Hello All, new member looking for some advice. Basic build of a 318 (1986) rings and bearings sort of deal, street car. Heads have been cut .015 (checked 60cc), the block decked .020 with .028 head gaskets. Hovering around 9.8+ to 10:1. The cam is a Lunati Voodoo 702, installed dot to dot it's phasing in at 2 degrees retarded. Cam card reads intake @.050 should open 2 degrees btdc, mine comes in just a fleck after tdc. Cam card reads 108 ICL , i'm reading 110.3 ICL. Should I leave well enough alone or purchase a 2 degree offset cam key to pull it into spec? Im wondering if I leave it alone it'll work well to bleed off some cylinder pressure for street use. Also the factory pistons are flat tops with very close (in fact the intake just kisses the piston) p/v clearance, however I'll be machining minimal reliefs to suit .
Cam phase suggestion advice
- Thread starter Cudabeen
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I would install it as designed.
ChargedDart75
Well-Known Member
You might also want to make sure there is enough piston crown to machine reliefs and that it won't make it too thin. I like to see at least .080" clearance on the intake, and with yours "kissing" the piston you're looking at taking at least 0.085" off the piston.
Yes, the piston crown measures in at .340 thick at its thinnest point, plenty of material to play with. Also I forgot to mention, the p/v clearance was done with out the head gasket. However as pointed out the cam should be installed as listed, so that with throw the intake valve out a little sooner. I will definitely push up the clearance! Another question; I see Mr gasket has a 4 degree offset crankshaft key available that will give me my 2 degrees advance I need but I assume that puts the harmonic balancer out 4 degrees correct? The cam key is a standard woodruff size so I'll hunt for an offset one as well or perhaps machine one up; anyone know what the offset dimension is for 2 degrees?
I just looked again, my bad, the Mr Gasket offset key is for the camshaft. The Woodruff key is the standard #606. Anyone have a Mr G 987 key by chance?
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yellow rose
Overnight Sensation
Unless that piston has NO valve notch, you have something wrong.
There ain’t no way in all of hell with under .500 lift that valve should hit the piston. Not even close.
So something is really wrong, unless I don’t know what Lunati “702” you have, which is possible.
FWIW, I never regard a cam. Ever. You will gain some intake P/V clearance, but you give up way too much closing the intake valve later.
If you are worried about CR and detonation then call a cam grinder and buy a custom cam.
And keep the engine temp at 180 and no more. 170 is better and 160 is better yet IF you don’t need a heater.
They are the factory flat top pistons, and the cam is installed dot to dot however checking this showed it in a 2 degree retarded position which I'd like to correct. I would have thought this cam would have been fine too as far as p/v clearance, but surprisingly it's not. I was a little surprised and checked it a few times to be sure. The pistons and bores are in perfect shape and being a budget build for my son he has to keep the cost down, also to buy the KB pistons with the valve reliefs are really pricey by the time they get to Canada! It is the Lunati Voodoo cam #10200702 a relatively mild cam but there is interference. Getting parts up here can get expensive, I just looked up the Mr Gasket 987 offset key and to have it shipped here and with the exchange it comes out to $55...for a woodruff key which is crazy. Hence the reason my son and I are getting creative with this build.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Are you saying the pistons are down .020 or that you cut .020 off the decks?
Which Almonte are you at?
or what is your local elevation?
Is this the cam?
10200702
Hydraulic Flat Tappet. Mid level performance street cam with excellent drivability. Works well with stock type exhaust manifolds and dual plane intake with mild 4 bbl carb. Great 4X4 and performance marine cam where dry exhaust is used. Improved valve springs and roller rockers recommended.; Advertised Duration (Int/Exh): 262/268; Duration @ .050 (Int/Exh): 220/226; Gross Valve Lift (Int/Exh): .475/.494; LSA/ICL: 112/108; Valve Lash (Int/Exh): Hyd/Hyd; RPM Range: 1400-5800; Includes: Cam Only
That cam wants to be in at 108 to center the overlap. But if you are at 400ft, and truly have a 9.95 Scr, then your cylinder pressure is predicted to be 168psi, and it is highly unlikely that she will run on pump-gas. Even if you install it at 111 (1* retarded), the pressure is then predicted to be 163, and still bordeline too high.
To run 9.95 Scr your Ica needs to be around 66*, which is a whole nuther cam, with a way softer bottom end, a different stall, and bigger gears.
