Packard Forum Index » Pre-War (1899-1942)

Hi guys, I know there are many knowledgeable people out there who can comment on my question. I have. 1929 626 standard 8 engine that has not been run for many years. It is complete but most likely needs to be rebuilt. I have the chance to buy a 1936 std 8 which also needs to be rebuilt. The problem with the 1936 std 8 is the engine mounts are different and I don't know if the 1929 transmission will bolt on. The 1929 std 8 is 90HP and the 1936 std 8 is 130HP. As I plan to build a speedster body on my 1929 626 chassis, I wonder if I can rebuild the 1929 engine and do upgrades to increase the HP to 130. What differences were made between 1929 and 1936 to increase HP from 90 to 130? Your comments are al welcome.
Cheers Malcolm (New Zealand)

Dear Malcom:

None of the parts are interchangible.

The 6th series Speedster used a hopped up 384ci Custom 8 motor with higher compression, hotter cam, and different carburetor. Although not documented, based on my experience, I also think they had a very expensive crankshaft that was far more stout than otherwise.

Tim, perhaps you want to read the post again. As I read it he's asking about an interchange between two 320 c.i. engines.

Mal, lots of internal parts will interchange. I made this little list up many years back looking for spares for my 34 Eight. The list isn't very comprehensive but is perhaps of some help, sorry I didn't go back to 1929. The original style stamped cam follower arms can be interchanged with the later forged style. 34 rods are finned and babbitt and 35-36 rods are for insert bearings but otherwise should interchange. Cylinder heads interchange. Reviewing the parts books and Service Letters should reveal more though, as is the case with the pistons, having different part numbers doesn't mean the parts won't interchange.

PS: And keep in mind there was a major lubrication system upgrade for 1934, full-flow oil filter instead of the EF-2 bypass, new oil pump, larger oil passages, etc.

Attach file:

---

  (71.74 KB)

I believe he would like to know what can be done to the 29 engine to get the horsepower of the 36 engine.I would also like to know for my project.

Major factor is compression pressure or compression ratio. Data from factory specs for the 320 engine.

1929 - compression pressure 84-87 psi
1934 - compression pressure 95-100 psi
1935 - compression pressure 110 psi
1936 - compression pressure 119 psi (optional 7:1 HC head)

The other aspect Mal raises is this "...The problem with the 1936 std 8 is the engine mounts are different and I don't know if the 1929 transmission will bolt on...". Looks like he's also exploring the engine swap option, anyone have any answers or thoughts on this?

Thanks for your responses. Owen-Dyneto, thanks for the parts interchange list and the compression figures. Do you think most of the HP increase between 1929 and 1936 was the increased compression ratio? Maybe I should just use the head from the 1936 engine on the 1929? My concern would be that this might put too much strain on the poured babbit bearings. Another thought re the engine mount differences - could I use the crankcase from the 1929 with the wide engine mounts and fit the block and head from the 1936? I could modify the bearings and rods to take shell bearings. Once again, please keep your thoughts coming. Cheers Mal

Mal, I'm on uncertain ground here, more wild speculation than speaking from experience. I don't know what you intend to do with this engine, but babbitt bearings certainly held up well-enough in the 6th and 7th series speedsters with higher HP than the 36 Eight, so within reason, I wouldn't be concerned unless you were going to really press this thing to the limit. If you were, I suspect the 36 rods would interchange but then the problem becomes obtaining the insert bearings - they've been NLA for decades though I hear from time to time that Max has repro'd them - don't know that for a fact but it's just a phone call or email to confirm. If you browse the Service Letters from 35 and later you will find information about fitting them to earlier engines. Modifying babbitt rods for inserts has a mix of absolute horror stories and success stories - some really good reseach into which method you use would be appropriate. I have some articles on this which I've posted before and can again if you haven't seen them. The conversion that requires the rod bolts to be notched for clearance is certainly one that I'd stay away from.

Yes, most of the power increase was from the compression ratio. The other significant component was manifolding. The camshaft change in 1934 might have been a minor factor, but I doubt it, I believe the lift stayed the same and the same valves are used.

I suspect that the cylinder bore casting from a 36 might fit onto a 29 crankcase though there were lubrication systems changes that may or may not be an issue; changing the bore casting only solves the engine mount problem and would also give you downdraft carburetion and the 45-degree manifold mounts that gave larger ports for better breathing.

Keep us posted, please.

Not going to happen.

O-D, thanks for your comments. For more background, I don't plan to race this but would like to have lively performance which I am sure the higher HP 1936 egine would give on the 626 chassis with lightweight speedster style body. I also plan to use an oftermarket overdrive to keep the revs down at highway driving. I do wonder if fitting the 1936 block/head with the down-draft manifold to the 1929 crackcase (for engine mount positions)and new poured babbit bearings would be a good way to go. This way the engine looks original but with higher compression and better breathing. Would need more information on the differences in lubrication and routing of oil channels and tubing as I believe there were some changes between these years.
Tim, what do you mean by "not going to happen"?