cylinder head questions..

[novaderrik]

what is the combustion chamber volume of the 3.8 Buick head?
and are there any better cheap heads cluttering up the junkyards for more compression without causing detonation problems?

 

[johnnyttype]

what is the combustion chamber volume of the 3.8 Buick head?
and are there any better cheap heads cluttering up the junkyards for more compression without causing detonation problems?

46cc. i believe. they are very small... i think ive read of people running thinner headgaskets to bump compression up. hope that helps some!

 

[novaderrik]

yes. thanks. that helps some.
i'm just brainstorming a good dedicated E85 combo for my car that i might get around to screwing together down the road- i'm thinking 9.5:1 or 10:1 static compression for day to day drivability and economy with a fair amount of boost for when i push the fun pedal down.
who makes the thinnest head gaskets for an 84? i can only seen to find about .035 and thicker- small block Chevs go all the way down to about .015. i'm a bleiever in the theory of keeping the quench nice and tight and build the compression ratio with combustion chamber volume with a reverse dome or preferrably a flat top piston

 

[johnnyttype]

i just found RJC's got a .017" thick head gasket. dont know if 84's r the same though.

RJC Head Gasket Kit

 

[eastwoodad]

You could use a factory GM steel head gasket at .020 or go with a copper head gasket at .020, both available through TA Performance. Obviously, it would be a good idea to have the head and block deck surfaced and squared up and you could take a bit of metal off that way too. There should be plenty of room even with a stock/stock type piston.

 

[VadersV6]

What I dont get is why buick went with the chamber design they did. Its an open chamber which is terrible for quench...an extremely important factor when dealing with elevated cylinder pressures and detonation.
When I was 18, I had a 70 cougar with a 4V 351 cleveland that had the sewer pipe sized intake ports and 2.19" intake valves. They had no velocity till 6000rpm. Everyone who knows clevelands, knows that the american cleveland head, whether a 4V head or the smaller 2V head, is that they both had the same open chamber which is prone to detonation. The chamber is pretty much identical to the buick heads. The head that everyone wants is the australian 2V head. It has plenty of flow but a high quench closed chamber. Same goes for the boss 302. The open chamber is prone to triggering dual flame fronts which collide and cause detonation. A closed chamber focuses the charge in the center of the chamber and with the spark plug right in the center. The top edge of the rings and upper edge of the pistons tend to glow just enough to trigger an unwanted 2nd flame. Combine it with a ridiculously thin cylinder head deck, which is so thin that the chamber itself lifts under extremely high pressures...not the whole head like many people think and waste their time trying to stop...its the chamber itself bending upward enough to blow the seal and blow the head gasket. All the studding and special headgaskets cant stop a thin deck/chamber from lifting. You look at any decent aftermarket head, and they all have thick decks. AFR heads have 3/4" inch decks to handle boost if you throw some at it. Even with the heads being iron, it doesnt make a difference. The buick heads arent designed for boost by any measure.

 

[turbofabricator]

The weakest part of a 8445 casting is between the head bolt holes on the intake side. You can install deck pins to strengthen the area, though. I use to do that many years ago, but if you control detonation it really isn't a problem. The TTA heads (FWD 3.8liter heads) have a MUCH smaller chamber. The problem with them is the need for TTA or similar headers. The exhaust ports are completely different than the GN heads. Using a steel shim head gasket will also require milling the intake manifold to get it to mate properly.
You can analyse the weakness of the Buick cylinder heads, but they DO make pretty dang good power. The combustion chambers are WAY better than SBC heads ('cept aftermarket, of course) Remember, the engine is under boost and combustion chamber swirl/quench is not really a big concern. The swirl is artificially induced. If we could get a Honda V-Tech cylinder head on our cars, I would do it. But, what we have tends to work pretty good, despite itself. Buick engineers got there stuff together on the StageII head, though. The production tooling was made in 1979, and they surely weren't going to spend the big bucks to re-tool when they made the GN. It would be nice to have a better combustion chamber, but if you want that, go with a GenIII or IV Chevy. That is the way to make good power. :smile:

 

[VadersV6]

