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#384105 - 02/16/17 08:08 AM Can oil troughs ever empty out on steep hills
28National Offline
Shade Tree Mechanic

Registered: 03/08/15
Posts: 55
Loc: UK
Hi Folks, drove up a couple of fairly steep hills in my '28 today and got what sounded very much like big end knock as I neared the top. This happened twice, but went away once over the top of the hill.

I'm using straight 20W.
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#384113 - 02/16/17 10:28 AM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
Chev Nut Offline




Registered: 01/08/02
Posts: 24490
Loc: West Allis,Wi.
I would suspect that it was a main bearing pounding due to the pressure on the mains when developing full power.
The amount of the dipper dippping into the trough is very small so if that measurement is a little off it could be a rod that is all ready on the too loose side.


Edited by Chev Nut (02/16/17 10:35 AM)
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#384118 - 02/16/17 11:21 AM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
SSG26K Offline
Oil Can Mechanic

Registered: 10/04/03
Posts: 582
Loc: Waterbury ,Ct.
I had the same thing with my '25. Don't ignore it as I did. Suddenly on a flat road the engine started knocking very loud. It sounded like a rod was ready to come through the side of the engine. Got it home and dropped the pan.Two of the oil distributor feed tubes to the troughs were in the bottom of the oil pan. Now I have to find someone to rebuild the engine.
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'25 Superior "K", '79 Corvette , '72 Corvette LT-1 & 1965 Corvette Coupe

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#384123 - 02/16/17 12:19 PM Re: Can oil troughs ever empty out on steep hills [Re: SSG26K]
AntiqueMechanic Offline




Registered: 12/02/01
Posts: 9572
Loc: Vancouver, WA


Just a word about the 25 engine (and the 26,27 & 28). The 25 is the only engine in the group that has any oil pressure to a bearing. The center main is pressurized. The other mains, and the cam, are oiled by reservoirs atop each bearing. These reservoirs are filled by SPLASH, that is the big end of the rods hit the oil in the trough and the dipper forces some oil into the big ends which oils the big ends of the rods. Additional oil is SPLASHED up into the reservoirs mentioned above. These reservoirs are relatively large and hold a considerable amount of oil to lubricate the bearings when the engine is not SPLASHING enough oil. This method of oiling justifies the use of the 10w-30 oil. As you can guess, the engine can run completely out of lubrication during long periods of idling. After the engine has worked hard and did not SPLASH sufficient oil, it will take a period of time at a higher RPM to refill the troughs.

All of us know how to drive the old 4-cylinders, but you need to be better informed about how things work to prevent damage to our engines. The more you know, the more you know!


Agrin devil
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Member Chat Group - Non-Geographical Region

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If you need a shoulder to cry on, pull off to the side of the road.

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#384138 - 02/16/17 02:47 PM Re: Can oil troughs ever empty out on steep hills [Re: AntiqueMechanic]
28National Offline
Shade Tree Mechanic

Registered: 03/08/15
Posts: 55
Loc: UK
Thanks guys, I'm thinking the troughs ran dry for a short while.

This is replacement engine I obtained and I had the oil pan and end caps off to check the bearings and they have all been re babbited, crank is perfect.

It has ally pistons which are not '28 and the rod caps have no brass shims nor the steel spacer as per original, looks like this is how they were poured. They may be later rods.

because of that I checked the dip with grease in troughs and it was tiny, so I left the gasket out and use RTV instead, this may mean that the dippers are too deep and splashing too much oil out, so much to think about and learn with these old Chevys..

Thanks AntiqueMechanic that's how I understand the oiling except that I reckon the lower part of the crank reservoirs appear to be sludge traps (my old engine had them full of 3/4 full with sludge) which means although the reservoirs are large it's only the oil in the top part that is above the hole on top of the bearing that can feed oil.

The '28 has a pressure oil bleed from the distribution block to the centre main reservoir so that doesn't rely entirely on splash.

Somewhere I read a theory that the front gear cover acts as a reservoir which spills oil into the front crank bearing when climbing hills, not sure about that but every bit helps!

