Cam and timing set install question

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69GT

69GT

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I bought and am in the process of installing a cam and timing set in my 400 big block I am rebuilding. It is on a stand with the heads not installed yet and I have the #1 piston at TDC. The cam I bought has 4 degrees advance ground into it. Do I still install the crank timing gear on the zero degree keyway and line up the dot with the cam gear or do I need to use the 4 degree advanced or retarded keyway to compensate for the 4 degrees ground in the cam? I'm confused because with the #1 piston at TDC, the lifters are not of equal height like I thought they were supposed to be on the compression stroke. The intake lifter is slightly higher out of the bore than the exhaust lifter. The #6 cylinder lifters are equal and slightly down in their bores.
 
With the marks at 12 and 6 you are not on no1 compression, but no6 To fire on no1 you must turn the crank 1 turn so the marks are both 12 o'clock

Cams have not been ground at "split overlap" for decades.

The correct answer is to degree the cam
 
69GT said:
I'm confused because with the #1 piston at TDC, the lifters are not of equal height like I thought they were supposed to be on the compression stroke.
Click to expand...
That's cuz the cam is not on the compression stroke, lol. Just turn the crank 360 degrees and then it will be ....... assuming the cam is already installed approximately correctly........ lol. and now both lifters should be on the base circle.
69GT said:
The cam I bought has 4 degrees advance ground into it. Do I still install the crank timing gear on the zero degree keyway
Click to expand...
The ground-in cam advance is just to make it easier to get to the correct advance position with less monkeying around.
Say;
you wanted to install your cam plus 6* advanced.
And say your zero-advance cam came in at 2* retarded.
You would then need an 6+2=8 degrees offset key/keyway.

But if the Cam company has already ground 4 degrees into the timing of it, and it now falls in a 2* advance, then you only need 6-2=4 degrees of advance, so a 4*offset key/keway will do it.

Why do you want to install your cam at a specific position, other than dot-to-dot?
>Well firstly, you don't know if the dots are correctly stamped. Which would mean that the cam-timing could be anything. What if the Dot is off even by just one tooth?
>Secondly, advancing a cam, generally helps the engine develop a bit more CCP (Cranking Cylinder Pressure) which usually allows the engine to be a lil snappier at lower rpms.
>Thirdly, retarding the cam a lil, usually extends the rpm a bit on the top-end before the power drops off.
> the working range of most generic cams is about 8 degrees advanced to 4 degrees retarded, which total 12 degrees. Your engine will run anywhere in that range, and run well. But it will run best at about 4* advanced.
If you are a racer, the top-end might be more important.
If you are a streeter, and your engine only has an Scr of 8/1, making 130ps CCP, well then the bottom-end might take precedence.
But for most applications, 4* should be fine.
The thing is this, if you don't measure it now, you'll never know where it fell in. And if the engine turns out to be a dog, you may not know why, until you actually do measure it.......... If you still don't measure it, you can tear your hair out trying to find the power that was just never there.
> How much power is lost if the advance is out a couple of degrees?
Zero power is lost, it is just moved.... as a percentage. If you lose 2% on the bottom, you're likely to get 2% over the nose. So 2% of say 160hp is 3.2hp. But 2% of 320hp is 6.4hp It's the same 2%, but applied to a different part of the Power-Curve.
> sometimes, a couple of degrees of advance could be worth a few rpm of stall.
>Say you slap it in dot-to-dot, and it comes in at just 2* advanced, and you leave it there. Then you put the rest of the engine together. On the roadtest, you find out that the bottom-end is very soft, but once she get up on the cam, she goes like a cat on fire. But yur a streeter, and rpm after 5000 is not really important to you. So you do your due-diligence with a Compression test and a LeakDown test.
You find out that the engine is leaking less than 2% so nuttin wrong with that. But the C-test shows just 135CCP. But you know that the cam is in at 2* so it's a no-brainer, you can pick up about 1.6psi per degree of advance, so advance it to 6*, and pick up the CCP to close to 4 x 1.6=6.4 total, plus the 135= 142psi, and now you got a "torque-monster". But you lost about 200rpm off the top, which you don't much care about cuz now she is still motoring along quite nicely al the way to 60/65 mph.
Is 6.4 psi worth it?
IDK about you, but to me, starting from 135, yes it sure is. If I had 165psi, another 6.4 would not be. In fact, 165psi may already be too high for iron heads and pump gas. In this case, I would give up 5 psi to reduce/eliminate any tendency for detonation.
> So the bottom line is this; in a perfect world, dot-to-dot would get you 4* advanced on your cam. Do you live in a perfect world? If yes then just slap it on and go.
I know that degreeing a cam can be a PITA for a newbe. But it it really is a necessary step. Even if for no other reason than providing a reference point for future changes.
The correct answer is to degree the cam
Click to expand...

