Inliners International Forums General Discussion Engines 320ci Roadmaster Straight 8 stroker kit

Hi,
I am thinking about to tune up my 320ci engine of my 1950 Buick Roadmaster. Does anybody know if a stroker kit for this engine exists and where to get one? Or may somebody know a good contact to ask? Thank you very much for any help or information!!!
Bernard

Hello Switzerland,

Welcome aboard. IIRC you the largest straight 8 Buick made. We have do a member with a few Buicks. He doesn't post often and don't remember his display name. You might try and do a search to finds his posts. I'm fond of Buicks myself, but don't own one, if I found a Sedanet cheep I'd certainly grab it. I ounce read that when Rolls Royce was going to improve their line they bought a 1938 Buick to look at. Best of luck with your beasts.

Larry

The 320 inch Buick would be a good candidate to offset grind the crank and use a longer rod and a shorter piston for a low rpm, big inch street engine. How far are you thinking on taking the modifications? Are you wanting to try and make some serious hp or just a torque motor?

Ron

Hi Ron
thanks for your reply!
I would like to make some "serious hp" on my straight 8, but as I am not so familiar with these kind of engines I don't know exactly the specifications, what to change and where to buy the parts. Does it exists something like a tuning up kit? I heard about a stroker kit for this engines. But I did not found any information on the net... Many thanks for your help!
Bernard

You might want to check out http://www.uncommonengineering.com

I'm not saying they have modified buick stuff, but the site might give you an insight into modifying inline engines.

When one considers modifications to these old engines it must be remembered that they are a long stroke/small bore design that imposes several restrictions.

Bore:3.4375
Stroke: 4.3125

About the biggest valves you can fit in this size bore is:
Intake; 1.85
Exhaust: 1.50
Those size valves won't allow enough airflow to make any serious power.

The connecting rod would have to be made longer to reduce the piston compression distance and reduce the piston weight. The piston would have to be custom made at about $100 each. The rods would be about twice that amount ($1600).

I'm not sure what you would have to do about the valvetrain but I'm sure you could easily spend $3000 on cylinder head modifications, valves, rockers, camshaft, lifters, springs etc.

You would have another $1500 in basic machine shop labor.

Then you would have to build intake and exhaust systems with carbs, linkage, etc for about another $1000.

If everything went ok you might be able to make about 275-300 HP.
I'm sure by the time your finished you would have $8,000-10,000 in the engine.

Now you can appreciate why the SB chevy is so popular. For less than $2500 you can buy a Chevy crate motor that makes 290 HP.

Ron

Bernard,
Since it is so admirable to try to hot rod a Buick 8, I will take a shot at commenting and see if I can learn anything.
The best I have is California Bill's Speed Manual, about 8 pages on the Buick 320 in there. He does show a 40 Hudson, powered by a .125" over bored 320 Buick for 343cid, running 98mph in the 1/4 mile. As best I compute it that is about 300 gross horsepower shifting at 5200rpm. Is the 320 Buick good for that? No idea but it is hard to argue with the 98mph it got there somehow!
CA Bill also says to use the 1949-up rods as they take an insert bearing, and at least .003" clearance. Other than that here is my guess at the recipe:
Start with a stock Buick 320
Bore .125" (CA Bill says this is the max for race, but you might want to only bore .030" or .060" - no mention of a stroker, that is a pretty long stroke already)
9.0 compression, my guess. I think custom pistons would be needed with a healthy dome, just milling couldnt get you there
Custom log intake with 4 Stromberg 48 carbs
Headers, I guessed 1.625" x 29" pipes
Howard cam, my guess was 212-212 duration at .050", .440-.440" lift, 112 lobe separation, 4 degrees advanced. But I have no idea what the cam specs were, it just said "Howard cam".
Intake and Exhaust ported to flow 20% extra, again a guess.

This calculated in my engine/car computer to
Torque 362 ft-lb at 3400rpm
Power 305 gross hp at 5100rpm
Also computed to send a 3200 lb Hudson down the 1/4-mile at 98mph with open headers, which is consistent with the CA Bill book and car.

