First and foremost, anyone running the GM 847 cam with stock heads, installed straight up? If you have vacuum readings at idle they would be more than helpful!

Lift with 1.6 is 575/595. Basically the car is a PIG after the cam swap.

Im 99.9% sure it was installed correctly and that i am not a tooth off on the roller chain. Still hasnt been ruled out.

I had ~4.5inches of vacuum at idle and went to the track. Ran low 14s at under 100mph. At the time i didnt know about the vacuum issue. Replaced intake manifold gaskets with some felpro, and jumped to about 8inches at idle. Good but still not great.

Havent been to the track since intake manifold, but ran side by side with a s10 LT1 truck which traps 105ish. Still to me that is way too slow for my car. Last year i was trapping 104 without complete valvetrain, cam, electric h20.

Replaced fuel pump, opti, coil, wires, plugs, new MSD box. Fuel pressure is good, ingition seems like it is working great unless the opti isnt giving it the timing it should be. When the opti was first installed it threw a high res pulse code, but i cleared it and it hasnt been back since.

Car has beened tuned. BLMS look ok, not split, as do WOT 02s.

Really just looking for suggestions on what to look for. IM starting to think the cam has too much lift for the stock heads and is just getting really turbulent. Anyone else running a similiar cam on stock heads with some numbers?

Power just sucks with this, it revs smoothly, but not quickly, its a slow rev-er. 4.33 gears out back, it should scream. Tires will not even spin pulling through first until you shift into 2nd. nitto dr.

Also car is running hotter than it should. Always used to run 180 or less, now it runs 180-to that middle line most of the time.

Any suggestions or hints would be awesome.

234/242 .575/.595 112

 

Also i have full tuning and logging abilities if a TTS log or something like that would help let me know and i can log one and put it up for you.

 

that idle vacuum seems very low


a friends car with a 230/236 on a 110(!) with stock heads/bottom end pulled about 11

 

very weird..if u want you can send me your LT1 program and some datalogs..ill take a look at it...send em to marcinwz@bellsouth.net.
Does the car idle rough?

 

Ya i know the vacuum is low, which is why im posting this

Ill send you those files tonight, i really appriciate it. The car idles really well actually. You can tell its cammed, but it will stay at a steady 900ish without jumping around too much.

If the intake is open too soon, it will kill the vacuum i believe. That could also explain the car running warm too right? I almost think it has to be a bad cam grind (maybe dowel in wrong hole) or something. If i was a tooth off wouldnt that put it off by like 20º? So hard to tell with really steep gears like i have. THey can make a 1.8L feel fast

 

Anyone else?

 

Try degreeing the cam. All you need is a light valvespring and a dial indicator.... you can find out exactly what degree in crank rotation the intake opens and compare it to the cam card..... I wouldnt expect all that great resaults above 5250 RPMS from stock heads with any cam on a N/A motor. My stock heads flowed better on the intake side at .400 lift then they did at .600
Exhaust was like 7 CFM different .400 to .600 But no gain after .550.

 

Well with a number of peoplel claiming impressive trap speeds with stock head cars, I am sure he was expecting better.

 

get it scanned for error codes

 

When I put in my GM847 cam I degreed it. Striaght up it was about 7 degrees off from where it should have been. With ported heads at idle I have 11" of vacuum.

 

Grease, 7º? Holy shiznit!

Not only did i not get the numbers i expected, i am making less power than last year with stock cam, worn out valvetrain, shot fuel pump and opti. I can see if the car was in a bad state of tune with worn out components, but EVERYTHING is new or in tip top shape.

I saw on guy on here (ellis) roll 348hp and 402tq with stock heads/bottom end and this cam through a 4l60e.

With ported heads and you are seeing 11inches, wow. I have the stock heads still and are only seeing 8ish.

Guess its going to get torn down in a few weeks. I cant believe it would be this far off and still be totally driveable and streetable, just lacking power.

 

I agree, you should definitely check the cam phasing. 7* retard would have any engine running like a snail across a salt flat. Not to mention, the engine would likely run much hotter.

For reference, I ran a 242/246 110 lsa mechanical roller in a 355 and pulled 9" Hg @ 950 rpm.... no leaks whatsoever. You should be at 11-12" Hg.

-Mindgame

 

Dumb question here but did you go back and check the adj. on the rockers to make sure that they were not to tight causing the valves not to seat all the way. Along with that are you sure that everthing is at the correct installed height and everything is happy in the heads as far as your valve train goes. Just one tight rocker arm could cause a severe loss in vacuum.

I would also check to make sure that the cam is running right and that the dots and the cam line up, just incase the grinder was running a little off that day.

Tuning could help it out some if it was off and not wanting to run the way it should. I don't know if a IAC reading to large would do that or not, if it was all the way open trying to keep the car running....would that cause a low vacuum reading? Make sure everything else like the TB and intake are not having any leaks. One other thing that happened to my friend's car was the rubber gasket on the brake booster had a crack and it was loosing all kinds of vacuum.

Just some things to think about.

 

I have re-adjusted the rockers 2x now. One time turning the car over by hand, and the other with it running. Same vacuum readings.


The intake manifold gaskets just got replaced, thats how i went up fromm 4.5 inches to 8. Also replaced the TB gaskets when i did that.

With the tuning issue, I think its in a pretty good state of tune. Marcin looked over a log and my lt1 file and agreed. Only thing he noticed was that my spark advance at high map and above 4000 was cut down a few degrees from stock. I think it may have been pinging when my buddy was tuning it in.

As for the IAC, i dont know? I cracked the TB blade a little b/c the IAC was going crazy trying to pull in so much air with that cam. Now i have split BLMs at idle only, but it idles well.

If you dont know how fast the car should be, you wouldnt even notice anything wrong with it. It runs really smoothly.

Im going to go back in and check that timing isnt a tooth off, lined up dot to dot (correct dot to dot (cloyes)), and degree the cam. Nothing else i can think of outside of timing

 

Did you get the cam grinded stright up? I remember someone telling me that you cant adv/ret the LT1 cam bcuz it will move the relation of the cam sensor in the opti in relation to the motor and will mess up your timing.