Happy HotRodding
 
Last edited:
AJ/FormS said:
That's cuz the cam is not on the compression stroke, lol. Just turn the crank 360 degrees and then it will be ....... assuming the cam is already installed approximately correctly........ lol. and now both lifters should be on the base circle.

The ground-in cam advance is just to make it easier to get to the correct advance position with less monkeying around.
Say;
you wanted to install your cam plus 6* advanced.
And say your zero-advance cam came in at 2* retarded.
You would then need an 6+2=8 degrees offset key/keyway.

But if the Cam company has already ground 4 degrees into the timing of it, and it now falls in a 2* advance, then you only need 6-2=4 degrees of advance, so a 4*offset key/keway will do it.

Why do you want to install your cam at a specific position, other than dot-to-dot?
>Well firstly, you don't know if the dots are correctly stamped. Which would mean that the cam-timing could be anything. What if the Dot is off even by just one tooth?
>Secondly, advancing a cam, generally helps the engine develop a bit more CCP (Cranking Cylinder Pressure) which usually allows the engine to be a lil snappier at lower rpms.
>Thirdly, retarding the cam a lil, usually extends the rpm a bit on the top-end before the power drops off.
> the working range of most generic cams is about 8 degrees advanced to 4 degrees retarded, which total 12 degrees. Your engine will run anywhere in that range, and run well. But it will run best at about 4* advanced.
If you are a racer, the top-end might be more important.
If you are a streeter, and your engine only has an Scr of 8/1, making 130ps CCP, well then the bottom-end might take precedence.
But for most applications, 4* should be fine.
The thing is this, if you don't measure it now, you'll never know where it fell in. And if the engine turns out to be a dog, you may not know why, until you actually do measure it.......... If you still don't measure it, you can tear your hair out trying to find the power that was just never there.
> How much power is lost if the advance is out a couple of degrees?
Zero power is lost, it is just moved.... as a percentage. If you lose 2% on the bottom, you're likely to get 2% over the nose. So 2% of say 160hp is 3.2hp. But 2% of 320hp is 6.4hp It's the same 2%, but applied to a different part of the Power-Curve.
> sometimes, a couple of degrees of advance could be worth a few rpm of stall.
>Say you slap it in dot-to-dot, and it comes in at just 2* advanced, and you leave it there. Then you put the rest of the engine together. On the roadtest, you find out that the bottom-end is very soft, but once she get up on the cam, she goes like a cat on fire. But yur a streeter, and rpm after 5000 is not really important to you. So you do your due-diligence with a Compression test and a LeakDown test.
You find out that the engine is leaking less than 2% so nuttin wrong with that. But the C-test shows just 135CCP. But you know that the cam is in at 2* so it's a no-brainer, you can pick up about 1.6psi per degree of advance, so advance it to 6*, and pick up the CCP to close to 4 x 1.6=6.4 total, plus the 135= 142psi, and now you got a "torque-monster". But you lost about 200rpm off the top, which you don't much care about cuz now she is still motoring along quite nicely al the way to 60/65 mph.
Is 6.4 psi worth it?
IDK about you, but to me, starting from 135, yes it sure is. If I had 165psi, another 6.4 would not be. In fact, 165psi may already be too high for iron heads and pump gas. In this case, I would give up 5 psi to reduce/eliminate any tendency for detonation.
> So the bottom line is this; in a perfect world, dot-to-dot would get you 4* advanced on your cam. Do you live in a perfect world? If yes then just slap it on and go.
I know that degreeing a cam can be a PITA for a newbe. But it it really is a necessary step. Even if for no other reason than providing a reference point for future changes.


