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Author Topic:   Question for KP or carb guys
ryan
Member
posted March 29, 2003 11:32 PM
I was wondering on starting size of jets and rods for a q-jet. 355 10.5 to 1 Bowtie Heads 530-550 lift cam. Headers are glowing I beleive we are rich. Went down in jet size and and primary rod size. The still started to turn orange but took longer to get there.
It kinda baffles me we ran the same carb at the end of last year with a .504 cam and stock 993 heads with no problems that I knew of. p.s I am not very fluent with carbs thats dads area. Dad has done a few things to make it work well, but I don't know what he all did.


outlawstock17
Member
posted March 30, 2003 04:36 AM
check the timing. retarded timing will cause high exhaust gas temps.


KPLugnut
Member
posted March 30, 2003 05:34 AM
That is true, retarded timing will cause headers to glow excessively. That'd be the first place I'd look rather than tearing into the quad.
You didn't say what your plug color looked like, or your engine temps. If you are off on primary jet/rod size, symptoms will show up there as well as in performance, i.e., "popping", low power, or "blubbering".
Also, by dropping down on BOTH the jet AND metering rod size, you may not have changed your fuel metering as much as you thought. To really change it, just change the jet size, OR just change the rods.
And don't forget that the main "brain" of every quadrajet is the secondaries. The air flat tension, secondary rods, and how the secondary rod cam positions them is where all your top end "lean" or "rich" conditions will occur because the primary side of a quad is far too small to feed a V8 motor on its own.
This is not to say it can't be done, tho.
Anyway, I'm rambling. sorry.

I'd start with about a 72 jet in the primaries, and if memory serves, there are 3 primary rod sizes available. The middle size is where we start our carbs at.
If you need jets or rods, let me know.

Hope that helps,
KPLugnut


ryan
Member
posted March 30, 2003 09:00 PM
Wouldn't an intake leak cause higher temps on the exhaust also or is my thinking reversed? Took off the intake today thinking that was the case and the gasket looked like it might have been the wrong one. It looked to be not centered on the heads(too low on the bottom fine on the top).We had checked the timing was o.k. When we shut it down it makes a blub blub type sound. It is also missing. Right now the carb has 73 or 75's don't remember off the top of my heads. Primary rods are 49's Don't remeber the secondarys either. Any light you can shine on this sure would help. Racing is 2 weeks away.

[This message has been edited by ryan (edited March 30, 2003).]

ryan
Member
posted March 30, 2003 09:06 PM
On a carb website I found 12-13 primary rod sizes. A guy I know said to run 47's and the 3rd from the largest on the secondarys. Plugs looked black.
How much for rods and jets.
rewessen@ptcnet.net http://www.carbs.net/rodshang.asp


KPLugnut
Member
posted March 31, 2003 10:07 AM
Go ahead and run the 47 primary rods, and like your friend said, the CK secondary rods, but I'd still put 72 jets back in it.
That site supplies more options for rods and hangers than I'm able to get my hands on, but our internal work goes beyond anyone's.
Anyway, if the plugs are black then you've got to jet the carb down, but your glowing exhaust is likely to be retarded timing, or some other reason for fuel burning while it's going out the exhaust.
Your intake gasket issue is not likely to cause your problems unless you are sucking oil into the ports from the lifter valley (which would explain black plugs).

Let us know what it does when you reassemble.

KP

ryan
Member
posted March 31, 2003 07:06 PM
Don't know what sec. he had in before but it had 75 jet with 51 primaries.

Secondaries I have
Dg- 0337 running currently
Au 0527
Cv 0527
Ch 0567
73 jet
49 primaries
We tried this setup and it took about 10 minutes for them to get orange. Dads setup has always worked well until now.
Dad wants to know why the little spacer in the carb (looks like a little black cup) fills up with fuel he says its not supposed to, but he doesn't know if it is hurting anything either. The float level is set at 5/16 on the bench. Also friends recomendation was 3rd from the biggest that chevy dealer had I don't know if its the same as what was on the site or not. Tried timing at anywhere from 34-39 no changes. Motor will be back in tommorow possibly.
Thanks kp


ryan
Member
posted April 01, 2003 09:28 PM
ttt


KPLugnut
Member
posted April 02, 2003 09:21 AM
Hmmm...sounds like you have an internal leak or mismatched gasket problem in the carb there. If I'm reading you correctly, the cavity you described should NEVER get fuel in it and if it does, the carb is leaning itself out there, and/or pulling unwanted air from somewhere.
Your jetting and rod combos should not be THAT far off to cause problems like that.
Also, keep in mind that a very overly rich condition can also cause glowing exhaust from fuel burning out the exhaust.
Your timing set at 36 will be fine there as well.
I'm thinking that your carb has internal problems that are causing the stuff you described to happen.

Hope that helps, but before you go digging much further, I'd have a look inside the carb to find why it's doing that.

KPLugnut

ryan
Member
posted April 02, 2003 09:20 PM
Exhaust ports looked liked it was burning quite a bit of oil. I think that was a factor.We will dive into the carb tommorrow. Thanks for your help kp


RACEINMUD
Member
posted April 03, 2003 06:11 PM
I read somewhere about lope sepration on a cam being off for intended use can cause glowing headers. Since you changed cams, maybe somthing to look at.


rico 08
Member
posted April 03, 2003 08:32 PM
The mismatched intake you described will also if causing a vacuum leak will probably pull oil from valley area and show oil in exhaust like you said smoke also,but never seen anything smoke bad enuf to turn 'em red.Seen an angle ground intake/head mismatched do this also.


ryan
Member
posted April 04, 2003 08:24 PM
I think it might be something in the timing or something in the heads. Built a carb from scratch with just minor alterations it didn't fill the cup up but it ran the same. Intake gasket was changed to the correct one still no change. A friend said that a guy he knew once had bought brand new bowties and had the same problem, turns out that his valve seats weren't quite right and he had to have them re-cut. I am going to compression check them all tommorrow also I will check my timing light against someone elses. I am starting to get very frustrated. Any other ideas?


ryan
Member
posted April 06, 2003 10:00 PM
We did a poor mans leak down test on it and air was blowing through the intake and exhasust. Tore the heads off and found out the valves weren't seating down on the heads like they should. Guess I learned a lesson. Even if you spend a bunch of cash on new stuff it isn't always right. Oh well least I found it. Hopefully I can get it back together and running right by this weekend so I can make it for the first race. Thanks guys.


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