I've been searching this and other sites all morning, looking for an answer to this question:

How much can I mill a P75 (B20/B18b) head going onto a B20b block (stock) with an OEM headgasket, and maintain P2V clearance for use with Crower 403 cams?

-I realize this is not the proper way to gain compression, but I have a spare head and they are cheap anyways, I don't want to build the bottom end at this time
-I realize I will need adj. cam gears to compensate for the milling of the head
-I realize that claying the engine is the proper way to do this, but I don't currently have the cams, I may never get the cams, I just want to plan for these cams

Any other considerations that I may not have thought of are welcome as well, but I'm really looking for some numbers or a method of doing this mathematically. I'm looking to have the head milled as much as .050 which would bring compression to the 9.8-10:1 range from the stock 8.8:1.

 

Anyone know? Can I clay the engine stock, and calculate with accuracy the clearance after milling and with the larger cams, or is there some reason I'm not thinking of that it wouldn't work?

 

Nobody can point me in the right direction with this? Help me build a "poor man's" B20z!

 

I don't know from experience, just from what I've read, but the stock B20 pistons dont have a large enough valve reliefs for large cams. Using proper pistons would yield a better result for a bump in compression and most aftermarket pistons have enough room for most any streetable cam you can put in there...

 

I can see that being an issue if I had a Vtec head with the bigger valves (diameter), but I guess that's what I'm trying to find out: how much material can I remove before I have P2V issues on a big cam? I do know the cam I want to run has no issues in a B20b before milling, how far can I go before I've gone too far?

I may end up having to clay the engine stock, and factor in the greater lift of the bigger cam, and then see what's left to mill out. I'm not sure how I'm going to account for the greater duration using this method though.

Thanks for the response!

 

Sorry, forgot about the smaller cams.
If you're wondering how much you can mill it before you have p2v issues then you probably should just clay it anyways. Is it worth someones 'word' that you'll be OK if you go .030" without troubles? I doubt it.
Why don't you want to get pistons?

 

There is no budget for building a bottom end right now, just looking to squeeze what I can out of what I have. I've got a B18b here as well that I would build for boost if I decide to go further with this car.

 

Think of pistons as future investments.
With milling the head you're losing room to mill later on if a problem arises and the need, be.
Even if you go 10:1 compression that's totally "boostable".
You would have to take off .030" to get a decent amount of compression increase and the headache of having to clay the engine and degree your cams.
RSMachines pistons are ~$180

 

I've got a spare head, and they are only worth maybe $100 anyways. Pistons are cheap, but rods, bearings, machine work, assembly, etc adds up fast, before you know it I'm $1000 into a bottom end with weak B20 sleeves that are no good for boosting anyways. On top of that, I won't likely have it ready in time for spring which is something I want to avoid.

I'm actually looking to take off somewhere in the .04-.05 range to get the compression I want, and I'm fully prepared to toss this head in the trash when I do move on to a better setup if that day ever comes.

 

OH OH! So it's the weak cylinder thing again?
Lol. Look it up. They aren't that bad. I'm running 12:1 compression on stock sleeves...

 

How high do you rev it? I would have no qualms about building an all motor B20 on stock sleeves, but I wouldn't want to redline much over 8K, because I know I'd see redline on a near daily basis, and I wouldn't expect it to last (if I build an engine, I don't want to have to build another one in the time I own the car) with that treatment, same as I wouldn't expect a stock sleeve B20 to withstand more than 10psi of boost. They aren't fragile, but they also aren't as durable as the other B's. That being said, I don't have a budget to build the bottom end right now so it's a non-issue.

Edit: I checked out your build thread, very nice! With a built bottom end I wouldn't feel as bad reving to 8500 or so, but I don't have a built bottom end, and I plan on setting redline for this engine around 7200, where ever my stock B18b cams stop making power, and maybe 7500 or so when/if I get the 403's.

 

if you didnt buy cams and stuff already you can buy my head setup it have less then 600 miles on it

i got ls head with stock valves, crowder spring and retainers with 403 cams for sale $600 shipped and it comes with arp rod bolts for ls/b20 rods

lmk if you want to buy it