milling a 320 head?

[Erik]

I read on www.teambuick.com under "referens" that it should be ok to mill 0.125 off the head. Nobodys answering over there so I thought I would try here.

Milling off 0.125 is ok, but do I have to mess with the push rods too or can the hydrolic lifters take the difference up?

The reference states NOT to go above 8.5 compression. The stock value of the '52 320 was 7.5. I can't see any place how much a milling of 0.125 will increase the compression.

Can I just yank out the head, disassemble it, mill it, put it back together with the old valves (if they look ok), throw it all back in with a new gasket and expect a little more oomph?

Any guess as to increase in hp, torque and milage

Thanks

Erik

[The Old Guy]

The 320 has adjustable rocker arms and should be able to handle .125 without a problem

[Guest Pushrod]

I've gone that route several times in the past. If you're using a stock cam, ok, but if not, watch for coil binding of the valve springs, and check the valve to piston clearance if using aftermarket hi-comp pistons. Not sure if just bumping the comp ratio will give you a whole lot of difference in normal driving. A good surface mill on the head, and a nice angle grind of the valves and seats will probably do the same.

[Gary_N]

Check out this thread. There is a lot of info on working the STR8.

http://www.teambuick.com/forums/showthread.php?t=12146

Gary

[Erik]

Does anyone have an exact height of the head on a 320?

It would be nice to know before I start grinding!

[NTX5467]

Erik, taking that much metal out of any casting is A LOT to remove. IF you decide to do that much, which might not be too advisable (from my perspective, regardless of your desired end result), it'll have to be done in a little for each cut. For that much metal removal, that will take a significant amount of time on the mill. Plus you'll need to let the cylinder head cool every so often, to ensure that each cut is true and straight AND just how much has really been removed. Sharp cutter bits will be a must, too!

In order to determine the starting compression ratio, you'll need to have a good idea of the actual (NOT "Blueprint") volume of the combustion chamber (valves installed, too). Then you'll have to do the calculations for the head gasket thickness and the cylinder's volume with the piston at TDC. That'll give you the "total chamber volume" which you can plus into the formula (with other appropriate values) to determine the ACTUAL compression ratio of your engine. Many times, as I understand, the combustion chamber volumes were greater than the "blueprint" specs, which makes sense after you think about it.

With the lower compression ratio of the engines of that era, adding compression with head milling would probably not be as noticeable as having a good valve and valve guide job done and making sure the head's ports are "clean" inside. In other words, not much "oomph" unless you were keyed-in to know the difference between "oomph" and "running better with a good valve job." The best "ooomph improver" might be a little more ignition timing and new spark plugs . . . from my side of the fence view.

To me, with all due respect, although the rocker arms might be adjustable, to keep the valve train geometry basically "as produced", shorter pushrods would be needed for a .125" head cut. This would also solve any valve spring issues which were mentioned.

Still, though, I feel it would be best to do a truing-up surface cut of the head at the most, then probably find a thinner head gasket to go with it. Then go in and port match the manifolds and cylinder head ports, plus you can do similar with the carburetor venturi area, to ease airflow INTO and OUT OF the engine, as modest as it might be, plus THROUGH the carburetor.

IF you're chasing compression ratio increases, then a better way to get there is "angle milling" of the cylinder head. This means that after the first truing cut, the head is set-up in the mill with one side slightly lower than the other side . . . an "angle" of a few degrees. This will take more metal off of one side of the combustion chamber than the other and in bigger gulps than if it was done "flat". But this could then affect the exhauat pipe mating up correctly without some tweaking and bending at the manifold flange area. Angle milling is an old drag racer trick to get significantly more compression ratio for a V-8 engine, but no reason it couldn't be done on an inline engine too. BUT once you go there, no turning back--a different proposition for a modern V-8 engine with a better supply of cylinder heads than for a vintage vehicle with a rather limited supply of cylinder heads.

The cylinder head castings might well still have good structural integrity with that much metal being removed. The adjustable rocker arms might keep everything moving well. But taking that much metal off of a stock engine, unnecessarily, makes me cringe.

Sorry if I might disagree with your orientations . . .

