I'm running a HSR on top of my 388. Ran the HSR last year with the 350 but have recently put in the new engine.

At idle I read 11g (55-65 kpa in EBL) at the plenum with all the other vac lines connected. Press the gas I get 14kpa. I get this even when I disconnect all the other vac lines and plug the plenum up. I am thinking this is low. So I test IAC housing,TB housing, upper and lower intake gaskets with both propane and carb cleaner. Nothing, no apparent leaks.

Whats happening when datalogging all of a sudden I get spikes up to 80 sometimes 90kpa then drops back. They're random then goes into a code 33, Map Hi naturally.

Where else could I have some type of random Vac leak or should I be testing a different way?
thanks

BTW- I have changed the MAP sensor out 3 times

 

Did you silicone the upper and lower halves together or just use the paper gasket? Are you still using the charcoal canister? Could be when it's trying to purge. Or maybe it's you brake booster/check valve.

 

Upper and lower are put together using Right Stuff
I've disconnect the purge canister and power brake vac lines and plugged them up at the plenum.
For the heck of it I took out #7 plug and was surprised at what I saw.
Then pulled plugs 1 and 5 to compare

Check this out.


Doesn't appear to be firing. Note all these plugs have less than 1 hour on them

 

Doesn't appear to be firing or doesn't look like it's getting fuel? Is the plug fuel soaked or is it really new. Maybe an injector/wiring problem. The other 2 plugs look too rich, possibly caused by the O2 sensor seeing the extra oxygen from the non-firing cylinder.

 

That plug is way too clean. That cylinder is definitely not getting fuel for some reason. I'd pull the rest of the plugs and make sure it's the only one...if they're as bad as the two in that pic they're gonna need to be changed anyway.

 

Spark tested out fine.
Injectors and Injector wiring tested good.
Threw on a compression tester and it read 0, so off comes the valve cover to see if I notice anything. Think I found my problem.

 

that'll do the trick... im having the same issue im wondering if im running to rich at this point and my o2 sensor is telling my computer more air which opens my iac. cause sometimes im idleing at 2500 rpm. but after warm up it will go down but still kicks a coad. and sometimes idle only gets worse. also i can tap my gas and it'll go down sometimes.

 

Did you break the rocker arm stud or did it just back off. I've broken a few but always on the exhaust which is a much more apparent situation. I would check/replace all of them if it was indeed a failure.

 

Ugg.. Can't tell you how many times that has happened to me...

More than once, I've had a car turn to absolute crap. I pop a valve cover and the polylock backed off the stud, pushrod bent, etc.


-- Joe

 

The engine wasn't making any unusual ticking noises? Yesterday my valvetrain was making a ticking noise, almost wrote it off as an exhaust leak. Decided to pull the valve cover, gave the the wiggle test and boom, found one with the poly lock backing off.