So I have been playing around... here is where I am at now!

[Anonymous]

Well I think Azcoupe and some others hit the nail on the head.

I called Schnieder this morning, and told them what was going on, low vacume, rough idle, rich, timing issues, etc...

First thing out of his mouth, sounds like the cam is retarded, try advancing it a little and see what happens...

But he said that at sea level, it should idle around 700, vacume around 15, and should be pretty smooth, he said it may have a slight lope too it, but nothing that would stick out to the ear of someone who did not know better... overall, he said it defeinitely sounds like retarded cam timing, now he also said that carb may be adding to the issue, but the low vacume and idle would not be affected that much, this sounds more internal timing related.

So now a good question, what is involved in advacning it? how difficult and what are the general steps? and should I play with the carb first, or try this first?

Because of the number of people who have said the 61 jets and 8.5 power valve worked fine in their engines, I am leaning towards this now as the most likely culprit...

thoughts?

 

[CobraSix]

Do simple first...try the carb first.

The cam may be a problem. Generally not too hard, I'll see if I can dig up some instructions.

Here we go...try this;

http://www.compcams.com/Technical/Instr ... _Instr.pdf

Slade

 

[Anonymous]

Well I read that PDF file and now I am more convinced than ever.
According to Comp Cams they recommend you use their timing gears with their cams because most aftermarket gears tend to retard the cam timing some... they do not say why? but they make that recommendation. They also say they grind 4 degrees of advance into their cams to help them be more streetable...

So I called the machinist to see what he thinks, and he was not sure.
According to him, they used the ceterline to degree the cam, I am using FSPP Dual Chain Timing gears.

He said from what I was saying it does sound like cam timing, he said if I have no vacume leaks, (which would be his first thought) then it may be that the gears and the cam are retarded a little for some reason, and it may be that I need to advance it a couple degrees... of course he did not offer any help in this area, but I could ask him to do it!

He also wanted me to bring it by the shop... so I may take it over there later this week, let them hear and see it...

So now I am back to the main things..
Vacume leak
Cam timing
Carb tune issues
trying to eliminate any and or all of these as possible culprits...


I keep going around in circles, I am going to play with the carb and timing some more before I tear into the block. And see if I can find any leaks, but I have checked everything twice and I have not found any leaks.

I think I am going to do XECUTE's cold compression numbers, those will help tell more about the cam... but I just have not had the time yet!

 

[BIGREDRASA]

Keep the faith Jimbo. Remember that you don't have an engine built "by the book."
Much of the final tweaking will be trial and error, not because you're inexperienced, but because you have a unique combination.
Dirt in the needle valve or a float set too high will cause excess fuel to flow into the engine. An overly rich condition will give you a lower vacuum.
Back in the old days, a hot rodder's trick was to set the valve gap closer to advance, and looser to retard the cam timing. The amount would be marginal, but still there. One thing you could do, to check if valve clearance is set too tight, would be to loosen each rocker, then tighten just until the clatter stops. That would leave you looser than required (temporarily), but would let you rule out valve lash as the culprit for low vacuum.
Cam timing is not something you can adjust without a special cam sprocket. There was an item called "adjustacam" that claim to give you that option. However, you can still get an idea of where it stands by usning a degree wheel. In lieou of the degree wheel, there is a tape you can attach to your harmonic balancer, which allows reading 360 degrees.

 

[strat1960s]

Jimbo

Man O' man. I have been paying close attention to everything you have been going through. I haven't even made it that far yet. I still have to fire my motor up for the first official cam break-in. I should get my air/fuel mixture screw sometime tomorrow. I took this week off so I could dedicate more time to getting this thing running. I may or may not get it.
I am very pleased that you are sticking with it. I know it can be frustrating and even a bit confusing, but you're sticking with it and in time you will get it figured out and then the real fun can begin.
I bend wrenches and bust knuckles Monday through Friday. In my free time I do the same on my 65 Mustang. I know how easy it is to get burned out and how important it is to take a break from time to time. I keep reminding myself that this is a hobby for me, this is a third car and I will still be able to get to and from work without it. Having said that, when I begin to get frustrated, I just close the garage door and walk away. On the other hand I have seen friends get so frustrated that after walking away they never come back to the project. From what I have heard from you and many other members to this site is as sense of dedication to their projects. That is something that I appreciate and will most likely depend on. Thank you for keeping me informed and focused.
Ted

 

[CobraSix]

Jimbo,

I'm using the comp cams with Mike's double roller chain. I'm not experiencing any troubles like you mention. I set the chain to 0* advance and my car runs fine. I had some tuning issues, but they were timing related.

Slade

 

[Anonymous]

Slade:

This is a Schneider cam, not sure if that makes any difference. I am also not sure if the cam is the trouble...

But I have decided on a course of action. I bought the Dial a Cam kit Comp makes that includes a degree wheel, and all the tools needed to do take measurements at .050" lift...

