Lobe separation for nitrous on custom grind Lunati - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-27-2008, 04:25 PM
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Lobe separation for nitrous on custom grind Lunati

I'm trying to determine what the difference is between a 110-112 separation, and what affect it would have on my motor. I'm not to familiar with a lot about cams but I have done a bit of research. I'm in the process of getting this http://www.lunaticamshafts.com/Produ...d=1984&gid=287
but With Small base and maybe a 112 separation, this is because the tech advice from lunati said he might go that but wasn't sure if it would make much of a difference with just a 150 shot. What do any of you pro's think about the difference between these two setups? a 110 or a 112 for a max of 150 shot.

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Old 06-27-2008, 04:49 PM
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Too small of a camshaft to get worked up on lobe sep. I think you will like the response on the street better with the 110 versus the 112, although the difference is slight. On 150 shot of nitrous not worth fretting over. Spend the time tuning the nitrous is better.

Last edited by Rick WI; 06-27-2008 at 04:58 PM.
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Old 06-27-2008, 05:14 PM
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that is what he said as well I think I'll stay with 110 if the resonse on the street was better than 112. Are there any other grind options that work well on steet motors? If I'm paying for a custom grind I want to get the most out of it I guess.
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Old 06-27-2008, 06:02 PM
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Quote:
Are there any other grind options that work well on steet motors? If I'm paying for a custom grind I want to get the most out of it I guess.
What other reason would you get a custom grind? If you are having a cam ground, there is certainly specific information that your cam grinder is going to need - whether they be a private outfit or one of the larger cam companies. If you had specifics for a custom, they would still have to be something the grinder would do, or advise against.
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Old 06-27-2008, 09:46 PM
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You can use a stock cam with a 150 shot and have descent results. OR you can use a slightly higher lift with a resonable duration and overlap and get a higher performance when you are not spraying and have virtually that same boost from your nitrous when you do spray. Contrary to some magazine articles you don't really benifit from special grind cams and pistons until you start into a 200+ hp shot.
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Old 06-27-2008, 10:03 PM
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Quote:
Contrary to some magazine articles you don't really benifit from special grind cams and pistons until you start into a 200+ hp shot.
Well, a lot could be said about no benefit from a custom grind. No one thing dictates the numbers. IMHO, custom cams, and pistons chosen as part of the whole engine-lada - including cylinder heads (runner size, chamber + efficiency, CSA) and intake can make a world of difference, nitrous or no nitrous.
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Old 06-27-2008, 10:24 PM
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Not sure if spending money to get a special grind for only a 150 shot is worth it, lots of better ways to spend that money that will actually make the car go faster.

You need to post more info on your motor to make any kind of recommendation on what you need, from your post it sounds basically like a stock motor your spraying there.
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Old 06-28-2008, 12:03 AM
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I have to go with a custom grind because of the clearance for H beam rods. There isn't anything stock about the motor except for the block, really I think.

400 SBC .30 bore
4.125 KB -22cc d-dish Hyper Pistons
GM Aluminum heads 58cc chambers 550 lift springs
bowls polished exhaust runners polished D-shaped exhaust ports all port matched
Hooker super Comp headers
Edelbrock rpm air gap intake
B/G Demon 750 with annular boosters
Moroso fuel cooler
NOS super powershot 50-150 jets
Eagle H beam rods
Speed Pro Rings
Summit 5.7 forged crank
Moroso Oil pump
Milodon diamond windage tray
Moroso street strip oil pan
GM Serpentine kit
Summit HEI dist. with a Mallory electronic ignition box
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All ARP fasteners
milodon main cap kit

1991 Camaro
700r4
2700 stall
3.42 Gears


Still working on the Cam?
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Old 06-28-2008, 12:11 AM
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I have to go with a custom grind because of the clearance for H beam rods
You mean a small base circle?
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Old 06-28-2008, 12:14 AM
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yep, small base circle.
the only way lunati does it is by custom grind. Thay don't sell the voodoo line in small base but Ive come to like the cam and the way it sounds and the RPM range is on target.
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Old 06-28-2008, 07:52 AM
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That cam is actually kind of small for your 400 and small for a 400 such as yours running on nitrous. The 110LSA is fine for N/A and moderate n20 use on a street 400ci SBC.

I would go with Lunati Voodoo #60105 installed slightly further advanced in the motor on a 104 intake C/L. (this is 2 more degrees further cam advance than the cam card indicates) This cam timing install adjustment will enhance the output of your 400 while running on Nitrous (earlier exhaust opening) "blowdown"
This cam is not too big, especially when installed as I discribed the 400SBC big cubes will eat it up quick. (acts smaller and a lot more torquey in a 406 than the discription indicates)
A much better "nitrous cam" "street/strip" cam for you.

