Street porting a 1.9 big valve head

[RallyBob]

Originally Posted by ddoyle Bob, any reason to use the 1.72 valves over the 1.85? Seems with the porting issues(the lip) it would just be easier to just go with the 1.85 valve. Thanks, Dan

In this instance the head was already machined for the 1.72" valves, so I used what I had for the demostration. Another concern is that with bigger valves and especially in conjunction with a higher overlap camshaft, piston-to-valve clearance is often at times an issue. I prefer to use 1.85" valves, but if I were to retain stock 1.9 pistons there would be an interference issue. Just something to consider.

[markandson]

Bob,
When ever you get around to posting a suggested cam profile for what has been posted previously I would be very interested. Take a look at my last post. Thanks

[RallyBob]

Originally Posted by markandson Bob, When ever you get around to posting a suggested cam profile for what has been posted previously I would be very interested. Take a look at my last post. Thanks

I can't find my cam master list, so right now I can't recommend a specific cam grind. Ballpark profile would be .450-.480" of lift, and about 240-245 degrees of duration. But with a split profile...just a few degrees more exhaust duration to make up for the bad exhaust port design of the 2.2 head. I just don't have a specific set of grind #'s to give you at this time.

[Tru-Craft]

I am also in the process of building a big valve 1.9 head like Bob recommends above. I will port as close to what his pictures show as I can. My porting skills are not as good as Bob's, so I cheated and used my milling machine to do the port openings! Clamped the head in my 6" vise and used a 1/2 dia. ball mill and went in about 3/16" deep to give me a straight and square opening. This is easy for me, just don't turn the handle the wrong way!
The rest will have to be done by hand, I'll just go slow.
Got most of my parts together.
Got a cam blank from OGTS today and will take it to Cam Techniques for final grinding, there shop is a 1/2 hour south of me, so I will check the place out.
He seems like a nice guy, and has worked with Bob when they were up north. So he knows Opels and he is willing to make one custom cam!!!!
I will have him grind the cam with 3-4 degrees of advance, so I don't have to modify the cam gear!
I will get information and pictures at Cam Techniques, I have never seen a cam grinder before, should be educational. Will also ask about a roller cam.
Thanks again Bob for taking the time to post all this information!
Lyle

[jeff denton]

Hey that's cheating.
Oh, speaking of which, does anybody know anything about acid porting, you know, to hide the tool marks you just milled into your port openings?
I'm just curious, you know. Not that I would ever try acid. Crown Royal is about the hardest stuff I do, and not very often, unfortunately...
But, what kind of acid? I once heard it is muriatic, is this correct? And how would a tinkerer apply it to an intake port passageway?
Lyle, do these guys regrind a new profile into a used cam? I kind of need to get something started in this department, Bob has a special circle track recipe I want to try.
Gotta go. I think I hear my mommy calling me.

[RallyBob]

Originally Posted by jeff denton Oh, speaking of which, does anybody know anything about acid porting, you know, to hide the tool marks you just milled into your port openings?

Jeff, I've tried hydrochloric acid (recommended by a chrome-plater friend of mine) for this before. It just happened that he had a 200 gallon tank of the stuff, so that was convenient as well.

We didn't use the acid to hide tool marks, but rather to enlarge the runners on intake ports. A piece of 1/2" polypropylene plastic was bolted to the intake face of the head to seal it, and a silicone plug inserted into the valve guide. The head was tilted so the valve seat was level, and acid was poured into the intake runner until just below the valve seat. Then you wait.....

In all, we let it sit overnight, drained it, refilled with 'fresh' acid, and then did that again two more times to get the results desired. Effectiveness apparently depends on the temp of the acid (we should have heated the head on a surface place in retrospect), and the acid concentration (I have no idea how strong his acid solution was.). So it was three days in this case, but you just fill it up and go home for the night, then drain and measure the ports in the morning. No waiting around really. IIRC, we removed almost 1/8" from the intake ports of a 'stock' class 305 Chevy head! But you didn't hear that from me.....

[jeff denton]

Thanks Bob, that sounds interesting. I just did a google search for hydrochloric acid, found a very informative site that says it is also commonly called muriatic acid, gives one popular use as "metal pickling".
I think a beginner would want to go easy on this stuff, huh?

[hrcollinsjr]

I believe muriatic acid is a weaker form of hydrochloric acid. Muriatic acid can probably be picked up at your local hardware store. It is commonly used to prepare concrete for painting or can be used to speed up the patina that copper takes on with age. As a lifeguard, many years ago, we used it to eat the concrete away from the agregate to make the pool deck less slick.

HTH,
Harold

[nobody]

There's another product out there that does real well. caustic soda and usually comes in beads you mix with water. At 75% strength it will take all the edges off car keys in under 5 minutes. Not that while working around a 500 gallon tank of the stuff the keys to my silver GT fell in and had to be fished out in a hurry or I was walking home. Takes off chrome in about the same time. We used it as a chemical polish for stainless and titanium parts. On them it took about 1/2 an hour.

[RallyBob]

I just did a little quick research and muriatic acid is just diluted hydrochloric acid (30% hydrochloric/70% water). So you may want something stronger for cast iron, or perhaps just heat it up a bit.

