Alfa Romeo Forums banner
1 - 18 of 18 Posts

·
Registered
Joined
·
156 Posts
Discussion Starter · #1 ·
73 spider 2L usa, spica, factory 105200320000 cams.
Lots of great info about this topic on many threads, but I still have a question.
I think my high RPM performance is less than it should be, say over 4000 RPM, but below that, I think it pulls strong, wouldn't change a thing there.
Is that a symptom of these camshaft timing marks, that I find to be off?
Engine verified TDC, by the P on crank, and #1 plug measured with a wooden stick, but i'm getting a dial indicatior to make absolutely sure, dist rotor at #1 too. cam lobes out. Just retentioned the chain too.
Water Tree Photography Wood Ice


The exhaust looks pretty close, Just a hair advanced. But that's okay, right?

Auto part Machine Metal



The intake look way off, and hense my lack of high RPM performance question, but a little over my head. The intake looks retarded, it should be advanced if anything, right?

Auto part


Much thanks. Love the forum.
Bill
 

·
Premium Member
Joined
·
15,015 Posts
The timing marks on 73's were at 114 intake and 102 exhaust - according to the Shankle catalog. Richard, wouldn't he be better to make a new mark for his intake cam?
 

·
Richard Jemison
Joined
·
8,390 Posts
Cam marks

his intake mark is at 114 BTDC. If he has a VVT that is where it needs to be. If cam sprocket is no longer using a VVT unit then it should be ar 102.
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #5 ·
Thanks guys, you're right, both are retarded. I'll be sure to set the exhaust first though, hadn't heard that before. No VVT, 1973. I'll report back on performance (specifically higher RPM). Gotta wait for lock tabs from IAP.
 

·
Richard Jemison
Joined
·
8,390 Posts
Timing cams

If no VVT you should get the timing template from Centerlinealfa.com and remark the intake cap to 102.

With the mark at 114 and your intake cam another 6 degrees retarded it shouldn`t have any top end!

If you look at the pic of your intake as is with the cam mark where it is that is about 100 BBDC. If you change the exhaust cam place the mark similarly positioned but just past the mark which will be about 104 BBDC. That will improve drivability everywhere.

You should remember that these are the least "performance capable" of all Alfa cams, and these cams will not produce much upper end power by design.
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #7 ·
intake timing

Alfar7 and alfaparticle,
Thanks for your inputs, finally got to it. Had to fly to other coast for a week, and stuff.
So, here's what I got done on Saturday. First I wiggled things to get the exhaust cam exactly on its timing mark. Rolling the car forward in gear just so that the exhaust cam was perfect. Then easing back just a hair, the crank had enough "play" in the lower chain (?) to roll back about 1/2 inch to line up on the "P" mark - while nothing else up top moved. I think that is an acceptable amount of play. This left the intake cam retarded by a fair amount, but not quite as bad as the first intake picture above. Then I verified the timing marks.

Exhaust was right on at 102, just as it should be.
The intake cam is marked at 108, even though it should be 114.
Font Signage Wood Sign


So that made the cam timing look even worse at first, but in fact, it had been previously timed to be at 114. (maybe about 111 - 112).

So, I moved the vernier bolt (?) 6 holes advanced.
I think that should be (6x1.5) 9 degrees. And if it was 114 before, then it should be (114-9) 105 now. But when all buttoned up, it looks more like 102 to me. So that was far enough for me.
Auto part Engine Automotive engine part Machine Metal


I took it for a nice test drive and I give it a 100% success. Pulls much better right up to redline. Didn't notice any change in lower RPMs.

Thanks again for the inputs. I can only wonder why they put it to 114 to begin with, must have been a polution thing?

Ultimately, the real answer is better cams. Someday RJR cams.
 

·
Trained (ex)Professional, , 1953-2018 RIP
Joined
·
16,232 Posts
I'm afraid that the cam timing is still not correct.
When setting up to do the cam timing, the engine needs to be turned in it's normal direction of rotation (counter clockwise as viewed from the rear) to line up the P mark. By lining up the exhaust cam first, and then turning the engine backwards to line up the P mark, the cam timing is off by the amount of play in the chain(s).
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #9 ·
Papajam,
Oh boy, I'll will do it again. This time leaving it at the P mark, like it was in my first pictures on 4/9/12 (where the exhaust was slightly retarded), and then advancing the exhaust to 102, then I'll probably have to back off the intake just a hair then since its probably too advanced now.
Bill
 

·
Richard Jemison
Joined
·
8,390 Posts
Timing cams

From your pictures the cam template is cut too small to fit correctly in the recess to get an accurate mark. (slide it left & see...)
The mark on the cap is 114.

If it runs ok leave it alone.
Rj
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #11 ·
Rj,
Okay, I did notice that the template was a little small., I'll redo it this weekend.
Bill
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #12 ·
I did recut the intake cam template, I do think the factory mark is at 108, but its like spitting hairs. I scratched in a new mark, tried to get 102, missed, didn't quite get it right, close enough.
Font Wood


When all buttoned up and retentioned the intake fell a bit shy of 102, maybe 104. Oh well, good enough for now. At least better than before when it was probably 114 or worse. I'll play with it again in the near future.
Auto part Hardware accessory Metal Gear Engine


By the way, the exhaust is right on at 102, just as the cam is marked. And I'm leaving it there for now. I tried a couple of times to advance it a little, 104, like Alfar7 said, but I just kept chasing it, too far one way, then too far the other, even though I was just moving the bolt one hole each way. I don't know, poor technique on my part with tentioning the chain when done I guess. But its all good now at 102 exhaust.

Thanks everyone.
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #14 ·
Jim,
Yeah, lossened the chain, then when adjusted retightened it, first by rolling car forward a few turns and then making sure with a screwdriver wedge, like in Pat Braden's book.

Does that sound okay? Thank you very much,
Bill
 

·
Registered
Joined
·
2,984 Posts
I put some force on the cam when I do it to take up any slack.
I have a stick with pins in it that fits the holes on the cam.
depending on how the lobs are pushing it can and may slide forward a tad.
if you don't put too much force you can use the nut. but if you push too hard the nut will come undone. but this way is will make it consistent.

turn the motor over 2 times to TDC and recheck when done.
 

·
Trained (ex)Professional, , 1953-2018 RIP
Joined
·
16,232 Posts
You loosen the chain to do the cam timing?
Yeah, lossened the chain,...
Reason I asked is that there is no need to loosen the chain. Simply loosen the big nut, remove the small locating bolt, turn the cam and insert the bolt. The chain and sprocket will stay where they are.

BTW, in the pic in post #12, the left side nut on the #6 cam cap is on upside down.
 

·
Registered
Joined
·
156 Posts
Discussion Starter · #18 ·
Thanks Jim,
I see what you mean about the nut, I'll fix it soon, and check the others.
I love the knowledge on this bb and willingness of everyone to share.
Thanks again,
Bill
 
1 - 18 of 18 Posts
Top