Technical /SBC cam profile with Rocker Ratio

A CARB number is a California thing. It makes your parts legal and considered to be stock replacement parts in the state of California. It stands for California Air Research Board. My heads are one off.

To get the proper pushrod length you use a push rod checker, you can buy a set up complete with instructions from Summit racing. I don't actually use one I use a very old tool setup that I have had for over 45 years. Dial indicator, light spring and a brain basically.

 

Not all parts play nice together.
When the time comes and there is a good chance it will remember.......Smith Bros. Pushrods, Redmond Oregon

https://www.pushrods.net

 

Motors have a tendency to do one of two things, you either become a mechanic or you quit. Taking the time to figure it out, is the better of the two.

 

Yes and probably the better of the two options (run the heads and slap any ol ods in vs get 1.5-1.55 roller rockers with matched rods ) is to wait to swap the heads and cam until I can run my ideal set up. The 441s run well for now

 

Joe H can you reply again please? It’s not showing up here on the blog

 

The 441 and 461 heads flow just about the same. The only gain you with 461 heads is more compression, which is good when going with a larger cam. The original heads on my 350 in my 40 chevy were stock 1.94 441s. The exhaust seats went away so I built a new set of 441 casting heads with 2.02 and 1.6 valves, angle milled to 68 cc, and screw in studs and guide plates. The 350 had a stock cam and I didn't want to mess with it, so I used 1.6 rockers.
It made a huge difference in how it ran. More power through a very broad range.
Of coarse I wanted more, so last winter I put a comp 260h cam in it and left the 1.6 rockers. Now, of coarse it is a little dead off idle to around 2000 rpm. It has 308 gears and a stock converter, so it has a lag now. I'm tempted to put 1.5 rockers on just to see what it's like. My ultimate goal is to put 4.11 or 3.73 gears with a 700r4. With cam changed it is always a trade off. Increase power by increasing flow trough bigger heads, not so much. That's why a big block can get such a broad torque curve. The heads flow good.

Just giving you my latest experience hoping it might give understanding.

 

This is a perfect answer thank you so much for sharing that experience! I’ve heard a lot of guys go with 3.73s and since you have the over drive why not go with 3.90s or 4.11s and a 3000 stall? That eliminates the 0-2000 issue that may just be a an issue with the cam moving your power curve up.
Thank you again Dyce and good luck!

 

Experimental sohc

Sent from my SM-G935V using The H.A.M.B. mobile app

 

That is a manly looking power plant

 

What about one of those SUHC SBC's [Single Under Head Cam ]

That's an old engine! it has a 2 barrel manifold and old 265 style exhaust manifolds.
It looks like they bolted "Cam boxes" onto stock heads

 

It appears to be exactly that.

 

I don't understand how the gross cam lift changed by changing rockers?

 

You put 1.6's on what is pictured and you'll bend/break things up with those rotator cups. Even with 1.6 ratio you're still around a .500 lift so the 'Z-28 Drop In Spring' (I have no idea idea why its called that) will work really nice and replace the keepers & retainors with 10deg steel. You may not have to elongate the pushrod holes since the extra lift is on the other side of the rocker and if the pushrod didn't contact the head with a 1.5 then it won't with 1.6, length won't change either.
Dunno your questions about carb & intake or your idea of 'performance'. But if you want to make power, the 461 head is a decent one, you'd go with single plane intake and 750ish carb.

 

The 3927142 spring is considered a “drop in” because it needs no spring seat machining to fit the head. A regular SBC spring has an installed height of 1.720 and on the seat it is about 80# and 200# at 1.220.
The ‘142 spring, also known as the brown spring for the color GM painted them, is stouter with 135# on the seat and 290# at 1.220, or .500 valve lift.
GM doesn’t catalog them any longer, those were from the Trans Am race era but Crane might have a similar spring.

 

If you did not change the location of the valve or the rocker stud the only way to change the ratio is move the push rod end.

 

It doesn't. Net lift does.

Valve lift gets changed. Cam specs are listed by how far the valve is opened, with a stock ratio rocker arm.

 

I agree I was just looking at his numbers

 

Yup, your right, I hadn't given it much thought but the valve side must be fixed and just the pushrod side can be changed.
Good point.

 

Because cam specs are at the valve, in this case he said the Exhaust (?) was .460 with a 1.5 rocker ratio, so the cam lobe is (these number are not exact since the lift is @ .050 to get the slop out of the valve train, if you chuck the cam in a lathe and dial indicator for exact lift the number will different) anyway, divide the .460 by 1.5 (.30666, this is the theoretical lobe lift) and multiply time 1.6 = .49066, the new lift at the valve. make sense?

 

I ran stamped 1.6 rockers once. It was a 305 with ported small valve heads, and a VERY mild Wolverine cam. It ran quite well, all things considered. Had the cam been bigger, I'd have stuck with 1.5's though. Push rods were right up against the cast in guides, and should have been opened up. But I was young and poor, and threw it together. I pulled it apart for other reasons after about 40.000 miles, and they showed where they were rubbing, but no more than on a stock engine with more mileage. I have read that the friction from that can negate the power gained from the switch. But it was not run with both ratios to see what difference it might have made.

 

I’m in a similar process. Not sure if you watch engine masters on you tube but they did a dyno session rockers non roller to full roller 1.5 to 1.6. I recommend pulling up. Lots of real world info dyno proven instead of bench racing.

 

1.6 rockers were used by roundy round guys running under cam lift rules that allowed using big block rockers if you want more lift buy a cam with more lift aside from the fact you have to check the geometry see if all your valve stems are the same height ,check that all your rockers are the same going to need a box of them to find 16 the same,then find 16 pushrods the same size,then check that the rocker hits the valve stem through 360 degrees rotation , i could make any sbc cam-carb-head-comp. run but how well is another question , for me building the motor an drivetrain to do what you want is the holy grail weather its go fast or drive anywhere you feel like going ,my G.M 1/2 ton look's like crap i only washed it once since i got it when i retired in 2012 and it looked like shit so never washed it again but having said that i would drive it around the country in a heartbeat with no worry's and um it's an cam lift rules 360 cube an under roundy round 283 stroked to 354 um also what are you smoking cause i want some

 

converter an driveline have nothing to do with motor lagging um are you saying it's slow or slower or that motors not running well ? a well tuned balanced sbc should run crisp no matter what it's sitting in front of imo

 

We ran 1.60 rockers on the exhaust side of our hobby dirt cars that had a stock stamped rocker rule and a not too sharp tech guy. We were issued a cam at the start of the season with an etched number on it and if you got protested they would pull the timing cover and chain and read the number and it had better match.
He never did catch the rocker arm trick until after I moved to late models and told him about it.
It helped the top end pull at the end of the straightaway. We never saw much gain on the intake side, but an unported head needs help on the exhaust side.

 

This thread is like a Picasso painting....WOW
Figure out what you are going to use the beast for...drag only street and strip.
You call Crower, Isky or Summit to get the cam and other changes to make the
car fly. I used 1.5, 1.55 and 1.6 rockers on my dirt modified for different tracks.
I used a cam that would work on my hometown track. Different gearing for other tracks to keep the rpm's up at the end of the straightaways.

 

What was the jc Whitney story , this cam = 20 hp , these heads = 40 up , this carb =30 hp
20 + 40 + 30 =90 hp ..

 

Carb is California air resource board , whether or not a part can be used in California

 

Stock 461 heads show very little flow increase over .450 valve lift. 190 cfm only 192 cfm when they went to .600 lift