Engine and Transmission Tech

tips, technology, tools and techniques related to vehicle driveline components

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RBud215
Richard Budziak

(8 posts)

Registered:
11/29/2022 03:21AM

Main British Car:


Oldsmobile 215
Posted by: RBud215
Date: November 30, 2022 02:58AM

I am currently building an Oldsmobile 215 V8 with the high compression (turbo) heads, 6 inch Carrilo rods and custom forged pistons. Now that I have the short block solved I'm moving on to the heads. I've heard the Oldsmobile rocker shafts were a bit weak compared to Buick but Olds had the better rocker arm. There is very little info about the brass tack differences between the Buick and Olds 215 valvetrain but they are worth paying attention to when you intend to build high rpm horse power. Oldsmobile's valves are on center with the bore while the Buick/Rover valves are offset towards the inside of the cylinder center line.
Oldsmobile valves are farther away from the rocker shaft center line than Buick/Rover, The Oldsmobile rocker has more distance from fulcrum center to tip than the Buick/Rover. Further more I'm sure there is some difference on the push rod side of the two style of rocker arms as well. how does all this valvetrain geometry effect things when using rover parts?

What can the fine folks here tell me about using the Volvo B20 series rocker assemblies on our family of engines? From what I understand people have used them on both Olds and Buick/Rover versions of 215 v8 but how do they line up at the valve tip particularly in the Oldsmobile version. There is one picture I found within these forums that seem to have the Volvo rocker assy on the Oldsmobile head and to me they look a bit misaligned but they are not actually bolted in place and they had dry sump provisions on them so it may be because they are just resting on the head in the picture that they looked misaligned.

What is the Volvo B20 rocker shaft diameter compared to the Buick/Rover rocker shaft diameter?

Is there stronger rocker shafts in the Rover world?

I'm pretty sure the Oldsmobile shafts are smaller than the Buick/Rover rocker shafts and I'm not sure of the Volvo diameter. It seems I would just have to reem the Oldsmobile rocker shaft stands to accept the larger diameter Volvo shaft then choose a rocker that fits (possibly custom) from there, am I on to something or just spinning my wheels?


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Oldsmobile 215
Posted by: MGBV8
Date: November 30, 2022 10:14AM

You are about to slip down the rabbit hole, Richard.

My understanding is that the Volvo rocker shaft is a smaller diameter than the Olds. Not sure that the Buick & Olds shafts are a different diameter from each other. I didn't think so. The Olds shaft does have larger diameter holes in it for the head bolts.

More about Volvo rocker arms from Fred Key:

"Those are the Volvo rockers for sure Todd. From the B-18 / 20 / 30 series engines.
And despite all the claims to the contrary they are all machined to pretty close tolerances.
Checked properly they will show a 1.55 to 1 ratio almost every time.
The issue with them is that the adjuster screw tilts away from the center line of the rocker. So the farther out that it is screwed the lower your rocker ratio gets. This leads to all the conflicting ratio reports.

But for an engine builder it's actually an advantage. Size your pushrods so that the adjuster is almost fully retracted and you come very near to a 1.6 to 1 ratio. Shorten the pushrods to extend the adjuster and you can get to 1.48 to 1.

As Jim said, having a machine shop offset drill the adjuster holes to accept a 3/8 adjuster screw gives you all the latitude in rocker ratio that you could ever want."



DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Oldsmobile 215
Posted by: DiDueColpi
Date: November 30, 2022 05:00PM

I can't answer the Olds shaft question but I do have a Rover shaft and a Volvo shaft in front of me.
The Rover shaft is 0.800 inches or 20.32 mm The Volvo shaft is 22.0 mm or 0.866 inches.
The mounting holes are very close to the same so a minor touchup would get the Volvo shaft to line up.
The Volvo trunnions are steel and are very slightly taller than the aluminum Rover ones. Some minor machining might be required to use the steel ones. A test fit will be required to find out for sure.
This used to be the go to swap back in the day so maybe someone who has done it will have more info.

Live like you mean it.
Fred


RBud215
Richard Budziak

(8 posts)

Registered:
11/29/2022 03:21AM

Main British Car:


Re: Oldsmobile 215
Posted by: RBud215
Date: December 01, 2022 04:41AM

Thanks for the replies so far, I'm looking into buying a used b20 shaft assy from ebay and size things up. I live in WA state and the engine is with my dad in Detroit. I've been buying up parts we need to complete the project and plan on flying home this spring to get a hands-on look at where we are at with things. Dad is an experienced fabricator/body restoration tech and It's my job to build the motor and trans. Should be a fun rabbit hole. My current thoughts are to get the Volvo shafts and stands to fit then hang some custom t&d roller rockers. The goal is a 7000rpm red line with max power somewhere around 6k using solid cam.


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Oldsmobile 215
Posted by: MGBV8
Date: December 01, 2022 09:00AM

Thanks, Fred. I had read the the Volvo shaft was smaller. I did go out & measure a Rover 3.9 shaft & came up with .810. I am sure that you have much better quality calipers.


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Oldsmobile 215
Posted by: DiDueColpi
Date: December 01, 2022 01:01PM

Gee wizz Carl you made me go out and recheck!
The Rover shaft that I have is 0.803". I tried to fudge it to 5 so we could meet in the middle.
It's -6' here today so maybe like other shafts it had some shrinkage?

Cheers
Fred


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Oldsmobile 215
Posted by: MGBV8
Date: December 01, 2022 01:47PM

:) :) I did get .803 once. Could not repeat it. 67 degrees in my garage. So, we are pretty close.

Disclaimer: I used a HF digital caliper. :o



roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Oldsmobile 215
Posted by: roverman
Date: December 02, 2022 05:23PM

Tisk/tisk , 803"/.808", no importa... Volvo is best oem. for performance ! They lasted just fine at 8k. rpm. in my Huffaker TR8.
"IF" you can still buy from: Rocker Arm Rebuilders= a good bargain.
Happy HP. Art.


RBud215
Richard Budziak

(8 posts)

Registered:
11/29/2022 03:21AM

Main British Car:


Re: Oldsmobile 215
Posted by: RBud215
Date: December 06, 2022 08:03AM

I got an Email returned from T&D the other day...

"We Do Offer A Rocker Set Specifically For The Olds 215 head. the part number is 9210. Price on this set is $1463.00 plus shipping. Lead times right now are right at 20 weeks out from order date."


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