The Mechanics of Adv/Ret a Camshaft ?



The Mechanics of Adv/Ret a Camshaft ?

Postby Indycars » February 4th, 2011, 12:41 pm

Without getting into the $150 and up range for timing gears and chain. There seems to be only two ways to adjust the timing for under $75, the crank gear can have several keyways or you can drill the cam gear and use bushings.

Pulling the crank gear would be alot more of a pain to change, than 3 bolts on the cam gear. The bushing in the cam gear would be alot easier!

Both ways only provide increments of 2 degrees, this seem kinda coarse for adjusting the cam timing. Does someone provide a system for adjusting timing every 1 degree without spending $150 ???
Rick
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby grumpyvette » February 4th, 2011, 1:07 pm

they only provide 2 degree increments simply because anything smaller will seldom make a noticeable change in how the engine power curve is effected,
for every 2 degrees change advancing a cam you generally move the whole torque curve about 75-100rpm lower,
for every 2 degrees change retarding a cam you generally move the whole torque curve about 75-100rpm higher,
on average Ive found advancing or retarding a cam a full 4 degrees moves the whole torque curve about 150rpm on most of the engines I build.

now horsepower , is calculated as torque times rpm, divided by 5252
so lets say an engine makes 400 ft lbs of torque at 3800rpm and 370 ft lbs at 5500rpm
thats 387 hp
retard the cam 4 degrees
you potentially could get 398 hp or a gain of 11 hp but you also tend to loose about the same on the lower end of the power band, and because the lower end is almost always used far more than peak power its rarely a huge benefit, thats one reason why most cam manufacturers tend to have cams degree in 4 degrees advance on a dot-to-dot instal.
keep in mind port cross sectional area restricts flow rats as rpms increase, so your frequently not going to get the full potential benefits

viewtopic.php?f=52&t=1070&p=2054#p2054

viewtopic.php?f=52&t=148&p=182#p182

Image


BTW you CAN advance or retard the roller timing chain, as you mentioned, its done bye drilling out the cam index pin hole in the timing gear and installing an off set bushing

http://store.summitracing.com/partdetai ... toview=sku

Image

http://www.compcams.com/Technical/TimingTutorial/

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don,t make your self crazy, install the cam at split overlap as best as you can determine, verify all clearances and valve train geometry and see how it runs before getting insane on 1-2 degree changes that will have little or no real effect on performance in most cases

related threads with valid info

viewtopic.php?f=52&t=3280&p=8680&hilit=bushings+gears#p8680

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=90

viewtopic.php?f=52&t=788

viewtopic.php?f=52&t=1769

viewtopic.php?f=52&t=1376

viewtopic.php?f=52&t=528
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby Indycars » February 4th, 2011, 1:51 pm

I would have thought with all the talk about degreeing your cam, it would be important to get closer than 2 degrees. I guess in actuallity the worst you could be off is 1 degree. If you are 2 degrees off, then the bushing would put you right on. If it's 1 degree off, then that's when you have the hardest decision to make.

If using the bushing, do you drill all the way thru, or do you leave a shoulder to retain the busing in the cam gear ???

I assume they work just fine with the later cams that use a thrust plate....right ???
Rick
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby grumpyvette » February 4th, 2011, 2:13 pm

Ive always drilled all the way thru, just remember the nylon cam button and bolt retaining plate on all the early engines that came with flat tappet cams,,if your using a more recent roller cam block engine with a cam retainer plate obviously the cam buttons not required, but the bolt retaining plate is still used to secure the bushing and screws.


if your converting too a roller cam from a flat tappet design don,t forget the cam button, or cam retainer plate is mandatory on a roller cam

Image
You Identify them by measuring the retainer plate hole spacing

(#10088128) GM roller cam thrust plate, used on all roller cam engines.
First design with 3.620" bolt pattern.
1991-2000 engines use # 10168501 with 3.294" bolt pattern.Please measure your center to center mounting bolt pattern if unsure.
Image
Image
this button is improperly installed as its missing the lock plate, that holds in both the cam button and bushing on the cam index pin
Image
Image


Image
look closely theres three crank key slots and each is marked, with the crank key (R or rectangle) =(retarded 4 degrees) (0) strait up) and (A or triangle) =(advanced 4 degrees) located at approximately the 2 0,clock position the related mark(R or rectangle)= (retarded 4 degrees) (0) strait up) and (A or triangle) advanced 4 degrees) is at the 12 o,clock location that you use to line up with the cam gear while thats indexed at approximately the 6 o,clock location

BTW theres also 2 degree off-set crank keys

Image
http://www.summitracing.com/parts/MRG-985G/

your degreeing in the cam to verify its within that 1-2 degrees of where its intended to be,as there are plenty of guys who make installation mistakes and a few manufactures that feel "CLOSE is GOOD ENOUGH!"
you might be amazed at how often the DOT-TO-DOT install location is NOT within a few degrees of where you would ASSUME it should be!
ASSUMING things are correct rarely gets the best results, its true it takes a good deal of extra effort to verify everything but at least you know its done correctly,thats a huge advantage over the thousands of guys who slap components together out of the box without verifying and then remain clueless when parts start self destructing because they never checked clearances or geometry etc
.


viewtopic.php?f=52&t=4548&p=12128#p12128
yes there is a good reason to avoid those cheap import timing chain sets that auto parts stores frequently sell for under $30.........heres one with less than an hours of run time
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby Indycars » February 4th, 2011, 2:28 pm

When you are using a thrust plate like below, will the bushings still work ???
Have you noticed any negatives when using the bushings ???
thrustplate.gif
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Rick
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- Check Out My Dart SHP Engine Project: viewtopic.php?f=69&t=3814
- Need a Dynamic Compression Ratio Calculator: viewtopic.php?f=99&t=4458
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby grumpyvette » February 4th, 2011, 2:52 pm

Indycars wrote:When you are using a thrust plate like below, will the bushings still work ???
Have you noticed any negatives when using the bushings ???
thrustplate.gif


yes they still work and no Ive never seen or even heard of a problem using them,
yes you may need to also drill the cam timing gear retaining bolt holes in the cam gear a bit larger in a few cases, but with a 2 degree change thats rare
(obviously I use loc-tite on the cam bolt threads and a cam bolt retainer plate)
Image
Image
Image
this cam buttons correctly installed but thee retainer plate tabs have not been bent up to lock the bolt heads from rotating
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby Indycars » February 5th, 2011, 1:00 pm

I came across these CROWER bushings this morning while looking for a cam timing set. Looks like what I was thinking I needed, every one degree is possible with these. Along with a crank gear that has extra keyways, I should be able to get damn close.
CrowerCamBushings.JPG
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Rick
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- Check Out My Dart SHP Engine Project: viewtopic.php?f=69&t=3814
- Need a Dynamic Compression Ratio Calculator: viewtopic.php?f=99&t=4458
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby grumpyvette » February 5th, 2011, 2:02 pm

thanks for posting that I thought those were discontinued years ago.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: The Mechanics of Adv/Ret a Camshaft ?

Postby Indycars » February 8th, 2011, 10:59 am

Here is another option. Mr Gasket makes the bushings in

0, 2, 4, 6 & 8 degrees
http://www.mr-gasket.com/ProductDetails ... election=1

0, 1, 3, 5, 7 degrees
http://www.mr-gasket.com/ProductDetails ... election=1

TimingGearBushings.JPG
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Rick
Too much is just enough!!!

- Check Out My Dart SHP Engine Project: viewtopic.php?f=69&t=3814
- Need a Dynamic Compression Ratio Calculator: viewtopic.php?f=99&t=4458
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