Happy HotRodding
Click to expand...
AJ, I find your posts very informative, and I enjoy reading them:thumbsup:
 
69GT said:
I bought and am in the process of installing a cam and timing set in my 400 big block I am rebuilding. It is on a stand with the heads not installed yet and I have the #1 piston at TDC. The cam I bought has 4 degrees advance ground into it. Do I still install the crank timing gear on the zero degree keyway and line up the dot with the cam gear or do I need to use the 4 degree advanced or retarded keyway to compensate for the 4 degrees ground in the cam? I'm confused because with the #1 piston at TDC, the lifters are not of equal height like I thought they were supposed to be on the compression stroke. The intake lifter is slightly higher out of the bore than the exhaust lifter. The #6 cylinder lifters are equal and slightly down in their bores.
Click to expand...
What cam/specs are you installing. compression?
Cam and cam timing can make or break a stock stroke 400.
 
Without a degree wheel, you have no idea "where" the cam is. Crappy tolerances in machining of the timing set can cancel out any advance "ground into" the cam. I always disregard that anyway and simply degree it. That way, there's no guess work.
 
ive got 169.2 cranking psi highest cylinder 6 cylinders 163 166 psi 1 cylinder 155 psi no pingng on93 octane

68 340 100k on the block
replaced top end fresh 2.02 heads 218@50 454 lift 110 lsa 106 intake valve closes@60 thin head gasket comes in just under 10 to 1
same engine ran 14.3@85k miles stock with 3.23s now has a stealth 650 dp unilite 3.91s feels 13.6 13.7 now
no pinging
yes you need to degree it
10.8 to 1 is alot for pump gas depends on the cam specs
 
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What you are seeing is what I would expect for a cam correctly installed. The cam has 0.013" more exh lobe lift than the int, so that extra exh lift comes from reducing the cam base circle for the exh lobes. You are seeing that with the exh lifter sitting slightly lower than the int on #1 cyl, TDC compression stroke.
Without rotating the engine, #6 cyl at TDC is on overlap, with both lifters higher in their bores.
Exh lifter should be 0.010-0.030" higher than the int because of the extra 8* of duration.

With 4* of adv ground into the cam, the ICL should be 4* less than the LSA, with the '0' position used on the crank spkt. If LSA is 108*, ICL should be 104*. So instal on the '0' mark.
I do not agree that you need to degree the cam any further, unless this engine is an exact duplicate of another engine that had the cam tested at various ICLs to determine best HP.
I see people go to great lengths to degree a cam & finesses the position......but then do not check all the other cyls to see if any are 'out'.
Once the engine is running, you can change ICLs to see what difference, if any, it makes.
 
After Degreeing the cam you verify TDC on your harmonic balancer.
With the damper installed, you can verify the true TDC mark.
 
Last edited:
Nope,
TDC on the dampener has nothing to do with where the cam is installed.
 
Lunati Voodoo Camshafts
Camshaft, Hydraulic Flat Tappet,
Advertised Duration 276/284/110,
Lift .513/.533,
234/[email protected]
Good pick. High-intensity. Fairly mild in a 470
3.91 stroke x 4.37bore?

>Just for perusal, I took the liberty of running your specs thru the Wallace Dynamic Compression Calculator, with the following inputs; a true Scr of 10.5, at 200ft elevation, and an Ica(Intake Closing Angle) of:
at 62* the CCP comes to 177psi, and the Dcr is 8.5
at 65* the CCP, falls to 172psi, and the Dcr is 8.3
at 68* the CCP, falls to 166psi, and the Dcr is 8.1
Doing the math; 11psi/5degrees is 2.2psi per degree; worse than I thought.
>Smarter men than me, for high-efficiency, recommend a Dcr of 9.0,
which is what I run in my 367. For my engine this requires a Scr of 11/1 with an Ica of 61*, going to 11.3@Ica of 65* I have run both Scrs and higher Dcrs as well.
>But for your 470 , to get to 9.0Dcr, with the 704Voodoo, would require 11.4Scr @Ica of 65*.. The CCP would rise to ~191psi, which cannot be supported with Iron heads. It would require alloy heads with closed chambers and a tight Squish.
------------------------------
But here's the thing, on street tires, it would be a serious tire-burner, with even the smallest 4-bbl. The Volume/Pressure index shows 208!! read about V/P here:

