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I have a big ? over my head

2706 Views 23 Replies 5 Participants Last post by  ghnl
:confused: Setting the right cam timing, after re seating the valves, one was burnt then replaced and bolting the head down at 57lbs I thought I had the cams in ok but, found out the exhaust was 180 out so I re did it, checked the comp, at 135 average and then it fired up but ran rough
No problem, I had the air flow meter un plugged but, after I plugged it in, it wouldn't start?
I re-checked the cam timing, it was off just a bit 'cause of the chain slack, but, once again I thought I fixed that. While at tdc the exh just closed and the intake is just satrting to open. another comp check, this time its at 0, zero?
Is ther something I'm over looking?
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Just for referance - what model year Spider?

TDC with exhaust just closed and intake about to open is not TDC on compression. Remember that in a 4 cycle engine the piston goes to TDC twice. TDC on compression is where things are supposed to be measured - cam timing, ignition timing, etc.

I'm still trying to figure out how you went from a running engine with ~135 psi compression to a non-running engine with no compression...
Yeah, the running to zero compression is what really stummped me.
I'll go out now and redset the cams again, this time on comp stroke! thanks
Check the ignition timing, too. It is easy to get that 180 degrees off. When the #1 piston is at TDC on compression, check where the rotor is aimed. That is the place in the distributor cap where the #1 spark plug wire must be installed. Then connect the remaining wires in the correct firing order: 1-3-4-2.
I must be missing something somewhere, I just went out and it was 180 out so I put it at tdc on #1 and made sure the dist was at #1 also but it still had low comp, could the cam timing be off just a little bit for it to do that?, with a new head gasket and tourqed down it shold be more than that.
What was 180 degrees out? Remember that the camshafts & the distributor turn at 1/2 the rotations of the crankshaft.

#1 at TDC on compression should have the #1 cam lobes facing away from each other - exhaust amied left, intake aimed right. TDC on the exhaust stroke will have the cam lobes facing each other.
yes theyr'e facing away from each other, before the dist was 180 out.
I don't know what's going on, could I turn the cams a little for the comp reading to go up?
Make certain* the #1 piston is at TDC then align the marks on the camshafts to the marks on the backside of the front camshaft bearing top half.

*To make sure #1 is at TDC I like to use a drinking straw - it is stiff enough to work yet bendy enough not to ruin anything. Remove the spark plug (I usually remove all of them to make turning the engine over easier). Peek down the spark plug hole and you can see the piston as it nears TDC. Slip the straw in and slowly rotate the engine in the forwards direction (I just put the transmission in 4th speed and roll the car forwards). The straw becomes your indicator to know when the piston is highest in the cylinder.

**It is hard to see exactly where TDC is as the piston/straw moves only very slightly for the few degrees before/during/after TDC. To be even more accurate (using the straw), make a mark on the straw about 1 inch below the approximate TDC position. Now move the car backwards until that mark drops below the spark plug hole then roll the car forwards again until that mark is at the spark plug hole. Stop and make a temporary mark on the crank pulley adjacent to a fixed point (like the pointer that should be at the lower, left side of the water pump).

Next move the car forwards until the mark on the straw rises up and then drops down until it is again even with the spark plug on the down stroke. Make a second temporary mark adjacent to the sam efixed point.

TDC will be halfway bewteen those two temporary marks.

The pointer (if present) is 'adjustable' and thus be mis-adjusted. So it'd be a good idea to double check the accuracy of the TDC pointer. Once you know it is at TDC, set the pointer to align with the 'P' on the crank pulley. The pulley marks are usually hard to find - they are very shallow and usually covered with crud. Below is a picture showing the mark cleaned & highlighted with a bit of silver paint. ('White-out' is useful for making these marks easier to see after you've located them and cleaned them off)

The sketch from the Alfa Shop Manual shows where to locate the cam timing marks. It also shows the use of a dial indicator to locate TDC. That'd be the ultimate way to do that - my drinking straw method is just the eL-cheapo version of a dial indicator.

BTW, have you adjusted the cam chain tensioner? If it is way loose the cams won't stay 'timed' correctly.


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Eric has it all pretty well covered it looks like.

Just a couple questions/observations from the edge of things:

As the head and cams were all seperated from each other during the work, I'd not go by the dizzy when trying to reference TDC.

Yes, the rotor should point forward and be at least somewhat aligned with the tic-mark, but it shouldn't be the be-all telltale that you're on the right track AFA the cam index.

Get the TDC mark lined up using the drinking straw or dial indicator, then check that the dizzy rotor is pointed more or less in the right direction. If it's not, roll the engine over until you're at TDC again and the rotor is correct, then get after the cams, not the other way around.

With the rotor forward, the #1 piston at TDC, the pointer aligned on the crank pulley, both #1 lobes on the cams should point outward. (intake toward the intake port, exhaust toward the exhaust port and the little tick mark at the #1 journal lined up with it's corresponding mark on the bearing cap)

When you tensioned the chain, did you use a lever to ensure it got tight enough (good plan) or did you trust the tensioner spring to get it right (not so good plan)?

