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1988 350 SBC stuck inlet valves

tuna_man

tuna_man

Regular Contributor
"Its happened again. #3 &

"Its happened again. #3 & 5 inlet valves stuck, resulting in two very bent pushrods. Happened during start up. two days ago. engine last ran 3 weeks ago. Exhaust valves not effected.
This happened a few months ago, i found the valves locked solid inside the guide. Vise grips locked around valve stem could not move them. It was not bent. glued in by a black deposit inside guide. What is this stuff?
Last time i freed up valves by removing spring, Oxy Acet to guide, black goo started to ooze out and valve started to free up. Finished with WD40 to disolve goo with cordless drill spining valve in guide. Why has this happened again? what is this black stuff in my inlet valve guides? Thanks for any help, Mark."
 
"where does the carbon come fr

"where does the carbon come from in an inlet guide? Id understand carbon in ex... Guides were replaced in 2005. head guy told me he had Knurled the guides to prevent valve sticking. Dont know why he did it, valves had never stuck before. Ive had this 260 Merc for 15 yrs. took heads to him due to a burnt ex valve. He put one new ex valve and all new guides. Mark."
 
Guy

I responded without rea

Guy

I responded without really thinking about your comment..can worn guides contribute to carbon??
 
Carbon molecules in gaseous fo

Carbon molecules in gaseous form can travel thru any opening w/in the combustion chamber. When they mix w/oil the two become a semi-solid until the oil cokes at which time it hardens. JMHO
 
Might be "phase-seperation

Might be "phase-seperation " in the fuel. The ethanol has been doing some nasty things with rubber hoses and gas tanks. fiberglass and aluminum mostly.
 
"Mark:

I assume you did not

"Mark:

I assume you did not remove the two valves to inspect the guides. You may have defective guides from the box or damaged when they were knurled. Crud is getting inside the guide per Bt. Dr.'s comment. You might want to magnaflux the head for cracks, especially at the two cylinders.

Is there alot of smokey blowby gas going into the carb? Was there a layer of sludge in the engine when you did the valve job? Clean oil w/a 1/2 pint of SeaFoam added can free sticking valves."
 
"Hmmmm... would that still onl

"Hmmmm... would that still only apply to exhaust valves??? gaseous carbon couldnt get into inlet ports as inlet valve closed at that moment???

Bt, Ok, ethanol fuel, dont think im using it, as I use straight unleaded pump, how ever i buy off a cheap independant, so its possible. Tank is fibreglass, I removed and flushed it out december 09, It seemed ok.

Guy, I inspected the guides last time, 6 mnths ago, just a visual with heads still fitted (accidently dropped valve down onto piston when air pressure went off.) Couldnt tell much, knurl looked about 4TPI.
Yes I do have some Blow by as block was 17 yrs @1000 hrs old 2005, when honed only, not bored. re-installed original pistons with new cast iron rings, ring end gap was at the limit. Figured id take it to the first oversize at the next 17 year reco 2022.
wink.gif

It does fume a bit. when this happened six mnths ago, flame arrestor was a bit choked up, but this time it was clean as. Oil i used is penzoil 10-40, six mnths ago.

what is sea foam?"
 
"guy/Bt

do you mean the blo

"guy/Bt

do you mean the blow by to the crankcase (gaseous carbon)is being drawn thru the carb via rocker cover breather tubes to flame arrestor!!!!
into the inlet ports, mix with fuel, uses the knurling to travel up the guides and bingo! glued valve stems!
Will Syn oil help?
Maybe a catch pot to the rocker cover breather tubes?"
 
"I had an intake valve seize a

"I had an intake valve seize and bend a push rod in a 289 once. The cause was bad gas with varnish forming. Had valves stick several times without bending push rod. Valve would stick slightly (not close all the way) on start up, would free up after a few minutes as the engine warmed. Once I burned up the bad gas never had any more problems. Taught me to not use smelly gas from a junk car even if it was free. I was lucky it only cost me one push rod."
 
