problem converting to gt40 heads and cobra intake

jim crawford · 05-22-2006

I went from a stock 93 mustang 5.0 and added gt40 heads the b303 cam and a cobra intake all new parts to pick up the power a little.heres the problem, now i get alot more valvetrain noise and it seems to be running very rich. the compression is 155 per hole i stuck with the stock injectors because they were working fine, when i pulled the spark plugs they looked clean but the back 2 were much much darker then the rest.i thought this was a direct bolt in. was i wrong? any ideas? oh the vacumn is 12 inches is that ok.

Sniper · 05-23-2006

Did you get a fuel pressure regulator? I have the same heads with a GT40 intake and a Trickflow cam. After installing this stuff, I had to readjust my fuel pressure because it was running mad rich and would stall. I already had a Kirban regulator and 24# injectors with a C&L meter so it was a snap. 19# might be smallish

BTW, I also have a 93

jim crawford · 05-23-2006

sniper i will check the pressure, but all the stuff in the fuel system is still stock. i am hoping to see 300 hp which i think the stock inj and reg should be able to handle. btw this drivetrain is in a 65 fastback.

tmoss · 05-23-2006

The 193s are up to the task. If your running rich it's probably due to the low vacuum - the adjustable should help. If you can't get that to work, then look at cleaning/checking the MAF sensor.

scottzrt · 05-23-2006

Buy an adjustable fuel pressure regulator,Try about 38-42 psi.A GT 40 intake would work much better for you .The ports match up perfectly.

tmoss · 05-23-2006

The design of the lower intake for the GT40, Cobra and Explorer are all the same, your Cobra is fine.

jim crawford · 05-24-2006

i have cleaned the maf sensor with no help, i think its wierd that the spark plugs look progressively worse the farther back the motor they go, front 4 perfectly clean middle 2 slightly brown back 2 very dark?

Blade10 · 05-24-2006

Here is what I would do:
1) Recheck all the valve adjustments.
2) Do a compression test
3) Verify the intake gaskets are properly sealed. Propane torch (not lit, just spray the propane around the gasket area and listen for RPM changes), wd40, or other method.
4) Swap the injectors around. Move the back to the front.
5) If the problem continues - REPLACE the intake gaskets, lower and upper. It is possibly they are leaking under the intake, where no propane/wd40 trick is going to locate the issue.

Keep us posted.

Blade

jim crawford · 05-25-2006

this motor has the nonadjustable rockers, comp is 155 per hole +- 5.i will try the injectors this weekend and the manifold leak test.