manifold & carb swap sb350, need info

[dukcaln]

so I am pretty sure I have some carb issues with the original q-jet. I have a howards roller cam, bored .30 over, headers, balanced and still run the stock 1972 manifold and q-carb. I have available to me a really nice manifold and carb set up and want to make the swap soon. I want to put on a Weiand x-celerator manifold and Edelbrock performer 1406 (600cfm) carb..... will I gain or loose anything. I think the manifold swap will be good for the performance and I was wondering will the carb work good. benefits disadvantages, please post your thoughts.......

[oldblue1968chevy]

pix of intake manifold is it dual plane spreadbore

[dukcaln]

can get picture later, how would I know by looking at it....... also should I do anything while the manifold is off, motor was built less than a year ago.... other than the obvious gasket replacement..LOL

[dukcaln]

single plane, here is the description off of summit about the aluminum manifold

These 360 degree Weiand X-CELerator single plane manifolds make their power in the 1,500 to 6,800 rpm range, which makes them the ultimate manifolds for high-performance street, drag, marine, and Oval Track engines. The carburetor mounting pad is designed to accept all current aftermarket performance carburetors, and includes an open-style plenum for increased flow. Best suited to engines equipped with aggressive camshafts, headers, and high-output ignitions, these intakes are sure to put a smile on your face

also I think the edelbrock carb will be a nice street carb for my son to drive back and forth to school....

[dukcaln]

anymore thoughts on this guys...

[oldblue1968chevy]

Single plane, like 1 big open squared hole

[dukcaln]

not sure the set up is on my father in-laws 68... he is installing a 87 tbi set up in his truck and I am taking the manifold and carb I mentioned and putting it on my set up... I just figured the weiand manifold has to perform better than the stock manifold from 1972..LOL as for the q-jet vs the edlebrock, I just have been having issues with the q-jet and think it needs a rebuild so in the meantime I would swap it out, the entire thing.... just wanting to know if it is worth it performance wise and driveability wise...

[oldblue1968chevy]

pix are worth 1000 words lol

[dukcaln]

I know but unfortunatley the manifold is on the other motor right now until next weekend

[D.PASSMORE]

IMO - Q-Jet (Spreadbore) is the best driving carb. You just have to keep'em tuned. They are easy to rebuild, they will get leaky around the the throttle shaft after many years fo use. But, if you want to keep it original - just use a good carb shop like Daytona Carb - http://www.daytonaparts.com/ . I have a edelbrock (squarebore) on another one of my trucks. Its OK, you just don't get the seconadry kick like you get from a Q-jet. Edelbrocks are fairly easy to tune to your motor. You can change jets/metering rods/springs in a short period of time. Plus they have instructions. Q-jet's: you have to read up on the operation and every time that you want to tune, you have to take off the top of the carb. I got lucky with my last one - World heads (76cc) - Sm. COMP Cam - wieand spreadbore intake - 2.5 dual Borla exhaust - original Q-Jet. The stock Q-Jet was running a little lean - so I put a rebuild kit into it and just installed larger jets. Stock jets were 74's and I used a 75's. Didn't change any thing else. Little mouse runs like its a 4x4 drag truck...
When installing the intake manifold, verify the correct intake gasket or you might be chasing vacum leaks. Use a new intake to carb gasket too. Thicker one seem to work better.
Have fun!

[dukcaln]

so would it make a difference if I changed the jets in the q-jet..... I was told the q-jet was rebuilt before I purchased the truck... it runs pretty good cause I got the vacuum leaks fixed byt I noticed with one of the jets I took out it looked worn at the tip

[D.PASSMORE]

Talking Q-Jet - the main jets and metering rods are inside the carb. If you referencing the adjustable screws on the outside - lower front, thats the idle circuit. You can adjust those by turning CW or CCW for best idle mixture. You should get a rough idle when turning in. Back them out until it smoothes out.
There is the other side of tuning the motor. correct timing - ignition system wear - or just a plain old tierd motor (low compression).
What are your symptoms?

[dukcaln]

motor was built a year ago and carb rebuilt same time, I was told. seems to run pretty good, just seems to me it should have alittle more power. put new plugs in gapped correctly, timing set at 10-12, higher to 12 from what I can tell. replaced fuel filter too. wires seem fine, were on it when I bought it. Have mallory electronic ignition on truck..

[D.PASSMORE]

Ignition sounds good -
Stock 2" exhaust? Stock heads? Stock manifold? Stock Cam? Whats the plugs look like? White - Tan - Black?
Have you done a compression check on all cylinders?
Any poping or backfire from exhaust or carb?
What gears are you running in rear end?

