How to check if cam is timed right?

[Alf]

Hey guys. Ever since I freshened up my 307 it does not run right. I received this engine for free from a fellow Camaro enthusiast, so I never heard it run before but he said it was rebult not long ago. This past winter I decided to pull it apart and was totally surprised to find fresh hone marks, 30 over pistons, and basically a good to go engine. So I cleaned it up, installed new rod and main bearings, new timing chain, set of fresh 882 heads I had laying around, and buttoned it up. For some reason I did not remove the camshaft to check its condition which was just plain stupid since I did just about everything else.

 

After setting the engine in my car and hooking everything up, we started the engine and it fired right up and sounded great. Unfortunetally I had to drive it 1300 miles back to school only a couple days after first firing the engine so I couldnt put my super tune on it, but it was tuned. The first thing that gave me an idea that something was wrong was the gas milleage, I was getting ten miles to the gallon which is horible. This engine is basically stock so I was expecting at least 15(my stock, worn out 305 got 20 on the way home). Now about three months later and tons of fidelling I have it running decent, but it still isn't right. For all the time I've spent it should be running tens, haha. The engine will run up to about 3,500 RPM and then it just hits a wall, it sounds like a rev limiter, but my car doesn't have one.

 

My ideas were; not enough voltage to coil(jumper wire did nothing), pertronix ignitor went bad(replaced with points, does the same thing), way off timing(its not, 11 initial, 36 total), way off fuel curve(I have tried every combonation I can think of and am wearing out the threads on my poor Holley), weak valvesprings, flat cam(lifters looked okay), leaking intake manifold, and the one I think is correct: one or two teath off on my timing gear hence wrong cam timing.( I can't remember installing the timing set, I think I did it right, but then again that was the same day I didn't pull the cam)

 

Anyways I'm going to be heading back home in about three weeks and I don't want to hurt this engine. Is there anyway I can diagnose this problem without pulling the engine apart? Anyone have a similar problem? I've tried all I know, and any help would be greatly apreciated. Thanks.

[jt1]

Quick check is to pull the pulleys, damper, water pump, and timing cover and see if the dots on the timing gears are lined up vertically. If not, revise them till they are; the dot on the crank gear and cam gear should all be in a vertical line thru the CL of the crank and cam, with the dot on the crank gear on the top. It doesn't matter if the cam gear dot is on the top or bottom as long as they line up vertically.

 

More involved is to degree the cam using a degree wheel and dial indicator, this way you get the cam positioned exactly where you want it. BUT to do this correctly you have to know the grind specs on the cam. Most of the time the intake lobe centerline will fall between 102-110 degrees, without the cam specs you are cutting and trying in the dark.

 

I'm pretty sure Comp cams has a good writeup on cam degreeing on their website.

 

John

[grumpyvette]

after doing several comparisons between just installing a cam (DOT-to-DOT)

 

VS degreeing them in correctly, Im forced to point out that it depends to a HUGE extent on the CAM and how well it meets the specs.

while most cams Ive degreed in were well within about 2 degrees Ive seen some that were out of spec significantly (6 degs plus) if your useing a well known brand like CROWER,CRANE,LUNATI,ISKY etc. youll probably be fine, buy a bargin basement kit and your chances get better on problems, but youll still likely be ok. but degree it in correctly and you could easily gain(OR MORE CORRECTLY NOT CHEAT YOURSELF OUT OF, 5-10 hp) if the cams close to correct, if its well out side specs, youll never know it without degreeing it in and youll wonder whats wrong?

heres things/info to help

 

http://www.powerandperformancenews.com/store/merchant.mvc?Screen=PROD&Store_Code=PH&Product_Code=POW101400&Category_Code=CAMSHAFT

 

link to thread

 

keep in mind the cam may be within specs, and the roller chain gears or cam drive gears or the crank keyways ETC. may be out of speck also, thats one reason degreeing in the cam helps find problems

 

 

summit [color:"red"] $11 [/color] part # SUM-901064

ID ADVISE you spend the BIG BUCKS and get one before you screw up the crank or keyway

 

