1.9 Cylinder Head

[neuropel]

Greetings all,
On my way home from Carlisle, my 74 Manta started backfiring and missing as I was coming up the PA mountains. Upon arrival at home (luckily Tom Cavataio was following me), we noticed fluid leaking around the #2 spark plug hole. Since I'm home for a few days, I decided to investigate further. No sign of water in the oil (or vice versa), so I pulled the plugs. The #1 and #2 had a lot of black build up and were wet/sooty, while #3 and #4 were dry and tan/brown. Next I did a compression check and got 120, 120, 115, 115. As I was pulling the head, it was clear someone had been in there before - most telling were the hex head bolts holding the cam sprocket onto the cam. Also, I noticed that the bolts in the front half of the head were not as tight as the rear bolts. I've attached pictures that I took JUST after I pulled the head off and turned it upside down.
Tomorrow I'm taking it into the machine shop to have it checked. Perhaps some of you diagnostic gurus can chime in?

Todd

[First opel 1981]

The compression test doesn't show a huge difference in compression but the 5lbs does coincide with the small nicks that appear to be in the intake valves on those cylinders (if I read the pictures correctly)

The fact that the #3 cyl looks cleaner than the other ones implies a cracked head (or blown gasket) in #3 cyl.
It "could" just be a head gasket issue but the #3 cyl thing is suspicious.

The cracked head would cause missing but it usually doesn't cause a huge misfiring problem. A blown head gasket would cause a misfiring problem but usually you would experience a more significant drop in compression than the 5# you experienced. It could be something else entirely that cause the misfiring/backfiring issue and it just lead you to the head issue. Keep an eye out for that scenario.

Looks like you have some work ahead of you and might want to shop around for a new head, just in case.

[sawdust]

Must be a virus going around. Mine started the same thing today. It would start up fine but not idle on its own. It sounded like it was missing so I checked the plugs: they looked clean and grayish black. It had its expected power when driving and would backfire only when you let off the gas as one comes to a stop lite. I will preform a compression check tomorrow. I am not about to take of the head yet. I was concerned about Bad Gas. I just filled up at a cutrate (cheap) gas station.

[wrench459]

Double check your ignition system for carbon tracking and/or cross fire between one and two.

[neuropel]

I have a set of 2.4 valves laying here...might consider having them installed in the head if it checks out ok.

[neuropel]

When I dropped the head off at the machine shop, I also brought the head gasket in for the machinist to examine. I'm no expert, but I thought it looked fine. The machinist said it showed no signs of heat, and he thought it looked OK as well. He did say the head looked a bit rough in the #2 combustion chamber, which was the one leaking. If it checks out ok, I'm just going to replace the head gasket and reinstall the head as the car was running great up to this point. He's going to clean it and magnaflux the head first ($10 to clean, $25 to magnaflux - CHEAP!) and then go from there. He also mentioned doing a pressure test if no cracks are spotted - is that needed? I'm thinking this whole thing may have been due to the head not being torqued down properly. I'm finding LOTS of things on this car not torqued down properly as a matter of fact. I'm removing the automatic transmission, and found a couple of the bolts only finger tight ! Also, one of the exhaust manifold bolts was missing, which I had never noticed because it's hidden under the carb heat shield.
Today I also completely removed the entire exhaust, removed the dash, console, carpet, and pedals in preparation for converting from the automatic to the 5 speed. I then cleaned up the new pedal assembly and painted it black. Hopefully I can start reassembly soon. I'd like to actually drive the car some now that nice weather has arrived.

[GoinManta]

How sooty were the plugs?

Bens Manta has one cylinder in particular that has a bad valve stem seal, after about 3-4 months it cakes up bad and then doesnt fire well.. so the motor loses power, etc..

Could it be simply a few bad stem seals and fouled plugs?

[neuropel]

Originally Posted by GoinManta How sooty were the plugs?

The #1 and #2 plugs were very sooty and nearly caked over, whereas #3 and #4 looked great.