Would a 320 Buick really do this? Well the one in the book did but who knows, and I don't know if I'd turn an old straight 8 to 5200rpm either but it looks like somebody did way back when!
Your Buick is over 1000 lb heavier than the Hudson so it will not be as fast anyway.
Good luck if you try it -
Intake and exhaust ported to increase flow by 20% each

I have built a 320 Buick and have run it on the Bonneville salt flats. It will turn 5200 rpm. We bored it .1875", milled the head .25", put in 500 Cadillac valves, bbc valve springs, aluminum rods that are 8.875" center to center length, Venolia pistons, fabbed our own intake and exhaust, we just changed from a 4-71 blower to a 6-71 blower, and are in the process of going to efi and crank trigger ignition. The car has run 144+ mph, this is in a 1950 Super 4 door sedan. These engines are great and make a lot of torque, good luck with your project.

That 300 hp recipe also sounds streetable (cam isn't that big, CR is reasonable).
I agree about the pistons - getting the chamber shape right, adding quench where possible (even if it's just the extra bore size) and getting the CR up are important.
My taste: I'd use multiple carbs to improve the mixture distribution, but use something more modern such as big Rochester 2Gs (think: GM tri-power).
I have a gut feeling that some dual 4-2-1 variant may work better than the traditional dual 4-1, but will be harder to build.

GH:
Wow, was that head milled .250" or .025"?
Was the piston flat or domed?
Final compression ratio?
Cam details?
Ok a lot of questions, I like these old engines, learned on the Model A Ford actually!

Found a great site on the Buick 320:
http://www.roadmachine.fi/Buick/Rmaster.html
Chev Rat valves, Chev Mouse springs/retainers, bowl ported, headers, 2*2v (EFI?) intake, 7.6 compression
Didn't mention any cam change or bore/stroke:

1946 Roadmaster 320, 2.73 gears:
19.53 at 72mph in the 1/4 mile

A piece of Hot Rod History - an article by Don Francisco in the August 1950 HRM. No mention of stroking the 320. Not much, if any, useful information not mentioned by Ron and GH above, or in DeuceCoupe's link.
page 1, page 2,
page 3.

There is also a section (about nine pages) about the Buick straight 8 in the 1954 edition of California Bill Fisher's Speed Manual. Again, no mention of stroking. Bill discusses Don Montgomery's Buick-poewered Hudson sedan, which held some records, as I recall.

DC, the head was mill .250, 1/4". Don Wheeler out of the Denver area told us what we could do with the 320 Buick. Yes, the pistons were domed, they came from Venolia, don't remember the compression ratio, but was pretty high. When we went to the 4-71 blower we changed heads and didn't mill it to lower the CR. That worked great until last summer on the first run we suffered a burnt piston and our fun was over for the year. We are in the process of rebuilding and changing over to efi.

1961- 1966 Buicks were very popular on 1/2 mile county fair tracks in s.e. Iowa and won the club championship all but one of these years.[HUDSON] I ran a 320" in a '41 buick special. Used the stock front mount and moved everything back. I ran a engine out of a '49 ambulance. Low miles good cylinder walls, inserted bearings. Head was milled .25",extensive porting. Pistons were stock tubrolators as buick called them. 348" chevy exaust valves. Washers under valves spring, no idea of spring presure, as at that time I hadn't heard of the word. had a POTVIN cam, don't remember a thing about specs. Ran a '39 large series trans as it had the 2nd gear we needed. RAN A 3;90 rear gear with 820 15 super sports I got used from IMCA late model racecrs in KEOKUK IO. This engine turn 6000 top end of the straights every SATURDAY nightall summer. We narrowed the rods about .020 to let the oil flowthru the rods a little better. These engines were to be stock appearing from the outside, I ran the 2-2barrel intake and the stock "41 dual exaust manifolds. These were wonderful engine and hooked dumb "genius" kids like me on inlines for the rest of my life. I was 14 when I started woring on them AND drove in the MISSISSIPPI VALLEY SPEEDWAY CLUB for THREE[3] YEARS BETWEEN THE TIME OF MY 21st and 22nd birthday. Remember when you had to have your parents consent if under 21? Thanks for letting me ramble. 1 OL REDNECK