I would like to get under 50cc on 083 cylinder head combustion chambers.
I think it can been done but I have a few questions.

What angle to use?

When heads are angled milled do you mill the intake or head to correct the angle for the intake gasket?

Does the base of the intake need to be milled?

Is there a online calculator for all this math?



What I have gather so far from the Dart site for there Iron eagle heads is

Milling: Min. 58cc = .060” (.0065” = 1cc) Flat Mill
Angle mill .125” safely / .200” = 49cc 1.5° (carefully)

Another question is can you weld combustion chambers and profile them to what you like. I have welded cast iron manifolds and profiled them using a mig welder and a die grinder. You would never know that they werent cast that way then polished.

 

yes you will have to mill the intake surfaces, angled, since you've milled that much off the heads.
Not sure on the angle, have to do the math, or trial and error. Your machinist should be able to figure that out for you.

shouldn't have to mill the base of the intake. Which intake manifold are we talking about though?

You've Mig welded cast iron before? How'd it turn out? I heard you can't really do that (did you use normal steel wire?)
I've used a stick welder with some cast iron rods, but it's very tricky. Key is to preheat the head so it doesn't crack, the iron doesn't like to heat up /cool quickly, it's too brittle to bend or warp, so it'll just crack.

Good backwoods way to do it is to throw it in your BBQ on max heat for a while. Once it's good and hot, pop open the lid and weld what you want, then close the lid and leave it on medium for 10 minutes maybe, low 10 minutes, then off to cool for 1/2hr or so.

 

The milling work will be done myself at work.

I thought that the head intake face would be put back to same angle in referenced to the the head face rather then changing the angle on the intake, I don't know, that is why I am asking.

Using a tpi intake, I would like to keep it the same stock angle as I may go to different heads some day.

Mig welding of cast iron may not be the best way, but it would apply the least amount of heat and since it is just a filler it could have porosity in it.

If the chambers could be welded I would just flat mill to the max. and weld and contour until I got the correct size. (actual in the reverse order)

Factory cast, welded and cnc chambered heads are available for the LS1 engines In aluminum. Summit sells them Patriot makes them.

Some one must of tryied to do this before in cast iron. Can it be done?

 

Dart cylinder heads have a very thick deck. .400" I believe.
GM heads are not near so well made. The decks are much thinner. Got to ask why you have to have a 50cc chamber on a TPI motor?

 

I am shooting for 12 to 13 compresion with flat tops. I have a water alchol injection system coming. Fjo makes one that has maps similiar to a bin file for Map tps duty cycle.
The way the car is now I have the choice of running 87 octane with a mild timing curve or run 94 octane with a agresive timing curve with more power.

I have never seen detonation at cruise low map with as much as 50 degrees 87 octane 17:1 af mixture. (50 is to much by the way so is 17:1 - 45degrees and 16;1 is good.)

The idea is to run cheap gas 10% saving - more eficient - a big bump like 13 to 1 is 10 to 15 percent more eficient over 9:5 I have read. The alchol would be injected in at high map above 50 to 60 kpa.

I will try out the alchol on the current set up but the big gains will not be seen until the higher compresion.

There is many ways of getting higher compresion other then shaving the heads. But most other ways cost more money. Not that I would not spend it, but the fact is this is expermental and if I scatter a engine that has just got a bit a labour and a pair of head gaskets I will know not to do that again, but if I break a ring land, rod , crank and it ends up in a new set of aluminum heads I will not be happy.

I am open for feed back, information on normally aspirated high compresion engines with water alchol injection is scarce.
I drive 10,000 plus miles a summer and a 20% saving in fuel would justify the added expense of the injection system.

Today I took the mig melder and welded a scrap cylinder head bolt hole closed
then ground it down flush, cosmetically almost perfect, strength very strong chipped my chiesel on the weld. Looks like it can be done but any weld on the gasket face would not clean up with milling, to hard ( like machining a fly wheel with hard spots) - could be surface ground though.

 

huh, i'll be damned... I'm glad your welding experience went well, that's makes me feel more confident!

You're right, not much info on the high compression NA and alcohol motors... Maybe someone else can say why?

