rocker arms

johnnyrod

Well Known Member
Supporting Member 3
I have big block chev rocker arms in my 348 would this affect performance or does it matter? John :scratch
 

Bubbletop Bel-Air

Well Known Member
I believe BBC and W motors have a different ratio. I know for sure a BBC stock rocker arm ratio is 1.7, while I believe a stock W motor ratio is 1.75, so what you would end up with is slightly less lift and duration. I am not sure how the rest of the geometry lines up, but have heard of this being done before. Perhaps another member will provide the rest of the details.
 

Fathead Racing

Well Known Member
Supporting Member 7
Rocker arm?

Big block Chevy rocker arms have a ratio of 1.72 and as you know W rockers are 1.75. I can see no gains in such a small difference. At .500" lift there would be a difference of .005" I run with BB Chevy rockers also, don't sweat it. The difference is made up between the rocker fulcrum and the push rod so the geometry across the valve tip is not effected!
 

johnnyrod

Well Known Member
Supporting Member 3
Thanks guys I needed that. A friend of mine got all concerned that it might be a big deal. John
 

jester

Well Known Member
Supporting Member 5
fatride said:
Big block Chevy rocker arms have a ratio of 1.72 and as you know W rockers are 1.75. I can see no gains in such a small difference. At .500" lift there would be a difference of .005" I run with BB Chevy rockers also, don't sweat it. The difference is made up between the rocker fulcrum and the push rod so the geometry across the valve tip is not effected!

Does this combo in a 409 have the same effect? In other words, can I run BBC rockers in my HP 409 and if so, what would be the effect?
 

Fathead Racing

Well Known Member
Supporting Member 7
Rockers.

Jester, I run with Competition Cams Magnum roller tip 1.72 BB Chevy rockers with the 348 heads topping my 409. Except for the bigger pushrods the valve train geometry is the same for the 348/409 heads. Any gains or losses would be miniscule.
 

models916

Well Known Member
Supporting Member 7
do the math

A .300 lift at the cam with 1.75 is .524 with 1.72 is .516. Same story with duration. Not much impact on a street engine.
 

CHEV601234

Well Known Member
Variations

Keep in mind that stock rockers did vary a lot from their spec. serious old time racers bouht plebty of them, then checked each one to see which set gave the largest valve lift on their race engines. There are probably big block rockers that produce more lift than '09 rockers, and vice-versa. It all depends on how that tip was shaved and where it contacted the stem.
All the stupid magazine say center max lift on dead center of the stem, (that's fine if your biggest fear is valve guyde wear, but consider centering it outside or inside. Same as advancing ot retrarding the cam. But by selecting rockers, you can vary adv/rtd, on int & exh indepentantly, regardless of cam grind, or how you installed it.

Well, heck, on;y someone serouis would consider that stuff.... Kinda like the seerious guys did over 40 years ago. It's old science, just not well known. That's hoe you "cheated" back then.
 

jester

Well Known Member
Supporting Member 5
fatride said:
Jester, I run with Competition Cams Magnum roller tip 1.72 BB Chevy rockers with the 348 heads topping my 409. Except for the bigger pushrods the valve train geometry is the same for the 348/409 heads. Any gains or losses would be miniscule.
Just so I understand, your running a 409 bottom end with 348 heads along with BBC rockers, Is this correct?
 

JimKwiatkowski

Well Known Member
Supporting Member 5
Jester,if your going to rebuild your 09,I would upgrade your heads with teflon valve stem steals,7/16"screw in rocker studs and roller rockers,just an idea to spend more of your money :doh
 

jester

Well Known Member
Supporting Member 5
Thanks Jim , But I don't have any problem finding people to help me spend my money. I'm MARRIED with CHILDREN. I need to find a rich girl friend that will adopt me.
Anybody know a rich, good looking woman, looking for an old man?
I almost never eat twice my share of food.
:roll :roll :roll
 

jester

Well Known Member
Supporting Member 5
?

I didn't know that you could mix head between the 348 and 409. I thought there was a flow problem. Are you HP heads? Are you using a 348 intake with that set up? Did you need to do alot of porting ? Sorry for the questions but you have sparked my interest. :dunno
 

Fathead Racing

Well Known Member
Supporting Member 7
Heads?

I have the 1960 379 head. Low performance 250 hp. I have installed 2.07/1.72" ss valves. Heads are gasket matched to Fel Pro HP gaskets with the runners blended in 1". Under the intake valve, the bowl has been cut for the new valve size and pocket ported. 7/16" ARP screw in rocker studs were added. A 1960 stock three two intake topped with three tuned Rochester 2G carbs. Flow problem,,,,no,,,,but I could make more power with 690s! :grumble:
 
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