Author Topic: New engine build need help prior to dyno  (Read 322 times)

Offline equidr

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New engine build need help prior to dyno
« on: December 12, 2021, 03:54:11 PM »
Engine is a Pontiac 461, zero deck forged rods and pistons.  SD performance 300cfm D-ports with Dave's light valve spring and retainer package.  Dave's Old Faithful 2.0 cam (236/245@ .050 with 112 LSA). Compression is 10.7 to 1. Carb is a 17057274.
This Carb was on an engine prior to a flood. Previous combo was the same short block with 295 cfm D-ports and Dave's Stump puller cam (230/236@.050).  The Carb was flawless for 5 years, it ran like fuel injection.
Current Carb Specs,
Idle Tube   .038
Idle Down Channel .055
Lower Air Bleed  .070
Upper Idle Air Bleed .070
Main Air Bleed Body .070
Main Air Bleed Airhorn .070
Main Jets          .073
Primary Metering rods unknown but are Tapered
Secondary POE well rest.   .038
Secondary POE rest.  .059
Secondary Tube rest. .036
Secondary Hanger   F
Secondary Rods    DA
Idle Bypass Air .098
Idle Screw holes .100
Choke Pull off aprox. 1 sec

The current engine is going to the dyno soon.  I'm going to dyno it with a ported torker II and a Holly, and a port matched RPM with my Quadrajet.  Similar combos have made 600 HP and 600 torque.  I would really like to run my Quadrajet  on the street and strip.

I'm pretty confident that the Idle circuits of this carb are going to be very close for the new combo.
 I am getting ready to order parts to complete the build of this carb. I want to have everything I need for the dyno session. 

Here are my questions:  What should I have on hand as far as Hangers and secondary rods to optimize this carb on the dyno.  I feel that I need to go up to one jet size on the primary's from my  measurements of my primary rods to achieve the desired difference between the jets and rods? Do I need to go up to a .045 needle and seat to feed this engine?  What if any modifications do I need to make to the Idle circuit?  Which power piston spring would be the best place to start.

Sorry for the long post.  Wanted to give all the details I can of my situation.

Online Cliff Ruggles

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Re: New engine build need help prior to dyno
« Reply #1 on: December 13, 2021, 04:12:09 AM »
Measure the primary metering rods to see what they are?  Make sure they are the correct length for that style carburetor.  All factory rods were stamped but not a big deal if they aren't, just measure the largest diameter of the upper section and tip diameter.  They should be tapered between steps unless they are "K" rods then they will only have .005" taper on the upper section.
That carb has an APT system so they may be fine without changing them.  .073" main jets are plenty for what you are doing.

You will need the larger N/S assembly and I'd get one of my HP accl pumps at the same time.  The idle system should be close, I'd try it as is then go back and make changes if/as needed.

For dyno tuning it helps to have a nice assortment of custom machined secondary rods from the same cores, but not required.  It just helps make predictable changes without messing with hangers as factory rods are all over the place for tip diameter, length, included angle leading to the tips. etc.....Cliff

Offline equidr

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Re: New engine build need help prior to dyno
« Reply #2 on: December 13, 2021, 02:24:15 PM »
The primary rods I have must be K rods.  There is some corrosion from the flood that makes it impossible to read any stamping.  There is very little taper on the upper part, .005 with my calipers. Is there a better primary rod that you would recommend?  Do you sell the custom secondary rods?  If so I will add them to the order I'm going to place this week.  I'm asking all this so that I can make one complete order when I call.

Thanks for all your help!

Online Cliff Ruggles

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Re: New engine build need help prior to dyno
« Reply #3 on: December 14, 2021, 01:12:32 AM »
I have much better primary rods that are full taper for those units.  I'm here 7am-4pm M-F EST.  If I don't answer leave a good number and why you are calling and I'll call you back.....tks......Cliff

Offline 70GS455

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Re: New engine build need help prior to dyno
« Reply #4 on: January 02, 2022, 03:26:49 PM »
What is the sec air door opening?