Tri power rochester end carbs once and for all

If it stumbles when you crack the throttle you need a bigger pump shot. Just like the other guy said. Most bogs are lean bogs.

 

How does one increase the gas shot? I used stock accel pumps. Thanks again

 

Make sure your getting a full shot from the accel pump. Like I mentioned before, the rubber in the old pumps doesn't like the new gas.

 

Im getting good streams from all 3. I put new accel pumps in a month ago. The neoprene wouldnt fade that quick would it?

 

Could be an inadequate air bleed. Have had that issue on Harleys and with 2 Carter B&B's on a flathead six. Opened up the air bleeds- no more stumble.

 

On the 3-2's I just rebuilt for a customer the pumps screwed up 5 minutes after the gas hit them.

 

WOW!!! Ive been running fairly good- still really lean. Im going to pull them all apart this weekend and check the pumps. Thats scary. Youd think there would be some kind of effort to stop the manufacturing of them. Could get allot of pro mechanics in trouble.
I got a 1966 pontiac center carb that Im going to try. Hopefully it will cure the initial stumble

 

I have been trying for years to get either of the two major carburetor component manufacturers to make up leather pumps. They won't do it because of costs! We finally gave up, and started making our own leather pumps.

Neopreme was NEVER even as good as leather, let alone better, but it is about 20 times cheaper!

Jon.

 

I agree but you need to block off the vent by the accelerator pump on all three carbs. Part of the idling problem is the vent is letting to much air in at idle. That's why when the choke is closed, it will idle...less air. Accelerator pumps are needed on the front and back carbs but no idle circuits. Block off all vacuum ports on the front and back carb. Run you vacuum advance from the base on the middle carb.

Look closely, you see there are no vents on top of the carbs by the accelerator pump linkage.

DD

 

Sorry I was a little late with my comments...didn't realize it was an older thread.

About the accelerator pumps. If you have a bule skirt wih a spring around the skirt it should work fine with the newer fuels, thats what I was told.

DD

 

<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD colSpan=2>DeuceDog, Mine have the blue skirt with the spring. I think Im gonna go leather though. When you talk about the vent by the accelerator pump are you talking about "Idle Vent Valve" on top? I left the one on my center carb because I heard that it helps prevent vapor Lock. Is this the case? Thanks again



</TD></TR></TBODY></TABLE>
These are the ones I have

 

I'd suggest that you re-think what you just said here, as it is not correct.

 

Just realized, I did my own peeve about forums. Not concluding the result. It runs great. I had to fool with the jets a bit - running 60s in the middle and 55s on the secondaries. Seams to be fine. Dont really have a bench mark. I followed everyones suggestions in this thread and all is well. By the way, To seal the end carbs I sanded a little around the throats and added little lips using jb weld putty. I pulled the carbs off last week -about 8 months later -and they are still holding up. Thanks again for all your help

 

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I note in the speedway motors tri power instruction sheet, it states - On smaller cube engines, the amount of fuel supplied by 3 accelerator pumps may cause excessively rich condition when you put the foot down.

Cutting up to 5 coils on the outside 2 accelerator pumps reduces the shot supplied when the secondary&#8217;s come in.

Also it recommends #56 main jets for primary and #55 for secondary&#8217;s.

I am putting together triple carbs on a 283 sbc, with Edelbrock 3x2 intake using Rochester 2G carbs.

I will try to convert the stock bases by using thicker throttle blades &#8220;laped&#8221; into the small base using valve grinding paste.

If I can&#8217;t get them to seal I will go for aftermarket bases. As I was looking around for parts I came across - www.pontiactripower.com they have good amount of parts for tri power and the bases look good.

One thing if interest was DAG213 Throttle Blade Sealer - http://www.pontiactripower.com/shop/category/Carburetor_Parts/



..
.

 

Spark, Does the Speedway instruction sheet say anything about jetting for big cube engines? Is it downloadable? Im running a 390 bored .060- That pontiac site is great for rochester tripower info BTW

 

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It wont hurt to mention the some guys from the H.A.M.B recommended you try him.

 

my 3x2 rochester set ups ..(i have 2 of them) both end carbs on both set ups are running accel pumps. ..