Warning: use with adequate ventilation!

[nobody]

Outdoors maybe, after a period of time the fumes mess you up. 3 vats over from the caustic soda were the acid tanks. Now I remember why I quit that job. Another good one is electro static discharge. Wait that's anode and cathode with a big tank of water. I'd stay with the acids but keep some bicarb soda around.....and a garden hose.....and a fire extinguisher.

Just an FYI the inhaling of the fumes off these types of chemicals is mood altering and 90% of the workers near that room had side effects.

Ok outdoors and a big fan.

[WannaBOpelOwner]

do any of you know where i can get a "air powered die grinder". do they make cutting blades for these also?

[asdasc]

When decapusating semiconductors (computer chips), we use concentrated sulfuric, It can sit on the mold compound for quite a while with little effect at room temp. We set the parts on a hot plate to get them warmed up (too hot to touch) and then it eats away the mold compound in a few seconds.

What I am saying is, the added temp will make it potentially VERY fast, so do some testing and get a good rythem going at a controllable temperature.

[GTJIM]

The acid used in batteries (Sulphuric Acid) will do the job too and it is much less fumey than Hydrochloric Acid. Easier to obtain too - and we all have a pretty good respect for battery acid ... don't we?

[nobody]

wannabe, have a look at harbor freight near you, give your wallet to somebody else before you go in. Air compressors, air tools, hoists, presses lathes, mills, tooling, all at dirt cheap prices.

[Tru-Craft]

Back to porting!
I have my valves, they are Chevy 1.80/1.50 11/32" Pro-flow type, with under cut stem. The stem is under cut about 1-3/8" from the top of the valve head.
My question is should I machine the cast/bronze valve guides to match this distance?
Thanks
Lyle

[GTJIM]

Lyle, It is quite important that the under cut on the valve stem sits outside the valve guide or carbon builds up on the stem (particularly on the exhaust valve) eventually doing away with the undercut for a portion of the stem. Contra-wise - in the old British motor-cycle days - we used to counter bore the guides themselves to allow a ring of carbon to build up in there so that - theroretically - it acted as a close tolerance seal on the valve stem.
No use cutting the stem back further towards the guide as you may just form a stress riser on the stem - better to leave it "factory" finished. Of course, if the undercut goes back into the guide it is probably worthwhile to cut back the guide while porting as the unsupported bit of stem will do nothing for valve stability in the guide and removal may just improve the flow though the ports!

[Tru-Craft]

More useless info.
The stock Opel intake valve weighs 102g and has a head area of 1.945".
The 1.80" Chevy pro-flow weighs 102g and area of 2.544".
Same weight with a 30% increase in flow!

The stock Opel exhaust valve weighs 95g and has a head area of 1.410".
The Chevy 1.50" pro-flow weighs 89g, area of 1.767".
Lighter and flows 25% better!
Also with the under-cut stem they will flow better than stock!

The stock spring retainer, valve keepers and oil shield weigh 43g thats heavy!
Will check the weight of titanium ones next.
Lyle

[Tru-Craft]

The head is coming along good. Bronze guides and exhaust seats installed and valve seats roughed in!
I set it up in my mill, tipped the head to about 24 degrees, indicated everything square. Then bored and milled the combustion chamber and valve port area!
Then I un-shrouded the intake and exhaust valves and milled the valve guides down to match the undercut valve stems.
This will give me good straight lines and arcs to hand port to.
It took me about 2-1/2 hours to setup and mill as shown, milling is easy for me and this saved me alot of time.
I would like to mill the whole thing!
But to many arcs and decreasing radii blending.......
Guess I have to do it by hand.
Lyle

[Tru-Craft]

Still alot of work to go, but it's roughed in.
How polished should the combustion chamber be?
I will polish the Exhaust ports.
The intake will be rough 36#.
Also after final surfacing of the head gasket surface, what edge break should I do around the combustion area? (.005-.010 rad)?
Lyle

[nobody]

Sorry but I have to say this. For every CC you just removed from the combustion area it has effectively dropped your compression. Now with any standard piston your down in the 6s. To develope any power now you'll need custom pistons that are usually 160 per hole. Deck the daylights out of it might help a bit but you have to be carefull of chain slop and cam retiming then.

[jeff denton]

A piece of plexiglas sealed with grease around the edge of the chamber, with a hole to drop your fluid in and another to vent it. The head should be as level as possible, naturally.
Also, I would be curious what your head measures from the deck to the valve cover rail after you mill it. Both sides, in case it is angled hopefully. Just to have some numbers to compare, you know.
Yes flow is important but so is compression ratio. I'm sure you know Bob's spec of making the piston top out .005" above the deck.
There are tricks for taking up some extra chain slack and the timing part is simple.

[Tru-Craft]

Dave,I have Chevy forged 3.75 flat top pistons.
Tried to remove smallest amount of material to Un-shroud the large valves for flow.
Will mill the head about .020, and the cam ground with 3-4 degrees of advance.
I calculated about 9.5 : 1, but won't know until I'm done.
What is the volume of a stock combustion chamber about 53?
Lyle