So; Ima thinking you need to do some detective work,cuz to run 10.95 with just 318 cubes requires a total chamber volume of not less than 72.8cc. You can just make that with pistons down .020.
But with the decks cut .020, the pistons could still be down .037 or more, making your volume 74cc and your Scr to be 9.8, which is right on the upper limit of 91gas at 165psi. Ima guessing your heads are closed chambers, which would bring your Quench to .070, so if you get detonation,at least it it's not likely to be because of that.
That's a great size of cam for a 318; I'd hate to give it up; but IMO,something has got to give, before you put it together.
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Thanks for the reply! Yes the Ottawa valley area is basically at sea level, actually our average barometer is pretty high most of the time! The heads are the 302 closed chamber style and stock valves, I milled them .015 and the chambers came in at exactly 60cc. I haven't decked the block yet but my intention was to peel off .020, currently the pistons are down .056 in the hole, I found a .002 dip in between a bore on the deck that has me concerned hence the reason to mill the deck. We bought Mr gasket 1121 head gaskets that compress to .028 or an advertised 6.177cc volume. If I left it all alone (not milling the block deck .020) the Speedmaster comp calculator shows 9.43:1, also my quench space would be .084. Decking the block .020 brings the comp upto 9.89 but will bring the quench to .064. I picked the cam based on the quick rate and being exhaust biased but I figured the cylinder pressures would start to approach street fuel limits. Perhaps I should leave the block deck alone and be happy with the lower 9.43 comp ratio. I thought that having the cam centerlining at a tick over 110 as opposed to the recommended 108 ICL would help bleed off some lower end pressure but the folks at Lunati recommend bringing it to 108 period. Many years ago ( I've been out of the loop for a while raising a family and all of that!) I had run the old Ultradyne "tight lash" mechanical flat tappet cam in the past on a B block stroker combo and it just worked great. These voodoo cams (although hydraulic) remind me of really taking advantage of the larger lifter. We bought the Lunati cam complete kit, however, it comes with the three keyway crank sprocket and the advance keyway is too much. Might have to break the budget and get the 9 keyway setup. Or I can machine up an offset woodruff key for the cam if I can figure out the offset for 2 degrees.
yellow rose
Overnight Sensation
Ok, I just pulled my head out of my butt. Installing the cam at any number ahead if the ICL isn’t retarded. So at 110 you are not retarded.
The program I use says it should go in at 111 so that 110 you have is where I’d leave.
If you put the cam in at 112 it’s what’s called straight up. Until you get it in at 113 it’s not retarded.
I’m almost never a fan of moving the ICL forward enough to shift the overlap triangle from centered to advanced. At 110 you are nearly centered. I’d send it.
And as I said above, I never ever retard a cam. Which in your case that would be 113 or later.
AJ/FormS
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Your thinking on the cam is right. But in your case the 108 centers the overlap, which is a meager 45*. If you install it at 111 (1* retarded) your EFFECTIVE overlap will change to 38* .. If running headers this will give up some power potential, but if running log manifolds, it matters not, you will be giving that power-bulge up anyway.
The thing is, each degree of advance/retard in your size of cam is maybe around 1.5psi, so 3 of them adds up to only 5psi at most.
If you truly were at max-pressure of say 168psi with a tight-Q,and are running log manifolds, then, I wouldn't be scared to run it at 111, because it will move your powerband up just a lil, which, at the new pressure of 163 will not affect the bottom end very much , and you can't lose power that you don't have, vis-a-vis the logs.
But I see some other hiccups.
1) the first is the PV clearance. YR said;
2) If your valve timing is out, you will change your PV clearance, because the closest the piston gets is not at TDC . On the exhaust stroke the piston and exhaust valve are, for a small period of time, heading towards each other, before the piston chases it back to the seat which in your case will not happen until the piston has reached 22* ATDC.
But simultaneously, the intake valve begins to open at 23* BEFORE TDC, so it is now on a collision course with the rising piston. As the piston goes over the top, the intake chases after the piston.
Like YR says, with pistons down in the holes, and only .475 lift (1.5 arms) there should be plenty of room in there. The fact that your valves are kissing the pistons with unmachined decks and no gasket, is sortof pointing to the intake valve not being where it is supposed to be, or you are not using the correct method of measuring, or something appears to be wrong.