I have the progressive linkages set up so that the center carb gets close to little over 1/2 throttle then the front carb starts to come in, and when its at close to 1/2 throttle the rear one comes in and when the center carb roll over to full throttle , all 3 are at full throttle..this might help your bogging..maybe?

also check and see what jets you are running in your end carbs and be sure when the end carbs are closed, that they arent sucking air past the butterflys..this will cause a vac leak like no other

and, I would only run a choke on the center carb..period

 

??????

Why would cutting coils off of the pump spring change the pump shot???

If you are using Rochester 2G series carbs, take a look at the pump circuit. The amount of the pump shot is the volume of the pump well displaced by the stroke of the accelerator pump cup in the pump well.

There are several really easy ways to change the pump shot:

(A) Note that the pump operating rod (the rod connecting the throttle arm to the intermediate pump rocker shaft) has a bend in the middle. Changing the angle of the bend will change the beginning point of the accelerator cup in the pump well, and thus will change the amount of the accelerator pump shot.

(B) MANY Rochester 2G carburetors have two holes in the arm of the intermediate pump rocker shaft. This was a factory "summer/winter" pump adjustment.

(C) And if all else fails, the actual accelerator pumps come in a bevy of different lengths. Both the overall length and the articulated length change. Acquire different length and stroke pumps to help with your tuning.

And just for the record, cutting coils from the pump return spring might cause the pump not to return as it would weaken the spring. If the spring in question is the articulation spring, cutting coils from this spring would accomplish no change in the pump shot, but if cut too short might just cause the pump to not function period, as the articulation spring pressure MUST be greater than the return spring pressure for the pump to work.

Jon.

 

Spark - here is an article that mentions selecting the carbs to use:

http://www.thecarburetorshop.com/Aftermarkettripowersetups.htm

58 Ford - the fuel requirements for a 390 Ford (I have one) and a 389 Pontiac (I had one) are extremely similar. HOWEVER, YOU MUST CONSIDER WHICH CARBS YOU ARE USING WHEN YOU SELECT THE GASOLINE JETS. Many disregard tha fact that a carburetor by definition meters and mixes gasoline AND air. The factorys did a lot of tweaking using different combination of fuel jets AND air jets (the air jets, called air bleeds, are pressed in, and not considered removable by most hobbyists). You can take two carburetors of identical CFM flow, add the exact same gasoline jets, and get two entirely different calibrations if the air jets are different.

So for a 390 Ford, IF you have a tripower using 389 genuine tripower carbs, the original Pontiac calibration would be a good starting point to begin your tuning. If other carbs are being used; USE THE STOCK CALIBRATION FOR THE CARBURETOR YOU ARE USING AS A STARTING POINT.

Engineers (at the factory) did things for a reason.

And here are a couple of 390 pictures:

http://www.thecarburetorshop.com/Ford_3x2_passengers_side.jpg

http://www.thecarburetorshop.com/Ford_3x2_drivers_side.jpg

Jon.

 

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Yep all good info- I was just relating what I had read in the speedway instruction sheet- download- http://static.speedwaymotors.com/pdf/910-11589.pdf

in my case I am building a 283 using an Edelbrook 3x2 aftermarket intake so the small cubic part court my eye. as far as Rochester 2G go, most of the ones over here would of been on 283, 307,327 sbc. as far getting hold of factory ones...hens teeth! I have managed to get hold of 2 factory end bases and 4 ebay.com.au 2G. really want to do the research and rebuild and refinish the carbs myself, even if it means collecting more ebay carbs.

 

Spark - don't know what you might find; but Buick in the early 1960's had a 198 CID 6 that used a Rochester 2-G series. Also, both Buick and Oldsmobile had a 215 CID 8 cylinder that used a Rochester 2-G series. Later (late 1960's into the 1970's) Jeep had a 225 that used a Rochester 2-G.

Good luck with your project.

Jon.

 

Thank you Jon, apart from the Jeep all those cars you have listed were not imported into this country - Chev had an Australian delivered (Canada) from about 1954. W got mostly English cars and from 1948 had our own brand Holden and Australian built Falcons.

