engine problems

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    Author Topic: engine problems  (Read 1946 times)

    Offline Nate10

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    engine problems
    « on: September 24, 2006 - 01:34:31 PM »
    I would like some help, please.  I have a 70 Challenger 340 orignal engine with modifications.  Has a Holley 4 barrel 750 carb, a TCI saturday night special torque converter and a hot cam.  All of these up-grades were done by previous owners.(I think that they are more down grades then any thing.)  Now the timing is so advanced you cant see the mark when adjusting, something like 20-25 degs.  When trying to adjust the timing back to 5 degs it hurts the engine preformance.  Right now it lags off the start untill 20-25 mph then it takes off.  So what do you think will be the best up grade I can do;

    1. Change the whole carb down a size to a 650
    2. Change the jets down
    3. Change the cam out

    It also has MSD ignition.  Eventualy I think I want to upgrade to a HEMI but not for another 5-10 years.  Any advice would be much appreciated.  I can only get about 5" of vacuum, my friend says thats to weak.  What sould vacuum be?
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    Offline MEK-Dangerfield

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    Re: engine problems
    « Reply #1 on: September 24, 2006 - 01:46:53 PM »
    If you only have 5" of vacuum, that indeed must be a HUGE cam. It must be mighty lumpy at idle.  :grinyes: Check out your spark plugs. If they look good, then your carb. should be good. With a big cam, it wants to be set more advanced than stock as far as timing goes. So something in the 12-15 degree BTDC would be a starting point.

     As a side note, the weak vacuum shouldn't hurt you unless you have power brakes.


      Mike
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    Mike

    1970 Challenger - SOLD
    2016 SXT+.  1 of 524 SXT+'s in Plumb-crazy for 2016.

    Offline Challenger6pak

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    Re: engine problems
    « Reply #2 on: September 24, 2006 - 02:46:37 PM »
    It could be a timing problem.  Maybe a bad chain or the cam was put in advanced/retarded.  Another thing I would look for is a vaccum leak.  After those are found to be ok, I would look at changing the cam.  A 750 carb set up right is fine for a 340.  If you go with a new cam the carb can be set up to match it.  The low vaccum reading is a concern. 
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    1969 Sport Satellite H code convertible, 1970 Cuda 440+6, 1970 Challenger R/T 440+6, 1970 Challenger 383 R/T auto, 1970 Challenger R/T 383 4 speed,1971 Challenger convertible.

    Offline Nate10

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    Re: engine problems
    « Reply #3 on: September 24, 2006 - 04:07:37 PM »
    there is no vacuum leak I took 2 hrs trying to find one and nothing.  when we put the timing back to stock the vacuum came up to 7-10 but there was no muscle just hesation.  my friend told me that on the old cars the harmonic balencer could have sliped on the rubber.  ever heard of this happening?  and if you recommed changing the cam which one should i go with?  I have no bottom end I mean i cant even burn the tires, and I 've tried everything.  the engine just loses everything when below 20 mph.  it is very lopey at idle, and when stoped the car lurches foward due to the crapy idle.  It sounds awesome but just cant get up and go to much hesataion, very frustrating.  the plugs are plautium ones which look black on the outer ring and deep chocolate on the electrode and top of the post(whatever its called) I dont have power brakes but as a daily driver I was thinking of converting but not till I get some more vacuum.
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    Offline Bullitt-

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    Re: engine problems
    « Reply #4 on: September 24, 2006 - 04:27:06 PM »
    Nate, hang on for some of the HOT RODDERS to give you direction on how to time a cammed engine. In the mean time here is a link to sudy about carbs that has helped me understand them much better.
    http://www.chevyhiperformance.com/techarticles/83118_carburetor_basics/
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    Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
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    Offline Chryco Psycho

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    Re: engine problems
    « Reply #5 on: September 24, 2006 - 08:57:22 PM »
    the carb seems about right , the plug color is close & slightly on the rich side which is safer
     it sounds to me like you either have a mismatched parts combo or the cam is too large
     can you give us more specifics about the engine ? What cam, intake, stall rpm , rear gears etc 
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    Offline moper

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    Re: engine problems
    « Reply #6 on: September 25, 2006 - 10:05:09 AM »
    Definately need more info. From the sound of things, you may not be able to answer them. If you have cam part number, that would really help. Also, is the engine rebuilt or not? If so, how long ago? If you dont know, then the only thing really you can do is do a few tests and see what the results say. From the sound of it, it may only be tuning, and it may be a cam timing issue.
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    Offline 426 pentastar

