Just an update on the multi carb intake for the straight 8. I couldn't figure out what was bugging me so much about the original design of the intake for the straight 8. I finally figure it out tonight and could use a little input from you guys as I develope this thing.
What was bugging me was this.... The original manifold if you are looking down throught the top of it is set up as follows: The carb venturi closest to the block feeds the to innermost intake runners. The outer venturi feeds the front and rear intake runners. ruuner length wise there is a great deal farther for the fuel to travel to get to the outer intake runners than the inners. This seems to me that it would give an uneven fuel charge to the inner vs. the outer runners. Which in turn would result in either an over rich or an extremely lean condition somewhere in the fuel system.
What I am working on with the 3 pot manifold will be a log style manifold using a common runner that feeds off all 4 intake runners the exact same length. Setting of the primary carb (rochester 2G) in the exact middle of the main runner. This carb will be the main source of fuel during idle and part throttle acceleration. The 2 additional carbs will be placed an equadistannce appart between the center intake runners and the front intake runner and the rear intake runner. I am hoping that this will cure any inherent fuel pulsations in the primary intake tube.
Any thoughts or suggestions? I am hoping to have a prototype finished here in a couple of weeks. As a side note: The carbs will be restricted down so that the will only flow 400cfm total at wide open throttle. I feel this is more than enough fuel for a straight 8. graemlins/shield.gif

Hey Aaron, cool project, I want to ask my dad about this because he has old school knowledge on the engineering of the manifolds. He has told me about the straight 8 manifold set up-the runners go to the cylinders because of firing order (I think) and is not good to change- do you have one of the dual carb manifolds to study? Than might help think it through-my point is its not all flow oriented, there is the firing order to consider.

Speaking of exotic projects, Dad is working on a '38 V-16 Cadillac. Has installed a GV overdrive and wants to put a roller cam in. Has just got his 78 Malibu Classic 4-door back from the shop-it now has a 2001 LS6 (Z01) engine on it. Working on a opposed 12 airplane engine- that he has designed and built ( nagelengine.com ) Crikey, all I want to do is put a tremec 5-speed in my Wildcat! Ted

I've looked at a couple of the old 2 pot manifolds and they still leave me wondering the same thing. Then again I am also looking at this from a hot rodding standpoint. I'm looking at placing the actual runners at approximately a 25 to 35 degree angle to increase the velocity of the incoming fuel charge into the ports. By doing this it will actually place the primary log above the runners. since I'm dealing with a single common plenum it should balance out any irregularities in the delivery of the fuel. I saw an article once where a guy had bolted 3 webers directly to the ports. Since the original manifold is essentially a single plane, but divided I should be able to make this work. My concern is that the original manifold does not seem to be as efficient as it could be due to the unequal length of the intake runners. Basically it seems to me you're dumping the same amount of fuel into 2 differnt sized areas and expecting them to function the same.
Maybe I'm wrong, but this is what the website is for. graemlins/thumbsup.gif

Just found something really interesting in the August, 1952 issue of Hot Rod. A gentleman wrote in about his Buick to the Shop Talk section. He stated in his letter that he was running on his straight 8 a Edmunds aftermarket 2 pot intake with 2 Stromberg 97's a 3/4 cam and a mallory aftermarket dual point distributor. Any one have one of these manifolds they can send pics of?
I've been pouring over all of my old issues of Hot Rod looking for these sort of things.

graemlins/wavey.gif Aaron,

Have you looked at the article in the Buick.net Shop Secion on how to build a High Performance Straight Eight? They have a picture of one with 4 carbs. They mention using Strombergs, which are too finicy and tempormental for my liking IMHO. :( I would prefer the Rochesters or Carters.

graemlins/thumbsup.gif graemlins/thumbsup.gif graemlins/beers.gif


graemlins/shield.gif Tom Gallagher graemlins/shield.gif

I've read the article. However, it really doesn't address a number of the issues I'm looking at. Somehwere in one of my old magazines is a complete 3 or 4 part build up of the straight 8. First I gotta find it though. I know it's possible to do what I'm wanting to do, but for some reason I feel like I'm overlooking something

Something to throw in, the Chrysler dual quad cross ram. It's design pro were even length runners. The longer runners advantage/disadvantage being higher rpm.

