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Technical 315 Dodge hemi with 3 2 barrel carb setup

Discussion in 'Traditional Hot Rods' started by Cubzy, Dec 28, 2016.

  1. Cubzy
    Joined: Jul 13, 2016
    Posts: 56

    Cubzy
    Member
    from Canada

    I recently purchased a 1931 Ford coupe with 315ci Dodge Hemi motor. Motor has been rebuilt with 9:1 compression ratio pistons.

    Details:
    Offenhauser Intake manifold.
    Mechanical fuel pump with Holley fuel pressure regulator set to 2.25psig.
    Pertronix distributor
    Fuel log upstream of carbs. One Inlet and three outlets.
    Cam is stock. Unable to purchase reproduction cams for these early 315 Hemi's.
    Carburators are from Speedway. They are 9Super7's. Remake of the Stromberg 97's. Center carb has idle circuit, choke assembly and two outside carbs are different. Only accelerator pump on those. No idle mixture screws or choke. Comes with a No. 65 power valve and 0.045" main jets, identical to the stock 97. Rated at 150cfms per carb at 15 inches of vacuum.
    Progressive throttle linkage.
    Sanderson Limefire headers.

    Seller tried to run all three carbs when the car/motor was built . Said it didn't run well. Said camshaft wasn't lopey enough. What he did was install a ball bearing in the fuel lines to the two outer carbs to prevent fuel from entering them. Two outside carbs still take in air when throttle linkage is greater than 50% open. Only carb functioning is the center 2 barrel carb.

    Since buying car I replaced fuel pres. regulator as old one didn't regulate fuel pressure. It showed 5.5psig which is far higher than what the 97's are stated to like. No more than 3psig. Now currently showing 2.25psig. What I'm wondering is can I run these carbs with some tuning. Potentially re-jetting. Are the two outside carbs suppose to be different from the center primary carb? Was there just to much fuel pressure before when he tried running them causing problems? I would love to get them to be functional vs just for looks.

    What tools are required to do this? Do I need a Uni-Syn tool for syncing carbs? I have vacuum pressure gage and adjustable timing light. Car currently running 10 degrees BTDC and 32 Total at 3000RPM. Vacuum at idle is 16 inches mercury.

    Car is not very peppy currently. Wondering if it would come more to life with the extra 2 barrel carbs working? According to calculations with 315 ci and 280hsp it shows I need about 350-400cfm. Currently only running about 150cfm with the one carb.

    Thank You in advance for any guidance. I will post pictures later. Sweet looking Highboy Hot rod.
     
  2. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,856

    302GMC
    Member
    from Idaho

    I'd be looking for a 4 bbl intake & a 4GC Rochester or WCFB Carter, myself. Then, we got 14'' of snow ...
     
    LOU WELLS likes this.
  3. Hombre
    Joined: Aug 22, 2008
    Posts: 1,075

    Hombre
    ALLIANCE MEMBER

    I am sure there will be some folks chime in with some good tech information for you and your dodge Hemi, I will say this. Everything I have read and I mean every word speaks to the inadequacies of the Speedway reproduction of the 97. I am not saying throw them away and get some real 97's but you do have your work ahead of you --I think. Now with that said there are some cats here on the HAMB that know and I mean really know there way around the 97, listen to them!

    I am a guy who really likes a tri power, it is Hot Rodding 101 to me. I say do NOT go looking for a 4 brl make that damn thing you have work.

    Also I am not sure why you think cams are not available for the 315 Dodge but I am sure that Hot Heads can at the least regrind your cam, and they do have a Roller Cam and lifters for your engine. Granted the roller is not a cheap thing to do, but it after all a 315 Dodge Hemi and its not supposed to be cheap.
     
  4. First thing to do is take those speedway carbs off and throw them in the scrap bin, they are junk and made overseas. A set of real Strombergs, vintage ones in excellent shape for rebuild or brand new ones from england, will help you out immensely. The primary carb is in the center and it has the air fuel adjuster screws and idle speed screws. The outers do not have idle circuits as you have noticed. That is normal. The fact that the outer carbs are not blocked off at the base means you're running incredibly lean right now. Lean is bad in excess, causes hot running engine, no power, pinging and misfires, etc. The guy you got it from sounds like he talks out of his ass a lot, 3 small 2 barrels on that engine will be sufficient without a huge gnarly cam. It still might not even have enough cfm at prolonged wide open throttle but it will run hard. Also you should be able to run a later factory electronic distributor from the LA series mopar V8's. It's a drop in unit with an external control module the size of a big smart phone. Minimal wiring required to make it work.
     
    loudbang likes this.

