1.6 Rocker Arm Performance Gains over 1.5 Rocker Arms

[Demonstrator]

Hey guys I am going through my 340 this winter and considering using the existing Cam but upgrading to 1.6 rocker if there is some decent performance gains. Is it worth spending $600-$800 to utilize 1.6 rockers or should that investment be better used on something else?

Cam: Hughes old grind HE3038AL 230/236@050 .515/.535 110* lsa with 1.5 273 rockers. 1.6 would yield .552/.571.
10:1 compression Hughes Stage 1 porting X heads everything else pretty stock except headers.

Thanks

 

[Kendog 170]

Curious

 

[Newbomb Turk]

Hey guys I am going through my 340 this winter and considering using the existing Cam but upgrading to 1.6 rocker if there is some decent performance gains. Is it worth spending $600-$800 to utilize 1.6 rockers or should that investment be better used on something else?

Cam: Hughes old grind HE3038AL 230/236@050 .515/.535 with 1.5 273 rockers. 1.6 would yield .552/.571.
10:1 compression Hughes Stage 1 porting X heads everything else pretty stock except headers.

Thanks

Highly unlikely and you can’t just bolt on 1.6 rockers most of the time.

I don’t care what color or what name is on the rocker it will need the geometry will need to be corrected.

Best case scenario IF you can use the faster valve motion and IF you can control the valve train and IF you have enough spring pressure at the lift you actually have, not at some arbitrary lift number then the gains might be 10 hp on average. If the valve train stays in control.

Maybe.

 

[Demonstrator]

Highly unlikely and you can’t just bolt on 1.6 rockers most of the time.

I don’t care what color or what name is on the rocker it will need the geometry will need to be corrected.

Best case scenario IF you can use the faster valve motion and IF you can control the valve train and IF you have enough spring pressure at the lift you actually have, not at some arbitrary lift number then the gains might be 10 hp on average. If the valve train stays in control.

Maybe.

Agreed. LA geometry is an issue. I'm probably getting just over .500 lift with the stock rockers. My thought was at least with that Cam there would be no break in issues.

 

[jos51700]

That's part of why I chose to run Magnum heads. Six percent more lift all through the curve.

 

[Kendog 170]

273 rockers (I heard) are limited on lift? Any thoughts?

 

[Demonstrator]

273 rockers (I heard) are limited on lift? Any thoughts?

Well I used them back in the 80's with a .590 purple shaft. No issues, I think correct pushrod length is "very" important.

 

[PRH]

My question is, how much extra power would you have to see from the rocker swap to justify the cost?

And, does it seem reasonable to think it would play out that way?

 

[33IMP]

Return on investment? Next to nothing.


But I'm curious. Have you checked the actual ratio of the rockers you have? I used stock mopar iron adjustable rockers on a purple .590 solid
After lash, valves actually moved about .525. Rocker ratio was closer to 1.4 than 1.5.

 

[Dart Frog]

Probably not the way I would spend my money. small gains would be expected you most likely would fall into clearance and possible geometry issues as stated in previous post. I think really a lot would depend on the extent of your head porting. Even though it would be more labor intense it would probably make as much sense just to change the camshaft if more lift is what you feel you need.

 

[mopowers]

If it's running well as-is, use the 600-800 on fuel.

 

[Demonstrator]

If it's running well as-is, use the 600-800 on fuel.

It does run pretty well, 12.50's. The rear main is starting to drip more than i'm comfortable with. Going to pull the engine and go through it and looking to go 11.80 - 12.00 and run in Sportsman class next year.

 

[Bodyperson]

If you went from 1:4ish to 1:6 with a geometry correction, I belive the gain would be significant.

 

[Rocket]

What is your 60 foot time and the rest of your setup like tires, suspension, converter, …? I ask as this may be another option to work to get some solid gains for that kind of $$

 

[michiganpat]

can your heads support that much more lift and not coil bind or smash the retainer into the guide? have your heads been on a flow bench? do you know what their flow is at varying lifts?

 

[Demonstrator]

can your heads support that much more lift and not coil bind or smash the retainer into the guide? have your heads been on a flow bench? do you know what their flow is at varying lifts?