[opelnut10]

If you do find the head is not cracked, it will be money well spent to take a skim cut on the bottom to make sure it is flat, and have the valves ground and new seals installed, while they have the head. Also have them check the valve guides to see how loose they are.

[tekenaar]

Originally Posted by opelnut10 If you do find the head is not cracked, it will be money well spent to take a skim cut on the bottom to make sure it is flat, and have the valves ground and new seals installed, while they have the head. Also have them check the valve guides to see how loose they are.

. . . worthwhile doing, like said above, but do the criss cross straight-edge check on both the block and head surfaces first ($0) to get an idea of what you're actually facing!

For all the other previous "similar problem" responders, check your valve lash!! . . . STATIC - engine not running - but at operating temp!!

[neuropel]

Thanks for the advice. I'll have them check it and if necessary, skim it to make sure it's flat. What method do you guys recommend for cleaning the top of the block surface?

One other thought to throw out there - this particular car has always had one lifter that takes longer to pump up than the others. I never tracked down which one it was, but I wonder if it's in some way related? I have a couple of performance cams I could drop in at this time as well, one of which is is the Isky OR-66 "combo" cam.

[wrench459]

Originally Posted by neuropel When I dropped the head off at the machine shop, I also brought the head gasket in for the machinist to examine. I'm no expert, but I thought it looked fine. The machinist said it showed no signs of heat, and he thought it looked OK as well. .

Humm just from looking at the pictures. Number 2 cylinder is a dead hole. Also number one intake valve should NOT be white.
Definitely have the head fluxed,pressure tested and checked for flatness in that order.

[GoinManta]

Originally Posted by neuropel One other thought to throw out there - this particular car has always had one lifter that takes longer to pump up than the others. I never tracked down which one it was, but I wonder if it's in some way related?

Very much so..

From what you have said.. I think the head while tired wasn't bad..

The lack of power was due to the two fouled plugs.. Withs Bens Manta one fouled plugs just saps its strength. Two and your down a lot of horses..

Basically I think your in the clear as far as cracked head.. I just think the
valves and lifters were tired.

Like Loyld said.. mill the head, check the valve guides.. etc.. just do a good rebuild of the head and you should be good. If it doesnt have 2.0L or 2.4L valves I would take this time to do them, new valve lifters and a mild cam if it doesnt have a cam now.

Do all that and I think you should see a big improvement.

[opelnut10]

If the head gasket would have blown, you would have water in the oil or oil in the water depending on where it blew. Your compression check would been down on one or two cyls. You definently need to have the head magna-fluxed and pressure checked, usually these heads crack in the exhust seat and from the looks of #4 exhaust valve that is the first place I would look. Your lifter problem could be any of several causes. The first thing I would do is mike the cam lobes and make sure they are all making the lifters do what they should, next look at they bottom of the lifer (cam lobe end) and see if it is somewhat dished (sign of wiped lobe) and lastly check your rocker nuts to make sure they are not backing off the stud.

[neuropel]

Got word back from the machine shop today that the cylinder head is pretty much toast. The #2 and #3 exhaust areas have been "pinned" in the past - this is apparently a way to repair a cracked head?? I didn't know this was even possible, so perhaps someone can explain it further? In any case, at least one of the "pins" was leaking, and he said there were lots of other areas that were "tired". The cam showed a good bit of wear as well.

Edit - found this explanation after a quick google search:
http://www.enginebuildermag.com/Arti...r_process.aspx

[guyopel]

Time to Upgrade
New Cam and lifters and replacement Cyl.head w/big valves . Good luck on your project !

[neuropel]

Yup...I think the best alternative for me at this point is to have one of the heads out of my parts bin fitted with the 2.4 valves I have left over from another project. I believe that'd require the least expense as I could use my existing springs, etc. and would only have to have new seats cut. I'd have the shop cut the exhaust valves down to 1.5" and use the intake valves as is. From what I've read here in old threads, it seems ok to use an earlier head with the later timing cover. That's probably my quickest path to get the car back on the road.