 

ways to turn over the engine WITHOUT the starter

 

theres large bolts for your ballancer

 

theres crank sockets

 

 

Crankshaft Socket Tool For turning AND MOUNTING Degree Wheels

CRANK NUTS

 

 

crank rotaters

 

flywheel turning tools

 

 

and your going to need at least one when you degree in a cam or do a compression or leakdown test

 

 

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3292&prmenbr=361

 

this kit comes with a video tape instructions and most of the tools needed

its not a bad deal

 

HERES instructions to read over

 

http://www.thedirtforum.com/degree.htm

 

http://www.hotrodder.com/kwkride/degree.html

 

http://www.454ss.com/whitess/Camshaft.htm

 

http://www.cranecams.com/?show=article&id=3

 

http://www.holley.com/HiOctn/TechServ/TechInfo/IECCTech8.html

 

http://www.moroso.com/catalog/categorydisplay.asp?catcode=27019

 

http://www.moroso.com/catalog/categorydisplay.asp?catcode=27015

 

moroso and TAVIA

http://www.tavia.com/cat0.html

carry most other tools youll need

[Guest tony78_280z]

The engine will run up to about 3' date='500 RPM and then it just hits a wall, it sounds like a rev limiter, but my car doesn't have one.

 

My ideas were; not enough voltage to coil(jumper wire did nothing), pertronix ignitor went bad(replaced with points, does the same thing), way off timing(its not, 11 initial, 36 total), way off fuel curve(I have tried every combonation I can think of and am wearing out the threads on my poor Holley), weak valvesprings, flat cam(lifters looked okay), leaking intake manifold, and the one I think is correct: one or two teath off on my timing gear hence wrong cam timing.( I can't remember installing the timing set, I think I did it right, but then again that was the same day I didn't pull the cam)[/quote']Sounds like carb to me. Is it too small for the aplication? What is its CFM and What are your current jettings?

[dr_hunt]

If it's a sbc, you won't be able to pull the timing cover without dropping the pan alittle bit.

[Alf]

I would bet my life its not the carb, I have tried everything. The carb is a Holley 650 spread bore double pumper(its too big for the engine but it should run past three grand). Right now I have it set to Holley specs besides the primary jets which are 65's, 83's in the rear(sounds huge to me but it is a spread bore and thats what Holley says should be in there, plus I ran it with 67's and it did the same thing). it has a 8.5 pv in the front and a 7.5 in the rear.

 

It is a SBC and I know about the pan, but what are you gonna do. I have never pulled a timing cover off while the ehgine is still the car, but my buddy installed a cam in his vette while his engine was in so we can do it.

 

I just want this thing fixed, I don't mind taking it apart if that will solve my problems. What exactly are the symptoms of too advanced or too retarded cam timing?

[280zwitha383]

I don't think it's the carb either. If it's not valvetrain related I would vote for fuel pressure. Actually I would have voted for fuel pressure before valvetrain. Check your pump and filter if you haven't already.

[Alf]

I have already gone the fuel pressure route with no succes. I origonally was running the car with the stock in tank 85 300ZX electric fuel pump wich didnt work out that well. So i dropped the tank and tossed the electric pump and made a new sump for the fuel pick up. Then I put a stock replacement mechanicle fuel pump on the engine and it helped a little, but it still hit the wall at three grand. The filter is nice and clean also.

 

I just went out and pulled the driver's side valve cover to watch when the valves were opening and closing in relation to the TDC mark on my balancer. I found that the exhaust valve closes about 2.5 inches before TDC on a 6" balancer, I'm guessing this is about 40 degrees? The intake startes opening directly on TDC.

 

I went on the Crower cams website and was checking out some cam cards. Part number 00236 is a small cam for the SBC, under .400" lift, so I took the numbers from that which should be comparable to what is in my engine. The specs on this cam are as follows: Intake opens -18 degrees ATDC, intake closes 18 degrees ABDC. Exhaust opens 28 degrees BBDC, exhaust closes -24 degrees BTDC. I'm not sure what the - means, does anyone know? By looking at these specs it seams my cam is advanced by 10 to 20 degrees. What do you guys think?

