Choosing cam for 5.9 magnum

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1994redram

1994redram

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I've torn apart and repaired/overhauled engines but never done a "performance" build. I have a 5.9 magnum, the block and crank are stripped and ready to go to the machine shop next week. I have a set of new KB 107 pistons. The block will get bored .030 for the pistons. Crank looks great but ill have it checked and polished. I'm reusing the stock rods. I purchased a set of new Hughes 2.02 EQ heads last weekend, and will reuse my magnum air gap intake. Will replace the stock 318 727 converter with something that suites the engine build. I have 3.55 gears and don't plan on changing them.

So, I've been looking at cams and reading about how to choose one and what all the numbers mean. It's all pretty complicated concerning compression ratios and such. Plus the magnums 1.6 rockers add a bit of hassle to it since most of comps numbers are based on a 1.5 ratio. The Comp XR274 was what I was initially looking at them decided it was probably too much. The XR268 seems good. BUT then I realized the 1.5 vs 1.6 rocker difference. Hughes recommends .540 or less lift with the heads/springs I have.

I'm hoping somebody here has built an engine using the same combo and has a tried and true cam choice.
 
Swap springs? Is the head capable of that much lift?
 
For these Magnum street style builds try a Hughes cam... they reground one of my Magnum cams and it was a great cam and a good price.
 
1994redram said:
I've torn apart and repaired/overhauled engines but never done a "performance" build. I have a 5.9 magnum, the block and crank are stripped and ready to go to the machine shop next week. I have a set of new KB 107 pistons. The block will get bored .030 for the pistons. Crank looks great but ill have it checked and polished. I'm reusing the stock rods. I purchased a set of new Hughes 2.02 EQ heads last weekend, and will reuse my magnum air gap intake. Will replace the stock 318 727 converter with something that suites the engine build. I have 3.55 gears and don't plan on changing them.

So, I've been looking at cams and reading about how to choose one and what all the numbers mean. It's all pretty complicated concerning compression ratios and such. Plus the magnums 1.6 rockers add a bit of hassle to it since most of comps numbers are based on a 1.5 ratio. The Comp XR274 was what I was initially looking at them decided it was probably too much. The XR268 seems good. BUT then I realized the 1.5 vs 1.6 rocker difference. Hughes recommends .540 or less lift with the heads/springs I have.

I'm hoping somebody here has built an engine using the same combo and has a tried and true cam choice.
Click to expand...

Your intended driving style makes a big difference.
 
Not enough info, are you running a la style timing cover or mag?
The length of the cam snout are different.
Also plan on spending the money to balance the bottom end, KB-107’s require Mallory to be added to the crank.
 
It's going in a 1970 dart. Full interior using A/C and the factory Magnum serpentine belt. I go to the track quite a bit in my BMW. And would love to go with the dart also. BMW has gone 12.90s in the 1/4 with serious traction issues on high boost since it's an open diff. Ideally, I would like the dart to be faster than that. But im not sure if it'll happen with such a limited budget. It will also be driven on the street occasionally. Maybe 2k miles a year.
 
1994redram said:
It's going in a 1970 dart. Full interior using A/C and the factory Magnum serpentine belt. I go to the track quite a bit in my BMW. And would love to go with the dart also. BMW has gone 12.90s in the 1/4 with serious traction issues on high boost since it's an open diff. Ideally, I would like the dart to be faster than that. But im not sure if it'll happen with such a limited budget. It will also be driven on the street occasionally. Maybe 2k miles a year.
Click to expand...
Here's an idea sell that "snob- mobile" and put more money into the dart!
 
I'm also not sure what lift the heads are capable of before the retainers hit guides. But i assumed they were good for .540+ since Hughes sells PN 1110 as the basic springs and recommends PN 1129 springs for anything over .540 lift. I'll call Hughes and see what they say. Or figure out a way to measure mine.

j par said:
Here's an idea sell that "snob- mobile" and put more money into the dart!
Click to expand...

I love my Snob-mobile. It's comfortable, ice cold A/C, leather seats with real bolsters and it handles well. And the sound of the twin turbos spooling is addicting. Plus my wife likes it. She doesn't care for my old crusty dart much.
 
j par said:
Here's an idea sell that "snob- mobile" and put more money into the dart!
Click to expand...

Hey wait a minute.
Is a 91 325i convertible considered a "snob mobile"?:D
I don't drive it unless I have to by the way.

bmw3.jpg
 
That's a good looking E30! I've had several E36 325 and M3, which is the body style after yours. Ill have another one in the near future if possible.
 
Don't go too small on the cam either, with those high compression pistons you can run into problems with detonation. Watch your DCR.
 
