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Discussion Starter #1
Had a strange thing happen to my new to me 1974 spider. Drove it home from the PO's home
about 300 miles. Car ran well, no problems. When I decided to dive into it I checked the compression.
Intake side I got about 160 in #2,3,4 but dead 0 in number 1. Decided to think about it until I had worked on the interior.

Finally got around to checking compression again and now I had 160 in #1 intake. I'm just a little puzzled.
Started to install a new RML dizzy. Lots of back firing from #1. Did a valve clearance check again, all the exhaust valves were in spec, all intakes were OK in #2,3,4. except intake #1, clearance was 0.049. Crazy,, There was a lot of gas coming out of carb # 1. along with back firing when I working on the dizzy. Spark plug was dry.

I do know (looking at receipts) that the PO recently had a bit of work done on the head. Maybe he set the clearances wrong??

The cam buckets look good, they are used and they look to be spinning OK. Buckets came out cleanly using a magnet. Looking at the valves through the open plug holes (cams removed) seem good. I thought I might see the edge of the valve if the valve was bent or something like that. There doesn't seem to be any difference in the depth of the end of the valve stem compared to the others.

Question: Would this kind of clearance cause the presser to be "0" or do I have bigger problems here???

Any ideas are appreciated.

BTW: I just learned that the guy who has been doing my "big" repairs on my foreign cars has decided to retire..Bummer.

Any ideas as to a good shop in Eastern NC would be great.
 

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Why do you not believe the compression recheck of 160?

Pete
 

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Compression check, make sure throttle is wide open and car is hot. I’d reset your lash on 1 intake, put original dizzy back on and time it, see how it goes. If you have a leak down tester that would be helpful in ruling out valve issues
 

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Discussion Starter #4 (Edited)
Thanks for the responses. Keep those cards and letters coming.

Leak down test suggestion is good idea,. I'll look into buying one. (He who dies with most tools wins.)

"Why believe the compression recheck?"
Same gauge,same readings on 2,3, and 4,
Gauge has been used for more then 65 years. Got it from that old timer,
Roger Penske before some of you guys were born.. :whistle:
Compression tests run more then three times (hot and cold) almost with same results.
And yes my foot was on the "go thingy" under the steering wheel during tests..;)

"I’d reset your lash on 1 intake ". That's a given..
But the question is, Why so big.

Different Dizzy "should" have no effect...
 

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But the question is, Why so big.
Just a random guess - perhaps the valve is sticking? (or bent?!?). If it sticks slightly open that could explain the large clearance & poor compression. Valves can stick when hot and then free up when cool. I'm not an Alfa engine expert but it has definitely happened with bronze valve guides in cast iron heads.
 

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I don't think I asked my question clear enough.

So the first time you did the compression check #1 was 0, but the rest were 160. You rechecked #1 and it was 160. Why are you still worried about the compression of #1? I would assume that something went wrong when you first did it.

Fix valve clearances, if needed, and enjoy driving your car :)
Pete
 

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Discussion Starter #7
PSK asked:

"So the first time you did the compression check #1 was 0, but the rest were 160. You rechecked #1 and it was 160. Why are you still worried about the compression of #1? I would assume that something went wrong when you first did it. "

There was a third compression test done after trying to get the RML dizzy set up. There was a lot of spitting and back firing, so I did another test. (#1 intake was still 0 Lbs., all the rest OK)

I'm beginning to think that it is a bent valve. :cry: Not good as I've lost my local repair shop.

Right now I'm in the process of putting it all back together for one last test. I've made all the measurements on the shims. Looks like I need to do them all. Do the whole thing over again to make sure.
 

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could be. Not sure how that would occur unless the timing is way off. it sounds like a stock motor/head, correct? Remove the can bucket and shim, squirt some oil down the valve shaft, and POP the top of the valve with a brass drift and hammer - it may pop back into place. Maybe a piece of crud on the valve seat? Would have to be big (+20 thou) though --
 

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Have you disassembled it to look at the shim, the keepers? I've seen some crazy work recently. My guess, you'll be removing that valve before you get to the bottom of this...
 

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Get a brass punch or one made of hard wood. Turn the motor until #1 intake lobe is up then whack the tip of the valve with hammer and punch so that it lifts and snaps back against the seat. Then re-check the clearance. That should move any bit of junk on the seat.
 

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There is rarely junk on the intake valve or seat if the engine was running "well, no problems". But who knows. Can't hurt, right! Now junk in the trunk, let's see some pics!
 

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Many years ago I changed plugs on my wife's Audi. Started the car afterwards: it ran for two seconds and died. Wouldn't start or even try to catch after that.

Had it towed to my mechanic. He tells me there's no compression on all four cylinders. I'm panicking, thinking I f-ed up bad. He said "Nah, when you replaced the plugs you broke some carbon free from the top of the cylinder and it got under the valves. I'll flush it out and you'll be good to go." Sure enough it was an easy fix.

So I wouldn't rule it out.
 

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Discussion Starter #13
Gubi: I had that thought too. I just got it back together and tomorrow I'm going to give it a try again. Start and run the engine for a while. The bore scope did not show any obvious damage.
I will report back.

(Don't you hate it when a guy with a problem gets help for a number of days and then we never hear from him again with the resolution to the problem....:devilish:...)
 
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If you have the cams out, it is worth checking what andylarry said. It is not uncommon for the little bucket shims to dislodge holding a valve open. Usually only happens if a serious over rev has happened, but ...

Actually I'm not a fan of this design, but maybe it happens with normal flat shims too??
Pete
 

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Discussion Starter #15
PSK: It's all back together and I just did another valve clearance check.
Just a small bit of difference from the first check. This time the engine was cold.

Interestingly, I also did a check on the buckets and there was a small range of thicknesses in the eight of them.
So we need to keep track of where they came from.
I marked them on the top with a felt tip pen.
I measured again after marking them, there was no difference...;)
 

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Discussion Starter #16
Update: We got the head off today. Below are pictures of the damage. Looks like
a small screw driver tip was in there. Before getting the head off I thought I
let a nut drop into the intake when I was installing the air filters awhile back.
I would have remembered getting a screw driver stuck in there. It was not me... :)
It looks like the pieces were in there all the time I drove the car home from SC.

IMG_3345.JPG
IMG_3337.JPG
IMG_3340.JPG
 

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What is that broken piece of metal ?? I would try my best to determine where that came from. Screw driver ?? I doubt it. Part of your air box?? Can you snap another image next to a measuring stick?
 

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yes, more investigation into the terrorist in the combustion chamber please! Is it ferrous? Its not a spark plug electode I dont think --- its not a piece of a valve seat is it? Do the two pieces mate up ; ie it was longer then broke up? Anything in the air box or throttle bodies at all? Weird.
 

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Discussion Starter #19
The pieces fit together, about 1 in. long total.
 

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holy smokes! 1 inch long and .250? thick? Thats HUGE.
 
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