Cam Timing vs. Compression Analysis

Cam Timing vs. Compression Analysis
victorylibrary.com
The highest that any of my 367 combos have run is 169V/P at 900ft. For me this was already a tire fryer. I sacrificed some of that, by going to a cam with a later Ica, and I lowered the Scr. Now I run about 8.8Dcr@64*Ica, and the CCP is down around 180psi. This gives the 367 a V/P of 154 which is still, OMO, excessive....... but a lot of fun! and I picked up quite a bit of Power over the nose.
>Now, for a streeter with a 470, I see no good reason to chase these premium targets. ....... unless you want to go to the track a time or two, for bragging rights among your peers. lol. OR;
If you had only 367 cubes and wanted BB type performance, well then a V/P of 169 is pretty crazy in an A-body.
As always
Happy HotRodding
----------------------------------
BTW
the Scr used to run the show. 25 years ago I was told by a reputable engine-builder, that 9.0 was the highest Scr I could run, and he wouldn't built my engine at any higher Scr. But he was willing to do all the machine-work, and I could assemble it and blow it up on my own dime.
By that time, I had figured out that Scr was just a tool to use to get the Dcr up, to a competitive number..... but no one was talking about this.
So I build my engine to my "experimental specs", and it ran gangbusters great, and she did it on 87E10. So I knew I couldda run an even higher Dcr.
This engine, IMO, made way too much top-end power, sucked gas big-time, and did not like the 3.55s that I really wanted to run. So I yanked it out.
So then, I installed a cam, THREE sizes smaller. And the bottom end, at the new higher Dcr, came alive, even with the 3.55s ; and it still ran on 87E10. The fuel mileage jumped way up, too. But she lost quite a bit of power at the top. She still went 106 in the quarter, so, I could live with that.
So, in this modern era, Scr has become a tool. and
Dcr is running the show now.
I have been reviewing material from David Vizard, lately. It seems this guy knows his stuff, which he mostly got the same way I did; He went out and just did it. The thing is this; he was a racer, and was driven to experimenting every week, to win, and made a business off his thus-gleaned knowledge..
Whereas, I'm just an average-Joe, slip-sliding around, with my stupid-azz ear-to-ear grin, that is so hard to wipe off, lol.
If there is another combo in my future, (I'll be 70 this summer, so not holding my breath), I'm going to try some of his proven ideas.
 
Last edited:
AJ/FormS said:
Now I run about 8.8Dcr
Click to expand...
When I was putting my cam/piston combo together, many on the forum advised to stay below 8 DCR. I will be running a XE 262 in a 340, so I dropped the compression height down from the original 340 high comp pistons so I could run on pump gas with my J 202's.
 
iam quite happy 10 to 1 60 ica 169.2 cranking v/p index 138 dcr 8.21
crazy low end power and the 3.91s make it silly
218@50 454lift 110 lsa smallest cam ive ever run
from idle to 5600 rpm cant imagine a better street cam iam sure there are
thats on a virgin 100k plus pistons rings and bearings
oil pressure 25psi in drive 32 psi at idle 50 psi at 1500
 
Last edited:
AJ/FormS said:
Lunati Voodoo Camshafts
Camshaft, Hydraulic Flat Tappet,
Advertised Duration 276/284/110,
Lift .513/.533,
234/[email protected]
Good pick. High-intensity. Fairly mild in a 470
3.91 stroke x 4.37bore?

