Inliners International Forums General Discussion Engines Shave the 230 head .060" still safe?

I've been crunching my numbers and weighing my options here for a while, and this is pretty much what I'm looking at. I need to mill the head .060" to get 9:1 compression ratio that I want. (For my mild cam). Question is, is it safe to shave the head that much? I read somewhere that it is ok, but can't find the source now. Would that leave me room for one more trip to the machine shop if some day I end up warping the head? Or would I be using up all the margin. I don't think this head has ever been milled before, I'll have to measure it again. '70 230.

I would REALLY like to zero deck the block, but that option is out of the question for many reasons, and it would STILL require me to shave the head. Costs too much to do both. My pistons sit .033" deep in the block, and with a .040" crushed head gasket... my deck/quench are just disgusting. But those are my realities.
I'm doing what I can to curb detonation/pinging. Committed to higher octane gas too, it's an occasional driver, not a daily or a race car. Very mild build.

Why is decking the block, not a option? Strip the block, power wash it down to remove the greasy stuff and get it decked. Cost 50-100 dollars and some of your labor. Some shops will complain that it is not magged or hot tanked. Just get it good and clean for them.
After decking, repeat the power washing and blowing out of water and spray down with WD40 quickly. It will be fine.

I routinely deck from head .030 without blinking a eye. .050 is also ok by me under the premise of not using it for heavy duty continuous loads (like a large truck /trailer). 060 would also fit into that category and not leave room for more normal decking. Racing heads can go more.

It will be hard to "measure" the thickness of the head deck. I use the factory casting marks a my tell tale. There is a thumb sized area that is unmachined on the head surface. .060 will practically remove this area.

<sigh> I hate you.

LOL no I don't. Reason I didn't want to send the block to a machine shop again, is that it's all prepped and cleaned and buttoned up, all moving parts are in.... super clean and painted, you could eat off of it, inside and outside. I had the shop wash it too. It is ready for the head and oil pan.

I HATE the huge deck height, I really do. Anything beyond .040" is wasted efficiency, fuel economy and power, and higher risk of pinging. (IMHO). Now that you said milling the head .060" would all but use up all safety margin and not leave room for "corrective" milling later on if need be, I don't want to risk the head. I have too much money in the head alone.

So I guess I'll be taking the damn thing apart again and send it in for a .040" shave to bring the piston tops almost level with the deck. Just a hair below. Then I will have a little bit of play room with different head gaskets.
That's another cost my already quadrupled (?) budget will have to deal with, and another delay.

I will still need to shave the head some, to get the CR I want, just a little over 9:1. Deck alone won't get me there.

I would hate myself every time I drove the car if i knew I built the engine with that huge deck. I'm all about optimizing everything.

<sigh>.

Jan

Trying to compensate for a poor quench height by cutting the head excessively is not going to provide good results either.

Ok.

If anyone cares, here's the revised plan.
Did some more accurate measuring of what I have.

Zero deck the block, so the head gasket (.040") is also my deck height. Shave the head .050" to achieve 9.5:1 CR. The tight deck allows for more CR, and since I'm gonna hafta shave the head anyway, I'm not leaving anything on the table except that .010" safety margin. I am considering .060" to be my safe limit.

If anyone missed it, the cam is not stock, it's the mild Comp Cams 240H grind.

With a .040" head shave the CR would drop down to 9.1:1

I don't think going from 8.5 to 9.5 with a much better deck and chambers would be too much. I can commit to 100% 93oct pump gas if necessary.

Comments welcome and appreciated, as always. This is not my first engine build, but it's my first Chevy inline 6.

Jan

Your cam is a bit short on duration @ .050 to run 9.5:1.

If it does not ping on pump gas w/good timing, it will be a pretty torquey engine.

Are you going to run a 1 bbl carb? If so, you could get away w/that compression ratio, 4bbl, probably will ping more.

I say, give it a shot, if it pings too much, you could always drop in another larger camshaft, larger cam by adding 5 -10 degrees more duration,(say 205- 210 there abouts) I would also like a wider lobe center than a 108 more like a 112 lobe center.

Just my opinion.

MBHD

This cam is designed to use stock CR (Stock everything), they say anything between 8-9:1 will work fine. But the advertised duration is not telling the whole truth. As I have learned (?) the asymmetric lobe design causes the valves to open and close quicker, thus the valve has more "open" time than a traditional lobe that opens and closes slowly, causing the valve to spend much more time at half lift or less. It sort of tries to imitate longer duration by offering more lift earlier, without bleeding compression out.

I am doing some basic stuff to reduce pinging, radius sharp edges in the chambers and match the edges to the head gasket, etc. And the tighter deck is probably the biggest key to being able to run higher CR.

My carb choices are stock Monojet or the dual throat 2-jet I just got. Stock intake and exhaust manifolds with heat. I will not go to 4bbl. Timing will be trial and error, I'll be using an MSD box or equivalent (We sell a cheaper version made by MSD for less than $150) and Pertronix to eliminate the points (and subsequently, timing flutter). Already there.
Mixture will be set/monitored with an O2 sensor, already there. So I think I'll have fuel and timing management sorted out. With tighter deck and higher CR, I will need less timing advance. I'll see if the stock distributor timing curve needs to be tweaked, this is a new model for me but I've modified and recurved distributors for 20 years or so Like I said... trial and error. Just don't want too much error

In other engines I've built, most would run just fine with a mere one point higher CR, and the "error" can be made up with higher octane pump gas. I would feel stupid building any sort of performance engine to use the lowest octane fuel available, it just means you willingly gave up free horses. But that's just me

...my 68 beetle CR went from 7.4 to 10.5:1..... runs cool and strong and never pings

My Camaro went from 9.0:1 to 12.0:1 on pump gas 91 octane daily driver & ran fine w/out running hot. Of course could not run a stock camshaft.
I would not run exhaust heat to the carb, the intake manifold is stinken hot w/the exhaust manifold connected to it & directly underneath it. But that's here in So-cal.

I got the best mileage w/a small AFB carter carb over any 1 bbl I ever used, plus, it made a bunch more power.
I kept the 1 bbl intake & carb, air filter etc for smog checks.

Might want to upgrade to a truck exhaust manifold w/the larger 2.5" exit.
just a thought.

MBHD

I'm in VA, the summers are pretty warm here too. I hate the idea of heating the intake and carb if it is not needed. I may end up blocking the heat, and rely on conducted/radiated transfer.
The race VW engines we built, routinely saw 13:1 and more.... custom made cams like the one in my engine now. Most "builders" stateside don't understand the cam-CR correlation at all. Folks on this forum seem to be a step above the average rednecks

As a curiosity, here's something to ponder: my cam grinder guru showed me a few cam profiles for other race classes, that were designed for up to 22:1 CR. Gasoline, not diesel. Hint: class rules require intake restrictor plates.

Yep, w/a restrictor plate engine you can run a bunch of compression on them, but, if you take the restrictor out, watch out, engine will not last long.

MBHD