? for intake manifold builders - Buick Str8

I've been flip-flopping on what I want to do for an intake for a 263 Buick Straight 8 that I'm building for a Model A, so I'd like to get some input from you knowledgeable intake manifold folks to help me decide. I'd appreciate any input, pro or con.

First a bit about the motor. Freshly overbored .020 with stock configuration replacement pistons from EGGE. Both head and deck shaved .050 (total of .1) to bump the compression a bit. I had to machine a bit of clearance in each chamber in order to keep safe piston-to-head clearance. Cam (hydraulic) was ground by Demitri Elgin, just a bit different than stock:
Duration @.006" 250 vs 240 stock
Duration @.050" 191 vs 180 stock
.255 lobe lift vs .230 stock 1.5 rocker ratio translates to .382 lift vs .345 stock
running timing 13-57, 57-13 = 26 degrees overlap.

Block has been converted to full-flow oil filtering with an external filter.

The intent is to build the motor for as much low and mid-range torque as I can. You can't spin these too fast, because that lonnnnggggg crankshaft is know to twist violently at high RPM's.

The Buick straight 8 has four siamesed intake ports, cylinders 1-2, 3-4, 5-6 and 7-8. Exhaust ports are one per cylinder. Firing order is 1-6-2-5-8-3-7-4, so each individual intake port has one cylinder filling 180 crankshaft degrees behind the other. As far as the induction system, I've got three choices I'm mulling over:

1. My first thought was to use a pair of Weber sidedraft DCOE48's that I have. The biggest reason I would use these is probably more because my last name is Weber than any other reason. I'm certain that a pair of DCOE48's would be too much carburetor for the motor, plus buying jets, etc to tune them is kinda spendy. The intake would be a cinch to build, basically a pair of slightly bent tubes, one going to each of the throats of each carb. In most cases where I've seen Weber carburetors used, there is no common plenum, so each throat is basically dedicated to an intake port. I would likely follow suit if I were to use these carbs.

2. Not traditional, but I also have a quartet of Keihin 38mm round slide carbs, the bores of which closely matches the approximately 35mm diameter of the intake ports. Very tuneable carbs, and I've got a lot of experience balancing these things from years of motorcycle wrenching. Again, a very simple build as far as the intake goes. Four straight tubes, one carb dedicated per tube.

3. Probably most traditional would be a pair of Holley 94's that I have. This would require a little bit more work to build the intake, but still quite simple. I would probably run the front and rear pair of intake ports to their own separate small plenum, rather than building a "log" style manifold. I want to have as long of individual intake runners as possible, to take advantage of any ram effect that I can at moderate RPM's. Question: I know that there is a small "transfer" passage between the two throats in the base of the carb. In order to meet my goal of low to mid-range torque, would I be better off (a)having a small plenum under each carb, or (b) have each of the intake runners directly under the individual carb throats, with no plenum?

 

EBB
No plenum will net you a very peaky motor. Your plenum becomes a buffer of sorts and helps overcome imperfect runner length.

I am not a big fan of the webers dcoe. My experience with them is that they are real finicky, changes in altitude, changes in humidity, temp etc.
I know that you don't have a set but a brace of SUs or the Solex equivelent would be pretty cool and they are real forgiving.

Just my thoughts.

 

Those 38 mm Keihn carbs would have a bunch of folks scratching their heads, especially with some creative air cleaners. Due to the engine's inherent good torque characteristics I think you'll have plenty of grunt to spare. If it acts finicky just run a 3/8" balance tube from unit to unit, fuel line should work.

What ever way you go, this is gone be nice.

 

PNBeaner, I do have a pair of SU's off an old Volvo. I ran an SU on a shovelhead years ago, no problems with it at all. I may have to throw another option into the mix. I do like the idea of a CV carb, takes a lot of the tuning headaches away.