"thanks james

My valves are

"thanks james

My valves are stuck closed; they lock up whilst not running. push rods bend the moment I try to start. Im a bit concerned about my fuel, I buy it from an independant, brand X.
I wonder if guys sea foam can help, never seen it here in oz.
I just bought a new set of push rods, parts guy assures me problem is that I dont have stem seals. Mark."
 
"Mark, this isn't to go of

"Mark, this isn't to go off topic. Guy, if you think Sea Foam would clean out Mark's valve guides do you think it would help an intermittant stuck oil ring? Also to your suggestion for Mark, if you put clean oil with SF in, how long to run it before you change the oil again (and of course get it out hot)? Thanks."
 
"Go to SUMMIT and get a NEW se

"Go to SUMMIT and get a NEW set of completly assembled Vortex heads.
After its been running awhile, check the plugs and make sure its not running rich"
 
"Mark's engine is an 1988

"Mark's engine is an 1988 SBC. '87 and up used the center bolt valve covers and vortex style intake bolt pattern--middle bolts being a different angle. I figure he is good to go, mabey I'm wrong.
My main point being he should trash those heads and relace with new.
Chris"
 
"Mark:
read about SeaFoam bel

"Mark:
read about SeaFoam below. There may be similar products in OZ like engine cleaning products used before changing the oil.

I would stay away from synth. oil on an old engine; too many old seals/gaskets could leak.

No need to change the oil after using SeaFoam since it evaporates and the dirt reemoved is captured by the oil filter.

Yes, it will free up sticking valves and rings. It can be used to decarbon an engine thru the intake.

http://www.seafoamsales.com/how-to-use-sea-foam-motor-treatment.html"
 
"Mark:

The man talking abou

"Mark:

The man talking about valve seals is right; it is a good cure. Yes, I am talking about gaseous carbon filled blowby. Seals will reduce it entering the valve stems."
 
"1987 did use the center bolt

"1987 did use the center bolt valve cover type heads and a 90deg angle on the center 4 intake bolts yes...HOWEVER,these are NOT Vortec heads,its a common miss-conception.GM did not introduce the Vortec style head until 1996 and are easily identified by the intake only using 8 BOLTS instead of 12,the 4 center bolts being eliminated.They also use a hard plastic intake gasket with a guad ring imbedded in it.Aside from the better air chambers in the heads,the Vortec 5.7 also had roller lifters and a more "air friendly" intake.This is how the boost in HP from 260 to 315+ was achieved,in marine use anyway."
 
"It sure sounds like oil being

"It sure sounds like oil being sucked in through the valve guides and "coking" on the valve stem. Possible causes include; missing or defective valve seals, clogged oil return passages in the cylinder head, excessive stem to guide clearance or improper knurling of the valve guide. Almost all of these have been previously mentioned in the posts above."
 
"Thank you all for your commen

"Thank you all for your comments.

Guy; I gave engine 100% ohaul 3 years ago, did it myself, gaskets/ seals are as good as a new engine. Its done less than 100 hrs since then. Ohaul was new seals gaskets everywhere, bearings, rings, timing gears & chain, one exhaust valve, new guides knurled to prevent stuck valves
sad.gif
. new bolt ons are tstat housing, inlet manifold (centre bolts at strange angle), exhaust mans & elbows, water pump, sump, and a whole lot more...only machine shop work was cylinder hone for new rings, by Peak Rebores Sydney, and head job by Serviced Head Exchange Sydney. He replaced the burnt out ex valve and replaced the guides and machined seats etc.

After install to boat it ran like new, good compression and smooth as a sewing machine.
Engine is on its third oil change since rebuild.

ALL; This engine does not have valve stem seals. I know because i had all inlet valve springs off 6 months ago, as all odd inlet valves were stuck, only has SQ Oring below collets inside retainers. Head guy said it didnt have guide seals when i gave the heads to him, and shouldnt need em.

Im now thinkin i wouldnt need em if I didnt have Blow by from osize bores. (Guys comments)

I want to try to fit seals to all inlets, without removing heads. ill use my leak down test regulator to pressuris ea cyl. do em 1 @ atime.

