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EricF

850 Na (or Turbo?) Head, Mild Work Done

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Got myself an 850 NA head core, need to figure out what I'm going to do with it.

I could keep a tight squish and try to keep the CR by not removing any material from the chambers, and just focus on port work and polishing... Or I could do some chamber work as well and open up the ports more to be more suitable for a turbo application.

This would be a fairly cheap deal on a worked-over head too.

Anyone here interested?

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Bizump.

I haven't looked too much at the heads, but this could probably be a ~15 hp or greater increase.

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Depends how much time it takes to get it where I want it to be as far as work done, but I would guess in the 300-400 range probably.

We'll see, but I won't be charging more than 450.

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getting your head milled is very cheap, like 40 or 50 bucks, i have read that every point in compression is equal to 20 hp, so if you get it up to 11.5 to one you car would be a monster especially down low, then if you get cams it would be an even scarier monster! lol.

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i dont think we can mill a full point though, the valves will hit the pistons, i still think the motor will respond wickedly well to cams, most of the NA's ive driven are about as fast at 65% throttle as at 100%, something is chokin them more than the exhaust does. its def. the puny cams.

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getting your head milled is very cheap, like 40 or 50 bucks, i have read that every point in compression is equal to 20 hp, so if you get it up to 11.5 to one you car would be a monster especially down low, then if you get cams it would be an even scarier monster! lol.

Milling your head excessively isn't great for a few reasons...

First, doing so will probably make the head warp more easily in the chance of a gasket failure. I haven't looked too extensively at the 850 head yet, but milling the head reduces the thickness of the wall between the squish surface in the chamber and the coolant passages, this may or may not be an issue with wall flexing and cracking in 850 heads. Valve clearance is an issue, though probably not too much... 850s are already interference motors.

I'll only be milling the head enough to resurface it to ensure a perfectly flat and true sealing surface. The actual work will be done in the ports and chambers.

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the 850 heads don't leave too much room for improvement, no poor casting flash like american heads nor big radii

From my first cursory look over the cc's, there are some nice hot spots to be eliminated, some minimal valve de-shrouding, and then on top of that polishing will help some....

Haven't looked at the ports yet.

Also, I lied, the valve clearance issue is a pretty real concern. The intake valves are almost flush with the head surface when fully closed as it is... Probably milling too much more and the piston will be very close at TDC when the valve is fully closed. And I haven't looked at the cams and their timing yet, but that could complicate things further. Basically the stock cc depth is about as shallow as you can get :)

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i was under the impression the NA had the more agressive Cam. I've read here before about using NA cams in LPT engines.

My bored throttle body GREATLY improved throttle response and acceleration in 5th gear.

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the 850 heads don't leave too much room for improvement, no poor casting flash like american heads nor big radii

VMS found 10%+ in the heads they did

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Yeah that is true but we had access to a flow bench. Anybody that thinks that this is a simple process has never tried it before. I would bet money on that.

Terry VMS

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Yeah that is true but we had access to a flow bench. Anybody that thinks that this is a simple process has never tried it before. I would bet money on that.

Terry VMS

No, but with an above average to good understanding of head porting theory, you can make slight improvements without a flow bench.

I have two 850 heads I have been studying, and there are a few places where some simple work will improve over stock... Casting imperfections go without saying, there ARE hot spots in the cc's, and I haven't studied the port geometry too in-depth yet, but there is always room for minor improvement there, regardless.

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