VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 commpression

Does anyone else think the 1929 six cylinder engine may have been a cheap copy of another engine? If so, what engine? How many other valve in head sixes existed when Chevrolet designed the six? Has anyone noticed that GM is now making an inline six? This time they're getting about 5 times the HP as in 1929. Why is it an in-line instead of a V6?

Skip - it is interesting that the 30-32 Chev 6 at 5.2 CR had about the same compression test spec as the 28 Chev 4 with only about 4.5 CR!

The only compression test spec I have found for the Chev 4 is in the Chevrolet Engineering book that gives it at 88 psi - and this is with the engine running on 3 spark plugs at 1000 RPM.

I figure the spec for the Chev 4 that is warmed up, plugs out, throttle open, good starter and battery, after 5 cranks, is 78-80 psi at sea level. If someone claims he gets about 140 psi cranking compression, the engine has about 6.8 CR pistons in his Chev 4.

Interesting that it turns out to be the same as the the static compression ratio. That implies that there is no overlap in the cam profile. Interesting.

Hey Ken! My compression chart goes back to 1927 so I checked it out. The compression for the 1927 Chevy is listed at 61 pounds, and the compression for 1928 is listed at 65 pounds.....far under the 88 pounds shown in your source. Also interesting is that fact no compression listing is shown for the 1929 Chevy. The chart jumps from 1928 to 1930 and continues on up from there! :eek: :eek:

What is your Compression Chart source Skip?
The 88 psi at a fast idle of 1000 rpm is directly out of the 1928 Chevrolet Engineering Book. Doesn't the 32 Engineering book cover checking compression.

The standard Chev 4 camshaft has no overlap, however the 1919-22 Long Stroke Chev 4 does, and the so called "FB" camshaft is the racers choice.

Increasing the intake valve duration, or what is called "Late Intake Valve Closing," will actually lower cranking pressure. The point to remember is: cylinder cranking compression start at Intake Valve Closing and not at BDC.

Therefore an "Early Intake Valve Closing" camshaft design will raise the CR of an engine.

From past links on the piston slap problems, one can understand the importance of driving around town for 10-15 minutes to get the pistons to fit the hole so a valid compression test can be recorded. Cold engines don't have good compressions!

KenK

Ken: My information comes from the "Compression Chart For U.S. Compressometer", which was published by U.S. Gauge Company. It covers all cars manufactured from 1926 thru 1937, and the readings are at starter speed with a standard head.

The 1932 Chevrolet Engineering Department Specifications Manual doesn't appear to show the compression readings.....at least I couldn't find it in that manual. However, I did find something interesting in the 1932 Chevrolet Engineering "Features" Manual (which is a different manual than the one listed above), and that is that the compression ratio for the 1931 engine is listed at 5.0 to 1....which confirms Chipper Dipper's source. And...the compression ratio was bumped up to 5.2 to 1 in 1932! :cool2:

After reading this entire diaglogue for the first time, my head feels like it's under compression.

Rant on Rick!! You've got my concurrence!

Billy BaRRker , that is because that new hat JYD gave you is really a ring compressor!

Right Macky Wacky! But the problem was that I had a hard time finding a ring compressor large enough to fit Billy Boy Barker's head!! :eek: :( :p

d2d2, my new hero, asked why an L6 is prefered over a V6. The answer is balance. The inline six (L6) engine is inherently balanced. Ever notice how 'rough' an L4 engine is? The motor in my '88 M3 will vibrate all the nuts off the bolts, given a chance! V8s are two L4s at 90 degrees but also with a crank in two planes. The smoothness of the inline six is why Ferrari uses V12s in their front-engine cars. They are really just two L6s sharing a crankshaft! (The Ferrari V8 uses a single plane crankshaft. That is why it sounds like the old Offenhausers that used to run at Indy.)

Happy Thursday,

Rick

Cadillac began using a 2 plane crankshaft in the mid 20s, it reduced the vibration, changed the firing order and intake manifold design as well as the sound of the exhaust. GM also built an interesting series of V8s for Oakland, Viking, and Pontiac. Some had a two plane crank but others had a single plane crank with some kind of leaf spring device to make vibration less noticable. These engines have a one piece block and a chain driven cam located high in the V so the valve stems are in a horizontal position. Valves are in the block and all ports are on the inside of the V. Henry's V8 was not the first one with a single block casting.
Do you know who built the first production V6 and in what year? Do you know how they got the vibration down to an acceptable level?