Hey Ho it's all good fun, just glad I don't have to use it to get to work :-)


Edited by 28National (02/16/17 03:02 PM)
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#384143 - 02/16/17 05:08 PM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
AntiqueMechanic Offline




Registered: 12/02/01
Posts: 9572
Loc: Vancouver, WA
The front cover on the 4-cylinder is a serious leak area. Oil is provided by a special spiral cut trench in the cam gear bearing. If this is stopped up you will have problems with the fiber cam gear wearing out. Make sure this path is open for oil to get to the cam gears. Now, the bad part. This oil when used will settle in the pocket at the bottom of the cover. This is where the leak is at and it is caused by carelessness in the installation of the gear cover. Make sure the cover is hammered out to where the lip is flat all the way around. Use your sealer of choice all around, but give total attention to the bottom cover. The pocket formed at the bottom is about 1 1/2 inches deep and the area becomes a holding pocket for this oil. One cause is the overtightening of the bolts that hold on the cover. Snug, but not tight, otherwise you will distort the cover and cause a leak.

If you have any questions about the 4-cylinder engine and to learn principles that are applied to the 6-cylinder and to a small extent the V-8 engine, you should seek out the "School is in Session" dissertation that is in flipbook form.

http://vcca.org/docs/TECHNICAL%20INFORMA...e%20Rebuild.htm


Edited by AntiqueMechanic (02/16/17 05:21 PM)
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Member Chat Group - Non-Geographical Region

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http://www.vccacolumbiariverregion.org/



If you need a shoulder to cry on, pull off to the side of the road.

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#384169 - 02/16/17 10:47 PM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
beachbum Offline

Backyard Mechanic

Registered: 09/12/06
Posts: 435
Loc: Vancouver, Washington
Included in some parts I got some years back is an earlier timing gear cover. It is the type for an external oil pump. It seems to be made of heavier sheet metal than the later non external type. I was thinking of trimming off the bottom and using part of it as an extra stiffener for the lower timing cover section. It is in fantastic shape but I don't have an engine with an external pump. I really don't like preventable leaks.

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#384171 - 02/16/17 11:32 PM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
28National Offline
Shade Tree Mechanic

Registered: 03/08/15
Posts: 55
Loc: UK
All good info guys, can't have enough of that :-)

Something's different with this engine as I never had this problem with my old engine on the same hills, and that had an oval pitted crank, I'd removed all shims except the thick steel ones removed as it got looser.

I always ran 30W in that but put 20W in the new engine as it's winter.

Hard to work out what's different, this engine doesn't seem as powerful as the old one, it has bore wear but the compression is a lot better.

I'll drop the pan off again and report back.
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#384182 - 02/17/17 05:47 AM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
Chipper Online




Registered: 11/22/01
Posts: 16351
Loc: The Great State of TEXAS
Make sure the cam timing is correct. In that period some cam gears were mismarked. It will be necessary to pull the front cover and count the teeth to get the proper timing.
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#384319 - 02/19/17 07:55 AM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
28National Offline
Shade Tree Mechanic

Registered: 03/08/15
Posts: 55
Loc: UK
Got the pan off and it all looks and feels good, nothing loose or out of place.

I'm wondering if the knocking may have been no.1 piston slap, I now realise I forgot about retarding the ignition on the hills, but it didn't sound like 'pinging'

The no 1 bore is worn much more than the others probably because it runs colder due to the cold water flowing past it.
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#384345 - 02/19/17 04:44 PM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
Chipper Online




Registered: 11/22/01
Posts: 16351
Loc: The Great State of TEXAS
Is the noise louder at slow speed? Does it go away at higher speeds? If you remove the spark plug wire or short out a spark plug does it go away on a specific cylinder? Does it get louder with resistance on the engine like letting out the clutch to the friction point when idling or low speed?
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#390912 - 06/19/17 02:23 AM Re: Can oil troughs ever empty out on steep hills [Re: Chipper]
28National Offline
Shade Tree Mechanic

Registered: 03/08/15
Posts: 55
Loc: UK
Apologies for not updating this thread folks, things have happened, here's a progress report.