In any case, here is a quick test; with the degree wheel still on there, and the #1 piston at TDC compression, go to #6 cylinder and drop the lifters in there. Then stand a straightedge upright longitudinally over the 4 edges. Next, move the crank back and forth just a hair until ALL 4 edges are touching the straightedge. Now read the advance/retard. It should be within a few degrees of TDC. If it is out by more than (guessing) ~4* then Something is wrong. This is a quick-test, not intended to be dead-nuts accurate, but it will easily find a gross error.
3) You gotta do something about that .002 dip on the decks, between the holes. But simultaneously, you must not bring your Q into the zone of .050 to .080 which is, on most accounts, flirting with detonation. So currently you have .056 (pistons below deck) plus .028 gasket = .084 so you have only um nowhere to go,lol. If you went to the .039 FelPro, that adds to .095 so now, you can cut your decks to whatever, up to pistons proud .010. With an .045 Q-target, that would be .050 off the decks. That's gonna cost you, about 3 passes per side. And you will end up with way too much pressure.
So, IMO, the easiest course of action is to use the .039 gaskets, which are killer at sealing, and let the Q fall in at .084 which is outside the zone and adds a couple of more ccs, and increases your PV clearance all at the same time! So now we are up to 11+60+8.6= 79.6 before cutting valve pockets and at stock bore, that comes to 9.2 Scr. and the pressure is predicted to be 153@200ft elevation. Yeah that's a lil low, but be comforted to know that, that will probably run on 87E10. To get the performance back at the bottom a 2800TC will do nicely.
Now, what I would do;.
Is clean up the decks, with a minimum cut, say .010 ,which is 2cc, then go back to the rest of the previous plan. The Q is now .074, at the top of the danger-zone. But recall that; A) this is only a problem at WOT , and B) only if the chamber has problems, and C) or hotspots, or D) runs lean, or E) with too much timing. I think I can tune around those with closed chamber iron heads. The total chamber volume is now 9.1+60+8.6=77.8 for an Scr of 9.38, and pressure of 156@200ft, BadaBOOM! This is before cutting any valve reliefs, if required.
This should still burn 87E10, except if the .074Q makes trouble, then move up a grade, you got plenty of room.
So now, say you do have to cut some reliefs, say 2cc worth, that drops the Scr back to 9.2 again with the Q still at .074, and the pressure drops to 153 again.
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Your combo is in an awkward way because of where the Q wants to fall and where the pressure is ending up. It sorta needs a specialty piston, like a Step-D cup.
That cam wants a 9.8 Scr, (with iron heads); but with flat-tops, the Q falls into the NO-Go zone. A step D-cup could solve that.
As would alloy heads,lol, then you could run a lotta, lotta, pressure.
As would a different cam, with a later closing intake valve.
The thing is, each degree of advance/retard in your size of cam is maybe around 1.5psi, so 3 of them adds up to only 5psi at most.
If you truly were at max-pressure of say 168psi with a tight-Q,and are running log manifolds, then, I wouldn't be scared to run it at 111, because it will move your powerband up just a lil, which, at the new pressure of 163 will not affect the bottom end very much , and you can't lose power that you don't have, vis-a-vis the logs.
But I see some other hiccups.
1) the first is the PV clearance. YR said;
And that is exactly right. You need to get this worked out first, to get any valve reliefs cut, which will ADD ccs.
2) If your valve timing is out, you will change your PV clearance, because the closest the piston gets is not at TDC . On the exhaust stroke the piston and exhaust valve are, for a small period of time, heading towards each other, before the piston chases it back to the seat which in your case will not happen until the piston has reached 22* ATDC.
But simultaneously, the intake valve begins to open at 23* BEFORE TDC, so it is now on a collision course with the rising piston. As the piston goes over the top, the intake chases after the piston.
Like YR says, with pistons down in the holes, and only .475 lift (1.5 arms) there should be plenty of room in there. The fact that your valves are kissing the pistons with unmachined decks and no gasket, is sortof pointing to the intake valve not being where it is supposed to be, or you are not using the correct method of measuring, or something appears to be wrong.
In any case, here is a quick test; with the degree wheel still on there, and the #1 piston at TDC compression, go to #6 cylinder and drop the lifters in there. Then stand a straightedge upright longitudinally over the 4 edges. Next, move the crank back and forth just a hair until ALL 4 edges are touching the straightedge. Now read the advance/retard. It should be within a few degrees of TDC. If it is out by more than (guessing) ~4* then Something is wrong. This is a quick-test, not intended to be dead-nuts accurate, but it will easily find a gross error.
