Standard Rocker ratios

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Retroboy

Retroboy

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Hello. I just killed a ST21 Racer Brown camshaft and I've ordered a Lunanti 10200704 Voodoo Hyd as a replacement. I have a .040 over 360 with KB 190 pistons using J heads with adjustable 273 rocker gear. I'm new to Mopar and just read that the 1.5 ratio rockers are closer to 1.4 ? Is that the case with the 273 adjustable type or the later stamped non adjustable type as well. I don't have a million bucks to spend and our Aussie dollar is about 70c US which means if I spend $400 USD that converts to around $570 Aussie dollars. What is the easiest way to get my ratio up balancing cost with the end result?
Cheers
Tony
 
Whew! That can be a tuff one to balance between new rockers or having the ones you have corrected. Why don't you try hughesengines.com and see what they can do for you.

Perhaps selling the ones you have now and rolling the money over into new rockers is a good way to go about it all?
 
What are you goals with the car? Trying to build the fast car you can? Racing it for $$$? Just cruising around town? I wouldn't have a problem reusing stock rockers if I'm just looking for a fun car to take to shows and things like that. To be honest its probably safer in the long run vs buying cheap rockers as I've heard they have a tendency to fail. With that said I'm going to roll the dice with a set of old CAT rockers on my 440 and see what happens. Only reason I'm running them is I had them in stock so I'll give them a shot.
 
Personally i'd bite the bullet if i were you,stock rocker ratios were never accurate the Comp pro magnums are a good choice,i've been using them for 6 seasons on different motors no issues to speak of..as for that Lunati cam you'll love ran one in my 360 for a season great results..
 
Ive measured 273 rockers' ratio and they're fairly close to 1.5, with a .532 lift cam it was dynamically opening the valve roughly .470-.500. That was taking into account the poor geometry of the lifter,pushrod,and rocker. I checked 4 rockers, on cylinder 1,2,7, and 8 using a solid lifter. I wasn't impressed with the consistency of the total lift from different rockers so i switched to Hughes shaft rockers and they were consistent to no greater than .006 and my total lift was about .505

My 273 rockers were beat up and scored heavily but an old timer machinist/racer said he's seen those rockers (in worse shape than mine) scream to 7000 no problem.

You're best bet would be to measure your rockers on your engine with everything in place.
 
T56MaxTorq said:
Ive measured 273 rockers' ratio and they're fairly close to 1.5, with a .532 lift cam it was dynamically opening the valve roughly .470-.500. That was taking into account the poor geometry of the lifter,pushrod,and rocker. I checked 4 rockers, on cylinder 1,2,7, and 8 using a solid lifter. I wasn't impressed with the consistency of the total lift from different rockers so i switched to Hughes shaft rockers and they were consistent to no greater than .006 and my total lift was about .505

My 273 rockers were beat up and scored heavily but an old timer machinist/racer said he's seen those rockers (in worse shape than mine) scream to 7000 no problem.

You're best bet would be to measure your rockers on your engine with everything in place.
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Wait, wait, you want him to actually measure his own rockers? Wow, I prefer the old tried and true method of asking people on this forum who have never tested the rockers themselves and repeat only the rumors that float around.

Cummon, check it for yourself? Get real.
 
Yes, the stock 273 adjustable rockers are not true 1.5 ratio...
 
I measured a few of mine, they were 1.47, 1.42 and a 1.51, kinda all over the place, but for a mostly street car I would run them until you can get a good set of aftermarket.
 
So what killed the first cam?

Are your valve springs up to that cam and you'd better check valve guides clearance?
 
IQ52 said:
Wait, wait, you want him to actually measure his own rockers? Wow, I prefer the old tried and true method of asking people on this forum who have never tested the rockers themselves and repeat only the rumors that float around.

Cummon, check it for yourself? Get real.
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Interesting name - IQ You're what we in Australia would call a Dick Head.
 