[280zwitha383]

Then I put a stock replacement mechanicle fuel pump on the engine and it helped a little, but it still hit the wall at three grand. The filter is nice and clean also.

 

Elaborate on "it helped a little".

[Alf]

It just ran smoother throughout the RPM band up untill 3,500 RPM.

[Guest tony78_280z]

I have already gone the fuel pressure route with no succes. I origonally was running the car with the stock in tank 85 300ZX electric fuel pump wich didnt work out that well. So i dropped the tank and tossed the electric pump and made a new sump for the fuel pick up. Then I put a stock replacement mechanicle fuel pump on the engine and it helped a little, but it still hit the wall at three grand. The filter is nice and clean also.

yeah, this paragraph struck me too.

[John Scott]

I'm jumping on the fuel system bandwagon, too. I ran into an identical problem, http://forums.hybridz.org/showthread.php?t=77397&highlight=carb , with my procharged 4.3. I would rev it to xx rpm and it would hit a wall, just like my msd rev limiter. Find a pressure guage and verify that you have correct fuel pressure when the problem occures. If it is way too high, like in my case, too much pressure was overwhelming the holley at the higher rpms. At least you could cross it off the list before you start on the cam theory. I've also seen debris on the fuel pick up that only pulled up at high loads. John

[Alf]

Here are a few more things to think about. I hooked up a fuel pressure guage and took it for a ride. At normal driving the highest PSI was 5.5, and about 3.5 PSI when it hit the "wall" at about three grand in every gear. I think we can rule out fuel pressure as being the culprit because the engine spits black smoke when it hits the "wall", so it seams to have enough, and not too much fuel.

 

Another interesting thing I just discovered is that if I run through the gears using only the front two barrels it will go as high as I want, just really slowly. I already know that the carburetor is too big, and it should be a vacuum secondary too, but I have never heard of an oversized carburetor doing anything like this. Has anyone experienced anything like this? I have a Holley 600 spread bore vacuum secondary, but it has serious problems, I think internal vacuum leak or serious warpage and the engine doesn't run half as good with the 600 VC than as the 650 DP.

 

As I said earlier I roughly checked where the valves were opening and closing with the TDC mark on my balancer, and found that the exhaust valve was closing about 40 degrees before TDC and my intake was opening directly on TDC. From what I've read this is too far advanced. I think I may have two seperate problems here. But the advanced cam timing just seams to add up, car runs better than expected in the low RPM range and has snappy throttle responce, but seriously dies off in the top end. It sounds like it has a big cam in it at idle, but performs like stock, and its running hotter than it should. This would also explain why my timing and carb adjustments were useless.

 

I bought a timing gasket set and it was only $8 so if I do take it apart and find that the cam is timed right, I won't loose anything but a few bucks and some time. What do you guys think, am I making sense?

[280zwitha383]

Here are a few more things to think about. I hooked up a fuel pressure guage and took it for a ride. At normal driving the highest PSI was 5.5' date=' and about 3.5 PSI when it hit the "wall" at about three grand in every gear. [b']I think we can rule out fuel pressure as being the culprit[/b] because the engine spits black smoke when it hits the "wall", so it seams to have enough, and not too much fuel.

 

Another interesting thing I just discovered is that if I run through the gears using only the front two barrels it will go as high as I want, just really slowly. I already know that the carburetor is too big, and it should be a vacuum secondary too, but I have never heard of an oversized carburetor doing anything like this. Has anyone experienced anything like this?

 

Uhhhh, I would have used all of that information to argue that it is fuel pressure! Does it not make sense that your fuel pressure drops off as you reach higher rpms so you don't have enough and when you don't use the secondaries you have enough fuel pressure because you're only feeding two barrels? How about this, if you don't believe me try hooking the gauge up again and use only two barrels (disengage them if you like). If it reads higher than 3.5, please stop playing around with your cam idea.... haha. 3.5 psi is awefully low. How low do you think too low is?

[Alf]

Why would it blow black smoke if it didn't have enough fuel? I have never heard of a car that was leaning out blowing black smoke, its usually the other way around.

 

I don't understand why this pump would not suply enough fuel for my engine, the engine is stock. I had my Camaro in the 12's with a $10 AC Delco replacement pump, and thats a bigger engine.

