Engine question

Daren · Post by **Daren** » Sat Mar 04, 2017 10:03 am

Hello all,
I have just stripped my jeeps engine and on taking the head off I noted that the pistons are all at the bottom of the cylinders, is this OK and just part of the cycle, it's just that I have only ever worked on v8s. Also one of the exhaust manifold lugs is missing, can it be rebuilt or do I need to buy a replacement manifold?
Thanks for the help

Joe Gopan · Post by **Joe Gopan** » Sat Mar 04, 2017 10:28 am

Oh, oh.

rjbeamer · Post by **rjbeamer** » Sat Mar 04, 2017 10:29 am

Two of the pistons are 1/2 way down and two of the pistons are 1/2 way up. None of the pistons are all of the way down. Rotate the crankshaft a little more. Exhaust manifolds are very hard to repair correctly IMO.

Roger

Joe Gopan · Post by **Joe Gopan** » Sat Mar 04, 2017 10:31 am

Am I glad that Roger is around.

Bruce W · Post by **Bruce W** » Sat Mar 04, 2017 11:04 am

"Two of the pistons are 1/2 way down and two of the pistons are 1/2 way up."

So, are the cylinders half-full or half-empty?

BW

rjbeamer · Post by **rjbeamer** » Sat Mar 04, 2017 11:43 am

Well I guess you would say both.

Roger.

Daren · Post by **Daren** » Sat Mar 04, 2017 11:48 am

That puts my mind at ease. I didn't want to rotate the crank just incase it changed the timing for the distributor. Would it make a difference to the dizzy?

Post by **artificer** » Sat Mar 04, 2017 11:58 am

Would it make a difference to the dizzy?

NO. The cam is chain hooked to the crank then the oil pump is driven by the camshaft & next the distributor is driven by the oil pump [in this engine].

Also one of the exhaust manifold lugs is missing, can it be rebuilt or do I need to buy a replacement manifold?

Cut & shape file a piece if material similar to the exhaust manifold lug missing & braze it in place. You must gouge properly! Done this @ least 1/2 a dozen times successfully.
https://www.youtube.com/watch?v=LnlUJkdzaNU

Daren · Post by **Daren** » Sat Mar 04, 2017 12:26 pm

Great, thanks for the info. I may take the manifold to an engineers shop an get them to do it as I don't have any brazing gear.
Thanks again. I will turn the crank tomorrow and see the pistons move.
Regards

fernando mendes · Post by **fernando mendes** » Mon Mar 06, 2017 5:41 am

Mine was welded in 2008(electric weld).It is ok until now.In my recent engine restoration(nov-dec 2016) I noticed that one of the screws that hold the pipe is different diameter.The other screw is welded.Then I decided to buy one in EBAY.I think my problem will be solved.

Daren · Post by **Daren** » Mon Mar 06, 2017 9:02 am

Another issue I have noticed is that on the cylinders the bores are lovely and smooth with no scoring what so

ever however the top 10mm (approx) has a rougher feel to it is this normal. It looks to be fine for the travel of the piston rings but where they sto and travel no further this is where the rougher surface is.
Is this normal for these engines, please say yes.

Post by **artificer** » Mon Mar 06, 2017 10:18 am

YES, on a worn engine! That is called the ring ridge & is what the original bore diameter was & what the unworn portion @ the bottom of the bore is.

Wear is established by micro measuring across the bore @ the bottom & just under the ring ridge. Depending on that wear the engine might need re-boring oversize or re-sleeving.

& no the bore should not be all smooth but show signs of cross hatching achieved by honing.
@ the very least the bore, if still serviceable, will need ring ridge removal & de-glazing.

When the pistons are removed, if you plan on doing that, the ring ridge needs to be removed.
Don't do so & fit new rings & the top rings will break on engine start up.

Daren · Post by **Daren** » Mon Mar 06, 2017 11:36 am

Oh damp, I was hoping not to have to delve too deeply into the engine. I'm kinda on a bit of a deadline and money is a little tight, would it be reasonable to put the engine back together now, as is, and then when money and time are better take it out and do a proper rebuild. I just need it ready to drive to a wedding as the grooms wedding car.

Post by **artificer** » Mon Mar 06, 2017 12:48 pm

If it was running OK one wonders why it was pulled apart?
Yes you can put the head back on properly & away you go, again.

Chuck Lutz · Post by **Chuck Lutz** » Mon Mar 06, 2017 2:33 pm

An accurate assessment of the true BORE of each cylinder will tell you how much they are worn. Post that and post what the number you find stamped into the top of each piston is. If you are on a budget, a qualified mechanic (ask Marty or artificer to name a couple here) can then probably work out how MUCH they are worn and if there are some oversized rings for that bore that are available without going to the next step of boring the block and buying new pistons and rings and the associated costs with that.

There is always a risk in going in a fixing only the first thing you find though....that is why artificer asked you why this engine was torn apart in the first place. Most guys bite the bullet and do a proper complete rebuild unless they have a running engine with good compression and no obvious signs of a problem.

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