Spark plug

[AussiePhil]

Hi guys,

I'm running an 89 Mustang 5.0L HO roller engine in my 68 Mustang,  it's supercharged, stroked and boost increased to 9 psi, since increasing to boost it seems to be running rough on 7 cylinders?
The question is I'm running NGK BPR5FS-15 with 1.3mm gap, should it use a different plug and smaller gap.
I've just bougnt but not yet fitted NGK BPR6FS with 0.8mm gap.
Has anyone got any ideas, am I doing the right thing!

Cheers Phil.

[Husky350]

Yup definitely get the new plugs in. They are colder and you need the smaller gap most of the time. I am using bcpr6es on mine with the stock gap. I had a bit of blow out with the -11's' let alone the -15's you have.

[AussiePhil]

Thanks Husky,
Your help is appreciated!
Cheers Phil.

 

[Husky350]

No worries mate. Is it running rough just on boost?

Stroked and a supercharger....I hope you have money set aside for a dart block in the near future 

[shaunp]

5 is hotter than a 6 plug

[barnett468]

what ignition do you have?

did you do a compression test?

your gap is ridiculously large for a boosted engine, run .028" gap.

run a plug that is 1 to 2 steps colder than stock

[AussiePhil]

I'm running ICE 8+1 camshaft sensor and individual coils via Haltech Elite 2000.

Have changed plugs to BPR6FS with 30 thou. gap.

Need to increase boost because I've gone from 302 to 347 and it has a small SC impeller,  changing to larger impeller.

At the moment it's only producing 248Kwrw.

Cheers Phil.

[AussiePhil]

One more thing about it running rough, it was the injector plug connector wires pulled away as I was insulating them with tesa 51036 heat tape, next time I'd crimp and solder.
I'm changing over to pre wired plugs.
If you run  302 HO or a 351 and 2 and 7 don't spark right it's very hard to tell, just goes bad, just runs on 6 cylinders?

Cheers Phil. 

[Husky350]

You are talking about the pulley not the impeller yeah?
Yeah a 347 with a vortech should be pulling a bit more than that. What headers/intake do you have?

What you can do with the injector/coil looms is put some wire(like coat hanger wire) to support the harness at the terminals. You can bend them to what ever shape you need. Then you just cover it in tesa wrap. Takes pressure off the plug terminals, and can also neaten it up

[AussiePhil]

The engines running super victor efi manifold,  vdo 875cc injectors, 1000cmf Edelbrock throttle body.
I've recently cut down the adaptor plate to the vorteck lid giving less restriction.
I'm talking about a bigger impeller as I've reducer the supercharger pulley to 2.95", still not enough boost, and it's running only an sc impeller, I definitely need a bigger impeller!
Pistons are low compression, -12.5 cc dish.
As a 302 it was set up fine but stroking it I'm requiring more air/boost.

Cheers Phil.

[AussiePhil]

I'm also running JBA 1650 titanium ceramic headers.
Cheers Phil.

[shaunp]

so this is a standard 302 HO block stroked and a blower? if so be conservative on your timing, or you will find it breaks the center 3 main bearing clean out of the block. Keep a close eye on oil pressure, this is typically the signal the block is cracked, keep you revs down. a roller block will break just with a 347 crank and some revs.