Respectfully,

NTX5467

Edited February 4, 2011 by NTX5467 (see edit history)

[Erik]

Hi NTX5467

Now I'm not panning to mill the head with an angelgrinder

I've been planning this for 2 years - when and if I were to do head-work.

Because of all sorts different small irretants the head is coming off now and of course all surfaces are going to be planed, carburetor rebuilt, manifold like wize, valves, valvelifters etc. check or replaced. Everything cleaned etc.

So why not take a little extra off the head when i have the opportunity?

I'm not going for the full 1/8" just maybe 3/32"

The shop that is going to do this normally does precission work on large objects 1-50 tons so a 120 pound head should not be a problem.

But still I want to be sure someone hasn't been milling before so how high is a stock head?

[NTX5467]

Erik, thanks for the additional information. I'm glad you've found a good machine shop to do the work. I mentioned "angle milling" as more of an extreme option, but one which I've seen many racers use on V-8 cylinder heads . . . which also "marks them for life" in many respects. If my calculator is correct, 3/32" is .09375", which is almost 1/10", which is not that far away from 4/32" or .125". How do you plan to have the head marked that it's been cut that much, for future owners? I still recommend that only the minimum amount of metal be removed from the head. IF you want to cut something, then enlarge the intake and exhaust ports in the head to allow more air into the combustion chamber (increasing total cylinder pressure "by volume" rather than by mechanical compression ratio methods). The Fisher book tells how to do that, which apparently was somewhat common back then. It also mentions how to further port the head on both intake and exhaust so it all works together. Plus, that the 320 engine can be bored out to yield about 343 cid. But to "feel" these increases, you might well need a better under-car exhaust system to allow the additional airflow into the engine an easier way out.

I just looked at the "Chevrolet GMC Speed Manual" by Bill Fisher 1954 Edition. It also has a chapter in it on Buick Straight 8s, which was the only Buick 8 cylinder engine at the time. In the comments about durability, he mentions that he discovered that the Buick Straight 8 was a very durable engine, with many owners being able to "comment" that their engines had well over 100,000 miles on them and the head had not been off of it. That might tend to indicate that you might well be taking the head of for the first time, but that's just a speculation at this time. He talks about how much you can bore the Buick Straight 8s without seriously affecting the integrity of the block, but nothing about milling the cylinder head. In those earlier times, "milling" was something that usually wasn't done per se. The machines to do that with were in very few shops, much less the local machine shop. If any "truing" was done, it was probably done with a long file, I suspect, and just enough to "dress" the surface. Reamers and power grinders were around though, which allowed cylinder head ports to be "worked" and/or enlarged, but some of these same tools might have been used to run the various stones to do the valve seats with.

I do concur that, for general reference, knowing the dimension between the cylinder head surface and the valve cover rail might be good. These might also need to be referenced by casting number of the cylinder head and the model year, just to ensure the data can be compiled and sorted. If that information might not be archived by somebody in here, perhaps someone in the Inliners International club might have something?

Still, my orientation is to cut the least amount of metal off of the cylinder head surface to get a good, clean, reliable head surface of the correct texture. Your engine, your car, your money, your desires . . . your judgment call, which I respect.

Enjoy!

NTX5467

[sfair]

Increasing compression ratio will net you about 1.5hp per cylinder per point with NO other changes.

Grinding out intakes ports, venturi's??? and other such things while still retaining the stock cam will probably result in little change, if any.

[PONTIAC1953]

Erik, thanks for the additional information. I'm glad you've found a good machine shop to do the work. I mentioned "angle milling" as more of an extreme option, but one which I've seen many racers use on V-8 cylinder heads . . . which also "marks them for life" in many respects. If my calculator is correct, 3/32" is .09375", which is almost 1/10", which is not that far away from 4/32" or .125". How do you plan to have the head marked that it's been cut that much, for future owners? I still recommend that only the minimum amount of metal be removed from the head. IF you want to cut something, then enlarge the intake and exhaust ports in the head to allow more air into the combustion chamber (increasing total cylinder pressure "by volume" rather than by mechanical compression ratio methods). The Fisher book tells how to do that, which apparently was somewhat common back then. It also mentions how to further port the head on both intake and exhaust so it all works together. Plus, that the 320 engine can be bored out to yield about 343 cid. But to "feel" these increases, you might well need a better under-car exhaust system to allow the additional airflow into the engine an easier way out.

