What cam is installed? Do you know the base circle? I agree with Dan, if you are running stock length pushrods, you will likely be loose as the aftermarket cams decrease the base circle to obtain more lift.

Did you take any photo's during the work? All electrical connections are secure and in the correct place?

If you don't have compression, you can tell by the sound of the motor when it turns over.

 

Ive had this problem myself a few months back. When you bolt the rockers down you collapse the lifters. So you have to wait until you build oil pressure to fill up the lifter. Pull the fuel pump relay and crank on this baby untill you see oil pressure. You will not get an oil pressure reading while you are cranking but when you let off the key you will see the gauge work and bleed off. Once you get it cranked it will most likely act stupid for a bit but will get better. Hope this helps, Good Luck!

 

I talked to dpd(Donny) I we figured the stock length pushrods are to long.I did some measuring and there about .030 to .040 to long.Installed spring height 1.800 I came up with 1.76 something like that.I have written down,but its out in the garage.The stock pushrods are 7.400in so I guess I have to go to,I think they are 7.350.I'll double check again tomorrow,I'm beat Thanks everybody for your help,If you have anything else to add let me know.................Paul

 

Are you sure your LS6 intake seated properly? Did you go to the LS6 style front coolant pipe and rear plugs, or did you modify the bottom of the intake to make room for the stock LS1 pipes? I wound up cutting my stock pipe and flattening, folding and soldering the openings to make my own 'LS6-style' pipe and plugs. I also had to remove the green plastic clips from the knock sensor wiring harness before the LS6 intake would sit down flat. If you didn't change rocker arms to a longer length, then I think your stock pushrods should be OK. Other than that, it sounds like electrical connections.

 

Yes,I put the 2 plugs in the back & the LS6 style coolant pipe in the front,removed the clips.A few of the guys say the valves are hanging open,And I think there right.I'm going to do some more measuring and some other tests to make sure.

 

Installed spring height has nothing to do with pushrod length.

What cam is in the car? You need the base circle. Most aftermarket cams need a longer pushrod, and if you are at 7.4" you are likely OK. If you are at 7.35" it will still start, but will be noisy. I think you are fishing in the wrong pond and need to look elsewhere for your problem.

 

I agree with vettenuts,if the valves were sticking open your compression would not be as high as it is and it would be backfiring through the intake and exhaust.It is probably something that is small and being over looked.Put brand new plugs in they may be fuel soaked and not working properly.I know it sounds crazy but we spent a whole week-end on the race car chasing electrical problems.There was spark,compression and fuel but no starting,changed the plugs because it was the only thing left that we didn't change out and it stared right up.JER

 

If you have that much compression there is no way your valves are hanging open enough for the engine not to start. If you really have that much compression my guess is cam timing. Like stated before, there is no way to time one of these engines with the cam 180 out, because once you turn the crank one turn it is right back in time. Dot to dot is #1 TDC on exhaust stroke, both marks on top is #1 TDC on compression stroke using a factory timing chain. These engines will run fine without a cam position sensor, it's only there for quicker starts. I never pulled mine when swapping cams, no problems.

I'm running AFR 205 heads milled .042 with a slightly large cam (.592) and the 7.400 pushrods were still fine.

When you say the cam was "a degree or 2 off" was you using a degree wheel and dial indicator? If so are you 100% sure you were checking it correctly? Degreeing a cam can be a little confusing if you don't do it all the time.

When you say you had plenty of PVC (Piston to Valve Clearance), exactly how much did you have and at what point? Did you check at TDC? If your cam is near 0 degrees your intake valve should be the closest (the least PCV) and that will happen around 10-20 degrees ATDC, your exhaust valve will be the closest 10-20 degrees BTDC on the exhaust stroke. PVC depends highly on cam design and cam timing.

What timing chain did you use? Is it an adjustable setup? Some of the adjustable chains don't line up dot to dot if your not at 0 degrees. Specially the ones that have multiple keyways in the lower sprocket.

Also, are you sure your plugs are not fouled? When I did my cam swap it fired right up the first time I hit the key but it was running very rich. After a few times starting it and moving it around and not letting it warm all the way up it fouled the plugs. After that when I start it up, it would backfire, pop, crack, spit, sputter out the exhaust and sound horrible. I changed the plugs, put cheap ($1.30 AutoZone) Autolite 66 plugs in there temporarily and it runs great again. If you had a plug covered in gas it couldn't be firing, but the big question is why.

What cam are you installing? Which heads? How much has the heads been milled? Knowing what you have will help everyone help you.

Good luck

 

ok,i'm not sure his compression gauge was actually good.i agree if compression is that high,the valves shouldn't be hung open.i asked him what installed height was because with the cam off lift[valves closed]that's what you should have as a measurement.
the only other thing that we all can think of is electrical.the only thing that i can think of electrically is crossed o2 sensors[if you're running headers],as there are no faults stored and it's fouling plugs.it is also popping through the exhaust and intake that's why i was on the hung open valve theory.all the grounds,etc sound like they are all back on.

