Cam degreeing question

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mvh

mvh

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I bought a new Clowes double-roller timing set for my 273 Commando. It has three key positions, so you can install the cam advanced, at zero, or retarded. I understand that advancing the cam makes more low end torque, and retarding it makes more peak power. My question is, how much would the torque peak move given 2 degrees of cam advance? Would it come in 200 rpm lower, or 500, or 1000?

The stock Commando has a torque peak at 4000rpm, which is unusually high. So that's why I'm asking -- would it make sense for day-to-day driving to move it down somewhat?

The 273 is mostly stock, with .030-over TRW hypereutectic pistons and a Crower hydraulic cam (advertised duration 264, .427 lift). I'm running a 904 with stock converter and a 3.23SG. So my thinking was it only sees 4000rpm for a few seconds at a time, and then only rarely on WOT acceleration.

But someone told me they once tried 4 degree cam advance on a small block, and hated the result. Of course, there are small blocks and there are small blocks, with very different characteristics -- for comparison, the 273 2bbl has a torque peak at 1600rpm -- a very different kettle of fish.

So I was looking for any real world experiences. Thanks in advance.
 
Regardless of what timing set you have, please do yourself a favor and degree it in...those marks on the crank gear may say 2* adv/ret or 0*, but if the cam is ground wrong, or the cam gear is dimpled on the wrong tooth, you could be as much as 16* off...been there done that.

With a mild aftermarket cam in a stock small block, you may not even notice 2*, but it certainly couldn't hurt on the low end unless you have issues with detonation-might help your mileage too. If your friend had issues with advancing their cam 4* and hated the result, their combo may've been wrong, or timing could've been off...or they may've actually retarded the timing by mistake...any number of reasons could've affected the outcome there.
 
The answer is "I don't know" whether you'd gain something by changing this cam

What you might do is to carefully plot out lift and duration, unless you KNOW what the cam is for certain, and then look around. Many times guys who've built many engines have a good idea by comparing to others, and past results "where" to stick a cam.
 
txstang84 said:
Regardless of what timing set you have, please do yourself a favor and degree it in...those marks on the crank gear may say 2* adv/ret or 0*, but if the cam is ground wrong, or the cam gear is dimpled on the wrong tooth, you could be as much as 16* off...been there done that.
Click to expand...

Agreed. A few yrs. ago I degreed a cam in on a buddy's 454 Chevy and it was 18* off. After some diagnosing we found the timing set was marked wrong. I also rounded up 4 different brand timing sets and using the same block and cam degreed each. None were the same. Only 1 was close enough to use as-is. 2 of them were 4 degrees off. In your case I'd be tempted to degree it to 2* advanced but not more.

Correct me if I'm wrong but I believe the 273 commando's used a single plane intake and a solid lifter cam. That along with the small cubic inches will generally produce a fairly high rpm peak torque.
 
Yes. the 273-4bbl torque peak was at 4000rpm, stock. Still running stock manifold and carb. This engine has a Crower hydraulic that is just a tiny step up in duration and lift (264 vs 248; .427 vs .415/.425), so I figure the peak didn't change much. I did degree the cam and verified the timing set was dead on. But before I buttoned it up I thought I'd check into whether advancing (or retarding) it would be of benefit.

Researching the archives, it seems that advancing the cam will build cylinder pressure faster. That is not really something I need since it is already high compression (nominally 10.5:1) and runs on the verge of detonation (with today's crap fuel). It sounds like advancing it is something you would do if you had a low compression motor or a really big cam with lots of overlap, neither of which applies. Since it was running good before (I had to pull the heads because of a crack in the water jacket, and was replacing the water pump and timing chain "while I was at it"), I am thinking I should just leave it straight up. Thanks for the input.
 
advertised 10.5:1...in reality it's probably closer to 9.5:1. All that being said, regardless of which position you choose, degree the cam in with a wheel, and I'd almost bet money what you pick, ain't what it'll degree to.
 
Give Crower a CALL,not an email. Ask for Oliver Reed. He's their sharpest, cam guy available. Email gets generic answers at Crower.Oliver,knows his Crower sh*t.
 
I was thinking they were defunct (this cam is well over 20 years old) -- I wasn't finding any info at all. Thanks for the tip.

Responding to other posts, yes, I did degree it, and the timing mark was dead on. So the Clowes double roller with 3-position sprocket is apparently a well engineered piece.

Abodybomber said:
Give Crower a CALL,not an email. Ask for Oliver Reed. He's their sharpest, cam guy available. Email gets generic answers at Crower.Oliver,knows his Crower sh*t.
Click to expand...
 
Many years ago I used one of those 3 keyway timing sets. Unfortunately I misread the marks and installed it in the 4 degree retarded slot. Car would barely run.
 
I went to the Crower site, and they have a "get your cam card" feature. My cam # was no longer listed on the site, but when I typed it into this form, the cam card came up. So now I have the complete specs. The important thing I found out was that this cam had 4 degrees advance ground in. So I definitely don't want to dial in more advance.

If you're interested, it's the 31914 Baja Torquemaster. The "Baja" cracks me up. I don't recall seeing many jacked-up off-road Barracudas back in the day.


Abodybomber said:
Give Crower a CALL,not an email. Ask for Oliver Reed. He's their sharpest, cam guy available. Email gets generic answers at Crower.Oliver,knows his Crower sh*t.
Click to expand...
 
mvh said:
I went to the Crower site, and they have a "get your cam card" feature. My cam # was no longer listed on the site, but when I typed it into this form, the cam card came up. So now I have the complete specs. The important thing I found out was that this cam had 4 degrees advance ground in. So I definitely don't want to dial in more advance.

If you're interested, it's the 31914 Baja Torquemaster. The "Baja" cracks me up. I don't recall seeing many jacked-up off-road Barracudas back in the day.
Click to expand...

You're welcome,LOL.... Those were designed in the mid/late 70's,as their "R.V cam". Designed to make low compression vans/4WD's make more torque . It's a decent grind,as a daily driver kinda thing.
 
Just because the cam has 4* ground in doesn't it may not need to be advanced. It all depends on where it ends up on the degree wheel.
 
i have the same timing set.and had to use the four devree advance slot.for my cam.max you should still degree your cam in as the cam carc calls for
 
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