1971 Dodge B100 Sportsman Van; 225 cid engine w/ E.C.S.; Std. 250 trans.
Issue: Backfiring on deceleration after carb rebuild.
Condition is not too bad but unacceptable, of course. Especially as I live in the mountains - use gears to control speed on downgrades all the time.

Prior to working on timing, dwell, etc. I started to install new plugs, points, condenser after checking voltage reg & ballast, etc.

Bought new set of plugs - Champ N11Y - which is the plug I used since the rig was new.
They don't fit!
What?

In 1984, I had a short block put in - at least that's the way I remember it. Garage & mechanic who did the work is long gone. Somehow, the paperwork also seems to be un-findable. Drove the van since then, doing tune-ups and other maintenance work myself until 2004 when I had to have work done by others.

A while back, 1,737 miles ago, I was told I had a burned valve because of a cracked exhaust manifold. At that point, the exhaust manifold was replaced and the head sent out for R & R. Seem that the R&R shop swapped heads on me. If I could find the rebuild paperwork, I might have some serial numbers to work with, but otherwise I'm stuck with what I got right now.

This is the first time I personally have done a tune-up. Got some stronger glasses and a friend to help. Have had three mechs work on this rig that I never had a problem with until I let others [1] drive it a while, and [2] work on it. Since then, I have been trying to get back to ground zero, I guess.

I'd like to have a list of the standard plugs for the various versions of the slant six. Have googled and parts-searched myself cross-eyed because all the listings I find are by make, year, model. Truthfully, I don't know what version of head I have on there. Maybe someone can tell me how to find that out?

Last time I asked for help, I was overwhelmed. Can't thank the members enough.
wilki

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David Wilkinson
wilki-worker
POB 173
Twisp, WA 98856

Would it be possible for you to post a picture of the spark plug side of the head, looking at the spark plug holes? Alternatively, does the head have the stamped cups that go around the spark plug and that fill a big hole in the side of the head or does the head have no cups or big holes and dip in towards the plug holes?

Pic one of the head types in the picture below:

you should be able to find out at least what year it is if you take off the
valve cover. a year should be stamped on the head somewhere, but your backfire problem still sounds like the timing to be but since you have
already checked that my next check would be your fuel mixture. What kind of carb is it.

'75 and later heads use taper-seat spark plugs rather than the gasket-seat plugs used thru '74. Champion #11s are way too cold; kind of surprising you didn't get a lot of cold-fouling. Also, Champions and Autolites are currently of poor quality. Use an NGK # UR5.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Reason for my wondering what the standard plugs are for later heads - wiht taper seat plugs is that the plugs currently in the engine are Champion RV17YC. Pulled plug was dry, brownish, pretty clean.

Just wondering if Champion RV17YC are OK as I seem to find them listed mainly for other applications.

_________________
David Wilkinson
wilki-worker
POB 173
Twisp, WA 98856

Champion #17s are too hot, and Champions are of poor quality. Use NGK #UR5.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I've seen people put taper seat plugs in a head that should have 3/4" reach gasket seat spark plugs. If there are tubes in the head which surround the spark plugs you need the 3/4" reach gasket seat plugs. The only problem may be carbon build up in the threads. If there are no tubes you want the short reach taper seat plugs.

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Joshua

There are no tubes in the head.
I am on my way to see if one of the local parts stores has NGK #UR5's per Dan's advice.
Many thanks - logging off for now.
Will send a report after we doo some more work.
wilki

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David Wilkinson
wilki-worker
POB 173
Twisp, WA 98856

OK. Someone has swapped heads on your motor to a later style head, AKA the "peanut" head. Ask for plugs for a 79 Dodge b150, but get NGKs if available. Unless the part number Dan gave you is for the peanut head plugs...

Yep, the part number Dan gave him is for the taper-seat plugs that fit '75+ heads.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan gets a gold star!