Plug gaps closing on a 351-W

I bought a rebuilt motor form someone selling off the internet and I had some plugs close the gaps,it does not look like anything is hitting the plugs as there are no marks but I have a blown power valve in the holley and its running a little rich right now and that could hide it. From what I can tell I think the block is probably from a mid to late 80s crown vic as it had a hole for the dip stick in the block plus had the one piece rear main seal and I dont know what the heads are from,the builder supplied me a complete long block including intake and its probably pieced togather using whatever he had in the shop at the time. What could he had done or installed wrong to make some of the gaps in the plugs close or could I have installed the wrong plugs but I got plugs for a mid 80s truck. I talked to a few builders locally but they wanted way too much money to do a stock rebuild with a RV cam but I know you get what you pay for as I have heard on another forum nothing but complaints about this builder. Jeff

Are you using the long or short reach plugs, Jeff??? Ran into the same deal on a 351 once, had to go to the short plugs and it worked great......I think the deal was that it was older 302 heads on a newer 351 block or something like that....

Yep, Dave has hit it. Your plugs are just too long. Let's face it, the only thing that can close up the gaps is something hitting the plugs.

It really makes it tough when you are dealing with something someone else put together, there is no telling what years or parts are in it.

Just take your plugs to the auto store, and start looking at plugs from other year applications, Mustangs, LTD's, etc.
When you find one that is a little shorter you will be in the ball park.

Evidently your plugs aren't way too long, as you would have seen more than closed gaps.

Don

It could be 302 heads on it as who knows what he used,I knew I should of had someone do up the 76 351-W I had since it was not touched only sludged up a bunch. Every shop around here wanted what I thought was way too much for a basicly stock rebuild with a RV cam or wanted to sell me a crate motor and I found this deal on the internet that was not too far from home. Jeff