The Power valve and jets arrived this morning.

I am stopping by the parts store on the way home and getting a new cap rotor, and Autolite Platinum plugs. First I am going to install the new distributor parts and plugs, (my cap and rotor are a little worn, these are about the only two re-used parts I am going to replace them...)
At that point I will swap in the 4.5 power valve and set the timing and RPM's and see if I can get it down to 700 at all and have the timing at 16 and see what happens.
I also plan to take compression numbers at this point too...
If after this my vacume levels are still low, and the rich condition was not the culprit.

Then I am going to pull the Oil Pan, Timing Cover, and so on and get a wheel on the cam, map the lobes, set the degree on the cam correctly and adjust the valve lash at that time... from there if I find no errors I will feel pretty silly, but that is one way, perhaps the only way to 100% ensure that my Crank, Cam, and valves are in sync...

Since I know now, the cam was dialed in on the centerline, it is possible, maybe not entirely, but possible it could be off as much as 2-6 degrees, if I map the intake and exhaust lobes, I can LUCKILY, advance the keyways on the timing gears.

Only problem now is finding the time, this will take a little while, and I have to do a bunch of removal... so I am going to start with the simple first... then move on to the harder.

 

[Anonymous]

Jimbo,

I really hope you can crack this nut by changing some carb & ignition components, making some adjustments and not have to start taking the engine apart. Best of luck with it and of course keep us posted.

 

[Anonymous]

COLD COMPRESSION NUMBERS:

Taken this afternoon outside temp was 80 degrees, engine cold, as per Hot Rod magazine and XECUTE!

1. 170
2. 175
3. 170
4. 180
5. 180
6. 175


These are cold engine readings, five pulses each, taken twice.
Each cyl built this pressure in two pumps...
Jimbo

Having fun now!
The remote starter was a nice touch!

 

[weeds]

In my younger years I owned a VW Rabbit with quite a few miles on it. I replaced the timing belt (among other things) and it ran crappy at low RPM. Get the revs above a certain point and it ran very well. I took it to someone and guess what. The timing belt was a tooth off. He fixed it, and it idled well, but I was dissapointed at the loss of top end power.

I feel for pain and have appreciated the dialogue concerning the fix, it has been very educational for me and I can only guess what you have learned. Let me know when you are done and then you can tune mine.

 

[Anonymous]

Yeah, I cannot even tell you how much I am learning about the things that make this engine go round and round.


And I am learning more and more... check out this article from Hot Rod magazine, XECUTE turned me on to this, this is fantastic, and then also check out the one from Comp cams, these two pages of information explain things in better english than I could ever have dreamed, if you have been following my post, check this out, it is great reading.

http://www.chevyhiperformance.com/techa ... index.html
http://www.cranecams.com/master/degree.htm


Now for the apparent good news...
The key here is to give you one more tuning device you can use to dial in your engine to perform better. If your engine checks out with around 170 to 185 psi of cranking pressure, then you’re right in the ballpark.

it would appear from some of this, that my numbers are actually great! If they were higher then the cam would be advanced... 190+ seems to be the limit... I am at the end and average through the optimal range for a great burn. Now I think more and more this REALLY is a fuel delivery air issue... according to where I am right now, my best work would be to install the jets and power valves, and go for some road testing.

And I changed to a new set of plugs to get a better read, now that I am approaching the end of the break-in... 410 miles woo hoo!!!

The plugs I pulled looked better, there was still a fair amount of carbon and oil on them, but most of it had burned off around the plugs, and they were much lighter this time, so it may be these plugs are toast from those first couple hundred miles...

I also put on a new cap and rotor, and cleaned and greased all the connections...

I am going to go ahead and pull the carb, install the 4.5 high flow valve, and the keep the 61 jets for now... I want to see how the power valve affects these jets.

And my cam manufacturer said if I can get 14 inches vacume at 16 degrees, then I am in range, and to drop the rpms to 750. and tweak out the fuel ratio from there, if the vacume drops below that range then I am either leaking, or retarded.

Now I have some methodology! This is getting fun!

 

[Anonymous]

I cannot get a dang break.

I opened the power valves from Summit, and the 4.5 was a 3.5 in the 4.5 box... so now I have a 6.5 and a 3.5...

I think the 3.5 might be too small... I am going to call Summit today and see if they will send me the correct one to replace this one...

I may just install the 6.5 for now and see how that runs. But I wanted that 4.5 inch valve... man another few days setback.

 

[xctasy]

My pick is to use the 4.5 Hi-flow power valve. A 6.5 may be better, but when tunning its better to go from safe extreames, and then back off. You may find that change of PV fixes everything.

You could just try the 6.5, and use the 3.5 if there are still issues. On an LPG engine, I've tried a late delay to the economiser at about 3.5" Hg, and it's been just fine.

