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Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by ed rex, Nov 26, 2001.

  1. ed rex

    ed rex Registered Member

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    Good day. Put headers and 2.5" exhaust on my 454, a change from stock BB exhaust and 2" 'peashooters'. Should I dial in the timing differently? I have it currently at 8 degrees before. Also, what about the difference in back pressure? I noticed an increase in overall power but going up hills and under measurable load, she seems to lose significant power. Suggestions?

    Thanks, Ed
     
  2. Steve_Chin

    Steve_Chin 1/2 ton status

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    Congrats on getting the headers on that monster!

    Initial timing doesn't mean anything WRT power production. What does your ignition curve look like? I'd try to build a curve that got 34 degrees of total timing (initial plus mechanical, no vacuum) at 2400-2600 RPM. Try to get a distributor kit and set up the distributor accordingly.

    Did you make any carburetion changes? Often, headers increase the efficiency of breathing and require the carburetor to be jetted a little richer.

    The need for backpressure to make power is an old wives' tale. If the headers are designed properly for your camming and the other tuning aspects are correct, you should make more torque and power with the header than with manifolds. If that old wives' tale were true, don't you suppose that racers would be running restrictive exhaust systems? FWIW, on one of my cars the supposed experts in this state told me that the header I was going to run was way too big and that I'd lose power. After I got the exhaust setup and tuning done, I gained .15 sec. in 60 foot times and 4 MPH on the far end of the quarter mile over the suggestion proffered by those "experts."
     
  3. ed rex

    ed rex Registered Member

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    Thanks Steve for the clarification. With your response in mind, sounds to me like she just needs the basic tune up. On a positive note, I could swear that the header/2.5 inch exhaust combo dropped my operating temp another 10 degrees.

    Ongoing exploits last night: swapped the rear end out. Yup. Removed the 1-ton/detroit locker with 3.73 gears in favor of a 1-ton/detroit locker with 4.56 gears. Theory being that if I like the performance for the last 2 weeks of pheasant hunting, I'll go ahead and do the front axle swap as well. This axle has sat for awhile and the brakes are 'sticky'. The passenger side would hardly even turn so I took it apart, readjusted (shoes looked like new, but then again has anyone really ever seen 3 inch wide brakes that were worn?), douched with brakleen then reassembled. Now the drivers side has intermittant sticking but it was getting late and I decided to finish tonight. Initial results down the road and back were very favorable!

    Next operation will be to swap out that 'useless' torquer intake manifold with the performer. A buddy of mine really wants that torquer for some street rod he's building and has a new performer to trade. Just waiting for delivery.

    Ed
     
  4. Steve_Chin

    Steve_Chin 1/2 ton status

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    Cool beans, Ed. That Torker is a lousy manifold for a truck anyhow, so you're doing yourself a favor trading it with your friend for a dual plane. Is that Performer an RPM or a regular Performer? The RPM offers a bit more top end because it's a high-rise design and has larger port cross-sections.
     

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