Cam choice

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Duster 72

Duster 72

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Ok guys I know everything about cams and headers have been beat to death here so I figured what the hell why not one more time lol. In looking for input on a new cam. In running a .40 440 with dished pistons on 9.5 - 10 compression 727 trans in a 72 duster with hp manifolds I flattened a cam lobe on my purple shaft so now its time for an upgrade. Also looking at headers.....anyone attempted the build your own kits? The car is street driven however it does go to the track when I'm not pissing off our local hondas
 
What were u running for a cam? Or did it flatten on break in? What’s the useage? We need more info. A few ppl. Ud their oun headers. Kim
 
Can you give us details please? Especially how you figure your compression with dished pistons? You should verify your compression ratio 100% before a camshaft recommendation is given. Your cylinder heads would have to have VERY small chambers to achieve the compression ratio mentioned. We need every detail.
 
What gear is in the car ? What converter and stall do you have ? Is it a manual car ? What intake system do you have ?
 
Duster 72 said:
Its 3.55 rear sure grip 2500 stall 727 auto eddy performer dual plan with 850 cfm
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220 to 230 @50 110 LSA .510 to .525 lift ! Give you good idle and vacuum! Give you good low and mid range power with your 2500 stall and 3:55’gears and dual plane manifold
 
Rmoore said:
220 to 230 @50 110 LSA .510 to .525 lift ! Give you good idle and vacuum! Give you good low and mid range power with your 2500 stall and 3:55’gears and dual plane manifold
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Rmoore will I have to have any head work done with that much lift? Seems high my old cam was .450
 
Duster 72 said:
906 with porting
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If you already have ported 906 heads that cam will work great for you and the street ! Are the 906’s pocket ported of full port ! I was going to suggest a pocket port with the camshaft ! I think you will be very happy with the performance !
 
RustyRatRod said:
You need to seriously figure your compression. There's no way you have 9:1 with dished pistons and 906 heads.
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Rusty. In just going off of what I was told when I assembled the motor from the machine shop. I mean no disrespect but how would I calculate my compression all info is appreciated
 
Duster 72 said:
Rusty. In just going off of what I was told when I assembled the motor from the machine shop. I mean no disrespect but how would I calculate my compression all info is appreciated
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You need to figure out which pistons you have. Find their piston head volume. Unless you can find out whether the heads were milled and what their chamber volume is, you'll have to shoot from the hip with what a stock chamber is, which is "about 90CCs". You should be able to see the head gasket. I would "guess" they used a composition style gasket, usually "around" .039".

You probably need to either borrow or rent a boroscope and see if you see a part number on a piston. You'll need to look that up and find the head volume and the compression height. OR you remove the heads and then you could actually measure it.

Once you find "all that" missing information, you can plug all of it into one of the online calculators such as on United Engine's or Wallace's sites and find out your compression. I can promise you that if you have dished pistons and 906 heads, 9:1 is only a dream.

Not that you cannot make power on low compression.
 
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To choose a bigger cam, you first need to know WHICH Purple cam you have. The Word Purple by itself is somewhat meaningless.
If that cannot be ascertained, then you really need to know your exact Compression Ratio, to narrow your cam choices down to two or three. But
remember; each bigger cam will push the operating rpm up about 200 rpm, taking about half of that off the bottom. So it only takes a couple of cam sizes to ruin the bottom end of a nice street combo, which you will have to spend more money on, to recover.
So, if you really like your current combo, then it would seem prudent to replace the flatted cam with another same-spec cam. Jus my opinion.
 
It all depends on where you want your power. That being said a solid cam will start making power sooner and more up top. It'll require adjustable rockers and probably pushrods and of coarse the right valve springs. I'll never run a hydraulic cam again.
 
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