>Just for perusal, I took the liberty of running your specs thru the Wallace Dynamic Compression Calculator, with the following inputs; a true Scr of 10.5, at 200ft elevation, and an Ica(Intake Closing Angle) of:
at 62* the CCP comes to 177psi, and the Dcr is 8.5
at 65* the CCP, falls to 172psi, and the Dcr is 8.3
at 68* the CCP, falls to 166psi, and the Dcr is 8.1
Doing the math; 11psi/5degrees is 2.2psi per degree; worse than I thought.
>Smarter men than me, for high-efficiency, recommend a Dcr of 9.0,
which is what I run in my 367. For my engine this requires a Scr of 11/1 with an Ica of 61*, going to 11.3@Ica of 65* I have run both Scrs and higher Dcrs as well.
>But for your 470 , to get to 9.0Dcr, with the 704Voodoo, would require 11.4Scr @Ica of 65*.. The CCP would rise to ~191psi, which cannot be supported with Iron heads. It would require alloy heads with closed chambers and a tight Squish.
------------------------------
But here's the thing, on street tires, it would be a serious tire-burner, with even the smallest 4-bbl. The Volume/Pressure index shows 208!! read about V/P here:

Cam Timing vs. Compression Analysis

Cam Timing vs. Compression Analysis
victorylibrary.com
The highest that any of my 367 combos have run is 169V/P at 900ft. For me this was already a tire fryer. I sacrificed some of that, by going to a cam with a later Ica, and I lowered the Scr. Now I run about 8.8Dcr@64*Ica, and the CCP is down around 180psi. This gives the 367 a V/P of 154 which is still, OMO, excessive....... but a lot of fun! and I picked up quite a bit of Power over the nose.
>Now, for a streeter with a 470, I see no good reason to chase these premium targets. ....... unless you want to go to the track a time or two, for bragging rights among your peers. lol. OR;
If you had only 367 cubes and wanted BB type performance, well then a V/P of 169 is pretty crazy in an A-body.
As always
Happy HotRodding
----------------------------------
BTW
the Scr used to run the show. 25 years ago I was told by a reputable engine-builder, that 9.0 was the highest Scr I could run, and he wouldn't built my engine at any higher Scr. But he was willing to do all the machine-work, and I could assemble it and blow it up on my own dime.
By that time, I had figured out that Scr was just a tool to use to get the Dcr up, to a competitive number..... but no one was talking about this.
So I build my engine to my "experimental specs", and it ran gangbusters great, and she did it on 87E10. So I knew I couldda run an even higher Dcr.
This engine, IMO, made way too much top-end power, sucked gas big-time, and did not like the 3.55s that I really wanted to run. So I yanked it out.
So then, I installed a cam, THREE sizes smaller. And the bottom end, at the new higher Dcr, came alive, even with the 3.55s ; and it still ran on 87E10. The fuel mileage jumped way up, too. But she lost quite a bit of power at the top. She still went 106 in the quarter, so, I could live with that.
So, in this modern era, Scr has become a tool. and
Dcr is running the show now.
I have been reviewing material from David Vizard, lately. It seems this guy knows his stuff, which he mostly got the same way I did; He went out and just did it. The thing is this; he was a racer, and was driven to experimenting every week, to win, and made a business off his thus-gleaned knowledge..
Whereas, I'm just an average-Joe, slip-sliding around, with my stupid-azz ear-to-ear grin, that is so hard to wipe off, lol.
If there is another combo in my future, (I'll be 70 this summer, so not holding my breath), I'm going to try some of his proven ideas.
Click to expand...
Yes, 3.91 stroke x 4.37 bore. I appreciate your insight but I have to admit, I don't understand most of the technical data you posted as I don't know much about engine building. I'm just trying to finish up my engine that a relative was building for me before he passed away midway through it.
 
CFD244 said:
When I was putting my cam/piston combo together, many on the forum advised to stay below 8 DCR. I will be running a XE 262 in a 340, so I dropped the compression height down from the original 340 high comp pistons so I could run on pump gas with my J 202's.
Click to expand...
For iron heads that is close to correct, the limiting factor being detonation with iron open chamber heads.
However, I recently fell on some data from David Vizard that teaches a rule of 128. He says every engine has exactly one LSA with which it will make the most power and torque; it goes like this;
128 (less cubic inches per cylinder/valve diameter x .91) = the correct LSA.
For a 2.02 valved 340 this comes to 109*
Since your 262 is a 110Lsa you are close enough to in the ballpark.
But I'll tell ya, if you went to a 108 on the same cam, your Compression cycle would increase by two degrees, as would your Power degrees. This would increase your CCP, and your Extraction, increasing fuel-economy AND your overlap would increase by 4 degrees, increasing your power throughout the rpm band, assuming headers are used....... with no other changes.
However your CCP might be a tad high, so you Would then retard that 108 cam to in at 106, drop the pressure back to what it is now, and gain a maybe 50 rpm at the top.
Now as to your current combo, the Forum was right.
To get a Dcr of 8.00 in your combo requires an Scr of ~9.5, depending on the Ica. Assuming 4* advanced you are spot on, and your CCP should come in at about 161psi. This is a lil tight with open chamber non-quench heads, so watch for detonation.
This combo should make good bottom-end torque, a strong midrange, and for a 340, awesome fuel-economy. This is gonna be so much fun......
 