What SBC heads are you referring to? They all have closed chambers. The 80's heads have a crappy chamber design but its still closed. Quench is more important under boost than an N/A car by a long shot. You're referring to swirl as a source of eliminating detonation, (TR heads have a large dip in the valve pocket, behind the intake valve to kick it up into a swirl, so its not artificially induced by boost...boost doesnt cause swirl...intake port/pocket and chamber induce swirl)...and one of the important aspects of swirl is that you can fill the cylinder alot more when combined with high velocity ports, at low to midrange rpm. With higher rpm and boost, the swirl angle needs to be reduced since swirl causes peak charge velocity to happen much earlier in the powerband, but becomes a bottleneck when you want to wind it up. But it does also play a big part in reducing detonation. In 99, when the new Mustang GT came out, they had heads that flowed alot more and a big lump in the chamber, right outside of the intake valve, which kicked the charge into a serious swirl. It was great for power below 5000rpm, but was a problem at higher rpm. So people started grinding these lumps totally off when doing a port job, and found their motors were incredibly dead below 5000...like a serious loss which didnt start to recover till close to redline.
Back to the TR's, they do have a feature which induces swirl, but the open chamber design is a hindrance to keeping detonation at bay. Those heads werent designed for turbo motors. Alot of people have made great power with them, but everyone with high power levels tend to have constant issues popping head gaskets, and keep chasing the wrong rabbit to cure it. You have a chamber that sucks for a single happy flame front and a super thin deck that cant handle even slight detonation without pushing the center up. The heads are keeping contact around the bolts/studs...its the chamber thats lifting. Under those kinds of stresses, even iron cant start to act like plastic. If someone were to get crazy and drill out the heads from the top, over each chamber and weld in a thick hardened steel pin resting ontop of each chamber, then weld it back up, I think alot of iron headed, high power GN's would suddenly stop blowing head gaskets...but its just one dumbass's opinion.

 

[turbofabricator]

The pinning of the deck is just what I was refering to. I have posted pictures of the deck pinning in the past. Here is how it was done, without welding. http://www.turbobuick.com/forums/general-turbo-buick-tech/210845-top-sekret-teknology.html I would have continued to do it, but just controling detonation works better. I use to do that back when the biggest injector was a 30 lb Tomco. You can over anylize the Buick head, or just fuel it, and turn the boost up. It WILL go faster. The SBC has TERRIBLE combustion chambers for turbocharging, but opinions on what is better will always be dipusted and proven/disproven at the track. Port volume is where its at with the Buick head. Yes, the biased port of the Buick makes for good swirl effects, and if you capitalize on the biasing, you will make good power.
On one of your previous posts, you stated that the best intake port design had "golf ball dimples" in them. I have worked on some really high tech heads over, the years, and have never seen a dimpled port wall. Can you elaborate where this is done? Is there a process that makes this possible (besides acid work)? (It "should" work better) Cylinder head porting has many theories to it, and alot of contradictions, too. I would enjoy shootin' the sh!t with you over a beer or two. I might learn a thing or two. I haven't been doing heads for all that long. (only about 28 years, my first set was a SBF back in '78-79) It is always fun and somtimes educational to talk with new folks on head flow ideas.
Years ago, I was building 5,000+ hp gasoline race engines and wanted to do some serious porting/cam changes to the engine. The crew chief just smiled and said, "we'll just turn the boost up 10in. hg. and make more power." He was right of course, so we just cranked it up top 130in. hg. and went racing. ( and went through 65 gallons of fuel, 25 gallons of water/methanol-ADI- and 150 lbs. of nitrous oxide)

 

[Junior Samples]

What SBC heads are you referring to? They all have closed chambers.

i just got rid of a pair of 487x casting open chamber 2.02 sbc heads found on early 70's Lt1

sorry to butt in

 

[VadersV6]

Chevy has their own idea of what they call an open chamber head...I wasnt referring to those. Those things suck balls and then more balls.
You mean these, right?

http://books.google.com/images/cleardot.gif

After machining so many thousands of heads for so long, I get the chills and feel the need to call my psychiatrist every time I see those things.

Turbofab-
I dont remember referring to golf ball dimples making a port "the best" or anything like that. There are places in the stream where you can place these "dimples" (actually looks like a cheese grater was taken to it if you use the right burr and spin it slow) in order to prevent the boundary layer from growing...in places where they have a tendency to grow and become a turbulent wake and cause all sorts of issues. The airfoil shape around the valve guide is one place. (well, this is after you grind that into an airfoil shape) An intake runner inlet is always a good place. Theres a million ways to get flow out of a head or intake, and unless someone actually forgets about car magazines and those kinds of sources of info, and goes out and gets some simplified fluid dynamics books, they can really waste their time doing things they think will improve flow, but wont. For instance, if I were to port a TR head, I'd braze up that entire pocket below the intake valve whereas some would probably cut it deeper.
Gotta go take a dump, I'll be right back..