Part of the reason I've gotten so serious about this the last couple of days is due to the fact I traded my 50 Super 4dr parts car for an almost, but missing the manifold 50 Special 2dr Sedanette. So instead of tracking down a manifold I decided it would be a whole lot more challenging to fab up a new manifold from scratch. I've done it enough times on my hot rod motors and they always been streetable, so why not on the the straight one. Bob, thanks for the input. I'll definitely be keeping that in mind as I start the building of this thing graemlins/beers.gif

Aaron, I spoke with my dad to get some ideas on the straight 8 manifold.
Ok, on the single 2bbl its set up so one side of the carb feeds the outside cyls, the other side of the carb is for the inside cyls. So the important stuff in the original design are that the runners are equal length, and the paired cyls like 1+8, 2+7, etc are fed from the same side of the carb. This means that side of the carb is “seeing” an even flow from the cyl pulses.
Some fuel from the carb is in liquid form as it goes to the cyl, if the runners are unequal length the closer one will see this liquid fuel, the one further away may run lean.
I wish this was firsthand knowledge, its from my dad who worked in Detroit as a mechanical engineer in the 50’s and 60’s. Did a lot of engine work, design and testing-and is still doing it!

With all that said, I say build it and test it. There is no substitute for testing graemlins/beers.gif

Ted,
Thanks for the input. I've a couple of the old u-fab manifolds from the 50's and seem to have pretty good luck with them on the street. I started taking the measurements today an will probably start working on the prototype early next week. If all goes well I'll test it somewhere around Halloween. I just have to make sure my girlfriend doesn't wonder why I have her 50 Super taken apart. I don't want to have to explain that one. "Ah, honey, no, I swear I'm not using your car as a guinea pig" graemlins/thumbsup.gif

graemlins/wavey.gif Aaron

You seem to have a pretty good handle on things in regard to designing a manifold. graemlins/thumbsup.gif Are You going to experiment with 3 or 4 carbs? Is it possible to have one carb fuel two cylinders?
You are correct. I will we difficult to explain to Your Girlfriend about the Manifold. That will probable be the hardest part. I tell my Wife and 6 Sisters: Women like Jewelery and Shoes. Men like Tool and Parts. Women seem to grasp that. ;) If You have something teats or tires, you know your going to have problems with them LOL :D graemlins/thumbsup.gif graemlins/beers.gif

graemlins/shield.gif Tom Gallagher graemlins/shield.gif

I've been looking at the means for the fuel supply. I've been thinking about using 4 covair carbs. They're a 1 barrel setup and would not give as much fuel as running the 3 rochester 2Gs. I still may go with the 2Gs, but 4 carbs would look a lot cooler than 3 and should be easier to meter down to the amount of fuel I want the motor to recieve. Actually my girlfriend will probably be pretty understanding of the matter. I had mentioned it once before and she didn't seemed to be bugged by the idea.

hey aaron,
your knowledge far exceeds mine. as a new straight 8 owner, i have been doing a lot of research in hopes of building my dream car. i am trying to figure out how to provide you with easy links to the info i think could help you. sadley, i am also learning the computer. you should really check out the H.A.M.B. (hokey *** message board) on the web site www.jalopyjournal.com (http://www.jalopyjournal.com) .there is an amazing wealth of knowledge there (if you can weed through all the riff raff). search for straight 8's. also look up the member "scotch". he is doing some ground breaking work in regards to rebuilding and modifying the buick straight 8. i'll try to get his email info and hook you two up. i also have a link to a site where a guy is doing amazing things with a straight 8 (including making his own intake). however it is at my work. i will get you as much info a.s.a.p. by the way, i'm hoping your knowledge can benifit all straight 8 guys. i really want to know how your manifold turns out, so keep us posted!

aaron,
i sent a private message to scotch,hopefully i'll hear back from him soon. i'm waiting for his permission to give you his email. i also sent this thread to him. i'll try to find the link to the other guy who built his intake when i get a break at work tomorrow. also check out inliners.com. mostly about sixes, but some i8 info.
best of luck,
scott

chub chub,
Thanks for the info. I had forgotten about the sites you referenced. It's been a long time since I have logged onto either one. Any info and any conections with input regarding this would be great. I've been messing around and modifying the 300, 340 for so long I'm having to look at things in a different manner. At least I have the headers figure out without having to modify or change out the driver's side motor mount. One of my big concerns with this manifold is wether or not I'll get enough of a mixing effect inside of a smooth runner to promote good fuel atomization. I look at it fron the hot rodding standpoint of that nothing ever fits and will always have to be modified.