3) You gotta do something about that .002 dip on the decks, between the holes. But simultaneously, you must not bring your Q into the zone of .050 to .080 which is, on most accounts, flirting with detonation. So currently you have .056 (pistons below deck) plus .028 gasket = .084 so you have only um nowhere to go,lol. If you went to the .039 FelPro, that adds to .095 so now, you can cut your decks to whatever, up to pistons proud .010. With an .045 Q-target, that would be .050 off the decks. That's gonna cost you, about 3 passes per side. And you will end up with way too much pressure.
So, IMO, the easiest course of action is to use the .039 gaskets, which are killer at sealing, and let the Q fall in at .084 which is outside the zone and adds a couple of more ccs, and increases your PV clearance all at the same time! So now we are up to 11+60+8.6= 79.6 before cutting valve pockets and at stock bore, that comes to 9.2 Scr. and the pressure is predicted to be 153@200ft elevation. Yeah that's a lil low, but be comforted to know that, that will probably run on 87E10. To get the performance back at the bottom a 2800TC will do nicely.
Now, what I would do;.
Is clean up the decks, with a minimum cut, say .010 ,which is 2cc, then go back to the rest of the previous plan. The Q is now .074, at the top of the danger-zone. But recall that; A) this is only a problem at WOT , and B) only if the chamber has problems, and C) or hotspots, or D) runs lean, or E) with too much timing. I think I can tune around those with closed chamber iron heads. The total chamber volume is now 9.1+60+8.6=77.8 for an Scr of 9.38, and pressure of 156@200ft, BadaBOOM! This is before cutting any valve reliefs, if required.
This should still burn 87E10, except if the .074Q makes trouble, then move up a grade, you got plenty of room.
So now, say you do have to cut some reliefs, say 2cc worth, that drops the Scr back to 9.2 again with the Q still at .074, and the pressure drops to 153 again.
Page 2
Your combo is in an awkward way because of where the Q wants to fall and where the pressure is ending up. It sorta needs a specialty piston, like a Step-D cup.
That cam wants a 9.8 Scr, (with iron heads); but with flat-tops, the Q falls into the NO-Go zone. A step D-cup could solve that.
As would alloy heads,lol, then you could run a lotta, lotta, pressure.
As would a different cam, with a later closing intake valve.
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yellow rose
Overnight Sensation
That cam is on a 112 so at 111 it’s still I degree advanced.
How do you figure 108 centers the overlap??? The program I use show 111 centers it.
The cam card reads 2 degrees btdc on the intake @ .050, but I'm getting just a tick past tdc and as well the card reads a 4 degree (advance) machined in hence the 108 ICL, whereas I'm reading a tick over 110 so both numbers corroborate. I mean at the end of the day we're hoping to get more than 100hp! This dog motor got my son through high school without a stupid power incident, it literally could not spin a tire! Now he's a bit more mature and so we're having some fun especially doing the build.
But yes, now to deal with the p/v clearance, but I have a plan and will hopefully figure out to post a couple of pics.
But yes, now to deal with the p/v clearance, but I have a plan and will hopefully figure out to post a couple of pics.
yellow rose
Overnight Sensation
I’ll take a couple of screen shots of why you can will look like installed at 108 and 111 where I think it should go (the 110 and change you have is close enough) so you can see what I’m talking about.
yellow rose
Overnight Sensation
If you look at the top screen shot, you can see the cam is installed on a 111 ICL and if you look real close, you can see the overlap “triangle” is centered around TDC. This is also called split overlap, but that isn’t always correct.
If you look at the bottom screen shot you can see it’s installed at the 108 ICL and the overlap triangle is advanced (moved to the left on the graph) and IMO, when you do that, you compromise the very thing that overlap helps accomplish.
If installing the cam with overlap centered loses power IMO you have the wrong cam and advancing the cam is a crutch to fix an issue with the timing events.
Jeepers, thanks for the visual! I never knew this stuff existed. I just realized i'm getting old! I'll take some time and take a close look.
Thanks for the help! awesome
AJ/FormS
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From the website I got this; so in post #7, I asked
112+108/2=110LSA
From that I determined that overlap is ;
(262+268)/2, less 2x110= 45*. I split that and gave 23* to the intake and 22* to the exhaust .
262 is the intake duration; taking one half of that, and subtracting the 23*, I get an ICL of 108*
Did I do it wrong?