 

[Junior Samples]

Chevy has their own idea of what they call an open chamber head...I wasnt referring to those. Those things suck balls and then more balls.

I didnt say they were worth a damn, first generation smog with hardened seats, old tech and with so many better choices today id rather use a 462 camel hump as a boat anchor then install it

 

[VadersV6]

Sorry about that...
Turbofab- thanks for the kind words, but if anyone could learn a thing or 2, it would be me learning from you. You were building actual engines when I was building my first pseudo functioning model engine with my dad.
I ported my first set of heads at 15 in high school auto shop. I used to ditch classes and spend like 4 periods a day in auto shop. I got some award for top student in a class, while barely scraping by everywhere else. I'll never forget my high school math teacher, Mr. Cummins. He had a 12.40 2 tone orange/white 55 chevy with a 327. Beautiful frame off resto. We used to talk cars all the time, and it would be time to go to his class, and Id use the auto shop teacher's phone to call his class and tell him I was in auto shop and he was cool with it. That was one seriously corrupt school, lol. I remember at the end of one semester, I had amassed 34 absents in his class but he passed me with a C. I hadnt done 1 homework assignment in his class lol...
Anyway, I ported my first heads for my .125" over 283 (301ci), that came out of my 72 vega, which was going into my 2nd Nova...a 64. I had sold the 63 I got when I was 12 for 200 bucks. I bought the 64 for 50 bucks from a friend. The interior was GONE, and the whole car looked like hell, but it was original paint and didnt have 1 single dent or even a ding on the whole car. So those heads came out horrible, but I was proud of myself at the time. The ports on 1 head were probably 20% bigger than the other one. It was a major hog out all cut at random with 1.83 intake valves and a 75 dollar rebuild from some crap shop in L.A. It took several years at JMS before I was doing really clean work, but I still didnt really know what I was doing. It wasnt until we got a flow bench, a dyno and I really studied the 4V Honda heads they were making in the 90's, as well as the mustang TFS twisted wedge heads which had just come out, and started applying some of what they had done, that I saw what worked and didnt. The 4V hondas from that era are a great model for learning. They can flow 220cfm, bone stock, which is ridiculous for an N/A 1.8 liter motor, but its the reason those motors can be wound to over 9000rpm and still make power. We're talking 100hp/liter in stock form, with emissions and economy minded cam designs. Back in 94, I started doing heads and blocks for JG engine dynamics, and these guys were getting 450whp out of 1.8's even back then. It would take a 75 shot and 20psi, but it wouldnt be possible without those heads. They dont have an angle below the 45 degree seat to speak of and get all their flow from the pocket and throat design. I also learned alot from the normal 2V heads they made in the 80's. You look at what chevy came up with, with the LS1 motor. It took a long time for the U.S to get on board, but you could se they started applying what honda had been already doing for 20 years...dont get me wrong, Im not an import guy at all, but they do know their **** when it comes to flow.

 

[VadersV6]

And these are flow numbers for K20 heads- Straight from JG's site:

The K20 heads flow pretty good right out of box. We have seen on average appx 270cfm through the intake ports and 475'' lift and at 28'' of water. With this new valve job and dozens of hours on the flow bench we have come up with an increase of appx 15 cfm with out any port work. 285cfm with stock ports and with out manifold. With one of our custom intake manifolds we are seen close to 320 cfm with stock ports

With a good intake manifold, 320CFM from a STOCK head on a 2 liter motor.
I recommend anyone with a few extra bucks who wants to learn how to port, go buy a junkyard honda head, tear it apart and study it.
And the heads that flow 225, I got the number wrong. its 235CFM, with a 1.6 liter motor
I know these are 4V heads, but there is still alot to be learned from the throat and pocket design.

 

[novaderrik]

wow.. some pretty technical talking going on here. .glad i asked about heads..
so, anyways, i could use a set of FWD heads and wind up with more compression and a better chamber? and all i'd need to do is make a different set of headers?
so, say i theoretically worked in a metal fabrication shop and had access to things like CAD programs, laser cutting machines, TIG welders and people that know how to use them and had a boss that is the original owner of an 87 GN- hey, wait, that does sound like my situation right now- which heads would i want to look for? would they happen to be in the same fwd Buick that i want to get an ecm out of to upgrade my 84 to the 87 spec?
and if i was to make a set of headers for the swap, what alloys would i use? i think we have stainless in stock up to T409 grade, but T316 is more common and much cheaper. and if i was to get plans for headers made up, would there be a market for something like that?

