Okey, I've got an engine that was built about 2000 miles ago, and, well, lets just say something is not right. From the way it acts I'm suspicious that the cam is off, like too far advanced (I didn't degree it in, for lack of a degree wheel) but the dots lined up perfectly. ??? So what is the easiest way to check that the cam is installed correctly, and that the cam was ground correctly as well? I'd like to also check the lift on it. What do I need, and can I do it without removing the timing cover? Can I just stick a dial indicator on the valves on #1 and get an accurate reading?

 

an indicator on the valves will give you lift, no easy way to check duration or lobe seperation. i'd guess the timing gears aren't lined up as perfect as you think, if it is a cam timing problem. i doubt if you have enough room for a degree wheel with out removing some of the stuff off the front of the engine, plus you need someplace to put a crank nut and you can't with the cover on.

 

I wonder (without thinking this totally through) if you could mark the HB with timing tape, pull the plugs, pull the valve covers and attach a dial indicator? I'd imagine you could get to within a degree or two, depending on how accurate you could lay the tape and read it, plus add in inaccuarcies from the HB mark.

I dunno, just morning babble.

 

Mike, that's what I was thinking. I had the tape on the balancer, but it didn't stick (to the bare metal on the balancer , yes I cleaned off all the paint. The tape had, for a small section of it, every single degree marked on it. That was in the range where the engine timing would be advanced. The rest of the tape had 1/4 marks all the way around. If I used this method, I'd have to mark the balancer better than that.
So if I pulled the balancer off, wrapped the tape back on it, and used sections with the 1* marks for the whole balancer, I could accurately measure it that way? I'm really trying to avoid pulling the cover off, as I don't want to cause any oil leaks on my brnad new motor.

And Ede, I lined up the marks with a straight edge ruler between the centers of the crank and cam gears. Please don't insult my intelligence by implying that I just slapped the engine together.

 

Sorry to hear about your engine troubles,

What are the symptoms you are experiencing that are leading you to believe your cam timing is off? Seems like the cam should be right on the way you installed it.

 

I'm sure you know what you are doing,but it might be something other than the cam.Friend of mine had a 396 professionally rebuilt and it ran like crap,turns out they had tightened the rocker arms way too much.A local guy reset them and it runs like a different motor now.Just a thought.

 

Well, the engine seems to run fine, other than the fact that it lacks power. It has absolutely no low end; no throttle response. And the engine, overall has no power. So I stared thinking, a possible cause of this could be that the cam is either the wrong grind or installed wrong. For example, if it were too advanced, that would explain the lack of low end power. And TPI? Can't breathe in the higher rpms. It's just an idea, and I'm trying to find the easiest way to check it. If anyone is interested in the engine specs and specifics, they are in the engine section of my webpage. Thanks guys.

whoops (edit) I suppose I should include the link:
http://www.fbody.com/members/ViciousZ/engine.htm

Oh yeah, and as for the rockers, they were adjusted correctly. I've done a compression test, and all cylinders passed with flying colors. Timing is set at 7*. I have not tested the fuel pressure while the engine is under load, although it is set at 50 psi. I also used a scanner on it, which showed that the integrator is aroung 115 under load, indicating a rich condition. Which suggests that the problem is probably not fuel related. That's about all I've checked so far. I'm at college now and the car is 150 miles away in my garage. So it is a little difficult for me to work on it, or test it right now. But I am open to suggestions as to other probable causes.

 

Just a few ?'s

Are you still using your stock chip? If not what are you using? Which injectors are you using? I couldnt tell from the web page.

 

First, if you advanced the cam, it should build MORE low-end TQ with lower high-end HP. It sounds like maybe the cam is retarded.

But, what have you done for the eprom? Especially with SD, where you have to have the fuel tables match the VE characteristics of the engine. The difference between the "right" eprom and "wrong" eprom can make a world of difference.

Lastly, I noticed that you have some "serious" lift numbers with that cam. Is that with 1.6 rockers? Have you had serious porting work done to those Vette heads? Generally, the Vette heads don't flow any more after .500 lift except with MAJOR work.

 

Glenns right, advancing the cam 3-4* generally will shift the power band down about 500 rpms.


Another thing is that you could probably use more base timing with your cam, right now you're sitting near factory spec's. Glenn can probably tell you how much initial you can give it, before you start to run into issues where you must do some EPROM tuning.

 

With hydraulic lifters, you will NEVER degree the cam in correctly by measuring valve lift. The plunger in the lifter can compress up to a 1/10 of an inch.

You need to get a degree wheel and dial indicator (one with a 12 inch extension) to measure cam lift at the lifters. The timing tape can be substituted for the degree wheel.

 

Very good point by A73Camaro, that's why you use a solid lifter when degreeing the cam.