All;
Is the gaseous carbon getting into the guides from top via rocker cover area or from bottom of guide via inlet port? If top then seals, if I can get them to fit, will help.

below link shows my heads, looks like im missing parts 8, 9, & 12? it shows 2 seals, which one? hard to tell, bad image...

http://www.dougrussell.com/partscatalog/components/index.cfm?fuseaction=viewpart s&colid=04&coldesc=260%2F5%2E7L%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20% 20%20%20%20GM%20350%20V%2D8%201987%2D1995&index=1014&block=240&BlockNumberList=8 0,70,50,60,470,490,180,140,160,170,130,150,270,250,260,240,110,440,450,460,90,10 0,350,340,190,200,370,360,120,290,300,480,0,410,400,310,280,390,380,430,420,320, 330,210,220,230,20,40,30,10

Thanks Mark."
 
"Cheif

Thanks for the link,

"Cheif

Thanks for the link, I saved it and will compare later today after I start pullin down engine. from memory, my plugs looked good but cant wait to compare to your doc. Mark."
 
"Guy, Im confused, when you ha

"Guy, Im confused, when you have refered to sea foam in the past I thought it was in reference to removing water from fuel system. Now are you proposing to adding it engine oil?? does this stuff go in fuel tank or crankcase?
Ill check the link..Mark."
 
Mark:

SeaFoam does it all w

Mark:

SeaFoam does it all which is why it is such a good product. It disolves built up fuel varnish and carbon. It can be used in the fuel or oil to clean the fuel system or to free sticking valves and rings. It does a great job removing carbon from the engine.
 
Mark:

Since you did overhau

Mark:

Since you did overhaul the engine then synth. oil would not cause gasket leaks. It will reduce or eliminate oil coking. Try to use a heavier wt. oil such as 25W40 or 15W50. One of my concerns during the rebuild is the same valves were used w/new guides. There has to be some wear on the valve shafts allowing oil to seep past the guide. Seals will stop it.
 
"Guy

I smell a rat...

We

"Guy

I smell a rat...

Went to the sea foam website. theres a guy called Guy, in a video, pourin sea foam all over the place..is that you?
do you have shares in this company?
lol.gif


Mark."
 
Chris

i would love to wave

Chris

i would love to wave a magic wand over this donk to change the top end to vortec.
Unfortunately its not an option due to time and cost restraints. It would cost several thousand $ to do this. Mark.
 
"I wish I owned SeaFoam! Was

"I wish I owned SeaFoam! Was he a bald and chubby fella w/a graying mustache?
sad.gif
"
 
"errr... no
my wife would say

"errr... no
my wife would say he was a good lookin sort of chap, with dark hair, about 40.

Change of subject, I just pulled the rocker cover, its all turned to S__t. Water droplets and signs of grey milky oil on rockers. Dipstick all good, with clean clear oil.
After the rods bent, i pulled out the two bent pushrods, I ran engine for about 1 hr after (low RPM) so they couldnt break like last time...I couldnt pull the two spark plugs as I didnt have the right tool in the boat. Id pulled the two leads from dissy aswell. you see we had to keep fishing... It was Australia day, couldnt let a couple of frozen valves ruin the day.
Do I have a blown head gasket?

ps cant sea foam here. Mark."
 
"Mark, I'm just now readin

"Mark, I'm just now reading this thread.... thought that too many chefs may ruin the stew .... but here goes:

If I understand you, this has now occured twice???? Replacing the heads may not be a bad idea, but I think you have several things to consider first!

A 1988 5.7L may be using the dished pistons, in which case the small 64cc chamber heads may have also been used!
If so, the 64cc Vortec heads could be a candidate (along with the new intake manifold). However, don't expect the performance from the Vortec head to be that of 315 horse power..... (a common misnomer).
Notice that most all of the Vortec roller cam marine engines are rated at/near 5,200/5,400 RPM...... hardly an RPM that does us marine guys much good!

If this '88 engine used the flat top pistons, the 64cc chamber Vortec heads are a bad choice, IMO.
Your C/R will be incorrect for marine use if this is a cruiser type hull!
For this, the 76cc chamber becomes a better choice. (maintains a correct C/R for marine use)

IMO, it would be best to replace with a like casting number!
There are some decent and affordable Dart heads available these days.
http://www.dartheads.com/products/cylinder-heads

."
 
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