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    Re: engine problems
    « Reply #7 on: September 25, 2006 - 10:07:46 AM »
    You need a total of 32 degrees total timing
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    Offline Nate10

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    Re: engine problems
    « Reply #8 on: September 25, 2006 - 04:00:51 PM »
    Man I feel so car dumb right now.  I have no idea what cam it is, all I know is that it was put in two owners ago at least 5 years or more and thats the last time anyone has touched the engine. The rear end is the standard 8 3/4 without posi was the A66 package but no other info on the fender tag.  Has an Edlebrock intake dont know which one (where is the part number) and for the stall it was TCI saturday night special.  I know that all the parts are mismatched, so if I change the cam out which one should I go with?  Or just leave it as is and wait untill I get a new engine 5 yrs form now?  As far as 32 deg Im probly pretty close right now only have about 1/16 turn left on the advance side.  I hope that this helps a little, I do know some about cars but not the total ins and outs so I really appreciate all the inputs!
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    Offline MEK-Dangerfield

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    Re: engine problems
    « Reply #9 on: September 25, 2006 - 04:15:12 PM »
    It would be nice to know what intake you have, what the stall converter rating is, and what gears you have in the rear end. I have a feeling someone took a basically stock/mild set-up and put a HUGE cam in there. I say that because you have no bottom end performance.


      Mike
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    Mike

    1970 Challenger - SOLD
    2016 SXT+.  1 of 524 SXT+'s in Plumb-crazy for 2016.

    Offline Chryco Psycho

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    Re: engine problems
    « Reply #10 on: September 25, 2006 - 10:31:20 PM »
    Tuning will help it but May not fix it
     a driveable street cam is the Engle K56 , it works well with mild upgrtade & could solve the problems
     there may or may not be a part # on the intake but usually somewhere there is a name cast on it , see if you can find something on it 
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    Challenger - You`ll wish You Hadn`t

    Offline moper

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    Re: engine problems
    « Reply #11 on: September 26, 2006 - 06:08:16 AM »
    At this point, I dont think replacing anything wihtout knowing where you're starting from is a good idea. Find a local performance shop, have them take a compression test, and get numbers for the intake and ignition. If you dsont know about stuff, buy a few books and learn. You'll spend a ton of money on testing hunches unless and until you know what you have now. From the sound of it, you need to do some reading.
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    Offline Challenger6pak

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    Re: engine problems
    « Reply #12 on: September 26, 2006 - 10:08:27 AM »
    Quote from: moper on September 26, 2006 - 06:08:16 AM
    At this point, I dont think replacing anything wihtout knowing where you're starting from is a good idea. Find a local performance shop, have them take a compression test, and get numbers for the intake and ignition. If you dsont know about stuff, buy a few books and learn. You'll spend a ton of money on testing hunches unless and until you know what you have now. From the sound of it, you need to do some reading.
    :iagree:

    You will need a matching package for your engine to perform properly.  What performance level you want from your engine will dictate the package.  You may just have a mix-matched package of good components that is causing poor performance.
    « Last Edit: September 26, 2006 - 10:14:12 AM by Challenger6pak »
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    1969 Sport Satellite H code convertible, 1970 Cuda 440+6, 1970 Challenger R/T 440+6, 1970 Challenger 383 R/T auto, 1970 Challenger R/T 383 4 speed,1971 Challenger convertible.

    Offline Nate10

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    Re: engine problems
    « Reply #13 on: September 26, 2006 - 12:34:01 PM »
    I looked up the intake and have an Edlelbrock Performer RPM.

    This is the description of it:
    Performer RPMs are dual-plane, high-rise intakes with 180° firing order to produce incredible top-end horsepower while retaining good throttle response. Their larger plenums and runners match the free-flowing exhaust, high-lift cams and other modifications of a high output engine. They are intended for high-performance street or competition engines that run up to 6500 rpm. They are not for emissions-equipped engines. A Performer RPM gives you the ultimate in street high-performance.
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    Offline Nate10

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    Re: engine problems
    « Reply #14 on: September 26, 2006 - 03:32:25 PM »
    okay I found out a little about the carb:

    Holley 4160, 750 cfm, #0-80508-1

    these 2 sights tell every thing abuot it all specs

    http://oldholden.com/possible/index.php/Holley_Information_Table1

    http://oldholden.com/possible/index.php/Holley_Information_Table2
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