CRG Discussion Forum
Welcome, Guest. Please login or register.
Did you miss your activation email?
September 30, 2014, 08:54:06 AM

Login with username, password and session length
Search:     Advanced search
Welcome to the CRG Discussion Forum!
Forum registration problems: Make sure you enter your email correctly and you check your spam box first. *Then* email KurtS2@gmail for help.
104927 Posts in 12260 Topics by 4727 Members
Latest Member: Z10 Paceman
* Home Help Search Login Register
+  CRG Discussion Forum
|-+  Camaro Research Group Discussion
| |-+  Maintenance
| | |-+  What causes fouling spark plugs in a new motor?
« previous next »
Pages: [1] Print
Author Topic: What causes fouling spark plugs in a new motor?  (Read 3539 times)
sdkar
Hero Member
*****
Posts: 654



View Profile Email
« on: August 04, 2007, 11:08:24 PM »

I have a brand new 502 GM crate motor in my 69 Camaro.  I have yet to drive the car other than in and out of my garage as I am rebuilding it.  It ran great at first but than started fouling the plugs.  I am on my second set of plugs already and they have less than 20 minutes on them.  I cleaned them but that only lasted about 2 minutes and they are fouled again.  This is the ZZ502 deluxe and came with a Holley 850 and I am running the fuel pressure at 7 lbs.  The timing is set to factory.  The engine starts running rough...then backfiring...then stalls and will not start until I clean or install new plugs, only to start the fouling all over again.  What do I need to do to stop this.  I am ready to drive the car to the paint shop, but at this rate I won't get 2 miles.  This is odd to me since this is a brand new motor.

Any and all help is greatly appreciated.

Steve
Logged
JohnZ
CRG Member
*****
Posts: 4112


View Profile Email
« Reply #1 on: August 05, 2007, 10:29:34 AM »

7# is pretty much the upper limit for fuel pressure before it overpowers the needles. Check the float levels, check the needles/seats for trash that could be holding them open, and make sure it's idling on the idle mixture orifices, not on the transfer slots - you should only have about .020" of the transfer slot showing below the throttle plate at idle so the idle mixture screws are effective (adjust them for highest steady vacuum).
Logged

'69 Z/28
Fathom Green
CRG
jdv69z
Hero Member
*****
Posts: 643


69 RS Z/28 52E


View Profile Email
« Reply #2 on: August 05, 2007, 11:37:04 AM »

Are the plugs black with carbon when you pull them. That's too rich

Jimmy V.
Logged

Jimmy V.
hotrod68
Hero Member
*****
Posts: 520


almost finished

rusticman48@aol
View Profile Email
« Reply #3 on: August 11, 2007, 10:06:58 PM »

I'd check and make sure there is no fuel dripping from the boosters, too. Your floats could be too high. With the engine running, look at the boosters--they should be dry with the engine running from the idle circuit only. Like John Z said, 7 lbs is a Holley's limit for fuel pressure--too much will overpower the boosters, too. Good luck!
Logged

HotRod'68  1968 SS350 coupe undergoing frame-off resto/rod. 386/350/4.11s
Butternut Yellow    black standard interior
sdkar
Hero Member
*****
Posts: 654



View Profile Email
« Reply #4 on: August 11, 2007, 11:24:45 PM »

When you say "dripping from the boosters" what do you mean and how do I check this?

Logged
JohnZ
CRG Member
*****
Posts: 4112


View Profile Email
« Reply #5 on: August 12, 2007, 02:14:59 PM »

See photo below - the boosters are the four circular devices in the middle of the airstream in each venturi - that's where the fuel is metered into the incoming air from the main metering system. At idle, there should be NO fuel coming out of the boosters at idle; idle fuel is metered from tiny round orifices BELOW the throttle plates.
Logged

'69 Z/28
Fathom Green
CRG
hotrod68
Hero Member
*****
Posts: 520


almost finished

rusticman48@aol
View Profile Email
« Reply #6 on: August 12, 2007, 09:48:13 PM »

If fuel is leaking past the needle & seat it'll drip from the underside of the boosters--I couldn't load the photo John Z posted--hope you did. With engine running, look for droplets of gas being sucked into the venturis out of the underside of the boosters. You can clearly see if they're leaking. The cure is to lower the floats--try turning the needle & seat screw down a 1/2-turn a a time until the leaking stops. Also, just after you cut the engine off, look for smoke coming from the carburetor venturis--if fuel is leaking from the boosters you'll see it clearly. It's actually raw gas that's atomizing from the manifold heat. Good luck!
Logged

HotRod'68  1968 SS350 coupe undergoing frame-off resto/rod. 386/350/4.11s
Butternut Yellow    black standard interior
sdkar
Hero Member
*****
Posts: 654



View Profile Email
« Reply #7 on: August 19, 2007, 12:46:54 AM »

Solved the problem.  The front float was either stuck or set to high (or is it low?).  When I opened the sight plug on the bowl gas poured out.  I reset the float until fuel was just below the sight hole.  I then installed new plugs and it runs good again.  I have a holley regulator 803 but the lowest setting I can get out of it is 6-1/2.  I have turned the adjustment all the way out and it does not go any lower.  Anyway...it runs good again and does not seem to have a problem.  At least this is the longest it has run without fouling the plugs to the point of uselessness.

Thanks guys for all of the help....as always...it is greatly appreciated.

Steve
Logged
Pages: [1] Print 
« previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!
Page created in 0.076 seconds with 17 queries.