 

You guys are right. I meant cam might be retarded. (Remembered that one backwards I guess )
Anyway, I have a custom burned prom from Fastchip.
The injectors are 24lb and were flowmatched by Cruisin Performance.
The heads I got used from a guy I know. He ran them on his corvette and used an almost identical setup to mine, with much success. They've been ported out, the intake flows around 180cc. The valves are also oversized, 2.00 on the intake, and 1.60 on the exhaust. With a three angle valve job.
The engine runs just fine; nothing seems amiss. But the problem is that the engine is lacking serious power. Something is VERY wrong. It's not a matter of, gee that cam was a little too much lift, or not enough duration, or the stock TPI, or too much timing advance. Something is seriously wrong! I'm mean, I seem to be missing, oh, around 100 hp. I know this because I got a hold of a g-tech and compared before and after times. Ummmm, the car ran faster with the tired old bone stock 305. Soooo.... WTF???
Keep the ideas coming guys. Next time I go home I'll start troubleshooting it.

 

There are other nit-picky symptoms, if anyone cares to read all the gory details.
The idle (in the prom) is set to 800 rpm. Too high IMO, but it seemed like a good idea at the time. Anyway, the idle is ... kinda screwy. I'll explain: It idles nice and smooth for a coupla seconds, then the idle gets a little shakey for a few seconds. And what is even more interesting, I can sit there and watch it on the scanner. Know how it's supposed to fluctuate between rich and lean? Well, when the scanner says rich, the car idles fine. But when it says lean, that's when the idle gets a little rough. The change in idle coincides PERFECTLY with the scanner.

So I took the car out for a drive with the scanner hooked up. And the first thing I noticed was knock retard!! Basically anything over 3000 rpm under load showed a knock. At one time I saw up to 14* knock retard!!! But I was suspicios of the scanner, so I hooked it up to my other car, a 92 firebird, 305 tpi. Anyway, the scanner said the firebird was knocking too. Although the knock retard wasnt as high on the bird. It also showed that my buddy's iroc was knocking. So I came to the conclusion that it was my scanner that was being retarded, not my car's timing. Now, I don't hear the engine knocking at all. And before anybody asks the obvious, yes I did use a 350 knock sensor. Besides, even if I was getting knock retard, that doesn't explain the lack of throttle response and low end torque.

That's about all I can think of for now.

 

Hmmn, I think I would suggest the "knock sensor bypass" test.

From what I know using my scanner and documentation with it, it *could* register false knocks...but not "false retard".

I/e the scanner may show X number of knocks, but the ECM actually tells the scanner how much retard it is giving and the scanner just reports the data.

Your lowend lack of power could be due to base timing, your WOT loss of power could actually be due to the ratard you see.

What did you friend use as base timing with his/her setup?

 

Also, the rich/lean coinciding with the idle condition...does it coincide with open/closed loop as well?

 

Actually, that is EXACTLY what happens when your ignition gets retarded...you loose throttle response and TQ. Also, I think your scan tool is probably showing the truth. Have you tried another scan tool and seen what it is showing? If you want a quick test, try and find someone local to you that has a different scan tool or talk to TPIS about renting Diacom for a week ($50) as a test.

I have looked at a lot of engines with scan tools and generally those running GM heads and/or small combustion chambered heads get a lot of knock retard. The heads that tend to have the LEAST knock retard are aftermarket wtih larger combustion chambers.

To get the most out of GM heads you REALLY have to play with the spark advance and control the knock retard. I have set my eprom to only allow 1* of knock retard while in WOT and I control my spark advance curve very tightly - to the point where an extra .4-.8* of spark advance can cause AUDIBLE knock.

And that the next point, the Knock Sensor is designed to be overly sensitive to pull out timing at the slightest hint of noise. By the time you HEAR the knock, the KS has become saturated with noise. And when the KS pulls out timiing, it is generally overly conservative and pulls too much timing out to stop the retard. Lastly, when the KS is doing this, it really screws up the spark advance curve and if the KS stops detecting knock, it tries to give you ALL of the spark advance it can...which usually triggers more knock.

This are the things that UNLESS you have hands-on access to the car and able to do a LOT of tests, you seldom will get the potential your engine is capable of. The difference in performance is "night and day". Ask any of the guys that finally got into eprom burning and started playing with the fuel mixture and spark advance and they will tell you the difference they have found in performance.

Last question, are you running an EGR? If not, that will definitely affect your "knock incidences" and spark. A lot of "custom eprom" writers will turn off the diagnostics of the EGR, but fail to properly disable it (by setting the EGR Enable temp to a very high value).

I am not saying that there is not something "mechanically wrong" with your engine - but even if you had your cam retarded a few degrees, you wouldn't loose that much power. The culprit I am most likely to suspect is your eprom and the heavy amount of knock retard you are experiencing - which is very common.

BTW, when you have knock retard occurring, your TOTAL SPARK ADVANCE displayed by your scan tool will not show the reduction due to the retard. The Total Spark Advance should really be called "Desired Total Spark Advance". You need to subtract the knock retard displayed from the Total to get your REAL EFFECTIVE Total Spark Advance. You can reconcile the number by adding your base timing to the Relative Spark Advance (the actual amount the ECM adjusts your timing).

