Hi I have a 94 gst motor I'm building it's an all b18c1 that has pr3 pistons in it arp rod bolts a built gsr head and I have to get it resurface and was hopeing to shave it down to .010-..015 would that be safe I heard you only have to adjust your timing 1degree for ever .030 of milling you do so atmost it be a half degree. But would there be enough valve clearance. I have to resurface my head no matter but just looking for some advice thankyou for your opinion

 

This is an Over Head Cam Engine... not a small block V8. You DO NOT shave down a head for more compression... if you have to cut a head just to straighten the surface, it is customary to increase the head gasket thickness the same amount as what is removed to keep the quench area the same, keep your valve relief orientation the same, timing events the same and increase your chances of being able to properly tension the timing belt.

Inicidentally, just for reference sake, 1 degree retard for every .030" cut off the head is incorrect... maybe someone was dyslexic that typed that. It is more like .003" per degree. A friend of mine has a Honda Challenge race car with an ITR engine. It had a head cut .012" and the cams were retarded 4 degrees, requiring a pair of 4' offset keys to get everything back in proper alignment.

 

Sorry I read the 1degree for every .030 on another post that's for the clarity. So .005 would be om1 to 2 degrees

 

Likely yes.

 

If I use a 2layer head gasket instead do I also have to retard the timing 1 degree

 

Also in other post it says to advance the cam gear. There alot of post on this and I'm just trying to get the correct info.. so any one that has milled a head and adjusted there cams please chime in I dont want to garnad my motor on first start up

 

Lol at not shaving the head. Idk why import guys are so against milling to get more compression. They would rather through heavy peaky dome pistons in instead.

 

Why would you use a thinner head gasket ? Again, this brings the head closer to the block, and thus, changes the needed locations of the valve reliefs in the piston tops... increasing your chances of valve-to-piston contact. There are TWO ways to properly increase compression in a "B" series engine: 1) Pistons with a larger dome volume. 2) The pistons that you have now and a longer stroke crankshaft (with the appropriate connecting rod of course).

Think about this logically for a moment. Reducing the distance between the center line of the crankshaft and the center line of the exhaust camshaft by milling either the cylinder head or block, or reducing the thickness of the head gasket does not change the length of the timing belt. So, in order for the belt to be tight, the cams would be RETARDED (rolled toward the intake manifold) to maintain proper belt tension. Now, where the confusion may be here is that what we have been discussing in this post is how much the cams would be retarded based on the modifications that you have outlined. To compensate for this phenomenon, you would ADVANCE the camshaft with an adjustable cam gear to get the cam-to-crank event back in sync. This change essentially creates the effect of a stock, unmolested engine. This does not make your cam timing events perfect... degreeing your camshafts is necessary for this.

 

Ok that makes since. Kinda sorry alil slow. And understand you dont particularly like milling heads. But I have a b18c1 with b16 pistons in twitch equals around 11.3:1 and grying to get alil more out of it. So would it be ok if I change my gears according to how much I take of and run my car atleast for break end then get it tunned

 

Lighter connecting rods could easily offset the additional weight of the dome top pistons. Since you are discussing weight... how do you feel about flat faced valves ?

My statements above simply outline the proper way to make this modification.

I am not sure why either of you believe I am against milling a cylinder head. I am against milling IF that is all you do... however, assuming that you are working within the confines of a specific rule/class and this is an allowed modification on an otherwise stock engine, I would embrace it. This change can offer an advantage... as long as you re-cut the valve reliefs if necessary and degree the cams to counter-act the change. You will still have the timing belt slack issue to deal with.

What I do have is an aversion to doing things wrong... and the reason that head milling is spoken of so often in the Import Scene is because it is a "cheap" modification... and many simply think that it is a singular way of increasing the performance of their engine. This thought path is simply untrue.

I cannot tell you how often I have seen individuals in the Import Scene try and build a car on the cheap. They routinely battle gremlins and pitfalls all along the way, or worse yet, failures... then get frustrated and give up. The project vehicle then ends up in a consistent loop on CL or FB for sale, trades hands a number of times over the next six to eighteen months, while all believe they got a great deal and it should only take a few hundred bucks more to get it running... ultimately ending up in a salvage yard or parted out and the body scrapped. Remember that if you can afford to fix an issue twice, you can afford to do the job right the first time.

 

Couldn't agree more JR. It should be a tool in the engine builder's box, but not something I would go right after. Even then, I'd be inclined to start with a thinner gasket rather than just going in and shaving .040" or whatever off the head.

 

Don’t like flat faced valves. For certain engines milling either the block or head is a great way to gain compression without the cost/ weight of pistons. My d17 stroker has piston to valve clearance everywhere the cam gear will go and I’ve taken .070” off the head and block total to get 11.5 to 1 comp with dished pistons being that the only high comp pistons you can buy off shelf are the gx pistons and they aren’t cheap and only go up to a 75.5mm bore size. I just hate when people act like milling is the devil or the half assers way of building something when it’s really not.