My giess is balance shafts, as used in the SAAB V4s.

Rick

No, the first production V6 did not have a balance shaft. Clue: This company built an expensive V8 automobile that was also to be built in the U.S. but never was because of the stock market crash of '29.
I think the SAAB V4 was a German Ford industrial engine.

I am coming in a little late with this bit of info.but here it is.This is from a book on hopping-up 6 cyl. Chev. engines (in the early 50's) The recomendation then was to mill the 216 cyl. head .125" to raise the compression ratio from 6.5 to 7.5. It says this can be done with absolute safety.Also the intake valve seats were to be cut back into the head the same amount to keep the valves from striking the pistons. There are other modifycations necessary.This is just an example as to how much would have to be milled to significantly raise the CR.I'm sure this will vary with different combustion chambers,bore sizes,etc. A friend did this to his '49 Chev. back then along with other modifycations with no problems.The same book also states that they don't recommend hopping up a pre-"37 3 main bearing engine...which was good advise.

Just noticed d2d2's question if the 1929 6 was a cheap copy of any other engine.The 1929 6 was already obsolete when introduced.Only two other common engines were still splash lubricated at that time ( Ford and Hudson) A few makes were still using cast iron pistons (mainly GM products).The modern feature was over head valves (also used in Buick,Some Nash cars, and in the 1930-38 Cadillac V-12 and
v-16's).With its strange combustion chamber,gravity fed main bearings,three main bearings,(most sixes had four or seven)(Hudson & Pontiac had three) and other low production cost features it bore no resemblence to other engine before it.Although the original 1929 design was updated several times by 1936 it still was considered obsolete. It was always a competitive engine inspite of its humble design. The only other engine that continued with splash oiling and gravity oil feed to the mains so many years was Hudson (until 1947 on the sixes and 1952 on the 8's) .The 216 0f the thirtys and fortys was the engine used by the Society of Automotive Engineers as a yardstick to judge all other engines against,so it wasn't all that bad.

WOW! I didn't know that! None of that, get out the Chevy Trivia game, we are ready! Thanks guys,

MrMack,I made some additions to my history lesson>>>>>you may want to reread.

Splash lubrication, cast iron pistons, and a 3 main crankshaft are the reasons I used the term "cheap copy."

What 3127 cc 6 cylinder pushrod ohv engine was built from 1922 thru 1929? Clue: It has seven main bearings.

I'll bet one thing it wasn't a common american car.What do the cc's equal in cubic inches? As in how many cubes would that equal???

aprox. 190 cubic inches.

Clues: 1. It isn't common and it isn't American. 2. It has a smaller bore and longer stroke.
3. What was the nationality of the man who designed the 1929 Chevrolet 6?

I didn't take the time to look up the answer but the long stroke would indicate a European car and Alex Taub designed the '29 engine so my first guess will be a French car,an engine that large in Europe would be a larger car.Thats is as far as I can go without doing reaserch,I don't recall any of the other engines he designed. ?????????????????????????

The mystery engine is not French. It was designed in a country where a tax was paid calculated mostly on the bore of the engine, so more displacement was obtained by increasing the stroke. Space required for seven main bearings may also have limited bore size, although bore and stroke were increased over the years. In 1929 displacement became 3669 cc, 3 1/4" bore and 4 1/2" stroke.
Remember that I said the 1929 Chevrolet may have been a cheap copy of the mystery engine, that also means it may not have been.
If you were the engineer assigned the job of turning the Chevrolet 4 into a 6, what would you have done? Several engines were built and tested. One was an L head 6 that became a Pontiac engine, the one with two cylinder heads fore and aft. The argument was made that Chevrolet was already tooled up for valves in the head but also because they wanted to keep that identification with Buick.

Ok D2D2 it is time to come clean and NAME THE DURNED MYSTERY ENGINE, I need to go to bed!

England was the country that calculated tax (or license cost) by bore size.that is where the term taxable horse power originated.I did find what I would call the most complete history of the 1929 engine .It was in a old issue of Special Intrest Magazine.Will ge back to that later.

I think with 30 or 40 lbs you are in trouble but give it try and see how it runs but don,t get to far away from home and shut it off,,all this uptown talk about comp scares me,and yes back in the old days we did mill heads to get more power inlines and flat heads,flat heads got milled alot, were easy to do that to because the intake wasnot bolted to the heads at an angle like todays engines and there was valve room so you could take the heads down...doc