Apparently, an cammed engine has a knife -edge tunning envelope. I miss is a mile, even with a few degrees of cam miss-timing or a few thou out in vlave lash. The extreme approach isn't so bad, you will get definative results, and may even get a combo that really works. A finicity race horse that needs a self assured hand to get the best from it.

 

[CobraSix]

I am either leaking, or retarded.

Sorry...too easy to pass up...

Seriously, I do think it is a carb problem. I would still suggest getting the "Adjust-a-jet" kit from Summit. $75 and you don't have to worry about your jet size, you can adjust it with a screw driver. I'm getting one when I get my Aussie head in...(which reminds me, I need to pay AzCoupe).

On a side note, anyone notice that the number of new topics has decreased becuase of Jimbo's problems? Jimbo, your sucking all the resources of this board.

Slade

 

[Anonymous]

The "adjusta a jet" only goes down to 60. I did not realise this might be a problem before I bought mine. Still don't have it installed.
http://www.holley.com/HiOctn/ProdLine/P ... 55001.html

 

[CobraSix]

what size do you think you'll need for your car? I noticed that too, but was wondering what people are running in thier cars for jet size?

Slade

 

[Anonymous]

Those compression figures look great. I still think it's worth checking the valve clearances, you said earlier a mechanic gave it back to you running badly after being asked to adjust them. It's not a 5 minute job but will give you peace of mind and is easier than changing the cam timing. you will have to pull the valve cover to alter the cam timing anyway and you will have to adjust the valve clearances afterwards.

Just beacause the valves are closing all the way (those great compression figures) it doesnt mean they're opening all the way. That would explain your rough running, low vacum, condition. I'm assuming thats still a problem. Your cam is relatively mild and like you engine builder said it would produce a 'lope" at idle not run like a highly cammed drag car.

Your power and cruise jets can't logically have an effect on a rough idle at 1000 rpm with no load, can they? Even excessive advance or retard on ignition timing is only going to raise or lower the idle speed, not make it run rough.

I know i'm banging on about those valve clearances but i've had a similar experience with my own dodgy valve adjustment.

If you diagnose a retarded cam you don't need to take the sump (pan) off like the manuals say. the balancer and timing cover have to come off. Have a look and you will see what I mean. There are 2 1/2 inch bolts you need to take out from the front of the sump that bolt into the bottom of the timing cover.

If you've got a 'front hump sump' with a crossmember behind it you can pull the sump off if you unbolt the engine mounts, jack the motor and put some 2 inch blocks underneath inbetween the mounts. messy uncomfortable job and unnecessary for a cam timing adjustment.

Don't take the sump off, use plenty of sealer where it mates to the sump gasket and you won't have any problems. It's a full afternoon job and you don't have to lie on the ground with crap falling into your eyes (ears, hair etc).

Dom

 

[Anonymous]

Those compression figures look great. I still think it's worth checking the valve clearances, you said earlier a mechanic gave it back to you running badly after being asked to adjust them. It's not a 5 minute job but will give you peace of mind and is easier than changing the cam timing. you will have to pull the valve cover to alter the cam timing anyway and you will have to adjust the valve clearances afterwards.

Just beacause the valves are closing all the way (those great compression figures) it doesnt mean they're opening all the way. That would explain your rough running, low vacum, condition. I'm assuming thats still a problem. Your cam is relatively mild and like you engine builder said it would produce a 'lope" at idle not run like a highly cammed drag car.

Your power and cruise jets can't logically have an effect on a rough idle at 1000 rpm with no load, can they? Even excessive advance or retard on ignition timing is only going to raise or lower the idle speed, not make it run rough.

I know i'm banging on about those valve clearances but i've had a similar experience with my own dodgy valve adjustment.

If you diagnose a retarded cam you don't need to take the sump (pan) off like the manuals say. the balancer and timing cover have to come off. Have a look and you will see what I mean. There are 2 1/2 inch bolts you need to take out from the front of the sump that bolt into the bottom of the timing cover.

If you've got a 'front hump sump' with a crossmember behind it you can pull the sump off if you unbolt the engine mounts, jack the motor and put some 2 inch blocks underneath inbetween the mounts. messy uncomfortable job and unnecessary for a cam timing adjustment.

Don't take the sump off, use plenty of sealer where it mates to the sump gasket and you won't have any problems. It's a full afternoon job and you don't have to lie on the ground with crap falling into your eyes (ears, hair etc).

Dom

 

[Anonymous]

what size do you think you'll need for your car? I noticed that too, but was wondering what people are running in thier cars for jet size?

I want to see where Jimbo ends up on his jets before I install my adjust-a-jet. I'm thinking I must just be inside the outer range although my plugs look great. My engine is stock with the OZ head.

On the valve thing I can say that prior to the diagnosis of valve lash my piston tops were black and plugs were fouled.

 

[CobraSix]

see, My Oz head has enlarged valves, and a 260 Comp Cam (.44 Lift). I guess I'll wait too...have too.

Slade