Today I finally finished my LT1 cam install. I was so excited to hear it running again. As soon as I could I went and took it for a test drive. At first it didn't seem like it made much of a difference. After further observation, I realized that I LOST some low-end power, but was able to easily rev to 5k instead of 4-4.5k. This was really pissing me off. I brought it back home, told my dad, but then I left for town because I had to do something and didn't have time to fool around with it.

Now, what's even WORSE, after driving it for about 30 miles, it drives even worse. I still don't have crap for down-low power (can't even come close to spinning tires when I could very easily before) I told my dad about this and he said it's probably the timing, so we'll just have to adjust this. This isn't all though: NOW, the car will only rev to about 4k before the engine falls on it's face. I dont know what happened, for it went to 5k earier. I don't know what's going on, but I know I need to change my oil, plus I'm a little low after losing a bunch while re-attaching the rockers. I dont' know if this is it?

Also, right now I'm running 4* timing. I haven't done anything w/ fuel pressure yet because I haven't had the time to do the AFPR mod. What might be wrong, I'm seriously bummed.

Nate

 

Another thing I remembered, though probably insignificant, I normally gas up w/ 93 octane from this one trusted place, but tonight, after running low on gas, I went to some other place and got 92. Bad gas maybe?

EDIT: Another thing I remember was that I just got done removing all the emission stuff: smog pump and hoses plus the AIR stuff off the manifolds.

2nd EDIT: OK, here's another guess, everyone check this out.... after checking some other posts about LT1 Cam installs, I thought of something else. I didn't change valve springs. I have a new pair and all, but my dad said that we shouldn't change them because the increased stress or whatever could snap the valves or whatever. Anyway, could my old springs be the cause of my car not bein able to rev high? Maybe valve float?

 

I'm no expert on cams, but these are a few of the issuses you could be facing (PS. I've been awake for about 36 hours now so if I say anything that sounds whacky, don't take my word for it)...

- Vaccume leak - are all the hoses back where they are supposed to be and various holes plugged? gaskets sealing good?

- EGR - removing EGR without turning it off in the ECM can result in a loss of power. Combining this with your additional 4* of timing could result in a noticable power loss (If I'm thinking straight)

- remember, you're gonna lose some of that grunt you had at 24-2500 rpms before (where your peak torque was)... it should be moved up slightly, although I can't hint as to how much.

- wait for other, more knowledgable guys to respond and don't listen to shmos who have been awake for 36 hours

 

I think i know your problem...... i had a similiar problem.... my fix was i needed to take the valve covers off and RE-ADJUST the valves............
you have to do it while the car is running to which kinda sucks.....

 

I would agree that the valves not being adjusted right might cause such as you are having. Did you degree in the cam? If it was installed slightly retarded (timing wise- not you), that would take off of low end. Unfortunately, it is necessary to get back to the cam to check or adjust that. I would put in more than 4° of advance. My car calls for 0°, but I run 10°. If you can, advance timing while watching vacuum. Advance until vacuum no longer rises.

 

How do you turn off the EGR? Does it have to be done with a custom chip or is there some other way?

Do you mean readjust the rockers? I had my dad do that one for me earlier cuz it sounded difficult. He just loosened till there was ticking then re-tightened till there wasn't any.

No, we didn't degree that cam, we installed it directly lined up, or at 0*, whichever you want to call it. As far as the ignition timing, I'm gonna fool around with that tonight. I'm also gonna do the AFPR mod on my own, cuz I'm sure the cause of the loss of power at 4.5k is due to lack of fuel, and even air (I'll have to get an open element)

All this sounds really helpful guys, I'll check some of it out on my own and then run it all by my dad as well (he's the mechanically inclined one since he does this kinda stuff everyday) Thanks for all the help. I"ll keep you updated....

Nate

 

You ran your car with the valve covers off? Didnt the oil spray at you through the pushrods? Plus the oil could get dirty from particles in the air

 

That's what my chilton said to do. We kept one cover laying on one, and had the one off of the head whose rockers we were adjusting. Oil wasn't spraying out, it was just leaking onto the exhaust manifolds. PLUS, I needed to change my oil, so there wasn't a biggy with gettin it dirty or losing some.

 

Um, iroc22, I'm hoping you're joking, particles in the air?

 

Did you change the valve springs? I would if you haven't. And like everyone else said, the valve adjustment can do alot too.