 

[JDEstill]

Lets see...

Stock engine I believe is 8.0:1 with a 0.060" head gasket. Going to a steel shim gasket at 0.018" would bump you up to 8.6:1.

For a head swap, the chamber size that's been kicked around for the TTA style heads (from FWD 3.0 engines I believe) is 41 cc. Put that on a stock GN engine (which has a 48 cc chamber) and you are looking at 8.5:1 with a 0.060" gasket.

Combine the FWD head with a 0.018" gasket and now you are at 9.3:1.

Of course, the FWD heads require new headers.

Once you start building a new engine and are looking to swap pistons, then you can do a lot more. Flat tops will let you get all the way to 12.5:1 at least if that's what you want, with stock GN heads.

The FWD heads supposedly have better design chambers. In aftermarket heads I thought the TA heads had better design chambers? That was my impression anyway.

I kinda figured that a max efficiency design would be to combine the TA heads with their chamber design (assuming I'm right, that they are improved) with the Diamond piston and their bathtub shaped dish (assuming I remember right on what they look like), and that would give you a nice overall shape when piston meets head, with a lot more squish than a conventional dished piston and stock GN heads.

On mine I went with a steel shim gasket to bump up the compression a tad and to get a tighter piston to head clearance. Not a lot of squish available due to the shape of the piston dish (I've got Wisecos), but what there is, I wanted to try and get. If I measured right I think that gave me a 0.053" quench (ie piston to head). Woulda liked it tighter if I coulda gotten it. But compared to stock, 0.095" I think, it's a big improvement. Again, probably not much difference, since there is so little quench area around the outside edge of the piston dish. But hey, every little bit helps, right?

John

 

[JDEstill]

Here's what the TTA heads look like:
Buick V6 Cylinder Head Guide

Looks to me like that head plus a piston with a bathtub shaped dish would be a nice combo. Seems to me that if possible, the piston dish shape should reflect the chamber shape. Having a small chamber and a big piston dish seems like it would make a weird, suboptimal shape when the piston comes up to meet the head. But maybe not, just thinking out loud here. I don't really know.

John

 

[DavzGN]

The problem is he already has an 84 regal so it should already have the steel shim gaskets.

David
87GN

 

[VadersV6]

Im a little curious as to why buick had 3 different 3.8 motors in the same year/years (86-87). Judging based on the head design of the TR, its almost as if buick knew the end was coming for RWD and carbureted motors, and had thousands of carb motor heads laying around that sucked on flow, were crap for power.....but hey, if we slap a turbo on it, it'll make up for it, and we'll get all that crap out of inventory and we can focus on the future, which is the aluminum headed, roller cammed 3.8 FWD. They knew the end of RWD was coming in 88 and had different plans. Wikipedia actually has a good page on the buick 3.8. Back in 86 when I first got a ride in my uncles turbo regal, I remember thinking it was the same motor as my parent's 86 buick century, with the aluminum heads and roller setup. It would have made more sense but I guess I was wrong. I remember rebuilding tons of those aluminum buick heads, and I always thought they would have been a MUCH better match for the turbo setup, not to mention the factory roller cam without all the issues the roller aftermarket has with our motors. In 85, Ford came out with the roller cam in their 5.0 with FI. Then GM does the same thing, but the one car it SHOULD be in, they throw the old antiquated flat tappet and crap iron head BS in it. Not all iron heads were bad, like the turbo trans am head with the thicker deck and closed chamber (much better quench, contrary to what that guy wrote on the cylinder head guide up there..he's wrong), but the aluminum heads flow better, are lighter and are cheap at the junkyard.

 

[novaderrik]

The problem is he already has an 84 regal so it should already have the steel shim gaskets.

David
87GN

when i got the car, it had a blown head gasket- but it wasn't a shim. the motor was replaced in the late 80's/early 90's some time with a parts store reman long block that had some thick gaskets in it. but the guy i got it from said it was a long block for a turbocharged application, and the pistons had a pretty deep dish in them like a turbo piston should- but when they screwed the heads on, they forgot to tighten the bolts.. oops...
anyways, at the time, i knew nothing about the Buick V6, so i just got whatever Fel Pro gaskets Bumper to Bumper had in stock and replaced them both.
but now, going on 4 years later, i want more power and i want it cheap. if i can get a set of fwd heads- and the roller cam setup to go with it- then that's what i'll do. those late 80's Buicks are plentiful in the boneyards and usually get junked because the bodies fall apart after 250,000+ miles, and not because of a mechanical issue...