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Modding a Buick Straight 8

Guest Rudy2

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Guest Rudy2


New guy here.

I have an opportunity to buy a rusty 1938 Buick straight 8 and manual trans for $500. I might want it for a future "rat-rod" project but know almost nothing about the motor other than the fact it is over-head valve and I think probably is 320 C.I. for that year. So, what I wonder is, can this motor be modded to produce horsepower in the 300 HP range? Can it be reliably boosted with a vintage supercharger such as a McCullough? Are there any inherent weaknesses with this motor? I know it has babbit rod bearings, is that a big deal? I assume the rods and crank are cast iron, correct? And finally, is there a source of info on these motors, some sort of guru who knows all the ins-and- outs of their quirks and capabilities?

Many thanks for your replies.


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Guest locoincolo

Kinda shooting from the hip here. If this is the larger 8, yes, it's a 320.

You could certainly get modern inserts for the rod bearings - maybe for the mains too, but I'm not sure about that.

As for getting 300 HP outa the thing, there's a few limitations that could probably be overcome, but are significant.

First, the crankshaft is what, 6 feet long? (kidding) It's long, and as such limits the ultimate Revs that you'll be able to safely

attain. Second, these babies ran at what, 6:1 compression ratio?

Having said that, my Special seems to be a torque-monster even in its old and decrepit state. I think it would be a fun (but not cheap)

experiment to re-bearing the thing, balance it to the nines, rework the head to open things up and maybe increase the compression a little.

Straight 8's did well in racing in their day, but were ultimately eclipsed by the V8 - still it'd be real fun to have a monster straight 8!

I like my Straight 8 more because it starts reliably and can chug straight up my neighbors steep gravel drive without any problems.

Maybe I should limit my "tuning" to simply trying to get things tightened up to eliminate all the seepage.

Have fun!

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Check the Packard sites, I know a few people have supercharger some of the old 327s and 356 9 main straight 8s and ran them at Bonniville. With the over head valve on the Buick you should be able to get 300HP easy with a supercharger. Try a custom intake for 4 weber side drafts and raising the compression to 8 or 9, open the head and bigger valves, Harvey Crane will still grind you a custom cam, He did one for a V12 Lincoln I built and a few for a friends 28 Stude President. Then just balance it to the nines like said before.

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Guest palosfv3

These engines are not made for more than 4,500 RPM. The push rods are way to long and prone to bending above 4,000 RPM. There are some that have figured out a better set up but I dont remember where I read the article . It may have been on the HAMB as I think there was someone running one of these in a Bonneville car .

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Shafer Indy cars used a Buick Straight 8's.

Here is Coker's replica of one 1937 Buick Shafer 8 of Coker Tire Company

I can't proved on any modification details but point being that they were raced so there must be some stuff you can do.

With regards to converting to insert bearings in lieu of babbitting. I did this in my 320 basically you have two options. 1. Find a set of 1949 or later rods which had factory insert bearings. or 2. send them out to be machined to accept inserts. I chose option 2 and used Terrell Machine in TX and actually it was an exchange. The mains are insert bearing from the factory at least on my '38 and later.

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  • 2 weeks later...

I talked to the guys from Crane cams while at Hot August Nights and they said they have a few different grinds that will make quit a bit more horse power than stock for all the Buick straight 8s. If your interested sand me a PM and I will find the card the guy gave me for the contact person at Crane Cams.

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  • 6 years later...
13 minutes ago, Ben Bruce aka First Born said:


 Morgan, he was only talking about an ENGINE.   Besides which he has not been back recently.  Almost two months.




 Two months and 6 years (Aug 2012)


The engine is the Buick. You ruin a Buick engine, you ruin a Buick.



Edited by Morgan Wright (see edit history)
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  • 1 year later...

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