And So It Begins- The Big Block Swap

Canadian Poncho · A Poncho Legend!

RE: And So It Begins- The Big Block Swap

67Poncho · Uber Guru

Don't believe you will be able to interchange the balancer because of the bigger crank snub of the big block... I will check but sure it will be larger!

-- Edited by 67Poncho on Saturday 19th of February 2011 01:30:10 PM

Canadian Poncho · A Poncho Legend!

The pully bolted on fine-it's just the aligment that's off slightly

69camarox11 · Addicted!

69Laurentian wrote:

The pully bolted on fine-it's just the aligment that's off slightly

From article by Ian Johnston:

I would also like to point out a typical error that I have seen on many cars. This relates to pulley alignment. The deep groove big block pulleys are also wider than a standard small block pulley. This moves the centerline out of a 1969 sb pulley v.s. a 1969 bb pulley. I recommend that either you use all deep groove bb pulleys or all sb standard pulleys, but not to mix and match. For instance if all pulleys are all deep groove bb pulleys except for one standard sb pulley, it will put unnecessary tension on that item. It can cause premature bearing failure on your water pump, alternator or power steering pump.

Why so many different pulleys? GM engineers had many things to consider when designing the accessory drive systems: physical clearances between adjacent pulleys and brackets, amount of coolant flow required, alternator amperage output at different RPM's, belt centerline and average operating RPM range.

Systems could range from very simple to quite complex. Let's look at pulley diameters. If you have incorrect pulleys on your motor, how does this affect performance? Look what would happen if we increased or decreased the water pump pulley diameter? Decreasing the diameter would cause the water pump to turn more revolutions for each crank revolution, which would increase coolant flow. When would you need that to happen? Well the hgh horsepower big blocks in 1969 had the smallest diameter water pump pulleys. In contrast, six-cylinder and two-barrel small block engines tend to have larger diameter pulleys for the water pump. If you were going to use a different water pump pulley, I would go smaller, not larger.

We have a different situation on the alternator pulleys. High performance motors use a large pulley to slow things down. This is a horsepower saver as the alternator drains HP to turn it when it is charging.

There are some more differences to be considered. It is what we call shallow groove vs. deep groove. The belt will ride deeper in the V and be harder to throw at high RPM's. All the HP motors that may see excessive RPM's, use the deep groove pulleys. In the case of a 1969 hi-performance big block deep groove pulley vs. a 1969 low-performance small block standard pulley, it is .625" deep vs. .5" deep.

Pulley Identification: All 1967-1969 pulleys are stamped steel for the most part. the exceptions are the 1967 big block crank and the 847 power steering pulleys, which are cast, and the 387 and 831 alternator pulleys which are machined.

Almost all pulleys are stamped with the GM part number. It may be on the front or rear. Note the two letter code following the part number. If you are so lucky as to still have your build sheet; you would see that two digit code.

Big block crank pulleys are easily identified. Note they have a large center hole vs. a small center hole on a small block pulley. Almost all 1967 and 1968 motors needed a add on pulley for power steering. With the change to the long water pump system in 1969, this was no longer necessary.

Note the 1968 522 smog pulley is to be installed with the part number facing forward for big block engines and rearwards for small block engines per the assembly manual.

There have many part number supercedes over the years, but just almost every pulley is still available, either used, NOS or reproduction. The following numbers are based off of the assembly manual and very early printing GM parts books.

1969 Pulley Configurations
Big Block High Performance V-8 Engines:

L78, L89, L72 (w/smog)........Base..............N-40..........Code.....Grooves.....Diameter
Crank Pulley..........................3955291.......3955291....AB.............2................6.75"
Water Pump Pulley................3947824.......3947824....BV/DV.......1................7.15"
Alternator Pulley....................1970831.......1970831....-------........1................3.2"
Smog Pump Pulley.................3932458.......3932458....DA.............1................5.3"
Power Steering Pulley............N/A...............3941105....DD.............1...............5.7"

FYI Todd,

Gary
69CamaroX11

69camarox11 · Addicted!

Question:
Do all 1967-1969 V8s use the same engine mounts and engine mount (frame) brackets?

