes. These accept all stock accessory brackets except Gen V where the bracket holes have been enlared to 7/16". The roller studs and exhaust bolt holes are heli-coiled for strength.

Technical Notes: These heads are made from 356-T6 aluminum alloy. The 9/16" deck surface is for maximum strength and greater head gasket sealing . Designed for 3/8" push rod diameter. These heads require cylinder head bolt kit P/N 12367779. Use the following performance head gasket 1965-90 with standard bore to 4.370" use P/N 12363414 and with 4.47" to 4.540" use P/N 12363413, and with GEN V 1991-98 engines with standard to 4.370" use P/N 12363412, with bores of 4.47" to 4.54" use gasket P/N 12363411. The semi-finished bronze guide can be finished either 11/32" or 3/8" . The inter-locking hardened valve seat will accept leaded or unleaded gas. Use intake gasket P/N 12366985. casting #12363391 you may have the casting #s 391/291 confused

 

http://home.hiwaay.net/~ppatter/patrick_budd_article.htm

http://rodshack.port5.com/t_torque_big_block.htm

 

3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber

3964290 427 and 454 1966-1970 Closed chamber

 

3963512 1969 - 71 427 454 390 / 425 COPO

360 / 365 hp 2 & 4 bolt

http://www.chevytalk.org/forums/Forum64/HTML/014034.html

http://www.chevytalk.org/forums/Forum64/HTML/014113.html

[Mike C]

Thanks for the info. The 427 is for my 3/4 ton pick-em-up truck. Looking to build a torque monster with the Energizer 266 cam with max rpm 5000. Because of WOT use for extended periods of time, I want hardened seats and would prefer the Vortec head. (I have had no troubles running non-hardened seats in my mild small blocks for over 100k miles on rebuilds)The info on the 291 head came from Mortecs site which is USUALLY pretty accurate... The Vortec appears to be a large oval port, small chamber that should net about 9.5:1 with TRW forged flat tops in the 427 and has induction hardened seats, correct? Thanks.