# Camshaft Replacement



## mighty454 (Mar 31, 2010)

Hi, I'm currently freshening up my engine. I'll be putting in a new billet HEI distributor, Kool Flow aluminum waterpump, edelbrock performer intake, Holley 4160 600cfm, Holley mechanical fuel pump, Comp Cam Roller timing set, Isky 270 Mega camshaft, lifters, and pushrods. 

I was not intending on replacing the rockers and was just going to buy Mr Gasket Poly locks but I read some where that it is necessary to replace the rockers as the pushrod wears the rocker to the personality of the original cam. I don't mind replacing the rockers if I have to, but I would rather use that money for a different part of my project if I don't have to buy them.


Any advise? Also, I'm new to the Indian motors and have a little bit of confusion. For me to be at TDC #1 do my timing gears need to be at (bottom) 12 o'clock and (top) 6 o'clock or I read somewhere else both gears at 12 o'clock?

I would like to have everything in place so I can slide my cam in, timing gears, distributor at the correct setting so I have the least issues when I go to turn the car on.

Thanks ahead of time for any info.


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## jetstang (Nov 5, 2008)

TDC is both gears aligned, crank up, cam down. What size motor, 600 is fine for a 350, but bigger needs more carb. Did you get matching valve springs for your cam? New rockers is a good investment and not that expensive. Good luck with the build!


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## Eric Animal (Oct 28, 2007)

I agree with Jetstang. What are the cam specs? The cam manufacturer should be given the engine size and max rpm and can use a formula to determine carb size. DON'T GO TOO SMALL! Sounds like you need a 750 CFM Carb.:cheers


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## mighty454 (Mar 31, 2010)

jetstang said:


> TDC is both gears aligned, crank up, cam down. What size motor, 600 is fine for a 350, but bigger needs more carb. Did you get matching valve springs for your cam? New rockers is a good investment and not that expensive. Good luck with the build!


The engine in my car is a Pontiac 350 currently with 7H1 heads but I have the option of putting 6X heads.

The Cam Specs for the Isky Mega 270 are as follows:

Adv Intake Duration 270, Adv Exhaust Duration	270, Int Duration @ .050" 221, Ex Duration @ .050" 221, Int Lift 1.5 Rockers 465, Ex Lift 1.5 Rockers 465, Int Lobe Sep Angle 108, RPM Range 2000-6200. Excellent mid-range performance. Fair idle. Stock converter. 9-1.5:1 compr., 3.70-4.11 axle ratio. Up to 650 CFM Carb.

I also have the option of putting on a Demon 750 that I had left over from another project but I was thinking my Holley would of been enough?

Also, I did not get matching valve springs as I was under the impression that the stock springs would work fine with the cam specs mentioned above?

If I absolutely need new rockers I was going to purchase the 1.52 roller tip rockers from Comp Cams?


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## mighty454 (Mar 31, 2010)

Eric Animal said:


> I agree with Jetstang. What are the cam specs? The cam manufacturer should be given the engine size and max rpm and can use a formula to determine carb size. DON'T GO TOO SMALL! Sounds like you need a 750 CFM Carb.:cheers


The Cam Specs for the Isky Mega 270 are as follows:

Adv Intake Duration 270, Adv Exhaust Duration	270, Int Duration @ .050" 221, Ex Duration @ .050" 221, Int Lift 1.5 Rockers 465, Ex Lift 1.5 Rockers 465, Int Lobe Sep Angle 108, RPM Range 2000-6200. Excellent mid-range performance. Fair idle. Stock converter. 9-1.5:1 compr., 3.70-4.11 axle ratio. Up to 650 CFM Carb.

I also have the option of putting on a Demon 750 that I had left over from another project but I was thinking my Holley would of been enough as it's the pontiac 350.