  5. bostonhemi
    Joined: Dec 1, 2011
    Posts: 695

    bostonhemi
    ALLIANCE MEMBER

    If you can find a 4v intake for the 315 it would probably cost nearly as much as the 3x2 maybe $80 less. The cam can be reground. I asked HH about having it done and they recommended racer brown. If you do have it reground, you should get adjustable pushrods or adj. rocker arms ($1000). I think the 3x2 is nice. A friend has them on his 315 and I think he used GTO carbs. gl
     
  6. 47streetrodder
    Joined: Oct 27, 2007
    Posts: 104

    47streetrodder
    Member

    Check to see if prior owner installed block off plates under the two secondary carbs. Then verify the accelerator pump rods on all three carbs are on the summer setting where the pup rod attaches to the throttle shaft. Disconnect the coil wire so the engine won't fire and crank it over a few times to make sure gas is getting to all three carbs. Check the secondary carbs for gasket leaks. The gaskets are probably dry and might leak and you don't want an engine fire. If everything checks out, reattach coil wire and fire it up. Stock engine should be able to handle 3 Strombergs with no trouble.
     
  7. Brett Wells
    Joined: Oct 13, 2016
    Posts: 54

    Brett Wells

    Hi there
     
  8. Brett Wells
    Joined: Oct 13, 2016
    Posts: 54

    Brett Wells

    Hi there, I have a 315 Ddoge Hemi, Offenhauser makes 2x4 and 3x2 alloy aftermarket intakes for them, as for cam try Chris Neilson in Utah, contact Hot heads they will have a contact number for him! I say stick with the 3x2 Offenhauser manifold and try a Stromberg 48 in center position, and Stromberg 97's on the ends, have you got a progressive linkage? It would run better with all three carbs with fuel and a progressive linkage bringin on the 48 first, then the 97's on with higher revs! Check distributor advance is working, a 331 or 354 Chrysler factory twin point dist will fit, vaccum advance for a street motor will give you improved torque low down in the rev's and won't drink gas like it's going out of fashion!
    Set initial advance by vaccum gauge, set where vaccum is highest at idle. Check your spark plugs are in good condition and correct for 315 Dodge Hemi, I have the plugs numbers if you need them, I will need to find the old champion plug book , I am only on the HAMB once a week at Library in town! If still motor still lazy, check compression in each cylinder, and you could lift valve covers and turn over slowly and check lift on each rocker arm to see if a cam lobe is worn out? If compression is low in a cylinder, borrow a cylinder leak down tester to see if leak is in Valves or rings/Gaskets/Pistons etc, hope this helps out. Keeping the the Firepower lit!
     
  9. 73RR
    Joined: Jan 29, 2007
    Posts: 7,174

    73RR
    Member

    Actually, it is not a drop-in. The LA distributor does drop-in to the 241-260-270 but the 315-325 has a taller deck.
    Cam is easily reground but, as mentioned, you will then need adjustable pushrods and new lifters.
    Happy to assist with the cam if you need.

    .
     
    loudbang likes this.
  10. Cubzy
    Joined: Jul 13, 2016
    Posts: 56

    Cubzy
    Member
    from Canada

    I was told cam was reground. Just not very aggressive. Quite stock. Was told it already has adjustable pushrods and new hydraulic lifters. Do you think its worth trying to get going with what I have? I was even thinking of putting fuel to one secondary carb at a time. Start with the back one. Currently primary carb is set to winter mode and secondary carbs are on summer setting.
     

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    bostonhemi and LOU WELLS like this.
  11. 47streetrodder
    Joined: Oct 27, 2007
    Posts: 104

    47streetrodder
    Member

    Running it with one secondary carb at a time is a bad idea. Every time you open up the secondary carbs, the carb without fuel will act like you have a huge vacuum leak.
     
  12. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 9,214

    mgtstumpy
    Member

    Some reading. I don't run either carbs.
     

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  13. 73RR
    Joined: Jan 29, 2007
    Posts: 7,174

    73RR
    Member

    Certainly easy enough to see what pushrods are there.
    If the first regrind was not very aggressive and the lobes are still good then a second cut is possible.

    I would get the engine running with what you have. I would block off the end carbs (remove them and plate the manifold) and after you are happy with the single 2bbl then add on the end carbs.
     
    loudbang and brigrat like this.
  14. bostonhemi
    Joined: Dec 1, 2011
    Posts: 695

    bostonhemi
    ALLIANCE MEMBER

    Thanks for posting your car pics. It a really nice looking car.
     
  15. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,795

    jimmy six
    ALLIANCE MEMBER

    Not familiar with the Offy for the Dodge but for other engines they were POS. I know the yblock was and there is a guy on the net who makes the Buick one work. It had to do with the way the passages were cast. I've run 3-2's many times and both w/wo end carb idle adjusters and had no mayor problems with each with out them the outer butterflies had to be closed. Due to the typical vibration of an engine you need to open them up often to keep the end bowls from over filling. I set the outer floats 1/8" low to help with this. Just as an opinion Rochester 2GC's were the best. Good Luck..everything looks better with a Hemi under the hood.
     

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