Cam Install Question

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midnight340

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I'm installing a Lunati Voodoo 740 Solid Lifter cam in my 340.

Advertised Duration (Int/Exh): 264/272 ;Duration @ .050 (Int/Exh): 235/243 ;Gross Valve Lift (Int/Exh): .526/.546 ;LSA/ICL: 110/106 ;Valve Lash (Int/Exh): .016/.016 ;RPM Range: 2400-6600.

This was recommended by Steve Slavik at Lunati. He said he's always thought this cam should be rated starting at more like 2000-2200. ? Anyway, since I'm more interested in street driving with only occasional strip time, and he said I could certainly advance it some more.

I looking for advice as to how much I might reasonably advance this cam?????


I did accurate cc and piston height measurements and with my .028" gaskets I'm at 9:1.
(really happy with this as I initially thought the head volume was more)

Details:
Using 273 lifters rebuilt by Gary at Rocker Arms Unlimited, Erson pushrods, Howards EDMs.
2500 stall PTC, 4.10 gear, LD340, 650AVS 2 (dialed in with AF meter), headers, MSD box and
"Ready to Run" distr. (22-34), maybe 3200-ish#.
 
If you want a real world picture regarding advance, do what I do when I build one. Get the long block assembled dot to dot. run a compression test on #1 to see where you are. Then you can adjust accordingly.
 
I have light springs to check piston/valve clearance every 10* or so. Can’t remember how much is recommended to be safe.

Running the Dynamic Compr. formulas off Wallace Racing it shows advancing the cam builds more dynamic ratio and dynamic cranking up to about 4* advanced and after that the gains drop off.

If I'm correct this cam has a fairly short 48* overlap. With the installed ICL at 106 it shows 62*ICA with a dynamic compression ratio of 7.31 and dyn. cranking at 140.
With it 4* advanced I get dynamic compression of 7.53 and dyn. cranking at 146.

Are these just numbers? or something to take into consideration. I could lose some top end and not miss it. Are there any other down-sides to advancing it 4*????
 
Get to the arts and crafts store and purchase a small amount of clay. Put a strip or two across the valve reliefs and rotate the engine around a few times to activate the valves and depress the clay.
The valve lash should be correctly set when you do this.

If the clay looks like it is thin, cut it in half and measure with the below handy tool for how much clearance you have. Repeat if you move the cam around. (Advance or retard.)

image.jpg
 
I am using a Cloyes Street Billet 9-keyway timing set, so have options easily available.

I might get some modeling clay to check. Good visual check.

The other way I'd seen was use the light springs, check as crank is rotated every 10* or so, pushing down on the valves with dial indicator on rocker. But didn't write down the safe number.
 
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With a 4.10 gear I wouldn't even think about advancing that cam. I run a 235@.050 SFT and wish I would have gone bigger.
 
I have light springs to check piston/valve clearance every 10* or so. Can’t remember how much is recommended to be safe.

Running the Dynamic Compr. formulas off Wallace Racing it shows advancing the cam builds more dynamic ratio and dynamic cranking up to about 4* advanced and after that the gains drop off.

If I'm correct this cam has a fairly short 48* overlap. With the installed ICL at 106 it shows 62*ICA with a dynamic compression ratio of 7.31 and dyn. cranking at 140.
With it 4* advanced I get dynamic compression of 7.53 and dyn. cranking at 146.

Are these just numbers? or something to take into consideration. I could lose some top end and not miss it. Are there any other down-sides to advancing it 4*????


You need about .050 on the intake and .070 on the exhaust if you are careful. If you drive like a retarded gorilla, add some in, although I've seen guys with .125 on the intakes smack them because they are just criminals in the way they drive.

Checker springs is my least favorite and the least accurate way to measure actual p/v clearance. If you have say .050 on the intake with checker springs, you probably have .020 more than you think.

The best way is with the cam degreed, and using the springs you be running, use clay to measure actual clearance.
 
With a 4.10 gear I wouldn't even think about advancing that cam. I run a 235@.050 SFT and wish I would have gone bigger.

I appreciate input like this. My old cam was a lazy old style 284 / 218@.050 / .458” lift.

This will be a real change but have no real idea what to expect.
 
It’ll be nice. The duration @050 points to a good driver and power. I have used similar duration @050 cams in HFT & Hyd. roller.