[RUSHNBOBO]

Originally Posted by dukcaln

so I am pretty sure I have some carb issues with the original q-jet. I have a howards roller cam, bored .30 over, headers, balanced and still run the stock 1972 manifold and q-carb. I have available to me a really nice manifold and carb set up and want to make the swap soon. I want to put on a Weiand x-celerator manifold and Edelbrock performer 1406 (600cfm) carb..... will I gain or loose anything. I think the manifold swap will be good for the performance and I was wondering will the carb work good. benefits disadvantages, please post your thoughts.......

What are your cam specs ?......on most all street applications a single plane kills low end torque, and will gain you some at 5500+ rpm (with the right cam and heads). The goal for a good performing street engine is average horsepower over the entire operating range..this is were dual plane manifolds rule. The best all around perfomance manifold for the street has been proven in test after test is a Performer rpm dual plane high rise.
It will beat the single plane in horsepower and torque almost every time until you exceed 5500-6000 rpm range. And you must ask yourself ....how often am I really spinning at 6000 rpm's ? probably rarely if ever, but from 1500- 5500 this is the range where most street engines live. And the dual plane will make you far happier when you feel the additional off idle through midrange torque, not to mention throttle response.

There are other brands which are comparable such as Weiand 8151C "stealth" dual plane.

[dukcaln]

some head work and stock manifold... roller cam hydr roller lifters. Headers and 3" exhaust. dual flows. cam is a tad over rv specs.. maybe the stock manifold is limiting the performance. 3.73 gears and I did have some back fire out the exhaust while letting off the gas coasting but since have fixed that with new plugs, and new vacuum lines. Would I benefit from more timimng. Set 10-12. closer to 12 right now. right now no popping, good acceleration no popping on deacceleration...

[D.PASSMORE]

I'm running a Weiand 8004/Spreadbore/Dual Plane. I have the original Q-jet on top with stock breathing system. Like I mentioned above, I just dropped 75 jets in the carb and it took away the lean condition. I could tell it was lean by looking at the plugs - white. A little backfiring on decel and aceleration was a little rough from 1700 to 3000 rpm. Let off the gas and it would smooth out. Secondaries hit with power - runs great - now.

BTW, you can get the jets - sold by Edelbrock. Check Summit Racing - they are there...
And, I looked on Ebay and there is a few good used intake manifolds up for auction. Look at the Edelbrock Performer too if you decide to make the change.

[RUSHNBOBO]

Originally Posted by dukcaln

some head work and stock manifold... roller cam hydr roller lifters. Headers and 3" exhaust. dual flows. cam is a tad over rv specs.. maybe the stock manifold is limiting the performance. 3.73 gears and I did have some back fire out the exhaust while letting off the gas coasting but since have fixed that with new plugs, and new vacuum lines. Would I benefit from more timimng. Set 10-12. closer to 12 right now. right now no popping, good acceleration no popping on deacceleration...

Unless your building a sprint car engine or a radical street strip engine a highrise dual plane is the best manifold for your application. The single plane is going to hold back your torque numbers and HP in all street rpm ranges. Especially with a "just above rv cam", you'll never even see the rpm ranges that the single plane thrives. The single plane will kill low to midrange fuel/air intake velocity (way to much plenum area), which in turn kills hp and torque, believe me I used to be into the bigger is better thing until I learned how engines work. It's all about velocity of the intake charge.

The 3 inch exhaust will also hurt your torque and hp numbers, don't use anything bigger than you need, it will cost you power and drive-ability. Save the 3 inch stuff for the big block crowd.

Don't get caught up in the 10-12 degree initial is the best for all engines. You want it as high as you can make it at all rpm's for max power.......here's how:

Alway's get the mechanical advance right first, then dial in the vacuum advance. Set your initial timing as high as 15-17 initial unless it's puts too much load on your starter, then back it down a little at a time . Next without the vacuum adv connected get the mechanical curve just short of pinging all rpm ranges; it should only ping in the most extreme conditions (high gear lugging engine up a hill) .....Now reconnect the vacuum hose and begin to dial in some vacuum adv a little at a time. You want to get it so it barely pings at cruising rpm then back off until ping goes away. (use an adjustable vac. adv. chamber) this is now optimized.....the max timing adv as possible in all conditions, which will give you max power, fuel mileage, and cooler running engine.

[dukcaln]

rush thank you, sounds very interesting and helpful

[dukcaln]

looks like we got the carb running pretty good. I think I am going to keep the q-jet and get a dual plane manifold