Inliners International Forums General Discussion Engines Why won't the spark plugs fit?

I have been to 4 different parts stores and they all give the same listing for spark plugs for a '67 292. None of them fit. They all have 14mm threads. I did a search on here and found a part number that someone else used and that was no good either. The hole is slightly larger than the plug it is calling for. The casting number on the head is 3864890 and the block is 1970. If that helps. Thanks in advance.

Looks like a 1963 to 1966 head.

http://www.inliners.org/tech/heads/headindex.htm

porkchop, I know what you mean. I've ran into the same issue too. I currently use AC Delco R44XLS and they seem to be just fine. Use that part number to cross reference for other brands if you can't get AC Delco. What part numbers were given to you? I'm sure you have an AutoZone near you (being in TX), they do have a website that you can put in all your info and get a listing of part numbers. Orielly's and Advance Autoparts also have a website to do some research. Check them out, you should find something there.

That R44XLS is the part number I used. All the cross references showed the same size plug in different brands. I am going to go back to the store today and look in all the books and see what I can come up with.

I figured it was an older head. Is the older head better than the newer ones? From the chart seems like it flows better, but could be wrong.

Gentlemen;

That issue came up a few years back & Mike G. had the answer, as I recall.

Perhaps the head was 're-drilled' or used for a different application/fuel (butane/propane/SMOG) etc.

Good luck.

Do you remember what plug he used? thanks.

The early and later heads do use different plugs. For a cross reference in Autolite the early head takes an AP404 and the late head takes an AP25. Due the interchangability of the inline heads, there is no guarantee a motor has the original unless you have owned it since new.

I tried the AP404 plug and it is also to small. It looks as though someone drilled the head for a 7/8 plug, which are no where to be found.

Hi Porkchop . . .

Maybe they re-tapped for 18mm plugs - like used on some motorcycles. A 7/8 plug would be huge - ~22mm - way oversize.

Or they re-tapped for an repair insert like those sold by Pyramid and others. With these you drill and tap an oversize for the insert and it is tapped for a standard plug diameter.

Check out: Pyramid Fasteners

I fixed a lawn mower head with this type of gizmo - one that I cross threaded myself the day before

regards,
Keith

Thanks for the pat on the back John but I've only ever come across 2 possibilities on those heads, the long reach plugs like the R44XLS, and the shorter ones like the 44, R44, or R44S. They are both the 14MM thread. The 18MM is the size that was used in Ford FE V8 engines as one example and they were a taper seat plug to boot. If his head has been reworked to take 18MM plugs it was probably to repair some badly damaged 14MM holes as Chopped 49 pointed out?

Cross ref'ing an 18MM Ford engine plug to a 14MM GM engine plug heat range sounds like it will involve some time poring over catalogs and decifering heat ranges. Standard application listings won't be any good if that is the case.

Please pardon the error. I meant to say STOCK 49.
Too many hours out in the garage today wrestling with fenders and running boards.

No problem Mike . . .

In case you weren't aware of it - you can edit any of your posts - even days later. All you need to do is click the 'pencil on paper' icon.

regards,

Ok so saying I happen to find the size I need. How long does it have to be? To long and it will hit the piston right?

Using the NGK web for an example the 14mm specs for 63-66 C-10 standard plugs show 3/4" reach; 13/16 hex; gasket type seat; resistor type for 4.8 292). BR6ES plug. Plugs & specs are different for 194 thru 250 CID.

Where are the plugs that came out?? Those could be matched by the parts people.

Otherwise; "Micky Mouse" has been there if 14mm is to small & 18mm to large.

Perhaps Bob308 would know as he works on bikes (motorcycle heads) etc.

It might end up & be cheaper/better all around to have the head re-drilled & put back to factory specs.

Good luck.

it sounds to me that the holes were drilled out for replacemant inserts, then the inserts removed/lost before you got the head. there should be nothing other than the normal threads for available spark plug threads! wierd!

That's an excellent evaluation!!

Take your head to the machine shop & see what they think.

Then let us know as It's wierd all right.

Thanks stock49. 2 years on this board and I just find out you can edit! Now all I have to do is remember that tip.

I went thru a similar problem on my 292 when I first put it together. Had a lot of ignition problems & to make a long story short I found the head had tapered seats & required a plug 11/16 long from seat to the base. AC # R44LTSM fit this pefectly. I believe I have a Mexico production head, some auto parts website had this listed, I found it later. I live near the border & there is a lot of junkyard cars & parts back & forth here. I've since put about 25K on it with same plugs, no problem. It taught me to Always look at the seat & reach required. It's in my '55 Bel Air, BTW. Doug

Ya know Doug; That makes perfect cents considering Corpus Christi is so close to Canada.

Where is the FTC now that we need them??

Here's hoping that plug works for him.

This is pretty much what it was. All the plugs were to short so they wouldn't thread which made me think the plugs were the wrong size. I finally went and bought a few different plugs and found one that fit. thanks for all the help. Hopefully you guys can help me figure out all the things with this engine. This is the first time I have seen the 292 engine and the bad part is it was not complete.