Yeah, I can't really tell if the heads were removed. They are 853 heads though.

The valve springs were replaced with dual springs.

 

853 heads sound like LS1 heads. dual springs, aftermarket, and why? no need with a stock cam.

I went back through your orig post. You reported -5% LT fuel trim. If so, then your system is biased to run rich, and your O2 sensors are telling the PCM to cut back fuel 5% from base setting. Base setting is computed based on MAF and MAP, which both are a bit high. Thus your idle speed should be maybe 1200-1500RPM with that much air going in. Since ST trim has gone to zero you have a new steady state.

If you had a vacuum leak after the TB, you would be introducing un-metered air and the engine would run lean, so the O2 sensors in that case should be telling the PCM to go rich, adding fuel, based on the O2 sensor feedback.

I don’t see anything to suggest your PCM is bad, but perhaps someone with tuning software did something wrong. Lots of guys do “bench tunes”. I would call PCM of NC and see what they say. Maybe they could bench your PCM and analyze performance.

 

Hello all, I got a interesting data point now.

I took a valve cover off and one set of rockers. I pulled out a push rod and it was also aftermarket. It had 7955 COMP CAMS 7.400 .080 written on the side.

So, aftermarket rockers (I think Harland Sharp rollers), Dual springs and Comp Cams push rods.

Now for the intersting part, I measured the lift with a dial indicator on the end of the pushrod while hand turning over the engine and got some interesting measurments.
Lift on both intake and exhaust push rods were .360 !! and if the rockers are really 1.7 ratio then the total lift is .612 !! Realy big for stock intake and exaust system !!

I think this is the smoking gun if it has stock intake, exhaust and tune. (not sure if it stock tune)

What you guys think ?

 

Interesting. A .612 lift is a lot. depending on the cam duration I sure hope somebody checked for piston to valve clearance on the exhaust valves. When I crammed my FRC, the shop put check springs on one head so I could measure.. Also important is measuring the pushrods. There is no adjustment for valves and the lifters need a certain amount of compression spec ed by the cam maker.

I found one good OEM rocker from a LS1upgrade I did several years ago. IF you want it PM me and I can send it to you. I sure don’t need it. You could use it to compare to what you have, then toss it.

 

After reading many, many posts about cams I think I'm on the other side of the fence on camshaft selection.

I would like to replace mine with a closer to stock cam for good idle and low reving driveability. I read that tuning for a good idle with a large cam is pretty tough and then gas milage still is going to be bad.

I called a major LS engine parts supplier and pretty much got laughed at looking for "such a small cam" stock cam.

I know there were probally thousands of stock cams thrown in the trash over the years but finding one now is impossible.

What I'm looking for is a new old stock or very simular to stock cam for a 97 to 04 LS1 Corvette, something like the following:

1997-2000 C5 LS1:
- Intake / Exhaust Duration @ .050": 202 / 210 Degrees
- Intake / Exhaust Lift: .472" / .479"
- LSA: 117 Degrees

2001-2004 C5 LS1:
- Intake / Exhaust Duration @ .050": 199 / 210 Degrees
- Intake / Exhaust Lift: .467" / .479"
- LSA: 116 Degrees

1998-2002 Camaro / Firebird LS1:
- Intake / Exhaust Duration @ .050": 198 / 208 Degrees
- Intake / Exhaust Lift: .500" / .500"
- LSA: 115.5 Degrees

Here is the million dollar question, I do not want to debate cams just looking for a stock or close to stock cam, Any suggestions ?

 

My suggestion would be to look for a LS6/Z06 cam. Not quite as small as an LS1, but with smooth idle and good street characteristics. Many have been swapped out at low miles for bigger and should be sitting around in cabinets and sheds. Heck I’ve got one in a cabinet.

 

I'm shocked Glad you figured it out.

 

Thanks for the info,

I did some more searching and it looks like Rock Auto has a 2001 LS1 cam, original GM too !

1997-2000 C5 LS1:
- Intake / Exhaust Duration @ .050": 202 / 210 Degrees
- Intake / Exhaust Lift: .472" / .479"
- LSA: 117 Degrees

2001-2004 C5 LS1:
- Intake / Exhaust Duration @ .050": 199 / 210 Degrees
- Intake / Exhaust Lift: .467" / .479"
- LSA: 116 Degrees

Specs are close to 1999 LS1 ! And I wouldn't have to worry about push rod lenth I think ? Stock 7.4 should work right ?

My ideal cam would be from a 2001 LS6 GM #12560950 its just a little more aggressive than the 1999 LS1 but they seem to be rare as hens teeth.
Any idea where I could find one ?

 

Try these guys:https://www.oregoncamshaft.com/ If they do not have it, they may be able to grind you a cam to your desired specifications. I had them custom grind me a cam from a donor bump stick I had laying around years ago. They did ,a great job, I was very satisfied with their service.

