73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: Wac93 on March 14, 2014, 10:05:10 PM
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Looking into buying a new carb, intake, and headers for my 76 K20 with a 400. The motor is stock and I have a few questions pertaining to the selection of these parts.
It already has a quadrajet, but my uncle wants to buy that off me so he can rebuild it himself. This question may start a hot debate, but should I get a Holley or Edelbrock carb? I will probably stick around the 600 - 650 cfm because it is a stock motor and doesn't need a big ol' 750.
Next, what should I get for a manifold to match the carb selection? I was thinking an Edelbrock performer rpm air gap, but am open to suggestions as long as it is a dual-plane.
Last question is what do you guys run for headers? long tub or shorties? 1 5/8 primary with 3 inch collector on a stock motor? Also, would it hurt if I run dual 3 inch exhaust with the stock motor, or is that too big?
Open to any advice. Hoping to get some input on how the headers fit on somebody else with a small block k20.
Thank you
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a stock motor you dont need anything over 570. tell you uncle to go the the junk yard and get a quad and rebuild it. keep the quad. most of us run long tube and 2.25 or 2.5" exhaust 3" is too big and 2.25 is a little big it can handle up to 200 hp.
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I got a pretty stock 350 and a 600cfm edel, long tube headers with 2.5 exhuast. I think I should have gone 2.25 to get some of the backpressure back but I love the sound and it is probably better for the mid to high rpm. also I'm putting resonators on (monza dual exhaust tips) and it may help with backpressure too
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I just read you have a 400 motor the 2.5 would probably be perfect you may even be able to go 3"
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also I think shorties will give you more low end torque where te long tubes give you more midrange torque.. I want more low end but I really love the look of long tubes
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Q-jets are great carburetors, and unless you really want to let your uncle have it, I'd recommend keeping it. But, if you get rid of it, I'd recommend replacing it with a Holley. I've had several, and they've always been great carbs. Easy to work on and fine-tune, from my experience.
For your intake, I'd recommend the Edelbrock Performer line of manifolds. The RPM range is closer to what a stock engine runs, and from what I understand, the 'air gap' feature often cools the carb area down too much. Too much as in if you drive your truck during the winter months, you'll likely have problems with a frozen carburetor.
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Couple things:
1) Small-block K10 here. Go with Hooker long-tube headers. People on this forum have had problems with other brands fitting on the 4x4 trucks. There is a clearance issue with the driveshaft.
2) 2.25" is plenty for a stock motor. As Irish_Alley notes, 2.25" can handle 200 hp per pipe -- that's 400 hp total, and you aren't anywhere close to that and aren't ever likely to be.
3) The air-gap manifold will keep the carb cool in hot weather. It will also keep the carb cool in cold weather. If you go with the air-gap manifold, you must keep the stock intake setup, with a heat riser off the headers supplying warm air to the vacuum damper in the air cleaner snorkel. I have the air-gap and love it, but you will get really bad performance in cold weather without warm-air induction. You know how an engine runs when you first start it in the winter, before it warms up? Well, that's how it will run all the time with the air-gap without warm air induction. That being said, the engine runs better with the air-gap and warm/cold air induction because the carb is always in the optimal temperature range. Here is my setup. Here's the write-up: http://forum.73-87chevytrucks.com/smforum/index.php?topic=27239.msg226597#msg226597
(http://users.rcn.com/weyand/smalls/dsc03923small.jpg)
4) The Qjet is the best street carb of your choices, with great mileage and throttle response. Rebuild it yourself. Your uncle can buy another old Qjet at the junkyard. Or you could buy the Edelbrock or Holley and spend more money to get worse mileage and throttle response. Up to you.
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rich whts kind of plug wires of you have?
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Rich, I remember seeing that write-up, and marveling at your skills. You made it look like it came from the factory that way. Outstanding, sir!
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rich whts kind of plug wires of you have?
No clue. The shop changed them when they put in the new engine. I do the planning, and I'll do stuff like the bucket seats and electric fan and stereo and the induction system, but if it's heavy, requires a lift, or is messy, the shop does it.
Looking at the original photo (much higher resolution), the wires say Belden Premium 8mm MAX PROTECTION MAX POWER. I think this is them.
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Spark-Plug-Wire-Set-Premium/_/R-BEL700254_0065544082
Rich, I remember seeing that write-up, and marveling at your skills. You made it look like it came from the factory that way. Outstanding, sir!
Very kind, but it wasn't hard. Within the skills of everyone on this forum for sure. The hardest part was finding a stainless steel exhaust tip that would work, finding the machine shop to cut the slots in the back, and thinking up using the dryer tube for the cold air induction. The heat riser pipe was the most actual work. I just cut the stock pipe up into pieces, cutting about a half inch away from each curve to leave some straight to bond to, discarded the straight sections, and then cut new straight sections from flexible exhaust pipe stock. I assembled these all to fit, then cemented them together with JBWeld, let it cure in place, then pulled it off and primed and painted it.
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also I think shorties will give you more low end torque where te long tubes give you more midrange torque.. I want more low end but I really love the look of long tubes
Long tubes are more for lower rpm torque.
Shorties are more for higher rpm horsepower.
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ive had both a holley and a edelbrock both are a good carb when adjusted properly as for an intake ive only had a edelbrock intake i forget what it was and as for headers get the longtubes if you can
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I have both a holley and an edelbrock. The Holley feeds fuel through my Edelbrock air gap intake and is quite a nice setup. The Edelbrock carb i have holds my walk-in door on my garage open on nice summer days and thats all its good for. They'll run alright straight out of the box and never be better than that. As for a q-jet, great carb as long as you have someone with a PHD around to tune it. Long tube headers are ALWAYS better performance wise in every rpm range. Sometimes the shorties are a more cost effective solution or a better fit, but they never flow better than a long tube.
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I personally like Holley carb's. An Holley 600, vacuum secondary would be a good choice.
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JMHO-
Stock, keep the Quadrajet.
Go fast streeter, Holley, Edelbrock Perfomer Air Gap.
And any truck, stock or modified, Hooker long tube headers.
I will differ from the other guys by saying I love the bigger collectors. The long tube headers will be the best choice to offer the proper amount of back pressure, and pulse timing, to prevent over scavenging of your engine. However, once past the primary tubes I want there to be as little restriction to the exhaust as possible. There will still be enough heat in a 3" system to keep exhaust flow velocities at an efficient level.......and the sound is deeper without so much of that small block cackle.