As I understand it the internal difference is in jet size and venturi - would this be a fair statement?

all the carbs I have look the same and are small base, have the same shaped leavers, all will get new jets, new <!--[if !mso]> <style> v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} b\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} </style> <![endif]--><!--[if pub]><xml> <bublication type="OplPub" oty="68" oh="256"> <b:OhPrintBlock priv="30E">285</b:OhPrintBlock> <b:NuDefaultUnits priv="1004">1</b:NuDefaultUnits> <bptlPageDimensions type="OplPt" priv="1211"> <b:Xl priv="104">7560000</b:Xl> <b:Yl priv="204">10692000</b:Yl> </bptlPageDimensions> <bxlDefaultTab priv="1504">359410</bxlDefaultTab> <b:OhGallery priv="180E">259</b:OhGallery> <b:OhFancyBorders priv="190E">261</b:OhFancyBorders> <b:OhCaptions priv="1A0E">257</b:OhCaptions> <b:OhQuillDoc priv="200E">280</b:OhQuillDoc> <b:OhMailMergeData priv="210E">262</b:OhMailMergeData> <b:OhColorScheme priv="220E">283</b:OhColorScheme> <bwNextUniqueOid priv="2304">1</bwNextUniqueOid> <b:IdentGUID priv="2A07">0'PLC[E>/&D&'0_('^P[8F`</b:IdentGUID> <bpgSpecial priv="2C03">5</bpgSpecial> <b:CTimesEdited priv="3C04">1</b:CTimesEdited> <b:NuDefaultUnitsEx priv="4104">1</b:NuDefaultUnitsEx> </bublication> <brinterInfo type="OplPrb" oty="75" oh="285"> <b:OhColorSepBlock priv="30E">286</b:OhColorSepBlock> <b:FInitComplete priv="1400">False</b:FInitComplete> <bpiX priv="2203">0</bpiX> <bpiY priv="2303">0</bpiY> </brinterInfo> <b:ColorSeperationInfo type="OplCsb" oty="79" oh="286"> <blates type="OplCsp" priv="214"> <b:OplCsp type="OplCsp" priv="11"> <b:EcpPlate type="OplEcp" priv="213"> <b:Color priv="104">-1</b:Color> </b:EcpPlate> </b:OplCsp> </blates> <bzlOverprintMost priv="304">304800</bzlOverprintMost> <b:CprOverprintMin priv="404">243</b:CprOverprintMin> <b:FKeepawayTrap priv="700">True</b:FKeepawayTrap> <b:CprTrapMin1 priv="904">128</b:CprTrapMin1> <b:CprTrapMin2 priv="A04">77</b:CprTrapMin2> <b:CprKeepawayMin priv="B04">255</b:CprKeepawayMin> <bzlTrap priv="C04">3175</bzlTrap> <bzlIndTrap priv="D04">3175</bzlIndTrap> <bctCenterline priv="E04">70</bctCenterline> <b:FMarksRegistration priv="F00">True</b:FMarksRegistration> <b:FMarksJob priv="1000">True</b:FMarksJob> <b:FMarksDensity priv="1100">True</b:FMarksDensity> <b:FMarksColor priv="1200">True</b:FMarksColor> <b:FLineScreenDefault priv="1300">True</b:FLineScreenDefault> </b:ColorSeperationInfo> <b:TextDocProperties type="OplDocq" oty="91" oh="280"> <b:OhPlcqsb priv="20E">282</b:OhPlcqsb> <b:EcpSplitMenu type="OplEcp" priv="A13"> <b:Color>134217728</b:Color> </b:EcpSplitMenu> </b:TextDocProperties> <b:StoryBlock type="OplPlcQsb" oty="101" oh="282"> <b:IqsbMax priv="104">1</b:IqsbMax> <b:Rgqsb type="OplQsb" priv="214"> <b:OplQsb type="OplQsb" priv="11"> <b:Qsid priv="104">1</b:Qsid> <b:TomfCopyfitBase priv="80B">-9999996.000000</b:TomfCopyfitBase> <b:TomfCopyfitBase2 priv="90B">-9999996.000000</b:TomfCopyfitBase2> </b:OplQsb> </b:Rgqsb> </b:StoryBlock> <b:ColorScheme type="OplSccm" oty="92" oh="283"> <b:Cecp priv="104">8</b:Cecp> <b:Rgecp type="OplEcp" priv="214"> <b:OplEcp priv="F">Empty</b:OplEcp> <b:OplEcp type="OplEcp" priv="111"> <b:Color>16711680</b:Color> </b:OplEcp> <b:OplEcp type="OplEcp" priv="211"> <b:Color>52479</b:Color> </b:OplEcp> <b:OplEcp type="OplEcp" priv="311"> <b:Color>26367</b:Color> </b:OplEcp> <b:OplEcp type="OplEcp" priv="411"> <b:Color>13421772</b:Color> </b:OplEcp> <b:OplEcp type="OplEcp" priv="511"> <b:Color>16737792</b:Color> </b:OplEcp> <b:OplEcp type="OplEcp" priv="611"> <b:Color>13382502</b:Color> </b:OplEcp> <b:OplEcp type="OplEcp" priv="711"> <b:Color>16777215</b:Color> </b:OplEcp> </b:Rgecp> <b:SzSchemeName priv="618">Bluebird</b:SzSchemeName> </b:ColorScheme> </xml><![endif]--><!--[if pub]><xml> <bage type="OplPd" oty="67" oh="266"> <btlvOrigin type="OplPt" priv="511"> <b:Xl>-87325200</b:Xl> <b:Yl>-87325200</b:Yl> </btlvOrigin> <b:Oid priv="605">(`@`````````</b:Oid> <b:OhoplWebPageProps priv="90E">267</b:OhoplWebPageProps> <b:OhpdMaster priv="D0D">263</b:OhpdMaster> <bgtType priv="1004">5</bgtType> </bage> </xml><![endif]--><!--[if gte mso 9]><xml> <o:shapedefaults v:ext="edit" spidmax="3075" fill="f" fillcolor="white [7]" strokecolor="black [0]"> <v:fill color="white [7]" color2="white [7]" on="f"/> <v:stroke color="black [0]" color2="white [7]"> <o:left v:ext="view" color="black [0]" color2="white [7]"/> <o:top v:ext="view" color="black [0]" color2="white [7]"/> <o:right v:ext="view" color="black [0]" color2="white [7]"/> <o:bottom v:ext="view" color="black [0]" color2="white [7]"/> <o:column v:ext="view" color="black [0]" color2="white [7]"/> </v:stroke> <v:shadow color="#ccc [4]"/> <v:textbox inset="2.88pt,2.88pt,2.88pt,2.88pt"/> <o:colormenu v:ext="edit" fillcolor="blue [1]" strokecolor="black [0]" shadowcolor="#ccc [4]"/> </o:shapedefaults><o:shapelayout v:ext="edit"> <o:idmap v:ext="edit" data="1"/> </o:shapelayout></xml><![endif]-->accelerator pumps and 2 factory end plates.