 

ebay has a few listings. Maybe call Vette Pros in Gastonia NC. also post on the ls tech forum too good guys over there


Whether 7.4 pushrods are correct depends on the shop that did the heads. If the head is unmolested, probably ok. Pushrod measuring tools are cheap, all you need is a 8 inch digital caliper and the measuring tool. I would still measure, I would for sure pull the heads and check the lifters, probably replace b/c of the dual springs. Also, with stock rockers, replace the bearings and trunnion on each rocker. Harmonic balancer, new HB bolt. timing chain and gears, etc, etc, etc

So, changing the cam is a money pit to say the least.

 

What I decided to do was to replace the cam and springs from a 2001 C5 specs are :

2001-2004 C5 LS1:
- Intake / Exhaust Duration @ .050": 199 / 210 Degrees
- Intake / Exhaust Lift: .467" / .479"
- LSA: 116 Degrees

I know this contradicts about 99 % of the cam swaps, but this car is going to be more touring and used for day trips with the wifey.

The one thing that concerns me is IF the previous owner(s) messed with the PCM. I'm hoping changing the mechanicals back to stock and the PCM is still stock and it should run smooth and report no more misfire codes. If not, I'll be looking for a stock tune.

I got eveything out of the way in the front of the car and now ready to disassemble the front of the engine. I'm curious to see what cam is in it. Hopefully know later today. I'll keep y'all posted.

 

The chances of the PCM having a stock tune are slim and none. Good news is....this is easy to do through various methods.

 

Well I got the cam out, its a Comp Cams 54-456-11 219/227 .607/.614 LSA 112. A little to big for a putts around cruiser.

The job wasn't too bad thanks to forums like this and you tube. Better than back in the day when you had to get your info from car magazines.

We'll see what happens after I get it all back together, probally next weekend. Parts are expected thursday.

 

Well, I swapped the cam for the stock one and as I was checking the pushrod length I found a lifter that blew its top !! The lifter cup was just sitting on top of the lifter so now the heads have to come off, bummer !

Took the heads off the got the lifter out with no damage to the engine other than the lifter tray. So now I need lifters and trays, ordered the LS7 lifters and trays and head gaskets. Lucky the previous owner used ARP head bolts so I can reuse them.

Now I put in the new cam, lifters, and trays, and back to checking the push rods. I found out they were .100 too long ! Now ordered 7.300 pusrods, this will give me .065 to ..080 preload. I think the heads were rebuilt, surface milled and lightly ported. The list of parts keeps growing.

Stock Cam
Harmonic Balancer
Oil pump
LS7 lifters and trays
Pushrods
New gaskets for eveything I took apart
Misc tools

Finally got it all put back together and started up. Intially made a little lifter/valve noise but then quieted down and purred like a kitten and smooth as silk. What I expected compared to other stock engines. I check the manual vacumn gauge and it was 20 In Hg which is perfect for stock. I hooked up the my scan tool to check the other vitals and everything looked normal for a stock engine and no more misfires !

Now for the test drive. Just sitting in it was totally different, it was smooth and quieter. Taking off from a stop in first gear was effortless, before I had to feather the clutch or give it some revs. It has ALOT more power/torque off idle and smoother. I did't take it above 3k yet, just want everthing to break in and change the oil first. (I know the roller cam does not need broke in). It seems to pull better from off idle to 3k better now and also I can putts around now at 50 mph just over 1k rpm without bucking or bogging. If I want to speed up just downshift.

I couldn't be happier. Learned alot in troubleshooting this and repairing a few issues from the previous owner(s). Now with the engine running to my liking now I can address a couple other things that need some attention. Front rotors seem to be a lttle warped, I have an PowerStop kit on order. Its wearing the front tires in the inside so a line up with a little less agressive camber will be soon too. Aslo the rocking seats need a little attention.

Thanks fow everyone help !

 

I hope you have it set. IMHO, the 7.300" long PRs sound very short compared to what most guys here run. Seems 7.400" seem to be the popular length, and maybe be stock length, IDK for sure....

 

I agree they would be short for a totally stock LS1 engine which I was trying to get to but with parts I had to use it made the pushrods required shorter.

The head gasket was slightly thinner.
The LS7 lifters (replacements for LS1) cup is higher in the bore which makes the lifter longer.
The heads were worked on sometime and I believe they were milled down (thinner).

I used a adjustable pushrod and measured the four corner cylinders (#1,2,7,8) to get a good sample of the size I needed. There was close to .020 difference in all the measurements due to the valve lengths. From what I read (alot) the ideal preload for the LS7 lifters is .070 to .080. So I picked a pushrod length that would get me close to this.

For another verification of the length of the new pushrods I counted the turns of the rocker hold down bolt from 0 lash to fully seated, I got between a little over 3/4 to a little over 1 turns then I torqued to 22 ft lbs. From what I read that would make the preload .roughly .060 to .080. If I went to the next size pushrod (+.025), that would make the preload .085 to .105, which I feel was too much.

If all the valves where the same length it would have been easier to select the pushrods.