Lelo Dart said:
Don't go too small on the cam either, with those high compression pistons you can run into problems with detonation. Watch your DCR.
Click to expand...

True that, I learned this the hard way on a 360 I built... kb-107s, Magnum heads (10.5:1 comp), and a too-small Voodoo 256/262 cam. Had crazy bottom-end torque but over time pinged itself to death, regardless of what I did for tuning.

What's the rest of your drivetrain combo? Auto or stick? Stall speed if auto? What rear gears are you using, and rear tire diameter?

I'm more into handling mods but I'm thinking you might need some suspension upgrades to run 12s, like a pinion snubber or CalTracs. And sticky tires of course.
 
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Oh and I'd also verify the retainer-to-guide clearance with those Hughes retainers, even though they say only .540" lift I checked the clearance on my heads with the same parts and there was at least .560" from the bottom of the retainer to the valve stem seal. My heads didn't have the guides cut down or anything.
 
j par said:
Here's an idea sell that "snob- mobile" and put more money into the dart!
Click to expand...
Snob mobile????
LMAO!!!
Only a snob mobile by the asshole who think they actually have something special and by those who can’t afford it/see I as something expensive.

A BMW is no different than any of the big 3 driving in America.
 
MOPEkidD-3 said:
True that, I learned this the hard way on a 360 I built... kb-107s, Magnum heads (10.5:1 comp), and a too-small Voodoo 256/262 cam. Had crazy bottom-end torque but over time pinged itself to death, regardless of what I did for tuning.

What's the rest of your drivetrain combo? Auto or stick? Stall speed if auto? What rear gears are you using, and rear tire diameter?

I'm more into handling mods but I'm thinking you might need some suspension upgrades to run 12s, like a pinion snubber or CalTracs. And sticky tires of course.
Click to expand...

8 3/4 axle with 3.55 sure grip. 727 with a Trans go shift kit. I'll replace my stock converter with whatever is required for the cam/engine. I' running some 245 BFG's for tires but I will definitely get some different wheels and tires for racing.
 
1994redram said:
I've torn apart and repaired/overhauled engines but never done a "performance" build. I have a 5.9 magnum, the block and crank are stripped and ready to go to the machine shop next week. I have a set of new KB 107 pistons. The block will get bored .030 for the pistons. Crank looks great but ill have it checked and polished. I'm reusing the stock rods. I purchased a set of new Hughes 2.02 EQ heads last weekend, and will reuse my magnum air gap intake. Will replace the stock 318 727 converter with something that suites the engine build. I have 3.55 gears and don't plan on changing them.

So, I've been looking at cams and reading about how to choose one and what all the numbers mean. It's all pretty complicated concerning compression ratios and such. Plus the magnums 1.6 rockers add a bit of hassle to it since most of comps numbers are based on a 1.5 ratio. The Comp XR274 was what I was initially looking at them decided it was probably too much. The XR268 seems good. BUT then I realized the 1.5 vs 1.6 rocker difference. Hughes recommends .540 or less lift with the heads/springs I have.

I'm hoping somebody here has built an engine using the same combo and has a tried and true cam choice.
Click to expand...
Call..
Oregon Cam Grinding, Inc.
5913 NE 127th Avenue #200
Vancouver, WA 98682
Phone: 360-256-7985
Fax: 360-256-7465
send e-mail
They are a favorite cam grinder ,for Magnum builds here . I am thinking 110-112 lobe centers ,218-224 Intake @ .050" , 222 -228 @ .050 " exhaust ramps. E.Q heads stall around .520"-.530" lift .Remember you are on a stock 1.6 rocker ratio . Most ramps are Chevy 1.5 ratio ,so shoot for a .480"-.490" lift. Remember: It's the valve timing that counts ,lift is secondary.
 
I'll try to pull a valve spring or two tomorrow and measure the retainer to guide clearance. I' also planning on calling Hughes, comp, and lunati after the holiday to see what and if they recommend anything. I'll add Oregon cam to the list of people to call. I would prefer to order an off the shelf cam for the sake of keeping it simple. But a custom grind is fine if its not too much more money.

Has anyone used these EQ heads with KB 107 pistons? What cam did you use and how does it perform?
 
Call Jim Dowell at Racer Brown cams after 5 PM ET and talk to him. You actually talk to the guy who grinds the cams.

Best money you'll spend.
 
measure retainer to seal clearance, then add little more clearance for safety. I see the kb107 at the same weight as stock-no rebalancing needed.
 
the only thing with sending a cam to have it reground, is you lose some of the center, which means longer push rods. Who has a nice selection of NEW cams that work with the factory valve train (rockers and push rods)? Upgrading springs is no big deal.
 
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