Any gains adding 1.6 rockers to stock 273?

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I actually was not trying to modify the motor. One of the valves was "Ticking". Inspection found the ball worn off the adjuster. When looking for a replacment, I found the 1.6 rockers. So I asked if anyone had info. since I don't know the particulars on this motor.

In fact I am trying to NOT modify the motor significantly. It is definitely a slug, so I am planing on changing to a 4bbl., but I don't want to "get into" the motor unless I have to. I know the slippery slope that could lead too.

Maybe one day after multiple other projects I might add turbos, or install a 383 I have, or even a 6.4 hemi. But for now I just was a fun cruiser to play in.
 
BPTracing said:
Lol... Just curious, exactly what question did I ask that was un-crew chief like? The only question I asked was about adding 1.6 rockers to a stock cam/heads. On paper, the lift gain would be similar to a "Mild" cam swap without having to pull the front of the motor off. I stated I have no experience with the 273 motor, and was hoping to gain insight from folks who had hands-on experience with the 273.

I got the information I was looking for, plus a lot of speculation of what I "should" do. I never asked what I should do, only asked if anyone had tried the 1.6 rockers. Using the knowledge of members on this board, I did not have to do trial and error to find the pushrod clearance on that motor (which i am unfamiliar with) could be a minor issue with the increased rocker ratio.

My full time salaried position is Crew Chief for Laris Motorsports Insurance Racing. I never said I was an engine builder.

Our Laris Motorsports Insurance Racing team entered 5 NHRA National events in 2023. We had a car in the FINAL at all 5 of these races. So I would think my abilities to work as a crew chief speak for themselves. The race team has 1 employee. My drivers are in the shop only a few times per year, and fly to the races.

A fresh motor as shipped to the shop vs a motor after I have it ready to run.

View attachment 1716183190

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It needs more blower.
 
Mean416 said:
Hey man, respect where it's due. That stuff looks truly legit.

However it begs the question. If you're orchestrating this level of organization, why do you need advice on modifying a street motor?

It's akin to a 5 star chef asking questions about how to make a PB&J sandwich. It's confusing is all.

Again, props on the race team stuff. That's really cool. Do you have any content you can share?
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Maybe he has little to no experience in old pieces of ****. There's a guy I know in town who is the dead best diesel mechanic most likely in Georgia. He's that good. Computer diagnosis and all. But put a carbureted gas motor in front of him and he is totally lost. He usually calls me and I go into town and give him a hand. Just because someone knows one method doesn't mean they know another.
 
I doubt the 273 head flows any major difference from .400-.500+ lift.
 
273 said:
I doubt the 273 head flows any major difference from .400-.500+ lift.
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....and in fact could quite possibly get into some stall. I use terms like I know what all that means. Don't take that for granted. LOL
 
BPTracing said:
I actually was not trying to modify the motor. One of the valves was "Ticking". Inspection found the ball worn off the adjuster. When looking for a replacment, I found the 1.6 rockers. So I asked if anyone had info. since I don't know the particulars on this motor...
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Did you replace the adjuster? I probably have extras.
 
Here open chamber 318 675 heads doubt 273 is much different. It peaks a 184 cfm @ .350 lift, but within 11 cfm difference between .300-.800 lift.

 
66-67 273 heads are different, besides being closed chambers.

www.forabodiesonly.com

302 heads

lelo, that was my next question, if i port the heads i have based on the head porting sticky on here and have them milled slightly that should be a big help theyre supposed to be 60-62 cc's am i correct in this thinking. and does anyone other than kb make a higher compression piston for the 318?
www.forabodiesonly.com www.forabodiesonly.com

See post #47.
 
I wish I had asked to have my 273 heads flowed. It doesn't matter to me but it would be fun and interesting to have some numbers. One was a 920 had and one a #238. (engine repairs done back in 73. There was one late 1972 rod bearing) If I ever take my heads off for any reason I should have someone flow them just for fun.

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CPDave said:
273 Cleanup Port/Valve Job 1.78"/1.50"
(pretty much a "stock" class vavle job)
0.100" 49 43
0.200" 98 85
0.250" 124 100
0.300" 145 112
0.350" 162 120
0.400" 179 125
0.450" 188 129
0.500" 190 132
0.550" 185 134
0.600" 177 135
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Depending how much clean up and valve job helped, which could be decent amount.
But let's say these are right so were talking .400-.450" range 179-188 cfm range. In a engine that's makes like 1 hp per cfm. Not saying there won't be a gain but highly doubt be much plus valve float could start earlier with 1.6.
 
