Recently I was helping a new friend sort out an engine that he bought and put in his Cuda. He was told that it is a stroked 383. I have a bad feeling about this engine. I think it may be a bunch of parts thrown together that may or may not be compatible with each other. He doesn't know much about it other than a machine shop receipt and the cam card. It does at least start and run and idle.

Upon pulling a plug I found it has 5/8 plugs with a gasket. Isn't this a plug for aluminum heads and his iron heads should have 13/16 plugs with a gasket or, if it is a motorhome head, 5/8 plugs with a taper seat and no gasket? Were there any other iron heads that used 5/8 plugs? Could somebody have put these plugs in heads that should have the regular 13/16 short reach plugs? I will pull a valve cover off and check numbers next time he comes over.

The harmonic balancer is the bullet nose style that comes on some cast cranks. I can't think of any way to tell if it is in fact a cast crank short of pulling the pan. I will ask him to bring over the machine shop receipt and see if there is any indication of parts used and whether it was balanced internally or externally. If he still has the 12" converter that came on it we will see if it has any counter weights.

I could not properly time the engine. Either the balancer has slipped or the old inexpensive non setback light that he has hates the MSD 6AL that he is using. Mark is bouncing at least 10deg. and no where near where I would expect it to be. I will get a fresh set of batteries for my self powered light and try it but I suspect a problem with the balancer and/or distributor. It has the MP distributor with the Mallory mechanical advance. Anybody ever have one of these that the phasing was way off? Maybe that is why I can't time it correctly.

Thanks for any hints on what this mess may be. LOL, I am used to working on engines that I put together and know exactly what is in them. I hate to start taking the heads, oilpan, and valve covers off just to see what it is but I might have to. If it comes to that might just pull the engine and tear it down. Won't tear anything apart until I have any needed gaskets in my hand during this Plandemic.

Well, from the title I was thinking RV heads, did you look at the spark plug seat on the head? Might be someone put gasketed plugs in a tapered seat application, no telling what people do anymore.

Exactly my thought. Or maybe it should actually have the typical short reach plugs in it
The only iron heads I have messed with have been 906 or 915 so I needed to confirm the small plug heads. I would guess these may have come from the same engine as the balancer. Who knows about the rest. . Next time I will pull the most visible plug and try to get a good look at the seat area. The one I pulled before was #1 and couldn't see the seat. If I have to I'll take a pic of the seat so I can get a more direct view of the area.

But just to confirm the info I have, there is no gasket seat 5/8 plug iron head, correct?
Valve cover is definantly coming off next to see what head it is.

Not that I know of, but like you I've only fooled with 906 and 3200 heads.

I wouldn't get hung up over the hex size, people swap to the smaller hex for header clearance all the time.

I would definitely look closely at the reach though, big difference there. I'm not aware of long reach gasket plugs on a big block. I have seen people stick small block plugs in a big block by mistake.

A friend recently got a rebuilt 327 for cheap because it was smashing spark plugs. The previous owner wasn't aware of the different heads taking different reach plugs and thought there was something wrong inside.

Two barrel 383's in 71 were cast crank engines, but I don't think they had the tapered harmonic balancer that you are speaking of. However, 400's had the tapered balancer and cast crank and could have come with motor home heads that have the peanut plugs in them. 383 and 400 cranks are interchangeable.

I’d check the timing chain for stretch. I’ve seen huge swings with some nasty old chains. I’ve had two cars from the south that got rattle can rebuilds passed off as fresh full tear downs. Seems common there. No biggie if you buy it right, but I’m suspect of any engine down that way now as I’ve seen others with same sketchy background for sale.

Late model motorhome heads used peanut plugs 5/8" usually 452 castings and yes they also came with standard 13/16 plugs for car motors

I had the same problem timing my late model 440. The balancers have 3 slots in them and it's very easy to get mixed up using the wrong mark. (ask me how I know) Pull number 1 spark plug, stick your thumb over the hole and crank till you feel compression building. Then look at the timing mark. The slot that's showing is the timing mark to use.

Actually that was why I had #1 plug out.

To eliminate the MSD from the equation, run it up over 3000 RPM and see if that stabilizes the timing. The box should go single strike after 3000.

Kevin

Does the distributor have vac advance? pull the vac line off of it then try timing it if it does. the line is probably on the wrong vac port on the carb.

Here's some interesting and related reading regarding timing, timing lights and the MSD 6AL.

https://www.chevelles.com/threads/t...d-new-design-msd-digital-6al-box.360036/

Yes it was pulled off and no it wasn't on the wrong port.