if all my efforts don't result in a driver-able car I will import a set of carbs from Dickster or someone that builds similar set ups.

.

I am just trying to add info.

 

The key is internal venturi size. The Rochester uses venturii which are cast as a part of the bowl (center section). Jets are removable/replaceable. But you need to start with carbs with the proper internal venturi size for your application. Using matched carbs (at least for the ends) is important as different carbs of the same venturi size could use different air bleeds.

Jon.

 

Great Info!!!

 

I'm rebuilding a Rochester tri power setup for an SBC 355. 4 of the 6 main jets have no size stamped on them and the 2 jets that are stamped 57 measure 54 with a number drill. Do you have any idea what is the correlation between actual drill size and GM jet number? My initial plan is to leave jet size alone and give it a try.

 

A good clue on where to look is that you say it idles fine with choke closed - it should not idle fine with choke closed, it is getting air from somewhere and the previous two guys suggest the 1st & 3rd throttle plates are likely cracked open. There may be more than one problem, like others suggest get it to run off the middle carbs first and go from there.

 

this is a good topic for a similiar but different thread, ok? We've all some some great answers and likely a fair amount of good intended bullshit but we aren't smart enough to respond to two people on the same thread.

 

Good one OJ. HAHAHAHA

 

Three stock non-tripower carburetors and bases, power valves still intact, home made progressive linkage, outer carbs have idle circuits plugged and butterflies positioned to seal as much as possible - the proof is in the pudding:

<iframe width="480" height="360" src="http://www.youtube.com/embed/xN4bd8fATF4?rel=0" frameborder="0" allowfullscreen></iframe>

 

the dag 213 product was used by the factory<<<!!!
i'm old enought to have rebuilt carbs on cars untouched? from the factory..........

did the factory use it or a dealer do it???