They are X heads with Hughes Stage 1 porting, I don't know the flow numbers. Springs that are in are supposed to be good to .550 lift

 

[Demonstrator]

What is your 60 foot time and the rest of your setup like tires, suspension, converter, …? I ask as this may be another option to work to get some solid gains for that kind of $$

60ft Sunday was 1.70, 7.92 1/8th, 12.57 quarter, stock springs, I do have Caltracs going on this winter. 904 with a 3400 converter. M/T drag radials 28" and 3:91 posi. Car has serious mid range power.

 

[michiganpat]

their "stealth" porting on LA heads in this article looks like flow peaks in the .450-.5" lift range, dunno how that compares to their stage 1 porting. you would end up getting a little more duration at peak (mathmatically speaking, .45" valve lift happens at .3" of lobe lift with 1.5 ratio, .281" lobe lift with 1.6 ratio)....guessing it wouldn't be a super significant difference.

https://www.hughesengines.com/TechArticles/1headflowchartscomparisons.php

 

[RustyRatRod]

Negligible on a dyno and you'll never feel it in the seat of your pants.

 

[Bodyperson]

their "stealth" porting on LA heads in this article looks like flow peaks in the .450-.5" lift range, dunno how that compares to their stage 1 porting. you would end up getting a little more duration at peak (mathmatically speaking, .45" valve lift happens at .3" of lobe lift with 1.5 ratio, .281" lobe lift with 1.6 ratio)....guessing it wouldn't be a super significant difference.

https://www.hughesengines.com/TechArticles/1headflowchartscomparisons.php

Ya, on a flow bench but how far is the valve really opening on a running engine?

 

[RustyRatRod]

Ya, on a flow bench but how far is the valve really opening on a running engine?

If it's with solid lifters, it's whatever the lift is, minus lash and pushrod angle. If it's with hydraulic lifters, who the heck knows? lol

 

[rumblefish360]

The answer you’re really looking for lays within the cylinder head. Of course, it’s start with if you have room to lift the valve. But we will pretend you do.

The heads you have below;

What, if any gains are seen after the .550 value? The head is already loosing flow after .500. While yea, you’ll see .500 twice, no big deal in my book at your level, none at all, the flow starts falling and lifting the valve higher only delays more time to get back into a higher flowing area while the air speed and more probably the quality falls off terribly.

It’s a no win situation.

The chart only gives .050 increments. If you’re actually getting your lift, what is the head actually flowing?

Having actual flow data from your own bench or done for you, you can take advantage of the head at its maximum. Don’t worry if it doesn’t match what they say it does. Just find out how it does. (For next time.)

This way you can get a cam customized to lift the valve higher and up to whatever point you need/desire.

A call to a company like Schneider cams with that information and what your doing with the engine/car will yield a much better cam and performance outcome for you next time.

For now, stay with what you have.
Have your rockers corrected for there ratio. I can’t remember who does this off hand. I know someone does this.

OR grab new rockers. I’d ask member @B3RE (If memory serves well) for his recommendations on rockers to use with stock heads. & his geometry correction kit that’s well worth the price.

He is an excellent fella to work with.
He gets the “Fishes fin of approval!”

 

[Mopar Sam]

Have your rockers corrected for there ratio. I can’t remember who does this off hand. I know someone does this.

Performance Rocker Arms

Performance High performance rocker arms 25 years experienced employee owned.

rockerarms.com

 

[33IMP]

Your 1.70 60 is very good for a 7.92. Could run as good as low 12.30s as is. Looks to me that what you need for your goal is more camshaft, not just rocker ratio.
7.92 corresponds to a 12.57 very well.

 

[TT5.9mag]

It does run pretty well, 12.50's. The rear main is starting to drip more than i'm comfortable with. Going to pull the engine and go through it and looking to go 11.80 - 12.00 and run in Sportsman class next year.

You need a bunch more than 1.6 rockers to drop .7 at the 12.50 range. You need more camshaft and compression, and that may not be enough. Possibly more cylinder head. That’s if the car is sorted fairly well and you’re not dumping a bunch of ET in the short times.