Mixing spark plugs ?

I currently have a new set of Delco R45TS plugs installed in a 350 SBC. One plug is too close to the header & I want to replace it with a short "header plug". Any thoughts on having one mis-matched plug ? What short plug number would be the closest match ?

 

prolly not a good idea. the only mismatch I have ever seen is different heat ranges in holes that burn odd.

 

EEEEEEEEEEEEEEEEEK!
One word: NO!

 

If you use the exact same heat range it probably won't matter, I once bought a 40 Ford with a SBC Chevy, drove it for many miles before doing a tune up. When I did, there were 3 different brand plugs in it! The solid lifter 327 didn't seem to really care - but plugs are cheap, why not replace them all so there are no questions about compatibility?

 

I only want to replace the one plug for two reasons. The current plugs have only about 100 miles on them & some are really hard to get at.

I think the Accel 0576S (short) is the same heat as the remaining R45TS, correct me if I'm wrong.

 

Just because its the same heat range or the same application doesn't mean it will work the same. Case in point: I used to ride snowmobiles and was going to an event. I figured I would install new plugs to be problem free. I always ran Autolites in the sled at the time. However the parts store was out of the Autolites that I needed so they sold me NGK's in the same heat range/application. The sled ran fine but the exhaust pipes got cherry red and melted some of my wires. On the trail with me was the tech advisor/editor for "Snow Goer" magazine. He checked out my whole sled only to find nothing visablly wrong. So he questioned me as to what I did different. I told him nothing other than change plugs. He asked why, I told him the reason. He then asked to see the ones I took out and noticed I went from Autolites to NGK. He put the Autolites back in and I had no problem and rode the rest of the season problem free. I asked him how could this be when the NGK's were for my application and he stated that "different plugs even if correct for the application can have different resistance which can cause multiple problems". He went on to say that you should never mix spark plugs and always stick to what has always works.

 

I'd fix the header before I ran accel plugs.

 

Don't mix them. Do them all or nothing. I have to agree with 53sled on the accel plugs.

 

Amen, exactly what I was thinkng

 

OK, I'm convinced, change 'em all. What "short" plug is best for a 350 SBC.

 

Look at NGK UR4, been told (unconfirmed) that this is a shorter replecement for the R45TS

 

Exactly!
Fix the problem NOT take the cheap or easy way out and make it work!
Remember! You get out of what you put in!

 

My Toyota came from the factory with ND in one head NGK in the other.

 

We don't care how they do it in Japan!

 

I agree with pro85fiero, jap cars ****........