Figured I'd throw in a teaser picture or two. I'll do a full build thread on this when I get a little more time. Here's some shots of the engine, and a couple of parts. The aluminum thing with the crack in it is one of the common issues with the rocker shaft stands in these motors. I have come up with what I assume will be a bulletproof solution.......

 

I love the idea of a straight 8 in a rod !!
Keep us posted with pictures.

 

SU or Keihn CV off a Evo motor. Yep way easier to tune, especially at low port velocities like the Buick will have.

 

I gotta watch this thread............I have a fully machined 263 (now 270 cu in) ready to assemble and could have written Ebb's intended result.......i.e. low and mid range torque......I also have a mild hydraulic regrind (Crower). I have a set of '41 dual carb intakes and exhaust manifolds that I have been considering. Not with the original carbs......but something.....I expect to use the exhaust manifolds but am open to building an intake setup.........Thanks, Ebb, for opening this topic!

Ray

 

Well, you know I'm kind of twisted when it comes to these things, but I'll throw my .02 in anyway!

I really like the idea of running small SU or Keihn carbs- 4 of them. I think a bank of 4 carbs, with a balance tube between them, and velocity stacks, would work good, and look great!

IMHO.

 

Well, this thread got me to thinking, so I browsed the web. look what I found on Wikipedia:

"Special"-8 At the General Motors Motorama for 1954, Pontiac debuted its all new Bonneville Special, a concept car envisioned by head designer Harley J. Earl. The concept was equipped with the "Special"-8, a high output 268-cubic-inch (4.39 L) engine that was painted bright red and detailed in chrome. This was a unique configuration for the "eight", installed in the only two Specials ever made. Similar in appearance only, this was a high compression variant that was modified with a high-lift cam and aspirated naturally through four Carter YH side-draft, single barrel carburetors, the same used in the 1953 Corvette, under open-mesh breathers. Total output was the highest ever for the "eight", rated at 230 bhp (170 kW), though some<SUP class=reference id=cite_ref-14>[15]</SUP> estimated it at over 300 bhp (220 kW). This estimate may be forgiven as "pride of ownership", but unfortunately it's not credible that these simple modifications would more than double the output of this fairly primitive design, and equal the power per cubic inch of highly developed and purpose-built contemporary sidevalve race engines such as the Harley-Davidson KR. Like the Special, only two of these remarkable variants were ever made.
Note: Pontiac’s new V8 was being considered for use in the Special but was instead held back by GM marketing. They directed that the straight-8 be used, to keep the V8 a secret from consumers for one more year until its debut the following year.<SUP class=reference id=cite_ref-15>[16</SUP>
<SUP></SUP>
<SUP>[FONT=Arial, Helvetica, sans-serif]What do you know- it's even traditional! Lol![/FONT]</SUP>

 

That engine is a thing of beauty.

 

I like the idea of 4 Keihin's. They are really great carbs too from my experience with them.

 

to cool glad im not the only person with one of these iron monsters around , mines a 53 263 with a 248 factory dual carb intake and dual exhaust manifold set up , got a pair of 97s going to try and run on it , best source of info is buicks.net the straight 8 board some good knowledge there and a couple guys who know their way around these mills ,

 

I to am putting together a 263. 1951 version. I am building an intake to use 3 2GC carbs. One primary and 2 secondary carbs using the Speedway kits. I will construct my own header. Can not decide if I want a try-Y or something normal.

Fritz

 

I'll pass on what I know from my own experience. bt 20 years ago I had a 63 Chevy II wagon with a 230 in it. That engine has siamesed intake ports also. I was young and broke, but couldn't leave well enough alone. I managed to scrape together enough funds to buy a cam and headers from Clifford's, but an intake was a whole different story. I designed and built 3 individual intakes, one for each port. each one was on a 45 degree angle, so that it had a bit of tunnel ram effect, and kept the carbs well above the exhaust. Didn't take much, just some 3/8x1.5 flat stock for each flange and some exhaust tubing, 1.5" I think, angle cut on the ends. I ran 3 stock 1bbl carbs, they were cheap then, about $20 each.

