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Old 07-06-2013, 01:12 PM
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Tunnel Ram Questions

I sent this PM to PJ (painted_jester) a week ago and he asked me to put this up on the forum for everyone else to see. Feel free to chime in, guys. I'm always looking to learn more from the guys who've been there and done that!

Little background on my build.

350 SBC bored .060 over
10:1 compression
Mallory distributor with the magnetic pick up, no mechanical or vacuum advance
Double hump heads with the big 2.02 valves, ported and polished for better flow
1 5/8 inch headers
MSD 6A ignition box
Weiand 1984 tunnel ram intake port matched
1.6 ratio rockers
Summit Racing Camshaft, Hydraulic Flat Tappet, Advertised Duration 313/328, Lift .508/.533

All on a 1968 Chevy Camaro RS

I've been wanting to change out to a solid roller cam in the future and AFR 210cc aluminum heads but that's still months away.

Quote:
Originally Posted by painted jester
Quote:
Originally Posted by GoFastStripes
Hey PJ, I know you're the tunnel ram guru on the board so I sent ya a PM instead of posting a new thread on the hotrodding subforum.

I posted a question a few months ago and you commented on how my Holley 450s were killing the performance of my tunnel ram. I used to run twin Holley 600s in place of them but I kept fouling my plugs even when I ran hot plugs.

If I put the 600s back, do you think I should put in smaller jets? I have 54s on my 450s (same as the 600s I had) right now and I'm running slightly rich, so what do you think I should do?

The 600s have vacuum secondaries, and the 450s are mechanical. Won't cylinders 3, 4, 7 and 8 run lean if I don't use mechanical secondaries?

Regards

I am not the tunnel ram guru LOL! FBird and a few others are in the same category and answer T ram questions the same (as I do).

Yes, The vacuum secondary's, cause lean conditions on a tunnel, till Rpm and fully open throttles and equall fuel and air flow are met the center squatters are the best for equal distribution. Jets are not the only thing that fouls out plugs, you may have unmatched power valves or need to remove and plug the power valves and and step up your jetting! High Resistance wires and plugs will kill your spark intensity run non resistor plugs and try to find low resistance wires I run 40 0r 20 Ohm per foot wires, the choke towers on the carbs effect air flow and cause gas puddling in the intake at street idle speeds idle! the PCV needs to be T'ed to both carbs! or plumbed to the intake plenum right in the center of the carbs so it is equalised to the runners! or install a pump or other type crank case evacuation system. Ignition timing and idle speed also effect fuel mixture, and low compression engines and high octane fuel will fowl plugs! The altitude in areas of the country and air temp will effect jetting ( one size jets when temp is cool in the morning or evening and a jet change in the afternoon as the air temp gets hotter) 450s are good for a street small block and around 600s up for a street big block, but at the drag strip or street racing much bigger carbs are needed because of the ram effect of the high ram intakes and tuned long tube headers with at least 18 inch collectors for scavenging and exhaust velocity!!! If the exhaust is slow and restrictive you will fowl plugs quick!

Please put this on a tread My eyes are bad and I have a hard time seeing and I am not on here much in the summer months and the info is needed by other members and guests. Copy this PM and past it on a new thread! and I know FBird and others can help add to this! You need to track tune or find a safe place to test and tune in real world conditions A Dino tune helps get you close but its in controlled conditions so on the street or track its not conclusive!!!

Jester

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Old 07-06-2013, 07:19 PM
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Chris is a great member and always helps when he has time. So thanks for posting and thanks to Chris for his efforts
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Old 07-07-2013, 05:03 PM
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Based on the cubic inches and the heads and compression that you used in your build your choice of cam is hurting you with excessive duration. I would swap it out for this:http://www.summitracing.com/parts/hr...make/chevrolet The vacuum secondary 600's will work as they will regulate the CFM's that your engine demands, you will want to use Holley's trick spring pack to find the sweet spot and try a 25 or 35 power valve in them.
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