IF! Your wallet can afford ported heads & 1.6 rockers, I highly recommend there use. You’ll make power right to that cams listed power range for sure. It’s a real nice driver friendly good powered combo.

(I have used this with 3.23’s & 4.10’s.)

Been there, done that. And yea, I’d do it again.
 
I had Gary at Rocker Arms Unlimited rebuild my 273 Rockers and they are beautiful. And saved some bucks over quality 1.6's. New chrome banana groove shafts, all new adjusters/bolts/hold downs, etc. Nice.

Rebuilt Rocker Arms.jpeg
 
And Rumblefish, I do have some very nicely ported X heads on the motor, port matched, etc. They will like some more breathing I'm sure!
 
That’s a nice combination and is going to have plenty of grunt, I think I would just put the cam in straight up and be happy. With the 4.10 gears you’ll have enough torque to overpower the tires at will, I don’t think you're going to missing any bottom end torque...
 
I have light springs to check piston/valve clearance every 10* or so. Can’t remember how much is recommended to be safe.

Running the Dynamic Compr. formulas off Wallace Racing it shows advancing the cam builds more dynamic ratio and dynamic cranking up to about 4* advanced and after that the gains drop off.

If I'm correct this cam has a fairly short 48* overlap. With the installed ICL at 106 it shows 62*ICA with a dynamic compression ratio of 7.31 and dyn. cranking at 140.
With it 4* advanced I get dynamic compression of 7.53 and dyn. cranking at 146.

Are these just numbers? or something to take into consideration. I could lose some top end and not miss it. Are there any other down-sides to advancing it 4*????

If that was a hydraulic cam, I'd say she wants more compression ratio.
But a solid is rated different, so your dynamics and cylinder pressure should be a lil higher than the calculator shows; perhaps 5psi higher.
Yes there is a downside to over-advancing it; namely your effective overlap shrinks, and with it a smidgen of midrange power and a smidgen more absolute power.That cam wants to be in at 108, which is where I would put it to take advantage of the rest of that combo. But for your stated useage 106 will be just fine.
 
You need about .050 on the intake and .070 on the exhaust if you are careful. If you drive like a retarded gorilla, add some in, although I've seen guys with .125 on the intakes smack them because they are just criminals in the way they drive.

Checker springs is my least favorite and the least accurate way to measure actual p/v clearance. If you have say .050 on the intake with checker springs, you probably have .020 more than you think.

The best way is with the cam degreed, and using the springs you be running, use clay to measure actual clearance.

Rule of thumb used to be , min. of .080 on intakes , and minimum of .100 on exhaust for drag engines , where the driver was careful in controlling his rpm`s . Was even recommended by cam maufacturers and Tom Hoover at Chrysler--------
NO VALVE FLOAT!
 
Rule of thumb used to be , min. of .080 on intakes , and minimum of .100 on exhaust for drag engines , where the driver was careful in controlling his rpm`s . Was even recommended by cam maufacturers and Tom Hoover at Chrysler--------
NO VALVE FLOAT!


Yeah, I know that ROT. The problem is, especially with the intakes is that you are making the valve pockets way deeper than they need to.

For the intakes, you can run piston to head clearance and that's plenty.

For example, if you have .040 piston to head clearance and the piston doesn't hit the head, that's all you need for P/V on the intake side. As the intake valve opens, it's following the piston down the hole. They can't hit. Of course, u less I'm doing the machine work and assembly I'm telling anyone to go that tight. You have no control over other people's work.

The exhaust is different. As the exhaust valve is opening, the piston is coming up. Because stuff moves around, and guys still think the timing chain is all that, you need to give some extra room for that. Any time you have two objects moving towards each other, you need to have a bit of fudge room.

And, since most guys still love timing chains, which retard dynamically, and retard with wear, you need to give the exhaust extra room. As the cam retards, it loses exhaust P/V. So give the exhaust valve extra room.

I've run as tight as .040/.060 and never had an issue. But I don't run timing chains and I trust my machine work and my ability to read measuring equipment to the 4th digit if need be.
 
An update, I really struggled to get this Lunati Voodoo solid lifter cam degreed in, mostly because my brain didn't want to accept what my numbers were showing me.

