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Which Spark Plugs to Use

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k5bobbo

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I have recently bought a 1986 Blazer with a 383 engine and a relatively high compression ratio. When I bought it, it came with NGK V-power plugs and they were looking a little fouled so I replaced them yesterday. I put in 8 A/C Delco R43TS plugs. However I am beginning to think those may not be the right plugs, because it is not starting easily and the RPMs are surging a bit.

What brand/type of spark plug do you suggest for my setup?
 
Mr. Janke built my 383 and he specifically said to use the NGK V-Power's. I started out with the 8's, but they were not hot enough, so I moved up to number 9's. Now I have no problem with the plugs. NGK stock 5238, R5671-A9. He has mine gapped at .035. My compression is close to 11:1.

Hope that helps.

Manny
 
I'd ask Brodix. (or anyone here that has experience with them)

I'd be concerned about length when choosing the plugs. I'm unfamiliar with Brodix heads, but as a for-instance, Vortec heads use a longer threaded portion...a plug for older heads (shorter) doesn't even reach the chamber on those.
 
Thanks a lot I appreciate it. I am about to replace my 2 dynomax mufflers with 2 40 series flowmaster mufflers, how do you like them? Also are you running a Carb, and if so what CFM is it?
 
k5bobbo said:
Thanks a lot I appreciate it. I am about to replace my 2 dynomax mufflers with 2 40 series flowmaster mufflers, how do you like them? Also are you running a Carb, and if so what CFM is it?
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I have 2 40 series flowmasters. I love 'em. They roar! I'm moving up to a 3" exhaust system to allow my 383 to breathe a little easier, so I'll let you know. I'm gonna stick with 40's if I can. The carb right now is a 750 Holley. Having a hard time tuning it. It seems to self adjust itself. I'm switching to an Edelbrock AVS Truck Avenger. Prolly a 700 or 770 if available. Still looking around.

Manny
 
I have 2.5" exhaust, but I cant wait to get the 40's. Do you think 3" would be better? I had a holley carb on their until I recently replaced it with an edelbrock performer 600cfm, I think I should have gotten a carb with a larger cfm though. But I hated the holley that was on there. I could never get it to tune right either.
 
k5bobbo said:
I have 2.5" exhaust, but I cant wait to get the 40's. Do you think 3" would be better? I had a holley carb on their until I recently replaced it with an edelbrock performer 600cfm, I think I should have gotten a carb with a larger cfm though. But I hated the holley that was on there. I could never get it to tune right either.
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Mr. Janke told me that a 3" system would be better so it's on my list of things to do. I too was lookin' at the Edelbrock 600 cfm. I've been told by several people who are very carb experienced that a 600 would be a little small and could starve the engine of fuel and air. They said a minimum 650, but 700-770 would be better.

Manny
 
I've got aluminum Pro Topline heads on my 496 and I use the NGK Vpower plugs as well. You will definatley need to look at the spec sheet for your heads to find the right reach. I'm not familiar with the Brodix product but I know my heads are totally reworked and the spark plug position isn't stock to anything. You'll also need to work with the gap setting to find the sweet spot for your setup and ignition.

The exhaust is a tricky one. Ask 4 people and you'll get 5 different answers. I don't know enough about the topic but for reference, I'll be running a true dual 3" mandrel bent system with an x pipe and large tube headers. This is behind a built 496. With a 383 you might not need quite so much flow. ???
 
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