What size valves are in 781 heads?
What size valves are in 781 heads?
The 049 heads have 255/119 cc port size runners, with 122cc combustion chambers. It’s really a toss up on which ones to use as the 049’s flow more but the 781’s will give a little more compression. Personally, I went with the 781’s and had 2.19 intake valves and 1.88 exhausts put in.
What did 781 heads come on?
The 781 heads are the best cast iron large oval port heads GM ever produced for the big block Chevy engine. They are worth rebuilding and respond well to pocket porting, bowl blending and larger valves. They will easily support over 500 horsepower. They are a very desirable street head.
Are 454 heads interchangeable?
You can use heads off a later vortec 454. They have a 100cc chamber which will maintain your compression ratio. 049’s would be a good head but have 119cc chambers which will kill your CR unless you add domed pistons. Big block vortec heads aren’t different like vortec small block heads and intakes will interchange.
What size valves are in 882 heads?
GM 882 Iron The smallest of the GM heads we tested at only 151 cc, the 882, turned out to be the best-flowing of the early iron heads. This head was tested with the 1.94/1.50 valves.
Are 781 heads open or closed chamber?
The ‘781 is the best choice for a 396 because it has the smallest open combustion chamber to help with static compression. Depending upon the year of the block you will have small dome pistons to make 11 to 1 compression with a closed chamber.
What are peanut port heads?
For the uninitiated, peanut port refers to the small, oval-port heads used on the Gen-V 454 truck motors run prior to the introduction of the Gen VI in 1996. In addition to the less-than-ideal, peanut-port heads, the Gen-V motors were also saddled with hydraulic flat-tappet cams.
Will 502 heads work on a 454?
They really dont match the engine, use open chamber oval port perf heads (I dont have numbers on me) and enjoy with less issues. 781 or 049 are the large oval ports, and they will run better on a 454 unless you are doing an above 6k rpm app.
What is the difference between 427 and 454?
396 and 427 have the same stroke, 454 has a longer stroke. To compensate for the longer stroke in the 454 – using the same length rod – they had to move the wrist pin higher on the piston. If they had’nt done this, the piston would be sticking out the bore above the decks of the block at the top of the stroke.
Are 041 heads good?
They are not the best flowing (not bad though), but can be pocket ported at home very easily. These heads are a replacement for the 186 castings. I think the only real difference is that the casting are a bit thicker (which is better).
How do I identify Chevy heads?
Chevy heads have often been identified by sight and most commonly by the different casting shapes on the ends of the cylinder heads. While these casting marks cannot tell specifics about the cylinder heads, they can help identify a performance head from a non-performance head.
Which is better open or closed chamber heads?
Open and closed chamber cylinder heads differ in combustion chamber capacity. Although open chamber cylinders offer easier flow, the closed chamber cylinder is better for performance. Compression ratios are also affected by the size of the chambers.
Can you port peanut-port heads?
The peanut-port heads received a light surface and performance valve job, but were not ported in any way. Additional power would be possible with porting, as the stock head flow was certainly limiting power of our 461 (. 030-over 454).
How big of a valve does a 781 block head need?
781 heads don’t need extensive porting to be 600 HP capable. They need a bowl port and larger valves installed. I would also install new 11/32″ guides and stainless valves. 2.25/1.88 diameters.
What kind of head does a BBC 781 need?
I guess 8.5 to 9 cr 496 with a 120cc head, which is about perfect for a BBC with pump gas and a cam between 205 and 225 duration. I think a stock set of 781’s would be good for a low rpm 496 with 9:1 cr and a mild to moderate cam.
Can a 781 head flow with Oval Port AFR?
Yes, the 781 and 049 can be made to flow a much, but a lot lift is required. The same flow numbers can be made with oval port AFR’s at 0.500″ lift compared to 781/049’s at 0.700″ lift. And running a bunch of lift has its problems in valve train abuse, plus could cost more in the end due to the requirent of more expensive valve train components.
How much lift does a 781 roller cam have?
A stock set of 781/049’s with the stock valve size is will flow around 265 cfm @.700 lift. I have a friend with a 9.5:1 468 with cleaned up 2.19 1.88 valve 781’s that made 560 hp and 560 tq with an hyd roller cam in the high .240 to low .250 duration @ .050 range. He had his heads flow tested and they flowed 290 cfm @.700 lift.