Chevy Tech Q&A - May 2014

Kevin McClelland Mar 7, 2014 0 Comment(s)
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Lose the Clutch Pedal

I have a 235 Stovebolt six-cylinder Chevy engine in my ’49 Chevy Truck. I want to convert it over to an automatic transmission. What type of transmission will I need to do this, and can it be done? I have looked all over for info and could find nothing in this sea of Internet misinformation! Thanks.

David Sanford
Chatsworth, GA

Back in the day, the only automatic transmission you could hang behind the second-generation Stovebolt 216, 235, or 261 was the original cast-iron Powerglide. You could just about kill yourself rebuilding one of these gems; they were so heavy you really had to be careful. The cast-iron Powerglide was introduced in 1950 in GM passenger cars a year ahead of Ford’s automatic, and Chrysler didn’t have an automatic until 1954. This gave GM a distinct advantage, as the customers were really pleased to lose the clutch pedal.

To move your Stovebolt into the 21st century, get in touch with Langdon’s Stovebolt engine company, specializing in GM six-cylinder performance parts. One of those is a very nice adapter plate and flexplate, which adapts aluminum Powerglides, TH350s, TH400s, TH700R4s, and TH200R4s to the back of your six. With these choices you should be able to fit in your framerails whichever trans tickles your fancy. You’ll need to fabricate a transmission crossmember to hold up the back of the engine and trans, as your current engine/trans is attached by bellhousing side mounts. The adapter is sold under PN 56-3001 and includes a billet-machined adapter plate and hardware to mount to the back of your 235 and give you the six bolt holes and dowel pin locaters for the above transmissions. It also has a re-machined flexplate to adapt to the specific bolt pattern on the back of your 235 crankshaft. Finally, Langdon’s recommends purchasing its starter that matches up with the billet adapter plate and is aligned properly with the supplied flexplate. The prices are very affordable and could save you many headaches during the install. Check with Tom at Langdon’s at 586.739.9601 for more information before you order.

Good luck with your swap. Yes, weeding through the info on the Internet can be daunting if you don’t know specifically what you’re looking for. This is why we’re here.


Really Blown!

I’m hoping you can help me out. I recently came across a 10-71 blower off a late-’50s GMC diesel. Is this supercharger worth rebuilding to put on a gas engine, or would it be better to get a more common 8-71 or 10-71 for the engine? If it would be a good candidate for rebuilding the blower, where would I be able to find parts for it? Thanks.

Liverpool, NS, Canada

ANice find. This would be a very cool display piece in your man cave. As for using it on your performance gas application, it’s a long way from being ready to rumble. The changes required to this early piece would be more expensive than starting with the blower of choice for your application. The 4-71 and 6-71 blowers were sized for specific four- and six-cylinder diesel engines displacing 71 ci. Above the 8-71, the first number was just an expression of added capacity. Seeing that it’s a 10-71 application it’s not really size-appropriate for a small-block, and with a big-block you’ve got to work out the ignition issue for street use. Again, you didn’t tell us enough to give you application info about this blower.

Now, when you’re ready to upgrade to a Roots supercharger for either street or race use, check with Blower Drive Services, The Blower Shop, and Weiand. These are three of many that offer very high-quality superchargers for both street and strip use. They may also be able to tell you if your find would be worth rebuilding, or going with one of their specific casting that have been upgraded over the past 60 years.


Missing Bumpstick

In your Jul. ’12 Q&A, you recommended a camshaft for a 1-ton dualie Crew Cab 496 big-block. I have been unable to locate that cam—has the part been discontinued or the part number changed? I was wondering if you can help. Thanks!

Lowell Breiter
Hurricane, UT

ASorry for any confusion. We’ve gone back into the archives and pulled up the issue. The camshaft we recommended for your Gen VII 496 big-block dualie application was a standard 454/502 H.O. hydraulic roller direct from General Motors. The part number in the edit (PN 24502611) was correct and it hasn’t changed. If you pop that part number into Google the first dealer that comes up is Pace Performance, then GM Performance Motors. Give it another try; they are out there, and it will kick ass in your application. Good luck.


Roller Locater

I have a question on Cam Retainer Plates. I have a ’71 small-block Chevy which had a solid flat tappet cam in it, but the cam went bad due to moving back and fourth in the block, wearing the lobes resulting in a chewed up distributor gear. I have a Dynagear timing set with a cam button. I’m stepping up to a solid roller now and I had seen in your latest article on moderate mouse about the retro roller with retainer plate and I was wondering if I should do that too, so the roller cam doesn’t move on me again. However, my block doesn’t have a spot to drill for a plate. I would appreciate any tips and/or options. Thank you!

Trevor MacNeill
Lincoln, MI

Your flat tappet camshaft should have never had an issue with “Cam Walk” because the camshaft lobes should have had a very slight taper ground into them. This taper constantly puts force pushing the camshaft back into the block. This keeps tension on the cam and loads the thrust surface between the camshaft gear and the block. If your cam manufacturer didn’t have their camshaft grinder set up with the proper angle on the lobes the camshaft will walk. We’ve only seen this a couple of times.

Now moving onto roller camshafts, they do not have any taper ground into the lobes and they will definitely walk. When this happens it gets real ugly as the lobes can run into the roller lifter next door sending hardened metal shavings throughout your engine. The late model thrust plate option is very cool if you can run a camshaft with the machined features from an ’87 and up roller camshaft master. Getting a performance solid roller profile ground on a late model blank could be expensive and isn’t really necessary.

For your street build, we would recommend going with a cast aluminum front cover that will prevent any deflection of the front cover. This front cover in combination with your camshaft thrust button will prevent camshaft walk. When setting up your cam endplay you will want to use the front cover gasket that you’re going to run, and torque the front cover into place to 80-inch pounds of torque. The target end play you’re looking for is 0.005 to 0.015 inch. You may have to either shim behind your thrust button and camshaft, or turn off a few thousands from your thrust button to achieve this tolerance.

As you stated in your question, your early block doesn’t have the retainer attaching features like the ’87 and later blocks incorporate. With your application, the thrust button is the way to go. Following these instructions above should give you a drama free solution. Enjoy your new roller cam power!



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