Can different rocker arms work together

I say flip a coin, the difference in ratio and any slight performance enhancement will never be noticed whether on intake or exhaust.
 
I experimented with this a few months back as I had a set of both, I made two sets and I tried 1.54 on intake and 1.43 on exhaust and vice versa.... To be honest there wasn't really advantage either way in fact it caused a untidy idle however putting the high ratio on all was the real advantage.. Really livened it up and smooth idle.
 
Tinker said:
Doesn't air expand under heat though... I mean doesn't something force the piston down.
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The explosion of the fuel/air mix forces the piston down. The resulting exhaust gas is less dense than the fuel/air mix and is forced out of the cylinder on the exhaust stroke. Since there is less exhaust gas by volume than fuel/air mix the exhaust valve needn't be the same size or open farther than the intake valve. If you have seen a flathead with the lids off you'll see that both valves are the same size. This worked OK but wasn't optimal for for developing horsepower. It wasn't until the horsepower race of the late 40's/early 50s that things changed and intake valves became larger than exhaust valves. A fairly common performance modification for flatheads is to hog out the intake valve pocket and install a larger intake valve.
 
Here is a little more info about this engine. The machine shop found that they had to put sleeves in this engine and due to the surface distortion of the top of the block they had to deck the block( both sides of course). Not sure how much yet but I do know that this should give me a little more compression. Does this play into the decision of where to put the high ratio rocker. This is a great discussion and I am learning more than I expected this thread to generate. Thanks everyone!!!
 
Actually this engine will have a little more compression than a normal stock block because we had to deck the block (both sides of course). Will this affect were we put the high ratio rocker arms?
 
Considering what it's probably costing you to have all this work done the cost of 8 more rocker arms is a proverbial drop-in-the-bucket. :p
The slightly increased compression shouldn't affect the rocker arm placement, but putting in some time to scrounge up enough to make a complete set is still the best option.
When I started asking around it took a couple weeks but I found a guy who gave me his extra 1.5's for free.
 
Is it too late to change my vote! ha ha.

I looked at a set of nos high lift barkers I have for the 223 6 engine. Instructions say to use on the INTAKES only. Doh! My bad. That and as Dobie says about larger valves on flatties (such as using chevy valves). Hey I'm not opposed to getting in a discussion and maybe be wrong, if learn something.

Guess I'm getting crow for thanksgiving. :)
 
I am very interested in hearing some one's opinion on what blackpearleb434 said about the rough idle. If I use this mix, is there any reason to think that it will cause a rough idle?
 
If you can't afford 8 new 1.54 ratio rocker arms then I am another vote for putting the ones you have on the exhaust valves. A lot of performance cams have more aggressive specs for the exhaust valve, so seems to make sense to me.

Also, below is a link to John Mummert's website. He shows 1.54 rocker assembly's with shafts and all. Listed as new parts (not reconditioned). Not sure if he sells rockers individually. He may be pricey too, but I'm sure of USA made quality parts.

Sal

http://ford-y-block.com/valvetrain.htm
 
Tinker said:
I think you are right fordors. So I'll stick with the exhaust vote.
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The instructions that the Barker rockers came with specify to use on the intakes only. My recent rebuilt 53 six runs real strong with them on the intakes.
 
41ford1, check post 29 of mine above. Glad they're working well for you. Still have another set so if I install them I will have to read the instructions again when installing. :eek:
 
cjc56 said:
And yes I would like to find another set of 1.54s. If anyone has a contact let me know.
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Call around to find other machine shops anywhere near your area that work on old Fords, they usually have leftover parts laying around in the corners.
Ask a restoration shop if they have any extra ones they'll part with.
Anytime you ask someone and they say they don't have any, ask them if they know someone else that might.
Join a car club or two near you that has members with similar cars and ask around for help finding what you need, but remember it's a two-way-street.
Good luck.
 
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For intake air flow, the rule of thumb is to increase the intake and reduce the exhaust as the compression ratio goes up. This is done either by valve size and/or rocker ratio. I have dyno tested the 1.54 Intake and 1.43 exhaust scenario and it does increase the torque and hp on the G headed Y engines versus using just 1.43:1 rockers across the board. But going with the 1.54 rockers across the board was also an increase in power over the split set of rockers. 1.6:1 rockers also saw an increase in power over the 1.54 rockers but all this testing was performed on an engine with a Crower Monarch camshaft and not a stock camshaft. The Y engines as a rule do like valve lift though so an increase in rocker ratio helps in that regard.
 
Ford heads have always had poor exhaust flow, I'm not sure adding lift to the valve would help, without some grinding...I've had 289, 5.0, 460 and 429 heads, all have these "humps" in the exhaust ports that need ground down...would a higher lift over come that?..I don't think so, but think it would help.

I'd assume the earlier heads have the same style exhaust ports?

Regardless, you'd want to find flow numbers for your current heads, untouched (assuming you are not going to work on them) and see what happens with flow through the lift range.

Although I am sure you won't fine a 70-ish percent ratio anywhere, it would give you and idea what to so.
 
I also agree with putting the higher lift on the exhausts, while agreeing in general with the principle of the bigger intakes. Due to scavenging effects, a better exhaust flow will help the intake side too but stuffing more air in without better exhaust would seem not as productive.
 
The exhaust flow on the Y heads is much better than the other Ford heads that followed. And especially on the G, 113, and 471 heads. As such, anything that can be done to 'stuff' more air into the intake side typically helps. As the compression ratio is increased either through milling, thinner head gaskets, or domed pistons, then the need for increased intake air flow comes to the forefront. Likewise, even smaller exhaust valve sizing can be incorporated to make room for larger intake valves without hurting the exhaust flow at the heads. The exhaust system being properly sized will also help with the scavenging as I've run into cases where the scavenging was 'too good' and hurt the performance simply due to too much intake charge being wasted into the exhaust during the overlap cycle.

As usual, this is just food for thought.
 
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