bluewhale,
i found that other link i was looking for. i hope it works. http://gamma.nic.fi/~marlin/Rmaster.htm check out the april 04 intake manifold link. amazing.

chub chub,
hanks for the link. I've been searching for that particular website for sometime now. Looks like he's come a long way since the last time I was at the site

chub chub,
hanks for the link. I've been searching for that particular website for sometime now. Looks like he's come a long way since the last time I was at the site

Aaron,
This is a great topic. I've been looking for information on manifold & carb set-ups for some time now. I have a 320 motor that I'm trying to build a log manifold for, and use twin Delorto DOCE40 side draft carbs on. I thought of using 3, or even 4 but that would be too much for the motor (would look great though!). I've been watching Jyrki's site for some time now, and he's doing some great things to his Buick. He's the moderator of this forum as well - I'm surprised he hasn't jumped in yet. Keep us posted as this develops please.
Bains

You're looking at using some pretty impressive carburation! I thought about doing something along those lines, but my inner hot rodder won out, so I'll probably stick with the R2G's. Speedway offers new base plates that do away with the idle metering circut. That way you can run a primary and have the front and rear carbs come in progessively or set them to feed identically and use a completely mechanical linkage. I'm still toying with the idea of strapping somewhere between 4 and 8 one barrel covair carbs on it since they don't flow very much from the factory. I've started to mock up the manifold in cardboard to see how it will all fit togehter. If I can come up with a manifold that will work correctly I'll let everyone know and will provide the measurements, plans, and diagrams to anyone who wants a copy. It may take a little time to get this all done, but it's definitely on my top priority list right now. I'm going to have to lay off of it for a bit, I have a customer's 40 Buick sedan coming in next week for a mechanical rstoration, but will still be working on the R&D side of the manifold while this is going on graemlins/shield.gif

I apologize for not checking this site and jumping in sooner. I have been so busy with other things that when it's time to surf web, it's well over midnight!

I have now 300 miles on the Buick - still breaking in the engine - and unfortunately have to park it for the winter without having the chance to "step on it". What I can tell you is the car runs well on the highway and pulls hard. However I have problems with idle quality and low rpm driveability. The throttle blades are now synchronized as well as feasibly can. At first, I thought that if the engine runs well with only one carb (OE), accelerator pump link at the stock location = center hole, I should decrease the pump shot with dual carbs. WRONG! Actually, the pump links on both carbs have to be at the farthest hole which gives maximum shot. Even this didn't cure the off-idle stumble entirely, but helped a lot. This leads me to think that I may have a condition called fuel dropout. Some of the fuel, already mixed with the air, will separate from the airstream and from droplets on the plenum and runner surfaces. Ideally, the surfaces should be rough, especially at the plenum. In my case they are very smooth (stainless).

Also, the engine surges and cuts out at low rpm, and the exhaust pops at the same time - sounds like symptoms of both lean and rich mixture at the same time! I have not found any vacuum leaks. The culprit might be idle-to-main jet transition, but I'm not sure.

What comes to log manifolds, I'm not sure if that's the best alternative. On a I-8 the plenum (log) volume becomes very large, compared to runner volume. The signal to the carb may become weak, imparting low-rpm performance. But, as it turned out, my design isn't very good either. And the problem with the Strombergs is the limited tuneability.

Good luck with your projects!
Jyrki

hey jyrki,
i never even realized i was promoting your site. i didn't realize you were the moderator for this site. i'm glad i now know the connection. keep both sites updated with your progress. your work is an inspiration to me and (i assume) others.

I'm planning on doing some pretty intensive cross hatching inside the runners to promote fuel atomization. I figure running a 60 grit hone inside the tubes and building a slight ridge right before it enters the ports should help to over come some of these problems.

I just met a guy with a 1948 Ford flathead with dual Strombergs(maybe 97's not sure)on an aftermarket (cast) manifold, and he's having the same problems as I do. He didn't know the cure for it, either.

If I won't get the dual Stromberg system run satisfactorily, I will build a fuel injection system, and leave the Strombergs acting as throttle bodies.