Hope this helps.

 

Actually, it's not a "false knock", it's the knock sensor hears what we don't. By the time we hear it, the KS has become saturated with noise. Disabling the KS and trying to go over 30-32* of spark advance on the GM heads will generally give you knock you can REALLY hear.

To get max power, I have found you REALLY have to play with the spark advance and controlling the amount of retard you will let the eprom give. I too, when I first got into eprom burning, thought they were "false knocks", but once I started controlling the KS, I learnt that it was "just the beginning" of real knock and the KS was just "over reacting".

 

Glenn, what I meant to say, according to my manual for my scanner, is that it could be damaged (the scanner) and register false knocks. There's no mention in my manual about registering "false retard". Or better put, displaying timing being removed when it's not actually occurring.

I agree, the KS will detect inaudible knocking and the timing will be retarded accordingly, that's why I was suggesting bypassing the KS and seeing if the scanner still showed knocks which would indicate a scanner problem.

 

But the scanner is not showing any knock below 3000 rpm, or when the engine is not under load. The lack of throttle response is there even when the scanner does not show a knock. I mean, in my firebird (anemic 305) I can give the throttle a little jab, and the car surges foreward. In the camaro (with the new engine) I jab the throttle and ... nothing. I'm sure 14* knock retard would be causing a serious lack of power at WOT. But what about the low end?
About the EGR, I'm not running one, since it is a PITA to set it up on vette heads. I had Ed Wright disable it in the prom.

 

Okay Mike, I see where you are coming from. Yes, bypassing the KS would help eliminate the scan tool as being faulty. Also, it would allow a method of "tuning" to prove/disprove that the eprom is off.

If the eprom was optimal, you should find that altering the "designed base timing" (I use 6*) of the eprom will just make it slower or induce audible knock if the KS is being "capped". On my car, that is exactly what would happen since I have my KS limited to 1* of retard and advancing it any further just causes detonation. But it only took me 100+ burns to find that optimum point.

Vicious, what you are experiencing is EXACTLY what happens: around 2,800 to 3,500 rpm the knock retard climbs (and 14* is not unusual) and 4,000-4,400 rpm the retard starts to decrease and often disappers around 4,800-5,000+rpm. But at 4,500 rpm the KS is actually starting to go "deaf" as it is getting saturated and stops to pull timing. The "noisest" time is during the up shift and that is usually where the KS becomes totally deaf and the first signs of audible detonation occurs.

Also, at "part-throttle" this generally is where you can run the highest spark advances. In fact, at part throttle cruising, I run 17.2:1 AF Ratio with 47* of spark advance. And I don't detonate whatsoever. The reason is that at part-throttle, you don't have complete cylinder filling. Thus, even though you may have a stactic compression ratio of 10.5:1, you really have a dynamic compression ratio of only 7:1 (or less) because the cylinder was never completely filled. That is your vacuum.

At WOT or high loads as when you climb a hill, when you step on the throttle you reduce the vacuum because the cylinders are now attempting to completely fill the cylinder. Also, other factors like the cam come into play and when the "cam" hits it's sweet spot is where you have the most complete cylinder filling. Now the dynamic compression ratio is much higher (and volitile). Hence, you must run a much lower spark advance or you will induce detonation.

At WOT I only run 28*-28.5* spark advance. But that is REAL EFFECTIVE Spark Advance as I have basically no retard (1* max) occurring. On most of the eproms I have seen (custom and stock), they try and give you around 30-34* of spark advance, and often too soon. This results in sometimes 14* (or more) of retard. This means you only have 16-20* of Actual Effective Spark Advance. Guess what that does to power?

This is why controlling how quickly you build up your Spark Advance is so important when you burn eproms. You want it to climb as quickly as possible, but not so fast as to trigger knock retard. Once you trigger knock retard - kiss all your power goodbye. And, when you start playing games (like I do) with the "Max Knock Retard while in PE", you can easily tigger audible knock.

When I was doing my testing, the moment I heard audible ping, I would note the rpm where this occurred and back it off a dash and try again. Slowly I found the max spark advance through out the rpm range where no matter at what rpm.

But, as a quick test of "the quality" of your eprom, try disabling the KS and play with the base timing. If you start to notice a performance improvement (or audible knock occurring), then you may want to look at eprom burning. One thing is for sure, I can reprogram the eprom and test my car quicker than most people can adjust the distributor - and I don't get dirty doing it.

 

Im having a similar problem, but no computer. At IDLE in neutral does your engine have good throttle response? but as soon as you put it in gear and step on it, your car is a slug? I have a high Stall and ****ty gears which could be my problem, but I suspect the cam timing as well. good luck if you figure it out let me know i will try whatever you did!