Still not knowing the series#/model year it's hard to tell if your compression @ 130-ish psi was right or not.

In a non-VVT engine, that's definitely on the low side, but in a VVT type, it's actually pretty normal due specifically to the VVT.

Unfortunately you'll not ever be able to test compression to full pressure on a VVT engine as it either has to be spinning at X rpm to operate the VVT (centerfuge type) or thier has to be oil pressure and the TPS switch activated (electronic solinoid type) so all you're left with is the readings it gets with the intake cam retarded. (which is usually in the 120-135psi range, or at least it was whenever I tested on a known good condition engine)

Once the VVT kicks, the intake cam advances and compression comes up due to more efficient use of the overlap cycle and a few other nuances in the valvetrain.

Do NOT try to get compression up by tinkering the cam index, especially on a VVT engine or if you don't know exactly what you're doing. (unless you want to try and clash the valves anyway)

Just go with the stock index and make it run correctly before you head off on a power seeking tangent. (and then don't bother unless you're prepared with an index degree wheel, dial indicator and a bit of specialized information)

Now as to why you ended up with zero compression, all I can imagine is that your cams are majorly out of whack index-wise, or your valve clearance is WAY too tight and the valves are actually hanging open off the seats. (you didn't just put the shims you had in it before right back where they were did you? Any work on the valve seats or valve heads would change the clearances making the original shims all but useless)

In regard to the exhaust seemingly 'slipping' it's index after being set, you did put that little throughbolt back into the drive gear to lock it after setting it didn't you?

Without it, the cam can still get out of whack even if the locknut on the end is tight.
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Now this is starting to get wierd, you say and the book say's the #1 spot on the dizzy is to the front, but, I didn't change anything there from before and the #1 plug wire is going to where the #4 should be??, now that say's it would be 180 out, so, I may have had it right the first time according to you and the book.
It's a '86 Spider by the way.
Can you find the little tick mark on the edge of the dizzy body where the cap sits? (image from the site linked in ghnl and my signature blocks)

The centerline of the rotor should be in line with that tick mark, both cams should have thier lobes pointing outward, and the engine should be at TDC. (and hopefully the crank pulley pointer agrees with all of that)

If your #1 is where #4 would normally be, you're either 180 out with your compression stroke or the dizzy was put in 180 out during some past removal/install. (the tick mark will let you know if it's the dizzy in backwards)
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It is not unusual for the distributor to be 180 degrees off. The car won't mind and it'll run just fine but you must install the spark plug wires using the 'new' positions - firing order is 1-3-4-2.

But you must be certain the engine is at TDC on #1's compression stroke. I fear this is where we're having difficulty. I also fear that the cams were OK but then you moved them (or one of them). And that could cause it to have no compression... I hope it wouldn't cause the valves to crash into each other.
Ok, it's all set the way it should be now, dist rotor to the front on the mark, at tdc on "p", cams lined up with marks on caps and int and exh lobes facing away from each other on the #1 cylinder.
I cranked it, it sputterd a little at first then nothing, I know the plugs are sparking but the motor isn't firing, it could be something else now, ARRGH!!
OK, once you are sure of all the above, I'd suggest you give the battery a good charge. The L-jet ignition system requires a minimum of ~ 10.3V even during cranking to wake up and send the "make spark" signals. And if no spark there is also no "send fuel" signal.

While the battery is charging, clean its terminals and all the electrical grounds. See the L-jet page in my signature for details.
Well, I haven't done anything ot it Today, it's been on a cherger all day.
So, I come home and turn the key to see what it might do and it was wanting to start ta first crank but, nothing after that, now I'll check all fuel connections, cold start valve wich was replaced last year. I did check the valve clearance, some were a little tighter than specs but not keeping the valves open, they should still be done right though huh?
Thanks very much for all the help, I'll let you know when it's running, cause I know it will!! Tim
Not to state the obvious, but you do have the Air Flow meter hooked up, don't you?

Ask me how I know.....
BREAKING NEWS!!, well, I kinda felt that excited, I went out to the garage just to "give it a try" and it fired on the first crank, it ran a little rough, I think it may be sucking air somewhere 'cause it was burning my eyes. I did't let it run very long, now I need to replace the starter solenoid (as per another topic post, "It won't stop cranking") I hope it's that and not the ignition switch, maybe a cool "push to start" button?
it ran a little rough, I think it may be sucking air somewhere 'cause it was burning my eyes

Did it smooth out but smoke heavily if you revved it up a bit?

If so, check the contacts inside the harness plug for the AFM to ensure that none are pushed back in a bit and not making the connection. (if the air temp sensor, which is in the AFM, gets disconnected it'll act like that)
I didn't check or do anything to it last night cause I was out there in my slippers and bath robe, maybe later.
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