dizwiz24

I did a compression test and got numbers like this:190,190,195, 195, 195, 210, 235, 205.

The last check I did, a few years ago, gave numbers arnd 190:

How do I get rid of the carbon?

Seafoam? Into vacuum line?

Or an additive to my fuel?

I've also heard about a product called gm top end cleaner too

WW7

Im going to post this then run for cover, because I know the naysayers are going to attack..Yes Seafoam will remove the carbon from your engine. You have to pour it into the vacuum hose on the brake booster until the engine stalls, let it sit about 15 to 30 minites, then start your engine and watch out for all the smoke..Give it a try.....WW

oldalaskaman

I really like this one, back in the day it was 'mystery oil' , same procedure.

cv67

Run the pee out of it, goodbye carbon.

being as you have forced induction doubt you have any at all. If theres some there its not worth worrying about.

383vett

I have slowly poured water down a carburator to clean carbon. It turns into steam in the combustion chamber and loosens the carbon. You can spray water into the throttle body when the motor is running. Actually the port in the middle below the throttlebody blades is the opening for the iac. Squirt water or seafoam in there when the motor is running. Willie

dizwiz24

Well, actually I am a little worried that the carbon in there could raise the static compression ratio of those cylinders and make them more likely to hot spot/detonate under boost.

Since I still have stock bottom end, Im a little concerned about that possibility. However, ive never really heard of that happening.

I did send a note to greg @ blowerworks about this. He was surprised that there may be carbon in there - due to the meth/water injection system I am using as part of my blower setup.


He suggested seeing if I could get a hold of a fiber optic camera of some sort to see if I really do have carbon on the piston top or top of the combustion chamber.

Maybe my issue is like you say! I just need to step on the gas a little more !!

cv67

Bet those pistons are as clean as awhistle, carbon buildup wouldnt really raise the compression any measurable amount imo.

bjankuski

You can not rely on a compression test on a modified engine (with hyd lifters). The higher the stock valve spring pressure will cause a lifter or lifters to bleed down and that cylinder will give high compression readings, since the valves will close early building pressure early.

My 406 has shown over 300 PSI on the cylinders that bleed down. Start the engine get some oil pressure and recheck that cylinder and all is fine at 200 PSI.

You can actually perform a running compression test, that will give you a more accurate indicator of cylinder health.

dizwiz24

interesting! first time i have heard this.

yeah, the plugs looked fine from those cylinders. not sooty. the usual tan deposits on electrode, etc.

so if I fired it up, shut it down, and then re-checked those cylinders they should be like the others (if all is well?)

I also want to mention that those cylinders in question were the last 2 I checked.

Finally, I do have hotcam kit (1.6:1 roller rockers, lt4 springs, lightweight hats and the hotcam itself) installed.

96 lt-4

Run some seafoam in the gas tank and drive it hard.With the meth/water injection to have carbon buildup you would likely have a lot of blowby anyway.

Marvel mystery oil worked great back in the day.KIlled mosquitoes for a few miles.

LT4BUD

FWIW after reading this thread, I think the biggest question is what is going on that two cylinders have higher compression readings than the other six. Running rich seems unlikely since the plugs were the same as the others.

In other words, look for the problem, if there is one, before you remove the symptoms.

Might be worth doing it again to see if you the readings are repeatable.

Sandpiper59

I agree with a post further up about lifters etc. Many people believe carbon build up causes detonation because of raised compression, it causes detonation because the carbon can start to burn like charcol and cause ignition before the plugs do. I can't imagine there would be enough carbon to cause that much change in compression! However a lifter bleeding down and closing sooner, opening later can.

None the less, 2 best ways I know of for carbon, put a trailer hitch on it and tow a really heavy trailer up a long hill , or Seafoam in through a vacuum line (PVC line works good too or vent line on other side which will get some of the plenum). Trickle faster and faster as the engine manages to overcome it, then much more rapidly dump last 1/3 of a can and try to stall engine. Leave it off for 15 mins then go and flog it pretty hard.

Muffin

A thinking man's answer.

REDC4CORVETTE

Attack time!!!
If you run water through the engine DO NOT LET THE MOTOR STALL WHEN DOING THIS OR YOU COULD BEND THE RODS!!!
I use to do it to every car I had to tune at the chevy dealer to blast the carbon to keep the enigne from knocking.
Chevy also carries BG engine gas addative that you can pour in the engine or the gas tank or 1/2 and 1/2 and it does a great job!

Oklahoma_mike

QFT!! H2O works just take a little care to not over do it.

Sandpiper59

Keep in mind when using any liquid but especially water, it may pool in areas in the intake or heads then ingest a massive shot when the engine is reved. It may only cause 'hydro lock' requiring the plugs to be pulled, worse, it can cause a piston to be holed it the piston is unable to stop the weight of the crank spinning...

Tom400CFI

Yep-yep. BTW...you can lock up a motor w/seafoam, MMO, or any other liquid elixer too.

Water is the cheapest way to accomplish the goal here.

cv67

Warm/hot water in a spray bottle on 'mist"


His meth injection is doing just that though as far as the effect.

dizwiz24

Well, I started it up and recheckd those 2 cylinders. They were right at 185 to 190 psi.

Everything is good and I hope we all learned something new, I did!