I just looked at the "Chevrolet GMC Speed Manual" by Bill Fisher 1954 Edition. It also has a chapter in it on Buick Straight 8s, which was the only Buick 8 cylinder engine at the time. In the comments about durability, he mentions that he discovered that the Buick Straight 8 was a very durable engine, with many owners being able to "comment" that their engines had well over 100,000 miles on them and the head had not been off of it. That might tend to indicate that you might well be taking the head of for the first time, but that's just a speculation at this time. He talks about how much you can bore the Buick Straight 8s without seriously affecting the integrity of the block, but nothing about milling the cylinder head. In those earlier times, "milling" was something that usually wasn't done per se. The machines to do that with were in very few shops, much less the local machine shop. If any "truing" was done, it was probably done with a long file, I suspect, and just enough to "dress" the surface. Reamers and power grinders were around though, which allowed cylinder head ports to be "worked" and/or enlarged, but some of these same tools might have been used to run the various stones to do the valve seats with.

I do concur that, for general reference, knowing the dimension between the cylinder head surface and the valve cover rail might be good. These might also need to be referenced by casting number of the cylinder head and the model year, just to ensure the data can be compiled and sorted. If that information might not be archived by somebody in here, perhaps someone in the Inliners International club might have something?

Still, my orientation is to cut the least amount of metal off of the cylinder head surface to get a good, clean, reliable head surface of the correct texture. Your engine, your car, your money, your desires . . . your judgment call, which I respect.

Enjoy!

NTX5467

how incorrect this is, the buick 322 V8 started in 1953, and 1953 was the LAST YEAR for the buick straight eight. charles coker, 1953 pontiac tech advisor.

[NTX5467]

The book has "1954 Edition" on its outside cover. In the "Disclaimer" on the back inside cover (it's a paperback), it further mentions that the information was collected during the 1940s and early 1950s . . . precisely DURING Buick Straight 8 production times. Obviously, there were prior editions and the "1954 Edition" was the latest. Also, there were probably MANY Buick Straight 8s still on the road and in the hands of hot rodders at that time (1954) to warrant the "1954 Edition" being published. This particular book is a reprint of the original 1954 book which sold for $2.00 back then (stated on the back outer cover).

Although the bulk of the book covers Chevrolet and GMC engines, there is a short section on the Buick Straight 8 248 & 320 engines. There might well have been Pontiac and Olds Straight 8s, but I suspect that Buick was included due to the brand's racing heritage from its very early life as a vehicle manufacturer, with all due respect.

What's in the book is highly historic in nature AND reflects that state of the art of hot rodding in the 1940s and in the "inline 8" times of the 1950s (either as production motors or motors in "used cars"). Therfore, when the book was originally printed, the Buick Straight 8s WERE the only Buick 8 cylinder engines at that time . . . and most probably in the earlier 1950s when later printings of the book might have taken place. My apologies for my indiscretion.

The mentio of enlarging of the intake and exhaust ports in the cylinder head might well have been marginal at best, but the whole desire was for more available air to be able to enter and exit the cylinder. I suspect the limiting factors would be the basic flow characteristics of the manifolds themselves and the under-car exhaust system . . . but for a racer, they could be more significant.

Think ethanol-in-fuel is new? There's a chapter on mixing up to 20% Nitrate Alcohol mix on Chevy 6-cylinders with 10.0 to 1 compression ratio or less. Further, it mentions that nitrate alcohol should be used as soon as possible, as a 5% nitrate alcohol ful will eat through the solder on a metal gas can in about 1 week It also mentions that carb jet size, with the 20% mixture, should be increased by 20%. Key point is that as soon as "the meet" is over, the fuel system is drained of any nitrated fuel, non-nitrated fuel installed and run through the engine. And THIS was "back then".

Regards,

NTX5467