Any gains adding 1.6 rockers to stock 273?

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BPTracing

BPTracing

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Ok, once again to prove my ignorance of 273's......I see a few manufacturers selling 1.6 rockers. It got me to thinking maybe it would help my little motor breathe a touch more without actually having to open up the motor and change the cam.??

In all honesty, I have not yet actually measured the current cam to verify it is stock, and the motor paint looks a little to good to be original. But the lack of power has me leaning toward the idea it is "very stock". So until I get a spot open in the garage do some hands on inspection, I am just banging a few thoughts against the inside of my head.

Merry Christmas to all!

Scott
 
I would think certainly not enough to justify the cost.
 
If it's a stockish cam, it will increase the ramp speed of the lobes a bit and probably give a little more performance under the curve. It certainly wont give a big seat of the pants feel i think you're looking for.

Also, head clearance on the pushrods may become a issue.

Merry Christmas Scott.
 
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RustyRatRod said:
I would think certainly not enough to justify the cost.
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about .030 to .040 more cam lift , depending on what u got to start with.
But do u have the piston to valve clearance for it ???????
 
famous bob said:
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about .030 to .040 more cam lift , depending on what u got to start with.
But do u have the piston to valve clearance for it ???????
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I wouldn't think the stock 8.8 compression would have too much piston to valve clearance issues, but I do have a set of light springs so I could check without removing the heads.
 
I found a set for $300 which is much cheaper than installing a new cam.

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I guess we should ask what this 273 2bbl is in. Any added bolt on's, gear ratio etc. What do you you really want it to do. Maybe a few extra bucks would warrant a cam swap...
 
you have to elongate pushrod hole area, reason is they hit at max lift, i've done that for others . there's not much improvement for money spent, just food for thought. heads have to come off to elongate pushrod areas.
 
It's not going to be a night and day difference.
Before doing anything, I would make sure the rest of the motor is up to snuff with everything working the way it should. Compression and leakdown test, optimize the timing and advance curves. If it's a high mile engine, you may need to open it up to change the timing chain anyhow, and at that point it's not much more work to switch out the cam. They're fairly peppy when running right.
Is it a 2 bbl. or the 4 bbl. HiPo motor?
If you do decide to try the rockers, SpeedMaster has 1.6s for about $200.
https://www.speedmaster79.com/Mopar-Chrysler-SB-318-340-360-160-Ratio-Stainless-Steel-Roller-Rocker-Arm-Set
They're not top of the line, but more than adequate for a stock 273. Just be aware that with these and many other rocker sets, you'll also need different pushrods since the factory used ball and cup pushrods and these use ball and ball.
 
You'll come out WAY ahead of this rocker arm swap if you give the distributor a good hot ignition curve. Get the initial timing up between 16-20 degrees and limit total to around 34-36 degrees and put some light spring in it. That's a seat of the pants difference. Much cheaper, too.
 
man, i'd be looking at maximizing what you have now: ignition, timing, carb, exhaust

in getting there, a deep diagnostic baseline would be needed: leak down test, cylinder balance test, compression test.

then at least you'd know if you have something worth tuning or more work to do.

i'd be throwing a cheap cam at something like that before roller rockers. you can get a repop melling 340 cam and lifters for about $300 or send your stuff out and have it reground for even cheaper. which would net you real, tangible results.

what's your current set up?
 
Everyone keeps mentioning simple things. The Car already has an aftermarket electronic distributor. I have not had the chance to check timing curve rpm. Exhaust is stock manifolds, but aftermarket dual exhaust and Flowmaster mufflers (which I hate due to too much interior noise).
perfacar said:
you have to elongate pushrod hole area, reason is they hit at max lift, i've done that for others . there's not much improvement for money spent, just food for thought. heads have to come off to elongate pushrod areas.
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Thank you for that tidbit!!! I was unaware of the need to modify the pushrod holes!

As far as pushrods, I can change the adjusters out to ball style quite easily.
 
BPTracing said:
Everyone keeps mentioning simple things. The Car already has an aftermarket electronic distributor. I have not had the chance to check timing curve rpm. Exhaust is stock manifolds, but aftermarket dual exhaust and Flowmaster mufflers (which I hate due to too much interior noise).

Thank you for that tidbit!!! I was unaware of the need to modify the pushrod holes!

As far as pushrods, I can change the adjusters out to ball style quite easily.
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You are defeating the advantage of the 1:6 by changing back to ball adjusters. Plus I think you will still need custom pushrods.
 
I don't understand how the adjuster would "would defeat the advantage"??
I wpuld think the 1.6 rocker is still the same length no matter which adjuster is used.
 
BPTracing said:
Everyone keeps mentioning simple things. The Car already has an aftermarket electronic distributor. I have not had the chance to check timing curve rpm. Exhaust is stock manifolds, but aftermarket dual exhaust and Flowmaster mufflers (which I hate due to too much interior noise).
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well, yeah. you didn't tell us what your set up was to start with. how are we to know that you're not trying to put roller rockers on a 2bbl manifold with 4bbl adapter and a janky *** holley economaster, that's got a soft hole and slap *** wore out stock points ignition.
 
BPTracing said:
I don't understand how the adjuster would "would defeat the advantage"??
I wpuld think the 1.6 rocker is still the same length no matter which adjuster is used.
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The ball and ball pushrod takes less of a beating. Think of the location of the lever compared to fulcrum. It does not totally change the ratio but it makes the pushrod angle better.
 
1.6 rockers increase the effective duration about 2*. You would be lucky to feel the difference with a stock-ish engine....
 
Bewy said:
1.6 rockers increase the effective duration about 2*. You would be lucky to feel the difference with a stock-ish engine....
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Am I wrong to think that it has more to do with pushrod angle than it does rocker ratio or a combination of both?
 
A 273 is weak to begin with. Adding ever so slightly increased duration and lift won't amount to anything perceptible. Total waste of time and money imo.

Too many folks trying to forge different paths. But there's no shortcuts to power.

Get some headers, an improved intake, a 4bl carb, some upgraded valvesprings, and a mild cam. It'll be a significant improvement.

If you're crafty with your shopping it won't cost that much more than those 1.6 rockers.
 
I doubt that if he is running the 2 bbl economy carb, there won't be enough fuel there to take advantage of anything.

☆☆☆☆☆
 
Mean416 said:
A 273 is weak to begin with. Adding ever so slightly increased duration and lift won't amount to anything perceptible. Total waste of time and money imo.

Too many folks trying to forge different paths. But there's no shortcuts to power.

Get some headers, an improved intake, a 4bl carb, some upgraded valvesprings, and a mild cam. It'll be a significant improvement.

If you're crafty with your shopping it won't cost that much more than those 1.6 rockers.
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This is so true concerning a sound engine. Might add the fore mentioned ignition mods.:thumbsup:
 
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