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## jetstang (Nov 5, 2008)

I just built my 350 with a similar cam, and I am using a Edelbrock 600 on it, so that should be alright.
The machine shop said the stock springs are good for .450 lift, I went .464 lift, will see if they float, will replace them if they do.
The 7H1 heads are 175 HP heads, 7.6 cr. That may be due to dished pistons, which you would have to fix for those or the 6x heads. Are they 6X-4 or -8 heads? -4 are better, but either are way better than the stock heads you have. I would change heads for sure.


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## 66tempestGT (Nov 28, 2009)

float wont be the problem with the springs. if you have a problem it will be coil bind. rocker arms can be used from one cam to another as well as one engine to another with no problems as far as wear is concerned. the same with push rods.


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## jetstang (Nov 5, 2008)

66tempestGT said:


> float wont be the problem with the springs. if you have a problem it will be coil bind. rocker arms can be used from one cam to another as well as one engine to another with no problems as far as wear is concerned. the same with push rods.


Coil bind at .450 lift, I think not, lol... That's some thin stock springs that cant hande that lift.


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## 66tempestGT (Nov 28, 2009)

pretty crappy ones that float out with that lift too.


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## jetstang (Nov 5, 2008)

66tempestGT said:


> pretty crappy ones that float out with that lift too.


Yep, that's what I was thinking also. But, everything I have seen .500 lift is a lot of lift for a Pontiac, they tend to go with more duration then lift.


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## mighty454 (Mar 31, 2010)

jetstang said:


> Yep, that's what I was thinking also. But, everything I have seen .500 lift is a lot of lift for a Pontiac, they tend to go with more duration then lift.


My springs are currently rated for .450 lift so I'll see if I run into any issues. I did read that if you are going to use the roller tip rockers having the guide plates installed is must because they will travel if you dont??

I appreciate all the good tips from you guyz. I'm just playing the waiting game now and I'm waiting for parts. Isky says I should have my cam in about 3-5 days.

Meanwhile, I'm taking advantage and doing some detail in my engine compartment.


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## mighty454 (Mar 31, 2010)

Okay Guyz, I took the timing cover off today after setting it to the supposed TDC #1 when the compression blew on my finger and the rotor is pointing to #1 on the cap. Also my damper mark is set right on the 0 degree mark of the timing cover. Once removing the timing cover I discovered that the dots on the timing gears are at crank=12 o'clock cam=12 o'clock. 

Does this sound right for TDC #1? Also, when I receive my cam and I swap it do I have to put it back the same exact way or can line up the dots crank=12 o'clock cam=6 o'clock?

Sorry, for all the questions but I want to try and make sure I don't have any issues when I go to turn it on and I get a proper break in for the new cam.


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## jetstang (Nov 5, 2008)

Sounds like you are 180 out from TDC. The timing marks have to point at each other. 2 turns of the crank for 1 camshaft turn, so timing marks will show 0 twice. I check #1 cylinder and make sure both valves are closed, and check distributor to see where it's pointing, just valves if I don't have dizzy in yet. I don't understand how both the marks are at 12, it doesn't work that way, last mechanic probably screwed it up and motor never ran. Anyway, set it up 6 and 12 and you will be good.


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## Koppster (Jul 27, 2008)

Jetstang...if he's 180 out why would the rotor point at #1?

I thought TDC was when the #1 cylinder blows air out and the rotor points to number 1 as mighty454 describes?


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## jetstang (Nov 5, 2008)

mighty454 said:


> supposed TDC #1 when the compression blew on my finger and the rotor is pointing to #1 on the cap. Also my damper mark is set right on the 0 degree mark of the timing cover. Once removing the timing cover *I discovered that the dots on the timing gears are at crank=12 o'clock cam=12 o'clock. *


The last wrench to touch it dropped the distributor into the motor 180 out, while the timing mark will show TDC, it is at TDC of cylinder 5, not 1. This configuration would of never ran. Check any chiltons, it will show most engines pointing at each other.


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## 66tempestGT (Nov 28, 2009)

http://www.romac.com.au/Factory_Timing_Marks.pdf


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