 

The high compression could have been caused by fuel soaked cylinders! With that much compression, your valves are NOT hanging open!!! If you had #1 cylinder at TDC and the cam and crank dot to dot. it should run!!!

I would do the simple stuff first! PLUGS! DVS 99's theory sound spot on!! Get the lifters pumped back up, install the new plugs and see what happens.

Don't start rippen stuff apart until you exhaust the simple stuff first!!!

Bill C

 

Well,I'm getting some where I think,I had new plugs in,I checked them after it tried to start,Some were black & sutty,some were clean,Now It started to idle for about 3 sec. and then popped 3 times out the exhaust.I went underneath the car,The passenger side headers were warm and the drivers side were cold.I will try a new set of plugs tomorrow.The cam is 595in & 603ex and PP LS6 heads.And The pushrod length is fine.Everything checks out,My connections,I took off the intake again,All the wires and hook ups are fine.I checked P/V clearence as the piston comes up and I checked it after TDC.I had soft valve checking springs so it made it easy to do.It sounds like it wants to start.Here is how I did my cam timing.

 

Ok,,,here are some passengers side verses Driver side things to check:

There are TWO fuel injector/ignition coil fuses, one for each side!!
INJR 2 (mini fuse# 18) & INJR 2 (mini fuse# 22) Check those fuses.
PLEASE let us know what you find.

If you dont have any fire on one side, you narrowing thing down!

Bill

 

I checked those,they were OK.I'm going to try,I forget who said it,And put new plugs in.Is it possible since the car has been sitting at the end of November,I didn't put in any gas stabilizer,Maybe the gas went bad?It didnt have that gassy smell out the exhaust when it tried to start.

 

Naa,, I doubt it,, but anything is possible. Pop the cap on the tank. If it smell like good fuel, it most likely is. If you are absolutely sure that all eight coils are firing, Try this,,,Spray a good shot of carb cleaner into one of the vacuum ports near the TB. Then crank it. If it runs better and then dies,, it's fuel related and should be easier to track down.

BC

 

Great photos!!! That looks like the Crane/Rollmaster chain, if your dot to dot with that one it should run. Hard to think the plugs could foul in 3 seconds but sound like they could be. Did you crank the motor over for a while to build oil pressure with the coil packs unhooked? That may have flooded the engine enough to quickly foul the plugs. Did you check for spark on each bank? Best way I have found is to pull the plug wire out of the coil, you should see it arcing back up into the coil off the end of the wire. If you pull if loose at the coil you won't get shocked like you will if you pull it from the plug. The cold header would make me want to look for no fuel or no spark on that side, but that could have simply been where the plugs were soaked and not firing at all. With the popping out the exhaust it sounds like it could be the plugs, when my plugs were fouled it would still run but it would pop out the exhaust and it sounded like you were shooting a 9mm in the garage! I don't ever remember it backfiring through the intake though. The gas shouldn't go bad that fast, I have had cars sit for over a year and still run fine. How much gas is in it now? If it is very little it would probably go bad quicker. You can eliminate the gas by shooting a little starting fluid into the intake. It should fire right up and run for a few seconds.

Remember, it only takes air, fuel, and spark to make an engine run. Of course they all have to come together at the right time in the right amounts. Figure out what is missing and it will fire right up!

Good luck!

 

Did you remove the coil packs from the valve covers at all ?

 

YES I DID,I WAS JUST GOING TO ASK ABOUT THAT.PLEEEEEAAASE TELL ME I PUT THEM ON WRONG,ITS GOTTA BE!!!!!!!!!!!!! Its a 97 I went to center bolt valve covers when I changed the heads

 

Good thought Chris! That is about the only way to get the firing order out on one of these motors! And that would make it pop! Unfortunately GM failed to include the coil pack connector pinout for the 97 and 98 Vettes in their electronic manuals. But here is the schematics for the coil wiring, they are pretty huge (pixles) GIF files but only 60K each. Looks like the coil pack plugs are C109 and C110, you should be able to follow the colors and trace them out to each coil fairly easy.

Since they are huge here is the links
http://CorvetteForum.Shelor.net/temp/Coils1and3.gif
http://CorvetteForum.Shelor.net/temp/Coils5and7.gif
http://CorvetteForum.Shelor.net/temp/Coils2and4.gif
http://CorvetteForum.Shelor.net/temp/Coils6and8.gif

 

I have the 97 manual it shows it,but for some reason the passenger side don't jive,Its running but not good.The drivers side is hot all 4 pipes.The pass.side 2 pipes were warm 2 were cold.BUT AT LEAST WE HAVE FOUND THE PROBLEM!!!!!!! I have to thank Chris at ECS and all you guys I'll check those threads SpeedyZ,Maybe someone can look at there pass.side coils and tell me what goes where.Thank you.............Paul

 

Sounds like you about got it! Isn't it good to hear the train at the end of the tunnel? I have been told the left and right coil packs are exactly the same, have not tried swapping them myself but they should be the same. So you should be able to look at your right side coil pack wiring and tell. You could also swap packs let to right if you wanted to see it that made all the right pipes heat up. Really easy, just a few minutes.