Round 10 here. Crank gear on -6 slot @050 to get TDC on piston it is 12.5 on the wheel both sides Lifter @050 open ramp was 30 Lifter all the way up is .333 @050 on close ramp is 41 So 12.5+41=233.5 233.5รท2=116.75-12.5=104.5 If Im doing this correct if cam has 5deg adv is thqt 109.5 or 99 ?
Should the valve start to open when piston is still on the up stroke or when its going down to pull fuel mixture in as stupid is flowing good today it seems
So once you get your tdc. When it's the same each way ..........as in your 12.5 that number now doesn't matter. Your @.050 numbers should match your cam cam card. To do icl find max lift. I go back .200 lift from max lift. Then go in normal rotation direction buck up to .100 b4 max lift. This will get any slack out of the chain..........record your number. Continue to and beyoynd max lift to .100 beyond record that number..... some ppl do .050 on each side of max lift...... add your 2 numbers together then divided by 2 this is intake centerline.
The intake valve will begin opening while the piston is still coming up on exhaust stroke. Exhaust valve closes after piston begins going down on intake stroke. The period at the end of exhaust stroke and the beginning of intake stroke, near TDC when both valves are open, is called the "Overlap" period.
Another question I have dished pistons with valve relief cuts where to measure deck height on the edge I have 037 should it be decked 020 and be good ?
If the motor is already assembled I wouldn't take it apart just deck the block. I made some assumptions and plugged some basic number in and but decking that much.........the .020 you will gain about .5 in static conpression. I assumed you were using a .040 gasket. But using a .027 gasket gets you about .4. Cometic makes them, about 100 each. Wouldn't have to tear the whole motor apart. Or you can see if you can find some original steel gaskets that were .015. Just have to make sure your bore isnt bigger than the gasket. This would get you more compression that just decking alone
I have one set of factory steel head gaskets that are thin not sure of thickness 015 to 020 and I only have crank cam and one 2 rod pistons installed its $160.00 to have it decked 020 and still have 017 in the hole so if it will help I rather do it now before assembly if anything it would true the block up but if the difference wont help much I will continue assembly the way it is thanks for the advice
Is this going to be a street/strip or track only set up. If you deck the block, does that 160 cover rewashing the block, you already have the cam bearing in.........I doubt you would fully get the block clean with them in, or they would fully survive a good washing by hand brushes. I would worry about metal shaving gething in there and not out.
Whatever you're doing you're doing it wrong or at the very least I can't understand how you're doing it. The first time you came up with 243* intake duration @.050" and then the next time you came up with 233.5* intake duration. So what ever you are doing you measured it or calculated it two different ways and neither was right if that is a MK3 with 240* intake duration @.050". The other problem is just going by your numbers(#34) I actually see 258* intake duration @.050" plus the cam is advanced 7* using IO or retarded 11* using IC going by the numbers I supplied from KB. With the numbers you came up with in #41 I get 251* of intake duration. Duration is simple IO + IC plus 180. (A small cam may actually have negative numbers at the IO position but no way with this cam.) Maybe I'm missing something here. As mentioned you have to forget that 12.5 before/after or whatever. Once you determine TDC you need to place the degree wheel "0" at that spot so that the 12.5* or whatever is out of the equation. Then take your .050" measurements. Also why are you on the -6* crank slot. No way that works unless you want the cam way retarded or you do the old upper gear off one tooth trick but put that right out of your mind and forget I said it. If I was you I'd go on Youtube and watch a bunch of cam degreeing videos to actually see how it is done. Unfortunately they won't be using a lower keyway setup like the 455 Buick but you can get the drift from it on how to take the measurements. As you pondered earlier start with the +4* keyway and the corresponding +4 mark at the teeth.(You would effectively be advancing the cam 8* from the measurements in #34.) If your earlier numbers were close you should be in the ballpark and you can get some new baseline measurements. Just tell us the IO/IC numbers AND the EO/EC numbers. Getting the exhaust numbers would be very important. We can all figure it from there. If you have to move the keyway the duration of the cam should NOT change. If duration changes more than a degree or so after moving the position of the lower gear you've screwed up the measurements. If you can't get this figured out then take it to someone who can or go buy a +/-4* timing set and then place it at the "0" mark because the MK3 has 4* advance built in and forget about it. At a mile high(assuming) your cylinders will be crying out for more pressure with that cam. I'd check piston depth at #7/2/8. What ever is the minimum depth is what I'd have them mill it close to if the block is apart. That will make sure you don't have any pistons sticking out. Just going by the .037" at #1 I'd get .035" take off but you really want to measure the others. You can actually have them mill a different amount from each side of the block after you measure all four holes. I'd do that and go for a near "0" deck. Also to allow the intake to set on the heads have the intake side of the heads or the intake itself milled .020-030". Use some good orange crush head gaskets. The more compression you can get the better you'll be with that cam and elevation. I guess it just depends on how serious you really are.