The thing that makes me go is that you're wanting to buy cheap gas, save 10% on gas, then pay for alcohol injection. I'm guessing this would be financially, a net loss. Specially when you factor in adding the alcohol injection setup.

Sounds like you're pretty handy at fabricating (welding, flycutting, surface grinding), why not fab up a turbo setup, using stock CR ratio, and water /alcohol injection, linearly increasing with boost, starting at 4psi say? Much more HP, and that injection would be more...well, widely use in that application.

 

My question would be, why? You can get a much better performing head than your 083's. Building compression is just a simple as a piston change. I would be concerned about your head (cast) and your filler rod (mild steel mig wire?) expanding at different rates as they heat up. I would try the barbecue trick AFTER you weld up a hole. See what the result is after the head comes up to temp. and cools back off. Not saying you can't do it, just saying that is alot of work to get something that is relatively easy to obtain another way. With no question marks.

 

The turbo is a thought, bought after driving over 50,000 miles with 300hp the need for excessive horse power is not a goal. Fuel milage and eficence are more my goal. I broke lots of parts when I was younger to know a streetable limit.

Very little alchol will be injected, less than a gallon a week - none if i don't get on it.

Yes the weld may crack, it may not, I don't know, I used to work a R and D plant for ford, there was a machine wich used large burners and brought the head up to below the melting point then it would squirt water at the combustion chamber. Aluminum heads would last less then 24 hours before they cracked after being heated and quench several hundred times in this mater. With some number crunching they could perdict if the head would last the life cycle of the car. My point is all things will crack if put under the right conditions.

Domed pistons are not cheap and like I said before I don't know if things may let go and end up with a basket of scrap metal. To do this the correct way I should have, forged, forged, forged, $2,000 dollars in a short block??

I realize I am going out on some extremes here but is this not why we are here?

I do apreciate the feed back.

 

You're confusing mechanical efficientcy gain from a raise in compression ratio with the resulting gain in fuel economy.
Not the same. a 10% increase in mechanical efficientcy will not get you a 10% gain in fuel economy.

Any engine with such a high compression ratio and a cam with any hope of being economical (read that small) will cause the motor to ping pretty well all the time under even light load,requireing water injection even under ligh load. Water does not burn, does not create heat/pressure to push on the piston. Your net volumetric efficientcy goes down as you replace air fuel with water to temper the excessive combustion temps. The motor simply becomes less efficient.
Your net result would be higher emissions (HCand CO from incomplete combustion) increased cylinder bore wear.
Nox would be lower.

What you want to do is run a motor with say 10.7 /11:1 cr that will run fine at part throttle cruise and then inject a little water at high pressure for the short times you need power, at or near WOT to avoid detonation. The motor will not need water at light throttle cruise and have a little high(er) efficientcy.
Trouble with water injection in everyday use is sooner or late you or the wifey will forget to fill the water tank or maintain the injector nozzles. resulting in a damaged motor from detonation.

 

The easy /cheaper way to build a high compression 350 is to use 305 heads on it. You can flat mill these heads right down to the valve seat/ sparkplug boss. i got 52cc doing this.
built a 12.65:1 cr .060" over flat top 350 with .015" deck clearance and the .015" shim head gasket.

 

That is good way of going about it. Once the weather is more like fall I will pull it down and do some measuring on the heads it is my daily driver right now. If I can get 083 heads down to 56cc with a flat mill I will be happy enough. Maybe a almost flat mill .5 degree might do this. And avoid all the other machine work and welding. Have to look into.

F -Bird 88 is .030" enough quench distance? Have you tryed it this tight?

I just went by the .040" minum rule. Ten thou when you get into the smaller chamber sizes makes a big diference in the calculation. 12 to 1 in a standard bore using 5cc flat top speed pro pistons and 56 cc.

The pistons were under $20 can. 5 years ago. Good pistons, I avoid forged after taking 3 pistons out with .005" clearance and 1250 degree EGT readings in a hot 2 stroke aplication. Forging grow alot. And the stock tpI piston - found 3 piston skirts in the bottom of my oil pan @ 180 k.