347 heads

[gick70]

What spark plug are you guys running ,cast iron heads….

 

[gick70]

Stroker engine

 

[Broncobowsher]

Nowhere near enough information. Cast iron doesn't really tell us anything. Are they OEM heads, if so which ones. For absolute basics, there are 2 different thread sizes. Aftermarket, that opens up even more. Thread depth, taper seat or gasket seat? All available in different cast iron heads.

After all that, compression ratio and cam. Then a heat range adjustment guess can be made.

More than likely start with a set of basic Autolites, run them and read them. Once you confirmed everything is right, maybe get a fancy plug.

 

[gick70]

How about the guys running the blueprint motors from summit chime in,with the cast iron heads..

 

[Broncobowsher]

That gives a lot more information. I am 99.9% sure that Blueprint will have a recommended plug, if not already a set of plugs installed in the engine.
I tried to find a Blueprint 347 with iron heads on the Summit site. Didn't have any luck. Do you have a link to which engine you have? All I found was aluminum heads, and that is what you find on most 347 from anyone as well. So we are still stuck on not knowing what you have.

 

[73azbronco]

You run plugs for the ignition you have. Then decide how it runs to see if you need hotter or colder plugs.

 

[gick70]

Well I like to know close rather than losing 50 bucks

 

[gick70]

summit didn,t sell with ignition,but did have plug recommendations,I looked on their site also…I will call them Monday with the serial number to get specifics..

 

[Broncobowsher]

Well I like to know close rather than losing 50 bucks

Trying to help. If you have a link to the engine you got, that will likely get us started. Probably all we need to know.
Even if you said you had stock heads on a stock engine, there would still be questions. Being there were multiple stock options. I don't just mean brand or even heat range, thread size.
The spark plugs screw into the heads, being iron heads is probably the least valuable data point as there is to finding you a plug.

Once we figure what heads you have, we can find you a spark plug. With an ignition system, we can tell you what to gap them to.

 

[gick70]

A lot is unknown as I bought this engine from a guy that lost interest,I say cast iron heads as summit has recommendation on there website for aluminum heads…but it’s older ,when they used the cast iron heads

 

[gick70]

The heat difference with the cast iron vs aluminum

 

[Oldtimer]

What spark plug is currently in it?

 

[Broncobowsher]

A lot is unknown as I bought this engine from a guy that lost interest,I say cast iron heads as summit has recommendation on there website for aluminum heads…but it’s older ,when they used the cast iron heads

Start looking for casting codes. Post anything that is a distinguishing mark.
It may have been a short block that some stock heads were put on? Completely possible that blueprint didn't have anything to do with the top end.

 

[gick70]

blue print,hooked me up today !!!

 

[gnpenning]

Please share so the next person has an answer.

 

[Broncobowsher]

I'm more curious to what heads did they use?

 

[gick70]

I got the specifics by using the manufacture tag on engine,Bp emailed the information…

 

[gick70]

head information wasn,t there,nor do I care…

 

[WheelHorse]

Sp415a or Champion 4025.

 

[Broncobowsher]

Sp415a of Champion 4025.

Thank you for finishing what the OP refused to do