Thanks for your responses. The engine (built at home) is in a front engine dragster (built at home) using a 904 TF (built at home) with a basic 9" (also built at home home) other than the heads I'm pretty impressed with the LA engines factory engineering ( this is my first mopar after coming over from Ford Cleveland). I killed the engine not just the camshaft with methanol dilution in the oil trying to find a base line tune for our fuel injection - one of 3 sets built by a switched on guy (not me) in his home work shop. Thanks for your replys. Has anyone used Hughes rockers I have noticed they're not bushed?
 
Retroboy said:
Thanks for your responses. The engine (built at home) is in a front engine dragster (built at home) using a 904 TF (built at home) with a basic 9" (also built at home home) other than the heads I'm pretty impressed with the LA engines factory engineering ( this is my first mopar after coming over from Ford Cleveland). I killed the engine not just the camshaft with methanol dilution in the oil trying to find a base line tune for our fuel injection - one of 3 sets built by a switched on guy (not me) in his home work shop. Thanks for your replys. Has anyone used Hughes rockers I have noticed they're not bushed?
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I've put about 10k miles on Hughes LA shaft style rockers and have had zero problems. I took them off at 1000 miles for inspection and they looked good. Banana grooved shafts are a must and I've heard of folks totally trashing new rockers by putting them on new shafts without cleaning the inside of the shaft free of debris from the machining process. You have to pop off the end caps with a punch and take a hard bristle bore brush and scrub the crap out of the inside and tap and thread in an end plug. Not many guys do that. I can't speak much for Hughes magnum style rockers, I've only ran them about an hour so far. But they were so easy to install! The LA style rockers took several hours to get right with the shims, torquing and removing and taking measurements and getting everything just right. But that's likely why I don't have any problems.
 
the Lunati cam lift is .513"/.533" @ 1.5 rocker, stock J heads flow stalls at .500" lift. maybe your heads are ported, if your rockers average 1.47 U lose .010" lift-not enough to worry about in my head. if it does worry U, buy a cam with .530"-.550" lift
 
I Know nothing about dragsters but I know Marco knows stuff, and I gotto agree with the custom cam idea.
But since you already have the cam......................and the exchange sucks................it's awful tempting to run what you brung.
 
I agree, 273 rockers are good for you being 50 years old. I couldn't imagine the price after you buy the shafts, the recommended shaft hold down kit, and shim kit
 
I'd measure, then run the pi$$ out them. All the while I was enjoying the dragster I'd be saving my money to upgrade later.

I have a set of Hughes 1.6 rockers that I've ran since 02. First on my 340 and later on my 408. When I built the 408 I had the heads freshened and Ryan used Comp 930 springs which were a larger diameter than my previous spring. The rockers had to have a bunch of clearence work but have never given me a problem. Pretty good rocker for the money IMO.
 
Retroboy said:
Interesting name - IQ You're what we in Australia would call a Dick Head.
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See there, ya went and took offense at a song that wasn't even about you.

It was about my astonishment that T56MaxTorq had measured them and knew what he was talking about. Better yet, he advised you to check them for yourself.

Then I went and checked his other posts in this thread.......excellent advise has he given, I hope you follow it.

But what do I know, eh?
 
gtsdude said:
I measured a few of mine, they were 1.47, 1.42 and a 1.51, kinda all over the place, but for a mostly street car I would run them until you can get a good set of aftermarket.
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What he said.

I checked all the ones I had About 3 sets and the worst was 1.41 and best was 1.51 . Most were in the 1.44-1.45 range. They are strong and durable enough but they will hurt your lift.

Terry
 
Measure them all. Put the 8 highest ratio on the intakes. Exhaust get the lower ratio, assuming you run open header on a race car.
I did this with a Magnum 360 stamped 1.6 rocker set and it evens the valve lift the best you can for Zero $.
 
My point was that you can build a motor closer to blue print specs without spending more $; measure what you have and even it out. This is one way SS, Crate Motor, OEM valve train restricted racers get the most out of an engine.

In my case I was upgrading my cam and measured everything before deciding on lift/dur spec. Magnum exhaust port is very good design. I run open exhaust at the track with manual dumps.
I had Lunati grind a custom roller, steel core/iron gear core, for $20 more than off the shelf price.
 
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