'65 425 Cam Specs ??

[Guest]

I've been looking all thru the material I've got, but I can't find the cam specs for a 1965 425 with dual 4-bbls. The timing between this engine and a single 4-bbl. 425 is quite a bit different and I'm guessing it's because of the cams used in each engine. Can anyone tell me the duration, lift, opening & closing, etc. for a 1965 2x4 425? I have the bearing sizes, etc., just need the lobe specs.

Thanks,

-Bob

[DualQwad]

I don't think that there is a difference since my parts book only lists one 425 cam. <img src="http://www.aaca.org/ubbthreads/images/graemlins/confused.gif" alt="" />

part # 1362242

I don't know the actual spec's without some more digging around for them.

[Guest]

Thanks for the reply, DualQwad. A parts book is something I don't have. The timing for a 2x4 425 is 12º advanced, while a single 4 bbl 425 is 2½º advanced. I thought sure it would be because of different cams, but if there's only one cam listed, I wonder what else would influence timing so much ???

Anybody ??

-Bob

[NTX5467]

Seems like I posted those specs several month ago, from a copy of Peterson's "Complete Book of Engines" series that they started in '65.

Not sure about how the initial timing specs might differ unless there was a difference in standard transmission (usually retarded from what the automatics were) or emissions systems (if that was an issue back then). From what I've casually observed, using a "period" sevice manual (either GM/Buick or Motor or Chilton's) would be the best resource for that information instead of something published many years later where some of the settings might have been combined.

Seems like the 1x4 and 2x4 cams were the same with the main difference being the extra carb and dual exhaust. The 2x4 engine probably came with a 3.42 rear axle ratio instead of the regular 1x4 ratio.

The differences in how the manifolding works on the 2x4 manifolds versus the 1x4 manifold might make for a different idle characteristics and speeds even with the same cam.

In the mean time, I'll try to find my book and repost the cam timing specs.

Enjoy!

NTX5467

[DualQwad]

This may also be helpful to you.

I found this posted on the V8 Buick bulletin board, www.v8buick.com;

"These specs were taken from an old GSCA article. It was written by Dennis Manner...

1) Valve size...

Intake Valve size - 1.875

Exhaust Valve size - 1.5

2) Shape and size of exhaust ports...

If Round (inside diameter) -

If Square -

If Rectangular (Height x Width) -

3) Camshaft... (1)63-65 425 (2)63-66 401, 66 425

Rocker arm ratio - 1.6 advertised (actual is less...)

Intake duration (degrees) - (1)290 (2)295

Intake valve duration @ .050" (inches) - (1)209??? (2)209??? (not sure where I got this info)

Opens (degrees BTDC) - (1)29 (2)28

Closes (degrees ABDC) - (1)81 (2)87

Exhaust duration (degrees) - (1)299 (2)295

Exhaust valve duration @ .050" (inches) - (1)213??? (2)209??? (not sure where I got this info)

Opens (degrees BBDC) - (1)71 (2)76

Closes (degrees ATDC) - (1)48 (2)39

Overlap (degrees) - (1)77 (2)67

Lobe separation (degrees) - **Spacing** (1)109 (2)114

Intake Lobe centerline (degrees) -

Installed at (degrees) - (1)1/2 degree adv (2)5 degrees adv

Lifter type - Hydraulic

Bore - (A)401- 4.1875 (B)425-4.3125

Stroke - 3.64

Bore/Stroke ratio - (A)1.1504 (B)1.1846

True compression Ratio - 10.25:1 advertised"

There's lots of great folks that hang out there that know much more than I do.

If you haven't already been over there then I think that you should check them out.

Here is the link to the thread that I found it in;

http://www.v8buick.com/showthread.php?s=&postid=148923#post148923

[Guest]

DualQwad: Many thanks for taking the time to look up this information. I sure appreciate it. I'll check out the V8Buick site for sure!!

Thanks again, -Bob

[NTX5467]

Thanks for that information. I seem to recall that the cam specs I posted were for the small block and not the nailhead V-8. Still haven't found the book, but have found the later ones (post-nailhead).

The SAE specs are supposed to be something like at .006" lobe lift on the intake and similar (maybe .008"?) on the exhaust. The .050" lift spec was something the aftermarket put together as an "agreed upon" measurement to kind of make some sense of the "advertised" and "actual" specs on cams as some manufacturers might quote larger numbers than others for almost exactly the same camshaft. Many OEMs don't quote the .050" spec, but for stock cams it's supposed to be about 80% of advertised duration and closer to 85% for factory performance cams so that might put things into the general ballpark for comparison purposes.

By using the .050" spec, all of the "ramps" are not included so it's supposed to represent the "meat" of the lift curve. Chevy and some others tended to use "total duration" for their advertised cam specs back then, which made the numbers waaayyyy larger than anyone elses for duration. In one respect, using every bit of lift past the basecircle dimension would be accurate, but it would also allow all of the transition ramps to be included where there was basically zilch significant lift. This is where the .050" spec comes in handy.

Thanks again for that information!

NTX5467