I'm glad to hear that my website serves as inspiration to other enthusiasts! Originally my idea was to provide the kind of information that I myself was looking for on the web, but couldn't find at the time.

When dealing with multiple Stromberg setups I have found that what it takes to get them dialed in is just a days worth of R&D. You'll need multiple sets of jets and spark plugs. It seems every time I've had to set these up I've had to use smaller jet sizes than I nomally thought would be necessary. Install a new set of plugs and take the car for a drive. Pull them out and see what the tell you.Repeat as necessary to you've got it where you want it. The last multicarb intake I set up was a 4 pot Weiand dragstar manifold..I ended up having to use the samllest jets available to get the car to run right without stumbling or fouling out the plugs

Just thought I would give everyone an update on the intake manifold. I've figured out how to do this and make it functional, I think. Sticking with the original design of the 2 seperate plenums I'm going to build it as a divided log type manifold. From the outward appearance it will be a log style, but it will be divided inside like the original and meter the fuel off one side of each carburator as per Buick's design. I'll still be able to run it as a tripower, but the inboard venturies will feed 3,4,5, and 6. The outboard venturies will feed 1,2,7,8,like the original, just with more fuel and with a more direct intake runner. It's going to take some work, but I sat down tonight and figured out the math side of it and it should work.
If anyone wants photos of what a stock straight 8 manifold looks like when its split down the middle let me know. the pics are too big to post on the site. My original was cracked beyond repair so I cut it apart to do a little R&D graemlins/banana.gif

Hi Aaron,
I'd like to see the interior of the manifold-
curiosity only.

The 2 coolest cars I saw at he Nationals were Wild Bill's 66 4-speed Wildcat and a 35(?) coupe, black and lowered straight 8 dual carb split exhaust- it sounded so sweet and was just "right".
Good luck!

nagel@iac.net

Hey Aaron,

What's Up?
How is Your Manifold Project Progressing?
What I want to Know is How do You plan on casting the Finished Product?
What Material do You intend to use?
What are You using to make a Mold?
Most of the Original Straight 8's Intake manifolds are cracked. What causes that particular defect? Design flaw or heating cooling , expansion and contraction?
I have not had too much exposure to the Straight 8
I do know that it is a solid, quiet dependable motor and it weighs about 875 lb. It has a massive structure but the compression ratio is pretty enemic at best was 7.5 to 1 with the 1952 320 ci. I know Buick Engineering was estatic when the 322 Nailhead was developed with more HP and the engine weight with a high Nichol Content/Composition was decreased to Only 635 lb. What I find is really surprising was the development of the Buick 350 that weighed 470 lbs. 100lbs lighter than a SBC. That's Buick Engineering.

Tom Gallagher

hello aaron,
sorry it took so long to get back to you with this info. you should really contact scotch about your intake manifold. i will send you his email adress in a personal mail. you two will have tons to talk about. share it with us!
scott

I'm looking for general help in making repairs to my 1948 Buick Flexible Hearse w/ Straight 8
I cant seem to get the starter motor to work when I depress the gas pedal

I'm building the prototype out of steel tubing right now. Once I know I have a working manifold there is a guy here in Wichita that has been a dental casting tech for 30+ years. He used to cast parts for his friends back in high schol and seems to think that it should not be a problem for him to pull a mold from the original. If everything works they way I'm hoping we'll start casting them in aluminum. A local foundry said if I had the molds and everything ready to go I wouldn't have to worry about a set up fee which is quite expensive.
Once I can get the photos of my old manifold resized I submit them for the sight

Captnemo,
I would start by tracing the wiring from the ignition switch to the carb and then down to the starter itself. Alot of times the throttle linkage is not set right. Make sure the throttle is ajusted properly so that it acuates the switch on the side of the carb. If this doesn't work or you're still not getting anything let us know and someone here should be able to help you get it sorted out. I'm not the most knowledgable person when it comes to the starting systems on these motors.

hey aaron,
did you get my p.m. with the email for scotch?

Captnemo, The first thing to do is short across the two wires on the carb switch with the car in neutral and the switch on. If this does not engage the starter, you will need to look at the wiring. If it does , then you can proceed to the linkage and see what is going on

Aaron, Here is a link to a small picture of an Edmunds intake for a straight Eight. Unfortunately, it's already been sold. http://www.vapinc.com/buickspeed/main.html

Also, if you find your magazines with the build up articles of the straight 8 could you let me know which magazines they are in so that I could look for them?

