A460 cylinder head question

what kind of work/design does it take to do a 2.490-inch intake valves and 1.830-inch exhaust valves , is that common practice or is this a really custom piece.

bruno wrote:what kind of work/design does it take to do a 2.490-inch intake valves and 1.830-inch exhaust valves , is that common practice or is this a really custom piece.

youre starting to worry me...

The TFS heads would need different seats in the heads for that size valves.

Nick step away from the keyboard......

The A Plus cylinder head is offered from a 2.45" to 2.50" intake valve and from 1.82" to 1.88" exhaust valve. The peak airflow for the A Plus head is over 510 cfm on the intake and 350 cfm on the exhaust (depending on flow benches) with a large bore. The A Plus head was created for a bigger displacement engine (over 600 cid and bore diameters at 4.600" or larger) or use in classes were the C head was outlawed. The intake port matches to any newer TFS intakes including the tunnel ram. The first set went to Chris Holbrook a few years ago for an all motor class engine and produced some very good hp numbers.

bruno wrote:what kind of work/design does it take to do a 2.490-inch intake valves and 1.830-inch exhaust valves , is that common practice or is this a really custom piece.

Nick,

Previously I attended the Darin Morgan Cylinder Head and Induction class/school and in his textbook he devotes 7 pages to proper valve sizing. One of the questions he asks, and then explains, is; "how big is too big"? For canted valve heads, he's saying the maximum size is 52-53%, and for rotated canted valve heads the maximum size is 53-54%,,,,,, of the bore diameter. That's with the valve locations and pierce points being ideally located in a racing head.

Therefore, I'd say your 2.490" intake valve is just a little too big for an A-460 head, and it is not that common of a practice. Yes, it would be a really custom piece.

Darin goes on and gives supporting data of 2.450" intake valves, out running 2.500" intake valves in an actual engine, due to better valve efficiency and flow efficiency. There was a 40 Hp loss when they switched to the bigger valve. Like the Hooter's t-shirts say, you can have "more than a mouthful".

Charlie

dfree383 wrote:Nick step away from the keyboard......

i cant ......

Charlie,
In my previous post I spoke of the A Plus head being used for larger bores, 4.600" or larger and larger engine displacement. The A Plus head is offered from 2.45" to 2.50". Listed below are percentages for the bore to valve diameter. They are within 1% of Darin Morgan's criteria. I do understand that just inserting a larger valve into a head does not yield more performance and often can hurt performance. The port design, chamber design including seat machining with throat diameter, valve shrouding, compression ratio, charge motion architecture, type/amount of fuel, cam profile with rocker arm geometry and valve lift all play an important role into finding the best valve size for each application. Design parameters do evolve with time. Today's NHRA prostock engines (canted valve design) do use 55% to 56% intake valve to bore ratio and they are making over 3 hp per cubic inch. IHRA Prostock engine have a 54% to 56% intake valve to cylinder bore ratio. The Chris Holbrook engine using the A Plus heads did make 2.06 hp per cubic inch with a ratio intake valve to bore ratio of 54%. I thought that was pretty good with the limitations of the A head design.

Valve Size
Bore 2.450 2.500
4.600 53.3 54.3
4.625 53.0 54.1
4.650 52.7 53.8
4.670 52.5 53.5
4.675 52.4 53.5
4.700 52.1 53.2
4.705 52.1 53.1
4.725 51.9 52.9

Come on Nick we will attack these A-heads together..... Your getting in my ally now.

I agree with you Jay, their are applications where large valves are appropriate. PS being one of them, but those application are very specialized.

For average Joe weekend warriors, it may not be the best route. 2.35 Valves and small ports are much more forgiving.

I believed the question was NOT how they would work but, whether or not they would physically fit and what would be required to do so.

I have first hand experience that on an SBC engine with a 4.020" bore and a wedge head, the power picked up everywhere from 3,000 RPM to 6,200 RPM by simply increasing the intake valve size from 2.020, (50.2%) to a valve size of 2.140", (53.2%), and this was certainly no racing engine. It had a hydraulic roller camshaft under .600" valve lift.

Or is it that small engines don't count...?

I would presume that a canted valve head engine can use more intake valve diameter than an inline valve headed engine.

rmcomprandy wrote:I would presume that a canted valve head engine can use more intake valve diameter than an inline valve headed engine.

How big has people gone on the a heads? 2.45 intakes?

4.060 bore 414 Windsor with Aluminum C302b heads 2.190 intake valve flat top pistons 53.9 % 6.20's 3000 lb