Took off the main bearing caps to find way too much bearing clearance, and no shims left.

The clearance tapered across the centre main, leading me to think the cap had been ground off square at some time. The babbitt only showed contact at one end and was above the cap each side so bad rebuilding seems to be the problem.

The front was similarly condition.

Lots of cap rubbing on a surface plate and many test fits got the clearances down to around 1.5 thou on all mains using plastigauge.

Getting the centre cap lapped square meant the thrust bearings became tighter due to no longer being tilted, a few turns turning over a few times eased it off.

Checked everything else over, and the rear oil trough was lower than the rest, grease test showed almost no dip happening, so I pulled the trough up a bit using a G cramp and a bar across the oil pan. Test showed good dip and trough level with the others.

Filled up with 30w.

Seemed to run fine after that, did a few miles around locally, all good. Then coming back from a 40 mile run, 80 deg day, up a slight incline, suddenly it sounded like a rod bearing had failed, loud proper knocking! Pulled into the side and switched off.

After few minutes happy and carefree reflection as to my situation, I decided to re-start it and gently pull a few feet further off the road because of passing traffic. and lo the knocking was gone and so after revving it a bit to check, I bravely drove the last mile to home without problems!

Seems to be the same intermittent problem as last time but more long lasting!

Two things I can do now, rebuild an engine using parts from both ones I have, which means no more driving or shows for the foreseeable future, or fit a cheap engine of some sort just to keep it on the road while I get the rebuild done.

Any one know of an engine that will fit the gearbox?

Hey ho what fun!
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#391232 - 06/25/17 09:24 AM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
olgzr Offline
Shade Tree Mechanic

Registered: 11/17/05
Posts: 86
Loc: Vta,Ca
Hello, I have a 1960 235 that has just been rebuilt & I have no compression on #3 cyl, I poured a small amount of oil in the cyl & the compression still didn't come up; could the problem be that the lifters have not pumped up on that cyl? I appreciate all the advise I can get; Thx; Rich

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#391233 - 06/25/17 09:34 AM Re: Can oil troughs ever empty out on steep hills [Re: olgzr]
chevy1937 Offline

pumpjockey

Registered: 10/30/09
Posts: 885
Loc: Hubbard,Ohio
Remove the valve cover, that will tell you if the valves are operating. Sounds like a burned valve to me or blowed head gasket.

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#391268 - 06/26/17 02:16 AM Re: Can oil troughs ever empty out on steep hills [Re: olgzr]
28National Offline
Shade Tree Mechanic

Registered: 03/08/15
Posts: 55
Loc: UK
Originally Posted By: olgzr
Hello, I have a 1960 235 that has just been rebuilt & I have no compression on #3 cyl, I poured a small amount of oil in the cyl & the compression still didn't come up; could the problem be that the lifters have not pumped up on that cyl? I appreciate all the advise I can get; Thx; Rich


Hi olgzr, I suspect you may have posted in the wrong thread..
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#391272 - 06/26/17 05:07 AM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
Chev Nut Offline




Registered: 01/08/02
Posts: 24490
Loc: West Allis,Wi.
The hydraulic lifters must be readjusted after head removal as per shop manual. My first guess is the lifters on that cylinder are adjusted too tight (Adjsuting screw on rocker arm too many turns down). causing valve s not to close.
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#391280 - 06/26/17 06:50 AM Re: Can oil troughs ever empty out on steep hills [Re: 28National]
olgzr Offline
Shade Tree Mechanic

Registered: 11/17/05
Posts: 86
Loc: Vta,Ca
Where does it say to post NEW topic?

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#391286 - 06/26/17 07:41 AM Re: Can oil troughs ever empty out on steep hills [Re: olgzr]
28National Offline
Shade Tree Mechanic

Registered: 03/08/15
Posts: 55
Loc: UK
'TOPIC OPTIONS' button at the top, click for drop down menu, look for 'new topic'
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