Thanks,
Kyle

Thanks for the link. I'll keep you posted as I shift through more of my magazines and let you know

hey has ne one tried creating a custom intake where there is a carb for each individual intake port without creating a manifold, just run them right into the ports or is that a completely stupid idea??

It's been done a few times in the past, but what happens is it doesn't really run right unless you are at wide open throttle. This is due mainly to the firing order. The other problem you run into is intake runner volume and vacuum, then you have to consider how to meter down a carb to flow so little fuel at idle. Another thing one will run into is fuel pooling. The intake itself helps to atomize the fuel inside due to it's rough texture, Since running straight form a carb into the combustion chamber there isn't enough time for the fuel to mix properly. I've been searching for the last couple of weeks for one of my vintage Hot Rod mags that shows a roaster set up with eight 97's on long individual runners. So far I haven't come across it yet, but then again looking through every Hot Rod between 1950 and 1970 takes a bit of time.

Aaron, Please send me the manifold pics!! I'm trying to figure out the same things myself. Any other pics would be greatly appreciated and file size is not an issue...

Thanks,
Mark

Mark, If you would like copies of the pics PM with your email address or just email me at: monksvintageauto.netzero.net and I'll send you the photos. I'm trying to downsize them so I can post them on the site.

Aaron has sent me some pictures of a straight 8 manifold he x-sectioned. He thought someone might like to use them for reference. You will now be able to find them in the Buicks.net shop at:

http://www.buicks.net/shop/reference/str8_xsection.html

Thanks!

/Users/Castillo/Pictures/iPhoto Library/Originals/2009/Roll 137/!BV6WE9gCGk~$(KGrHgoOKkEEjlLm(0GPBKU53vkqKQ~~_1.JP G

I may be a bit late on this thread but will put my oar in a row anyway. I have just finished building a heated (very important by the way for a street car) four carb manifold for my modified 320. So far it appears to run very well on the test stand with terrific off idle acceleration with no hesitation or stumbling. I used Holly-Weber 2 throat progressives from Ford V-6 small pickups. I have used these on modified Chevrolet engines in both two and three carb setups with great success. It gives you kind of the best of both worlds with smaller venturi for cruise and then bigger secondaries when you crack the throttle over 3/4. Also they are very easy to jet and adjust.. If anyone is interested in further details on this setup, contact me at presten@comcast.net.

Awesome! Hot water heated?

I think you have a good combo there, with progressive throttles and heated manifold, which keeps the fuel in suspension.

Yes it is heated by hot water. I simply tapped into the hot water supply for the car heater right at the water pump and returned by the heater return fitting. Simple tees do the job. By the way, I have been made a true believer in manifold heat by Tom Langdon, a former engineer in the GM Engine Division who now owns a company that supplies hot rod parts for GMC and Chev engines. He says that every case of stumble or hesitation off idle he has helped with was cured by heat! Otherwise the fuel simply pools in the bottom of the plenum. I got the hot water heat by welding 3/4 by 3/4 angle full length to the bottom of the plenum chamber to make a triangle shape channel. That forms a nice channel where the hot water can apply heat directly to the bottom of the plenum and never gets too hot like it can happen with exhaust heat unless it is controlled by some kind of baffle or valve. The water goes in one tube and then I loop the opposite end tubes to bring the water back the other way in the other channel. Simple but effective. I start getting heat within about 2 minutes of starting the engine...long before the thermostat opens. The only regret that I have was that I wish I was a better aluminum welder and I would have made it out of aluminum!! Much lighter. As much as I have tried, when I weld aluminum it looks like I put it on with a butter knife!:shifter:

Going way back to the first entry in this thread regarding unequal runners creating leaner mixtures towards the outer cylinders. I'm wondering if the designers of old knew something back then that's been overlooked?
From my experience with multi cylinder race bikes, centre cylinders are often jetted richer to deal with overheating issues. Easy to achieve with multiple carbs.
But how do you do it with only one carby? It's possible that the "leaner outer cylinders" might be viewed as richer inner cylinders to average out cylinder temperatures.
Any thoughts ???