Yeah I guess I did,dammit. I didn't read the fine print, namely LSA/ICL
That makes all my pressure numbers about 3 or so psi less..... which is a bad thing because it paints a rosier picture than it really is. However this combo is so close to the line that 3 psi is not really meaningful to the discussion,IMO.
Nevertheless I'm wrong and
Special thanks to @yellow rose for the clarification. Good catch.
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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You got some nice tools man.
I love the juxtaposition, of super neat-O hi-tech stuff, and the lowly adjustable, one-wrench fits all, tool.lol.
I got a tape measure and 5ft level.
I wanted to run those heads once on my smog-era 318, but ran into the same math problems.
I love the juxtaposition, of super neat-O hi-tech stuff, and the lowly adjustable, one-wrench fits all, tool.lol.
I got a tape measure and 5ft level.
I wanted to run those heads once on my smog-era 318, but ran into the same math problems.
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Looking at the pics it is kinda funny, especially the old nylon cam gear just tossed onto the floor! Didn't have time to go through all the points you made, but I will. Thanks for everyone's input and I'll get back shortly ( a day or two) with updates. If anyone wants to borrow some pocket cutters let me know, lol!
gzig5
Well-Known Member
I think the way to go about the key offset is figure out the distance per degree on the surface of the crank snout. Circumferance is 2*Pi*r (or Pi*D) If crank is 1.5" diameter then C = 2*3.1416*0.75" = 4.712"
Divide by 360 >> 4.712/360 = .0131" per degree
two degree key would be about .026" offset.
Someone needs to check my math and you need to use the real crank dimension, I was just guessing and using 1.5" as an example.
Divide by 360 >> 4.712/360 = .0131" per degree
two degree key would be about .026" offset.
Someone needs to check my math and you need to use the real crank dimension, I was just guessing and using 1.5" as an example.
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Ok so I found out why the P/V clearance is not right! The rockers were preloading the valves. Which was somewhat strange because I took a couple of the old hydraulic lifters and welded them solid, I put the factory head gasket back on and tightened down the rocker shaft, I thought I could feel a hint of lash and could spin the pushrods (in hindsight the light checking springs gave me a false sense of zero lash!), set the indicator at zero on the intake valve retainer then backed off the rocker shaft bolts and bingo...the valves were hanging open. I don't have any adjustable rocker arms so I shimmed up the rocker shaft to get a few thou of valve tip clearance with the lifters on the cam base. Now the indicator reads .095 clearance on the intake at the tightest spot which appears to be right at TDC and the exhaust has about .145 clearance @ 2 degrees BTDC. So next time I'll leave the bottle of wine alone until after I get out of the garage, and I'll make sure I have a set of adjustable rockers! It's a shame too because I spent a few hours whipping up a couple of nice valve pocket cutters.
So yes this Lunati #702 voodoo cam can be run with a mid eighties 318 with eyebrowless flat top pistons, however this was checked with heads that have been cut .015 and the used factory head gasket (.040 thick) snugged down . Shortly I'll be getting the block decked (around .010) and will be using the .028 head gaskets so that will be bringing the intake valve probably a little too close for comfort. I'll recheck the set up tomorrow without the head gasket to simulate the final setup and let you folks know!
So yes this Lunati #702 voodoo cam can be run with a mid eighties 318 with eyebrowless flat top pistons, however this was checked with heads that have been cut .015 and the used factory head gasket (.040 thick) snugged down . Shortly I'll be getting the block decked (around .010) and will be using the .028 head gaskets so that will be bringing the intake valve probably a little too close for comfort. I'll recheck the set up tomorrow without the head gasket to simulate the final setup and let you folks know!
What diameters of cutters did you make?
beanhead
Well-Known Member
The discrepancy between what you're seeing at .050, and what the card says is simply because they 'grind in' 4 degrees of advance, meaning they grind it such that the specs on the card will only match (or should be real close) if you put it in on their recommended 108 ICL. (4 degrees advanced from the 112/'straight up' position). I think you had that figured out but yeah the cam's technically not retarded it's just not as advanced..
And something to keep in mind--even the best chains will stretch a bit and back timing up a degree or two at the least. So, if you run it where it is, you might as well consider it timed 'straight up' after a couple thousand miles.
(Unless you're running a gear drive..
)
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AJ/FormS
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Well then if you degreed the cam with the lifters like that, then you might want to do it again.
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