Before and after valve cleaning pictures (96-98 cobra)

[dville_gt]

got the intake off the cobra tonight, the secondary valves (the ones behind the secondary imrc plates) were completely coated. I am definitely losing air by the intake valves where they seat. I only did the worst cylinder tonight (and don't try this with the garage closed as I am high as a kite off of carb cleaner). Any way, after cleaning the leakdown numbers improved by around 15-20% but for this cylinder they are still showing around 40% leakage (on a stone cold motor, which might be skewing things). Going to knock out the rest over the next day or two then put it back together. I think I am also going to do imrc plate deletes then get it dyno tuned to correct the timing issues (assuming I can get it running right). Check out the video to see how much air is getting by when I try to seal off the port with my hand. It is better now but still not where I think it should be. When I sprayed carb cleaner into the port it gargles like crazy from the air escaping.

Before secondary


Before primary


After secondary*


After primary


After both


Imrcs completely caked

[dville_gt]

[90GT50]

Ha, fart noises.

[turbostang]

THat's pretty bad, it should make a healthy difference.

[dville_gt]

Got any idea's on why else the intake valve(s) would seal so poorly? Cleaning well around the seat was pretty hard, I kept the cylinder pressurized during the entire process so that none (or very very little) of the carb cleaner (or crap) made it down into the cylinder (plus I think the gurgling of the carb cleaner helped the cleaning process).

After I got it looking good I rolled the motor over and doused a toothbrush in carb cleaner and tried my best to clean the seat with the valves open but it is a very hard place to work and the brush didn't really fit in there real great.

I was thinking maybe the valves are not closing all the way. I presume that these motors have hydraulic lash adjusters but I am not sure if the followers are prone to failures or not.

Not that I necessarily would be able to tell but nothing looked bent or deformed in any way.

[Rick Modena]

THIS is how you do 4v heads...

[Captain Crawfish]

I have a brand new set of mmr imrc deletes i would like to sell for $150. Brand new never installed. run some sea foam through that thing every 10K the imrc's staying closed is a crap design

[Captain Crawfish]

when my motor lost compression all the valves looked good none bent that i could tell. the valves would not seal though when i did leakdown on them. i ended up putting a remand set on the shortblock and it was like a brand new engine. the secondaries on my 100K motor were half full of carbon

[dville_gt]

[stevo]

I have seen a valve seat with carbon built up on it between the valve and the seat, it was on a low-compression 429 head and when wd40 was sprayed into the intake port, it would leak through pretty quick. I did a quick hand lapping on the valve, and it cleaned off the carbon and the valve sealed up. So, it is a possibility that carbon is causing a valve to leak a bit.

Stevo