 

What is this 'valve adjustment' you guys are mentioning. Is it the rocker arms? You mean how tight or loose those bolts are? Please help

 

My view on this; you should have done the adjustable fuel pressure before all of this, other than that you're doing everything right . Just need to diagnose this problem.
When you said it was loosing power and not reving I was thinking it was timing (retighten and double check dissy hold down bolt) but then I figured you would have noticed that so then I thought it was the valves not opening far enough which would be the rocker arm adjustments. You need to adjust the valve lash with the car running, just be glad you don't have a mechanical flat/roller cam or you'd be adjusting valve lash more frequently than you change your oil!!!
Your dad adjusted them correctly but the engine needs to be warm with warm oil or it won't be accurate enough even with the hyd lifters.
Your dad was wrong about the valve springs. Sure they're okay for stock use but if you rev the motor up high and if the springs have high miles they're most likely shot. If the spring doesn't have enough pressure it'll keep the valve open and you can loose pressure, this is more likely than valve float (which is when the lifter jumps off the ramp on the cam). It's actually a combo of both if I remember correctly, so if I were you I'd remove the springs and go get them all tested for seat pressure and make sure they are all good. I think replacing them will sovle your problem but I also think you should do some code hunting and make sure it's just an EGR problem. With 4 degrees base advance, stock compression and 92/93 octane it shouldn't be detecting any knock.
Good luck and keep us updated.

 

So you're thinkin I'm gonna have to get the rockers re-adjusted then, but after I've driven the car a bit? Also, as far as code-hunting, my car's not throwing any codes, or does that matter? I don't have any experience whatsoever when it comes to checking codes to see what's wrong.

 

I don't believe re-using the valve springs plays into this equation at all. I re-used mine on a 103K mi. motor with no problems. I had great gains thruout the RPM range, but especially in the upper end. I also saw a .4 second improvement in e/t in the 1/4 mi. Look elsewhere for your problem. Lon

 

Should I adjust my timing this way? I can watch the MAP voltage on my scanner while adjusting base timing...is this what you're talking about?

 

Well I just used particles as a general term referring to anything that could be made air born.

In any event, its not really the greatest idea to run you engine with the valve covers off. Oil will get everywhere.

 

its fine to run the car without valve covers, if you dont rev it up no oil will spray. Im sure everyone who's done this can attest. A little might get on the headers though.

 

just an errant comment guys - has anyone had a problem with their car throwing a code when its cold if they jump on it? I've been playing with my fuel pressure thinking maybe its lean or something...i dunno.

TP

 

i think you said it all when you started teh thread dude. you haven't done the afpr yet and you only have 4 degrees of base timing. you are prolly gonna need about 8degrees minimum of base timing and at least 2more psi of fuel.
you are dealing with a lot larger charge than teh stocker could ever draw, you need to move the rest of the pieces to keep the ratios in order.

later
tim

 

Older hot-rodders often set valve lash with the valve covers off (duh) and the engine running. Summit even sells a set of clips that keep oil from spattering everywhere. while you're doing it.

 

Yea i have done it before.... just a little bit of oil will run out but it does not splash out by any means at idle........ BUT if you rev up the engine with the cover off...... watch out itll splash!!!

 

adjusting valve lash and replacing new springs, is a piece of cake, just make sure you have a very good air compressor if you plan to work on the heads still on the motor, this problem your having is most likely related to valve spring problems, Seal power spring are perfect there OEM spec and a whole set is 42.00 at Advance Auto and they will support a LT1 perfectly, or call up summit and purchase a set of comp cams springs for 53.00 its all up to you, and if you installed the Cam yourself, you should have no probem with installing new spring




mike

 

I've done it before.

My dad used to set the valve lash on our '65 L76 Vette (Til he sold it ) once a week without the engine running. He said you didnt need to.

 

Lol.. doing it once a week you get to the point where you don't have to have the engine running. But that's an experience thing. If you didn't have the engine running and you've never done it before or haven't done it enough on your motor to know about where it should be, then that's a different story.

 

There is setting valve lash while cold, this is usually what you do with a feeler guage or "turn 1/4 past zero". This is usually done with hyd lift cams roller and flat. Mechanical (including roller) solid lifters MUST have the valve lash set when engine is warmed up. I can't see how else it would be done unless you had a magical way to measure the thermal expantion of the valvetrain that I don't know about.
It's also good practice to tune valve lash with the engine running when the cam requires the "1/4 turn past zero" settings, this way you know exactly how far you can go before the valve doesn't close and can back off. I've actually never had to even do any valve lash tuning yet, this is just what I've observed so if some more experienced guys would include their opinions or methods I would appreciate it.
Again, I'm not expert and I would ask your local experienced mechanic and get second, third, and forth opinions.