Street/strip more street surely so if decking is not needed and cam is to big I have a lunati that is more in the MK 113 or MK 118 size 490/499 lift 112 lobe center 248 duration but want it to atleast sound and run like my other car it is a loose 040 455 poston 118 stage 1 heads stock 69 rockers 3500 stall turbo 400. 3:42 gears and runs a nice 13.0 at 100 to 101 pulls 1.8 60 times and consistant. Now the stock 430 ran a 14.2 at 89/90 mph with 4 speed 3:64 gears but only made 3 passes so getting dialed in on good tires that hook up need more track time
Sounds like things are running good when you take into consideration the altitude. What are the specs for the Lunati? 248 doesn't sound smaller than the MK3. A truly smaller cam would help keep the cylinder pressure higher if you don't want to do any milling of the block. The thinner .020" steel shim head gaskets would be the way to go for a slight compression boost.Hopefully it is not the 238/248 cam which pretty much needs some decent compression to work well also. Whatever compression they recommend for a particular cam at your altitude more static compression would be needed for good results.
Sp1228 part number 112 248 198u these numbers are on the end of the lunati cam Also I have a used mk 113 in the 430 I can put into this build
No idea on that cam except that they used to designate some of their cams "SP1" The GSCA used to sell them also. Another thing is that 228 may mean intake duration at .050" and the 248 may mean exhaust. The 112 may mean 112* LSA. That would mean it is something right around the KB C113. If I was you while it is in there engine I'd get some readings of the MK3 with the lower cam gear at the +4 or +6 spot of IO/IC and EO/EC. If you take the readings carefully you can confirm the numbers are something like the cam sheet says they are and hopefully you are in the ballpark. If those come out close to what the specs are for the MK3 then you can at least be confident you are measuring the duration correctly. Then stab in that Lunati cam at the same setting of the lower gear. Now get all the same readings off the cam and then when you post the numbers we can determine what it actually is. In the case of each cam the advance or retard of the cam doesn't mean much when just trying to figure out what cam you have. Once you determine what you have you can do the final adjustment of the lower gear to get it positioned correctly in your engine.
I can do that winter is almost upon us and in no hurry to get it done till spring will do some numbers over the weekend here thanks for the help
The deck should be cut using a machine that centers off of the main saddles. This assures that the decks are square to the crank, and it assures that the gasket surfaces are flat and smooth. What you "gain" with the thin gaskets is your machine shop is going to cut <0.010 to true the surfaces instead of 0.030 or even more to get the pistons to "zero deck".
I believe he wants to stay away from any more machine work on the block. It is ok to use the steel head gaskets as-is as long as your block and heads are 1971 and earlier. I'm not 100% 0n 1972. If either block or heads have the oblong holes you can't use the factory steel shim gaskets. You need the specifications for any cam before you can degree it. That is why I said you need to measure that unknown Lunati cam. Then you can degree it.