Answer:
No. Let's start with small-block Chevy (SBC) V8s. All '67-'68 SBC and '69 307ci and 327ci engines used the same engine mount bracket (approximately 2-1/2 inches wide). The 1969 302ci and 350ci engines used a shorter (~3/8 inch) and narrower (~1/4 inch) bracket. (The engine mount relationships for these brackets are best described in the table below rather than in text.) Note that, unfortunately, 1967-68 engine mounts will assemble to the 1969 302/350 engine mount bracket, but this is an incorrect assembly that results in driveline vibration and clutch chatter because the engine sits too low and can move on the bracket.

Looking at big block Chevy (BBC) engines, in order to gain engine compartment clearance the engine was offset 1 inch to the right (towards the passenger side) by means of asymmetric brackets. 1967-68 BBC engine mount brackets are 2-1/2 inches wide (but not the same as SBC) and use the same corresponding engine mount as 302ci and 350ci SBC.

For'69, BBC engine mount brackets were redesigned to use the new thicker, narrower, engine mount also used by 302ci and 350ci. 1969 BBC bracket pairs are easily spotted because the left bracket is noticeably taller than the right in order to achieve the engine offset.

To summarize the engine mounting differences, from the Dec. '71, GM of Canada Master Parts Catalogue 721, we see the following relationships:

Disticnt Engine Mounts:
--------------------------
a) 67-68 L6 (early 68)
b) 68-69 L6 (late 68)
c) 67-68 327 non-PS
     67-68 327 PS right
     69 327/307
d) 67-68 327 PS left
e) 67-68 302, 350, 396
f) 69 302, 350, 396, 427

Distint Engine Mounts:
-------------------------
a) 67-69 L6
b) 67-69 327
    67-69 350, 302
c) 67-68 396
d) 69 350, 302
3) 69 396, 427

Todd, FYI this info was for 1st Generation Camaros but it might help you!

Gary
69CamaroX11

-- Edited by 69camarox11 on Saturday 19th of February 2011 01:25:09 PM

Canadian Poncho · A Poncho Legend!

Thanks Gary,
The BB water pump pulley I purchased on Ebay was listed as correct for a 69 BBC however it's much larger in diameter than the water pump pulley that came with the engine. I am concerned about overheating. I think I'll try to find the correct crank pulley and see how things align at that point.

seventy2plus2 · Canadian Poncho Superstar!

69Laurentian wrote:

Thanks Gary,
The BB water pump pulley I purchased on Ebay was listed as correct for a 69 BBC however it's much larger in diameter than the water pump pulley that came with the engine. I am concerned about overheating. I think I'll try to find the correct crank pulley and see how things align at that point.

The water pump pulley you got is the same as what I run. Carl Stevenson made an excellent point regarding the crank pulley, the one from the small block is very different than for a big block. I think without the proper one neither the water pump pulley nor the power steering pump pulley will line up properly.

jonathanD · Poncho Master!

congratulation on the great buy can't wait for the summer so i can hear her running lol

Canadian Poncho · A Poncho Legend!

I just bought an NOS deep grove BBC crank pully from Ebay. Finger's crossed this works!

73SC · A Poncho Legend!

To close the loop on this problem of pulley alignment, I solved the pulley alignment issues by getting a late model K30 7.4 litre long neck water pump. I test fit it and it all appears to be working wonderfully.

If anyone is interested in an unused water pump casting # GM2 3931065T PM me. It is a 1969 427 style.

I will also have an unused 1969 B Body 427 Oil Pan in a couple of days once I get it off the engine. PM me if interested.

New Stuff....

-- Edited by 73SC on Tuesday 13th of September 2011 02:00:17 PM

gparis7 · Canadian Poncho Superstar!

So Ray - what is this engine going in I wonder?

73SC · A Poncho Legend!

gparis7 wrote:
So Ray - what is this engine going in I wonder?

Well it will bolt in my Cadillac Fleetwood as well as my LeMans since both are factory Chevy 350's. I'm leaning towards the LeMans. wink

In case there is any doubt the castings show this to be RPO LE8 454 CID rated at 230 Net HP through catalytic converter and single exhaust with 360 ft lbs torque. For comparison the new 6.0 Vortec Max used in the one ton GMC's produces 380 ft lbs.

I will be using a 1972 454 Quadrajet, 1970 Chevelle SS Cowl Induction air cleaner to take advantage of open NASA scoops in my hood, Edelbrock type intake and 2" tube Headers collected in a 4 inch collector and routed through 2 1/2" dual exhausts. This should be sufficient to chirp my rear tires I think.

-- Edited by 73SC on Tuesday 13th of September 2011 08:58:58 PM