I milled a type R head .005" because of a blown head gasket

I decked a b16a block .005" beacause of a deep enough scratch

If a stock OEM head gasket is .026" and I ad an extra layer it becomes .0347" thick

So -.010" ( milled and deck) off the new head gasket thickness =.0247" vs .026"

My question is, with .0013" thinner then stock head gaskett, should I consider advancing cam gears????

Thanks!

 

Wow I am impressed with your attention to detail I wish more out there would be that careful. No you don't need a timing change .0013 is a very small change which will cause a very small change in timing not enough to fret about. A rough guess would be about .1 degrees off maybe even less. Dan

 

Thanks! I have had no experience with milled heads before so That's why I asked!!

In this CTR head I have stock valves and springs but Skunk2 stage 1 cams ( the type R TB has been bored and the I.M. port matched to it)
In the b16a block I have 81.25mm CTR pistons that now sit .005" in the hole ( I balanced the b16a crank and rods) Comp is 11.39:1 and if my rods Strech .030" i'm still in the clear ( pistons not hitting valves)

My questions is, if I advance the intake cam 1 degree will that in 100% give me more power after tuning the A/F ratio and the timing (because of extra overlap) or should I leave the cam gears at 0,0? ( asking cause I can't afford to be playing with cam gears on the dyno I can just afford a couple of hours for now)

Thanks

 

I would leave it alone if money is an issue. The time can be better spent on the dyno on something else. Some of the more high end headers on the market like more overlap on the exhaust cam (timed retarded) but other than that leave it alone unless you dyno time your cams. Dan

 

I Have Spoon 4-2-1 one piece headers with a custom 2 1/2" cat back no cat so maybe the exhaust retarding route would be one to take!!!

But again cause I can really afford more then 3 or 4 hours of tunning I would have to set it -1 before towing the car to get tuned!

 

I agree with the previous statements. The milling is not enough to significantly affect your cam timing or to cause any clearance issues. If you already bought cam gears, just zero them out until you can get the car on a dyno and tune them properly. If you have the stock gears, you don't need to get adjustable ones until you are ready to dyno tune.

Good luck with your project.

 

Hey thanks man...yes I have the cam gears already! I think I will zero in both sides and concentrate All efforts on getting the a/f ratio and timing down good!

Tunning on a Mustang dyno and using Chrome software to chip my Obd1 P61 Ecu!

Thanks again to both of you guys...this is only my second all motor build and I appreceate all help!

Pat

 

Here a rough formula for figuring your cam timing error:

E = x/(D*Pi)*360

where E is your cam timing offset in degrees, x is change of cam centerline (sum of block milling, head milling and gasket thickness changes), D is the diameter of your cam gear. Oh and Pi is 3.1415927....

Multiply E by 2 for offset in crank degrees.

Don't know D for B motors, but if you assume 3", which is probalby pretty close, then your .0013" will only change timing by 0.1 crank degrees. . . Which I assure you is well below MFR tolerancing.

 

Thanks Man, now you are obviously a million steps ahead of me...MFR tolerancing =???

Thanks for the Help!

 

Don't know, but being competent with manufacturing processes and equipment, I assure you there are simply too many other tolerances that effect the final cam/crank synchronization for the final tolerance to be less than than .5deg.

They include, deck height, head height, cam gear mount, cam gear mount, cam gear teeth, belt, crank tbelt gear teeth, crank key slot, key, crank gear slot, etc. Just too many factors. . . .

 

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What he is saying is that the net change due to your machining is probably less than what might be caused just by normal variances in the manufacturing process.

 

Good...thanks for dumbing it down for me LOL

Pat

 

good info here

hey psegs80
check out the red link in my sig

 

If the car is up and running, I could see myself coming down for a little road trip!!

Thanks Pat

 

Sorry for bringing this back from the dead, but it seems that there could be something wrong with the above formula. Or I may be just plain stooopid.

Let me explain this. There's an obvious contradiction between the above formula and the common rule of thumb here, that 0.012" of head milling induces a 1 degree cam timing error.

D is 4". So,

E = x/(D*Pi)*360 = 0.012/(4*3.14159)*360=0.34 and not 1.

Also the formula is incorrect in theory, since it suggests a ratio between a diameter (x) and a circumference (D*Pi), instead of two diameters or two circumferences.

I would suggest the following formula instead:

E = x/D*360 = 0.012/4*360 = 1.08

It's still not perfect, but seems to work way better than the above formula.

 

Now i dont wanna steal your thread or anything but why make up a new one if you dont have too

Heres 4.2cc dome enydn pistons
mill.005
deck .005 this is all on a gsr build
this leave me with 11.4 compression and .002 piston to deck height using a oem headgasket

how are my tolercence's and any cam gears adjusting needs and how would i know my limits

for example i cant go past 3 degrees advanced or that equals a blown moor or 3 degree retard how would i know my limits thanks

 

"If in doubt, clay it."