I fiddled with it a lot and it ran pretty good in the end, and it was way different from anything else I saw on the street at the time. After I blew out the bottom end I let the car go, and later figured out I should have at least had some heat to the intake. Would have made it much easier to deal with since it was my daily at the time. I think the best idea I ran across was a water pipe run across each intake runner. The carbs had a bad habit of frosting up on cold mornings.

i didn't have any type of connection between the manifolds, each acted as a seperate carb for 2 cylinders. I would have done much better had I known about a uni-syn at the time. i don't believe that the lack of common plenum caused me any problems.

devin

 

I have a 48' 248 that I am going to set with 3-2's on a log type manifold. Who built your flange...it looks very professional? Great looking motor. Keep the pic's coming.

 

Flanges came from Hot Rod Chassis and Cycle, one of the HAMB Alliance Vendors. It took them a couple of attempts to get the port size right, but after sending them a template they nailed it, and should have the file available to make as many as you want.

 

So, you gonna clue us in on what you decided?

 

I'm pretty sure I'm going to try the Keihins first. If they don't work out, it'll be a simple change to put a little curve in the tubes and run a pair of SU's. For the time being I'm sidetracked getting my old Harley ready for a run to Sturgis, so the straight 8 is gonna sleep under a blanket for a few weeks.

 

2" SU's??

 

This side draft setup comes from Clirfford Engineering in Wildomar, CA. I know it will work for your application. It just takes one more yoke. This arrangement is using Weber (costly) carburetor's. I have set one up using Mikuni carbs from a Suzuki big motorcycle. All you need to know is what CFM's that straight eight will need. Then you can make an informed decision about what type of carburetor you will be required to use.
Normbc9

 

If you aint really going ape crazy with this thing I would reccomend a 4-barrel intake from a 53 Roadmaster if you can find one. Use your carb of choice. With my european experince if you use side draft carbs use LONG intake runners. J shaped over the valve cover so the carbs will be on the passengers side. Good for torque on such a long stroke engine, especially if you use webers. British, or Japaneese slide type carbs work well with long stroke engines with shorter intake runners. That is only because the slide-piston can only move up depending on vacum giving a very linear response.

I have a straight-8 buick, 41 with dual carbs. If I was me, with some money I would do the 4-barrel manifold with throttle body stand-alone injection You can program for best perfomance.

 

Cool I think I miss-spoke after I typed that last post. I was not sure it was the 52, or 53 with the 4-barrel. Anyway I was close.

 

the 4 barrel carb was on the big 1952, 320" intake only, but the 248" dual carbs were on both large and small blocks fits [263 also]. You can play around with almost any carb setup you want, see what works best. 4 bbl carb is usually the simplest to tune, make up a smooth curved, small long runner intake, will help a lot.They like compression, carbs and cam, a little of each, go for torq, it will rev good.

 

While # 2 may follow #1 by 180 degrees the problem comes when #1 follows #2 by 540 degrees. And so on. I thought a large plenum was a good idea for these motors. Or if running Hilborn type fuel injection, mount the butterfly and nozzle as far as practical from the valve. Try to have a volume there to balance the discrepancy in time to fill the runner

 

Check out Saltcat Racing on facebook

 

Yeah, but they took away their secret weapon. The 16 port head. Now that was cool. It's interesting that a couple of guys are making the big Buick's run good now, after all this time when they didn't seem to run up to potential

 

I like the idea of four carbs, but agree that you need some plenum volume. More than a 3/8 tube between the respective runners. As Rich Fox pointed out the air draw is not evenly spaced and you need some extra plenum to help equalize that out.

 

How much power would it take to get a full bodied 38 Buick coupe to turn 117 mph in 11.37 sec.? Gerry Dutwieler did it at Fontana. [blown 4bbl straight 8] It was impressive. Blower is one way to overcome that strt8 head.

 

does any body know anybody that can build a stock looking intake and exhaust for me

 

iron parts? Why?