a-bodyguy said:
iam quite happy 10 to 1 60 ica 169.2 cranking v/p index 138 dcr 8.21
crazy low end power and the 3.91s make it silly
218@50 454lift 110 lsa smallest cam ive ever run
from idle to 5600 rpm cant imagine a better street cam iam sure there are
thats on a vigin 100k plus pistons rings and bearings
oil pressure 25psi in drive 32 psi at idle 50 psi at 1500
Click to expand...
Looks and sounds like a great combo.
I once had the next bigger cam in my 360, 223/230/110 and it was and still would be my favorite cam, except it dropped lobes one morning. Like you say "crazy low-end power."
 
AJ/FormS said:
Looks and sounds like a great combo.
I once had the next bigger cam in my 360, 223/230/110 and it was and still would be my favorite cam, except it dropped lobes one morning. Like you say "crazy low-end power."
Click to expand...
When i bought that cam early 90s the split pattern 268 wasnt around and i had 3.23s i knew nothing of the .903 lifters i debated going with the comp 270h but with 3.23s i pussed out that cam only has 1 more degree ica that would have been a nice cam with the 3.91s
with a freshened short block id prolly be over 170 psi highest stock rated 340 was 175 i guess i got lucky
 
AJ/FormS said:
For iron heads that is close to correct, the limiting factor being detonation with iron open chamber heads.
However, I recently fell on some data from David Vizard that teaches a rule of 128. He says every engine has exactly one LSA with which it will make the most power and torque; it goes like this;
128 (less cubic inches per cylinder/valve diameter x .91) = the correct LSA.
For a 2.02 valved 340 this comes to 109*
Since your 262 is a 110Lsa you are close enough to in the ballpark.
But I'll tell ya, if you went to a 108 on the same cam, your Compression cycle would increase by two degrees, as would your Power degrees. This would increase your CCP, and your Extraction, increasing fuel-economy AND your overlap would increase by 4 degrees, increasing your power throughout the rpm band, assuming headers are used....... with no other changes.
However your CCP might be a tad high, so you Would then retard that 108 cam to in at 106, drop the pressure back to what it is now, and gain a maybe 50 rpm at the top.
Now as to your current combo, the Forum was right.
To get a Dcr of 8.00 in your combo requires an Scr of ~9.5, depending on the Ica. Assuming 4* advanced you are spot on, and your CCP should come in at about 161psi. This is a lil tight with open chamber non-quench heads, so watch for detonation.
This combo should make good bottom-end torque, a strong midrange, and for a 340, awesome fuel-economy. This is gonna be so much fun......
Click to expand...
Keep in mind too, the max for DCR with iron heads does not take other things into consideration such as good quench.
 
CFD244 said:
I am not sure what that means, or looks like. I have the original OEM 1971 J heads with 2.02's.
Click to expand...
Then no, there is no quench pad. Then all getting the piston to zero deck height did for you was raise compression. A quench pad is a part of the head deck surface that's totally flat opposite the spark plug. Like this. See where the red X is? That's a quench pad.
CLOSED CHAMBER PORTED (1).jpg
 
Gotcha.......I chose the pistons that I did to reduce the CR in order to run my XE 262 and keep my DCR under 8.
 
CFD244 said:
Gotcha.......I chose the pistons that I did to reduce the CR in order to run my XE 262 and keep my DCR under 8.
Click to expand...
dropped it to what?
you have the same setup almost as my cam you close @57 iam 60
iam 10 to 1 169 psi dcr 8.21
@57 close id be 174.30 dcr 8.4 i would haved liked that
 
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