The 400 will also eat up the nitrous pretty quick as well.
You'll soon get bored with the base 125-150hp N20 shot level.

You'll probabily want the 180hp shot for the street.
Find on 92-94 octane pump gas as long as you watch the spark timing and pay close attention to KB's recomended hyper piston top ring end gap factor for street nitrous/supercharged motors using their pistons.
You should be around .033" top ring end gap.

At the 200hp shot level and beyond, run the motor and nitrous on 100% 110+ octane unleaded race gas. (not street pump gas)

I run a near identical motor and car as you.

The "off the shelf" cam will work in your 400 if you check and clearance grind the connecting rods in the rod bolt area.
If you go for a custom ground small base circle voodoo cam you still must check and verify cam lobe rod clearance before you fire it up.
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Old 06-28-2008, 10:11 AM
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I'd rethink the hyper pistons. They are brittle and any nitrous misfire/detonation might cause a failure.

You're spending a lot of money, don't skimp on the pistons in a nitrous engine.
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Old 06-28-2008, 10:36 PM
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F-bird I like the cam you mentioned but what do you think about my semi daily driver situation? I was going for a higher cam but the tech at lunati said a little less lift because of the whole 80% street use of this car. I will also have to recheck the coil bind and seat pressures to make sure my springs now will still work, I also think with that cam wouldn't my less than desirable 113 heads choke it up? These are the only reasons that I sordof cammed down a little? You opinion is respected thank you
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Old 06-29-2008, 02:39 PM
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Quote:
Originally Posted by TorkMonster400
F-bird I like the cam you mentioned but what do you think about my semi daily driver situation? I was going for a higher cam but the tech at lunati said a little less lift because of the whole 80% street use of this car. I will also have to recheck the coil bind and seat pressures to make sure my springs now will still work, I also think with that cam wouldn't my less than desirable 113 heads choke it up? These are the only reasons that I sordof cammed down a little? You opinion is respected thank you
Don;t "cam-down" the cam to match the heads. Improve the heads to match the cam and engine and purpose.

The 113 GM aluminum heads are beauti except for one thing. In stock form they don;t flow well. The beauti is, you can fix that. With full porting these heads rock. Don't be shy on the porting, you need to remove a good bit of aluminum.
Should be 185cc or so intake port volume when you're done. Make the port taller, open up the pushrod pinch and reform the bowl and guiide boss.
The exhaust side of the 113 heads is paticularly good once fully ported.
The hot valve setup is the 2.00" x1.56" valve set up as used on the Gen II LT-1 - LT-4 motor.
The chamber can be layed back (deshrouded) near the spark plug plug to help the intake valve breath as well. Look at a set of AFR heads for some ideas and guideance. Check the valve retainer to guide boss (seal top) clearance at fill lift.

If you want power out of your 400 you need to open these heads up and make 'em flow. What you do to the heads will make or break this project.
Install the cam as I discribed and I think you'll find the motor a lot more torquey than you'd expect. Will need a very agressive spark timing curve.
I run mine with the mechanical curve locked out.
400's are always under headed so you need to cam them up a bit to make em go.
It will have a rough idle but I think you'll find the street driving quite acceptable overall once you let the engine warm up to operating temp. If you follow what I laided out for you, it will be a bullet on the juice. Hang on tight!!!

With the cam you picked and without a good bit of work to the heads, you'll find the motor is all bottom end, without much top end charge. (Horsepower)
With the larger voodoo cam installed advanced and full head port/chamber preparation this motor will still be very, very torquey and be all done by 5800 6000rpm. When you rug it, make sure its pointed where you want to go
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Old 06-29-2008, 03:00 PM
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Thanks for the help, I have been working on the heads for about 2 weeks I should be able to post pics when I go to the shop on tue or wed( I live an hour from the shop that I'm doing all my work out of). I have an old article from car craft I think that goes in the specifics on where to port these plus I have the added advantage of a cylinder head machine shop that a friend of mine owns not for from the shop I will have to discuss this cam with my buddy who is building this with me Kinda as my coach he has 35+ years on me building motors. I like what you say now I have to see how doable it is? I see what your saying about don't cam it down, but I still don't want a crazy motor that idles like a top-fuel dragster. I think it could work, I'm trying to still understand all the cam terms and functions. Again thank you for your help your always very informative
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