The cam lift and duration did check out spot on perfect, but in order to get the recommended intake lobe center as well as opening and closing numbers right, I had to set the Cloyes 9 position at the keyway marked 6 degrees retarded!!! I kept thinking I was doing something wrong, or not understanding what was in front of me.

I made a piston stop strap to bolt to the block, so I could make absolutely sure of my actual TDC. So in this process I installed/removed/re-installed the strap and removed and re-installed my degree wheel way too many times, before my brain accepted that "6 degrees retarded" was actually giving me the "straight up" numbers listed on the cam card!!!

I talked with Steve Slavik at Lunati today about this. We couldn't figure out whether the cam keyway was off, or the Cloyes notches, or just a matter of stacked tolerances ...or all the above!!

Steve said having done this for so many years, he still was amazed at how much over-studying and over-thinking guys do trying figure this cam thing out ... when the best thing is to simply call the cam gurus and get their help.

As a side note:
I went with this cam because I had decided I definitely wanted to run a Harold Brookshire design, and his last cam designs were the Lunati Voodoo line after his years with Ultradyne and Comp. He was the master by all accounts. And I appreciated the advice from Steve. He had worked with Harold for a long time and really seems to know his stuff.
 
That’s a nice combination and is going to have plenty of grunt, I think I would just put the cam in straight up and be happy. With the 4.10 gears you’ll have enough torque to overpower the tires at will, I don’t think you're going to missing any bottom end torque...
For greater clarification, how do you define "straight up"?
 
I always understood that to mean dot to dot or whatever the manufacturer recommended. Or 6 and 12, whichever.
 
An update, I really struggled to get this Lunati Voodoo solid lifter cam degreed in, mostly because my brain didn't want to accept what my numbers were showing me.

The cam lift and duration did check out spot on perfect, but in order to get the recommended intake lobe center as well as opening and closing numbers right, I had to set the Cloyes 9 position at the keyway marked 6 degrees retarded!!! I kept thinking I was doing something wrong, or not understanding what was in front of me.

I made a piston stop strap to bolt to the block, so I could make absolutely sure of my actual TDC. So in this process I installed/removed/re-installed the strap and removed and re-installed my degree wheel way too many times, before my brain accepted that "6 degrees retarded" was actually giving me the "straight up" numbers listed on the cam card!!!

I talked with Steve Slavik at Lunati today about this. We couldn't figure out whether the cam keyway was off, or the Cloyes notches, or just a matter of stacked tolerances ...or all the above!!

Steve said having done this for so many years, he still was amazed at how much over-studying and over-thinking guys do trying figure this cam thing out ... when the best thing is to simply call the cam gurus and get their help.

As a side note:
I went with this cam because I had decided I definitely wanted to run a Harold Brookshire design, and his last cam designs were the Lunati Voodoo line after his years with Ultradyne and Comp. He was the master by all accounts. And I appreciated the advice from Steve. He had worked with Harold for a long time and really seems to know his stuff.



This is EXACTY why you MUST degree every cam or you have no idea where the cam is installed.

This post should be made its own sticky with a big giant red flag stuck on it to point out how futile it is to "line up the dots" and think you have the cam installed correctly.

I've said it before and I'll say it again. Degreeing a cam is relatively simple. If you can't accurately do that simple job, you have no business assembling an engine.

Any engine. And I know several guys in my area who have no idea how to degree a cam. Big name guys. They dot to dot it and then check it. I learned that one of the guys had no idea how to degree a cam when he needed to degree a cam with a Milodon gear drive and had no idea how to do it.


Always always always degree the cam. Always.
 
Steve said having done this for so many years, he still was amazed at how much over-studying and over-thinking guys do trying figure this cam thing out ... when the best thing is to simply call the cam gurus and get their help.
FWIW... I'll offer an opinion as to why..... All too often, when you call a tech support line, you have no idea of the ability and knowledge of the person at the other end.

Good for you to double- and triple-check everything. When things don't 'hang together', it is time to re-check and resolve any questions.
 
Yes, manufacturers recommended installation.
I have to ask to make sure, because when I install a 110 LSA cam straight up, I set the ICL at 110. 106 ICL on a 110 LSA would be 4 degrees advanced to me. Even if the cam maker grinds the cam with 4 degrees advance, I don't call setting it there straight up, it's still 4 degrees advanced. But, that's just me, so in conversation I'll always call out the ICL and LSA so we know for sure where we stand.
 
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