I'm currently checking valve train clearance on a 360 magnum block with Edelbrock LA heads, hughes rockers, sft lunati cam. The difference in valve lift at the valve between a hughes 1.6 and 1.5 rocker is .010
 
66fs said:
Did you replace the adjuster? I probably have extras.
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Thank you. I called on a buddy in Arkansas and he had a set of adjusters he is sending me. Hope to have them Thursday.

I had looked online and didn't find any, which is how I came across the 1.6 rockers and started this whole mess of the thread! LOL

Scott Spies
 
Reminds me of when I ran my '67 318. Intake and small 4brl, electronic ignition; Halifaxhops on this site is great for a custom curve, and 3.55 gears. Make sure your trans is setup right and you should be good to go. Nice Dart you have there.
 
BPTracing said:
Thank you. I called on a buddy in Arkansas and he had a set of adjusters he is sending me. Hope to have them Thursday.

I had looked online and didn't find any, which is how I came across the 1.6 rockers and started this whole mess of the thread! LOL

Scott Spies
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Fun isn't it. :lol:
 
BPTracing said:
Thank you. I called on a buddy in Arkansas and he had a set of adjusters he is sending me. Hope to have them Thursday.

I had looked online and didn't find any, which is how I came across the 1.6 rockers and started this whole mess of the thread! LOL

Scott Spies
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This? This is a pretty clean, polite, well orchestrated discussion. Especially compared to basically every other 273/318 related thread
 
I have asked Dwayne Porter( Porter racing heads) several times about putting 1.6 intake rockers on my motor and he said he has rarely seen such a swap make a difference.
and I have only a 565 lift cam on heads that pull to 650.
so on a stock 273, it’s even more unlikely to make any difference.
standard bolt on and gears, or as has been mentioned, by a cheap 360 and toss it in, probably biggest bang for buck you could do.
 
RustyRatRod said:
Ok then why the heck did you even come and ask? You've got your mind already made up. When you spend 300 bucks and there's not one single detectible change, I'm sure you'll come on here bragging about how it has 500HP. We're just trying to save you 300 bucks for basically nothing. Go for it. You've made your mind up.
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Had a friend once asked me, " I just installed chrome valve covers and chrome air cleaner, what else can I do to make it faster?". I would look for a 318 forged crank and you will be good to go. A 360 you will need a few more items, as the balanced converter and different motor mount (one). 4-Bbl intake and headers would be a must for me on any of the motors. Skip the 1.6 rockers for now, unless you are ready to speed the "BIG" bucks for the complete package.
 
With 85k on the clock. I would verify that the original timing set has been replaced.
If it is not 185k there is a chance the original set is still hanging in there. The nylon teeth would have to be very brittle by now.
I put a street master intake and AFB carb on a stock 273 with manifolds and dual exhaust. Seemed to make a worth while difference.
 
Back in the late sixties, I went with my Dad to Smitty's Speed Shop in Dayton, Ohio to discuss replacing the 361 in Dad's 62 Dodge with a 440. Smitty had a fairly new Valiant wagon, 273 automatic. Originally a two barrel, Smitty said it was too slow with the two barrel, so he swapped in a four barrel. Can't remember about the exhaust. But otherwise, it was totally stock. He was happy with how much better it ran with the four barrel.

I'd say ditching the two barrel for a four barrel would be the single biggest - and easiest - improvement. Especially at higher speeds.
 
You will get some benefit in torque, something along the line of putting a "RV" cam in. You will pick up a slight amount of duration at 0.050" lift along with the almost 0.030" lift. The duration will not produce much, but the added lift on a low lift cam will be a benefit. Now you do not want to expect miracles. What is your installed valve spring height. If it is about 1.800" you could get beehive springs to aid valve control. The extra rocker ratio stresses valve control a bit due to the faster valve opening travel speed. Depends on how hard you intend to run it.
Down the road if you need to touch up.the valve seal, you could look to Magnum or LS valves. Larger valve diameters with smaller valve stems.
Ignore the NA SAYERS on here. Too many that are more race oriented and nothing is good enough until it is too much. As long as valve to piston clearance is good there is nothing but benefit.
I would be very cautious about stuff that is cheap. These days you do not seem to be able to trust expensive parts either, but you get more or less what you pay for. Look for American manufactured. Too much Chinese **** is just that, reconstituted Yak turds.
 
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As I said early on in this thread, you are unlikely to feel the difference going to 1.6 rockers.
There is NO guarantee that you will feel the difference. Nor is there any guarantee that you will get a 0.030" increase in valve lift. This is because rockers actually vary in design & actual measured lift. David Vizard comprehensively tested a variety of rocker arms in his BBC book. All were supposed to be 1.7 ratio. Actual measured valve lift varied from 0.555" to 0.636".
 
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