 

I guess I'll hook the guage back up and try a few different scenarios.

 

Thanks for the help so far.

[280zwitha383]

Why would it blow black smoke if it didn't have enough fuel? I have never heard of a car that was leaning out blowing black smoke, its usually the other way around.

 

You got me on that one.

How is your fuel pump hooked up? I know you said that you had a mechanical fuel pump but is that what you're using now? Is there anything else that could be constricting flow? Are you trying to pump gas through the in-tank pump?

[Alf]

Right now the car has the stock fuel tank, NO elctric pump in the tank, I took it out. I made a sump out of 3/8 tubing similar to the one in my Camaro. The gas tank looked brand new inside, besides some junk in the bottom which I cleaned out. I then put new rubber lines coming out of the tank to the stock metal fuel line which is 5/16. This runs up to the mechanicle pump on the engine, then to a G3 Fram fuel filter, then to my carb. The only thing I can see that might be hurting the pressure a little is the fact that I'm running a return line. The car already had the return so I figured it wouldn't hurt to run it, maybe I was wrong? The pump was made with the return nipple so its not like I'm asking it to perform an operation it was never ment to do.

http://album.hybridz.org/showphoto.php?photo=6202&cat=615

[jbk240z]

Do you have long lengths of rubber fuel line in the fuel system? I ask this years ago a friend had a problem similar to this. Anyway, he did have too long lengths of rubber line and they were apparently collapsing at higher rpm's. I hope this crazy idea helps. Good luck.

[280zwitha383]

I obviously need to reread things before I post....

When you were running the engine with the stock electric pump it behaved the same way (except a little worse) than with the mechanical pump? You said it didn't run right but I don't know if that means you still had "the wall" or if it was something else. You might have messed up your carb with the high fuel pressure. I can't remeber off hand what you mess up with too much pressure, I would think it's the floats. If your carb is putting way too much fuel in your engine that would cause you to lose fuel pressure and cause your black smoke (which sounds like a pretty good hypothesis to me). In diagnosing the fuel pressure problem we might be trying to get rid of a symptom rather than the cause.

[Alf]

jbk240z- I don't have much, if any more rubber line than what the vg30 had, but I am also not runnig double diggit fuel pressure numbers through fuel injection fuel line. Maybe some FI line would help.

 

280zwitha383- When I was driving the car with the electric pump it did the same exact thing, but it didn't run quite as well in the low RPM's. I had a good Mallory fuel pressure regulator on it set to 6 psi, and the engine showed no change if i moved the fuel pressure from 5 psi to 9 psi. I was about 90% certain that my problem was a fuel starvation issue due to the known fact that the stock 300ZX pump barely flows enough for the v6, so I put a mechanicle pump on the engine with the electric still in the tank, but not hooked up. After this I took it for a ride and it kept stalling out, so I made it back and hooked the electric pump back up and it ran okay untill I could run the tank out of gas so I could drop it and remove the elctric pump.

 

The only thing high fuel pressure into a carb does is overpower the needle and seat, which you can't really harm., Its just a viton tip into a brass seat.

 

The too much fuel idea sounds logical, but I've ran jets everywhere from 58's to 76's in the primaries and 63's to 83's in the secondaries with no change in full throttle power, it still hits "the wall".

 

It may be that the carb is just way too big and when I open the secondaries, which are opening too soon because its a DP carb, too much air enters the engine and it causes a BIG lean condition. But if this was true wouldn't it catch back up and then finally go, I can hold this engine against "the wall" as long as I want, it never clears up.

 

 

Here's another wierdo thing that happened with this engine. About a month ago I was running out of ideas, so I figured I would just mess around and try a side gapping spark plug trick a buddy showed me. http://performanceunlimited.com/documents/plugsidegapping.html

So after I reinstall the plugs I go for a ride and am totally astonished to find that the car pulled all the way to 5,500 RPM with the pedal to the floor, and it felt pretty good. Why spark plugs had an effect on that I have no idea. This is another reason I am leaning towards cam timing, it doesn't seem to make sense for anything else.