 

Alright guys, UPDATE!!!

Right away after I got home from school the other day I did my AFPR mod all on my own (I'm so proud of myself ) I was so pissed to see the setting that was on my FPR, it was almost to the least possible pressure I was like WTF!!!! Well, I bumped it up a little at first, went for test spin, didn't seem to have done anything. Then my dad got home. He came up to the garage, we did a timing readjustent, knocked her up to 8*, and WOW, BIIIIIG difference. Throttle response was great, plus I gained a lot of low-end power. Also that day I went out and got an open element. Another WOW, I mean that REALLY livened up my top end. I think that was my prob: not enough fuel/air gettin to my engine.

So, now that that's all done, I've only got 2 last things: first of all, I still don't think I am up to my full potential, car DOES seem faster, but it doesn't seem like 30-40 horses. SOOO, I think I'm gonna bump my timing some more, see what happens.

Next thing... my AFPR... How do I know where I need it at? I'm almost positive I'm running really far off, please don't get too pissed, cuz I'm sure what I did was bad: I kept bumpin up the pressure because I was mad I wasn't feeling a difference. Well, eventually I had the little tab on the FPR half way (right in middle of slot) If you guys know what I mean... Is this way too much pressure? Where should the tab be? Closer to the top? Bottom? This is the last thing I need to know, so that I don't F something up, ya know?

Well, thanks again guys, my car is DEFINATELY more fun to drive, plus I just LOVE the sound of the engine in upper RPMs with that open element

Nate

 

I think most guys are running around 15-16.5 psi. I need to get a fuel pressure tester from Autozone. They have these ACRTONIII or something like that for 40 bucks for TBI cars. What I did was screw it in as much as I could and then did a turn and a half back.

 

You have yours just about screwed in the whole way? What about everyone else? I just got done bumping mine down a bit thinkin it was too much, so now I'm about 1/3 of the potential.

Nate

 

Mine runs about 11psi.

 

Your FP runs 11psi??? Are you running bigger than 68lb injectors?? If not, 11psi sounds way low for your mods...

 

It is. That's why I've got to spend some time this summer to get this vAFPR to work. However, 11 psi is what the stock pressure is.

 

I thought stock fuel pressure for 305 TBI's was 9-10 psi

 

The stock fuel pressure spec for GM TBI (not just the L03s) is 9-13psi. 11psi falls in there, and I measured 13psi on mine, stock.

 

for my car it doesnt really start making power till it hits 3k like even if your slowly accelerating...once you hit 3k it will suddenly pull hard. Same throttle and everything...but once it hits 3k it will suddenly speed up and pull harder. 3k-5.7k is where my power is now. Kinda nice compared to the 1k-4k of the stock Lo3. All I need is a higher stall convertor. And some better tires.

 

What do you have for mods? LT1 cam?

 

You asking me? If so I have atcually L98 cam....close enough right? haha....that underdrive pulley, headers, exhaust. ANd a K&N open element. Not to much mods.

 

That's odd. I think the L98 cam is what my L05 comes with stock, and my power band is what you describe your L03 was originally - 1000-4000rpm...
I'm surprised it has power above 5000. Mine does NOT.

 

So what should I do to get the right pressure guys? Like I said before, I don't have guage to measure, so how should I adjust my FPR? Where should I have the tab lined up? Like I said, RIGHT NOW it's about 1/3 of the potential, but one of you said yours is almost to the top? Any help appreciated.

Nate

 

i have mine all the way in , its 16 psi on mine.........i juts removed the fuel filter and put an inline fitting in its place that i could screw a fp gauge into.........

 

Ok, I think I'll bump mine completely in then. Just to know though, is there such thing as TOO MUCH pressure?

Nate

 

im pretty sure the max a tbi system can run is 20 psi..... i dont know , i didnt use and scientific methods i just kept playing with it until the car accelerated the fastest and that was with it as high as i can get it.........im sure this has something to do with higher pressure producing a finer spray and atomization of the fuel but thats just an educated guess

 

Well, I guess that's a good enough answer for me. I'll go ahead and give her full pressure and see how she does.

Nate

 

IT is a little late for this post, but one thing that can make adjusting the rockers is go to the junk yard and pick up an old vaulve cover and cut the top out on it. So the sides are left intack. That way the oil has to splash up not just make it past the edge of the head. Just a thought.