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tore top end down for rebuild

TEK310

TEK310

New member
so i posted a while back about thinking i had a blown head gasket.

took things apart, found that none of the bolts were really torqued down, 90% of everything was pretty loose.

coolant was leaking out from under the SC under the throttle body, oil leaking out on the pulley side of the LIM.

the end cap gasket was torn up, like the guy took it off and didnt get a replacement so just bolted it back on, that was also leaking.

LIM and SC and TB were full of goop, mix of oil and coolant.

took off the heads the front head has a crack all the way to the bottom of the valve seats between exhaust and intake.


what really worries me is, there are marks on all the pistons where valve have touched, but none of my valves had marks on them, and they are not bent. the marks were not shiny, carbon had built up on top of the marks but you could still see them.

got a replacement cometic headgasket .010" thinner, i dont want to bend all my valves, if these marks are new or from a previous build., the bottom end was rebuilt from previously being locked up

ive cleaned everything. surfaced heads, 3 angle job on exhaust seats, new valves, comp cam valve locks and viton seals

ported outlet on my SC and matched the inlet to take out the casting that was sticking out in the air flow.

one question about the ported outlet, i milled down that center bar, that everyone else does. do i need to make any adjustments to my gasket before putting it back on?

also what are the consequences of the epoxy film coming of the rotors? bc the film has flaked off, leaving the rotors looking nice and shiney new lol.
 


carbon had built up on top of the marks but you could still see them.
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Suggests you shouldnt have to worry about it.

Shiny rotors = worthless rotors.

Pictures of inlet?

You can go too far.

But there are still a few degrees of separation in the stock design.
 
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so the SC rotors with no coating means they need to be replaced?? and what do you mean few degrees of separation, and going too far. i have a lot of questions in my post, trying to figure out what questions you just answered
 


Marks on the pistons suggest that a previous build may have had the timing off and the valves touched. Like Matt says..carbon is your friend there. No coating means you'll lose about 2-3 psi of boost and the SC isn't very efficient. I'd look to pickup a set of rotors to replace those. (wonders if the Gen 3 in the garage has good rotors..hmm)
 
BillBoost37 said:
Marks on the pistons suggest that a previous build may have had the timing off and the valves touched. Like Matt says..carbon is your friend there. No coating means you'll lose about 2-3 psi of boost and the SC isn't very efficient. I'd look to pickup a set of rotors to replace those. (wonders if the Gen 3 in the garage has good rotors..hmm)
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its gonna be hard to find a set of rotors, if you have a set, how much to get them off your hands?
 
y'all have no idea how much of a hassle and disappointment this car has been.

i got the car bc i have always wanted a gtp or impala ss. got the car babied it for two days while i did some minor things, like flushing out the water and putting actual 50/50 coolant, new t stat, replacing ect.

finding out the MAP was left off the car during the reinstallation. more than likely what pushed the car over the edge. car cant register pressure above atmosphere without the MAP sensor.

then i get the money rounded up to buy all the gaskets and seals for the head reinstall. then i find the front head has a giant crack between the intake and exhaust seats. and my valves are thin, so i have to buy new valves and another head.

now i found out the rotor pack in the SC has all the epoxy coating stripped off. now i need a new rotor pack.


i hope this car is legit when i have it back together.
 
how is that possible? how does the PCM know how much fuel to inject without being able to read boost (above 14.7psi)

this car may be the exception, but what i have learned so far at UTI, forced induction cars measure boost with a MAP sensor
 


I'm not a tuner, but the fuel pressure regulator has a vacuum line attached to it. The fuel pressure is increased or decreased the same amount as the boost/vacuum pressure. This will keep the differential pressure between the fuel pressure and the intake the same so that the fuel injectors always flow consistently.
 
At this point you might be better of buying a used motor and dropping it in. Wouldn't be a bad idea to redo the gaskets on the new used on for safety sake.
 
sseilmnop said:
I'm not a tuner, but the fuel pressure regulator has a vacuum line attached to it. The fuel pressure is increased or decreased the same amount as the boost/vacuum pressure. This will keep the differential pressure between the fuel pressure and the intake the same so that the fuel injectors always flow consistently.
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That too. And despite that, GM had to slope the IFR tables because the wiring for the fuel pump is so inadaquete. The injector offsets are also adjusted as such because of the changing pressure differential.

If you go with a fuel pump rewire the offsets should be the same for all vacuum values and the IFR should be flat. Otherwise stick with the stock sloped madness.

But to measure the amount of air and thus fuel required, our PCM's use the MAF for fueling almost exclusively.

Other PCM's will use the MAF's for primary readings then compare to the speed density tables for transients and as a sanity check.

Our PCM's still use the VE for a sanity check though.
 
so what is the MAP used for on our vehicles then?

and to the getting a new drop in engine. this engine just got a fresh rebuild minus the heads. new main and rod bearings, along with new cam bearings, and stronger timing chain. engine still has the honing marks in the cylinders.
 


To check for maf failure and so its drivable without a maf in case of maf failure.

Just make sure the bottom end is properly assembled. They're very picky.
 
just finished grinding out the casting sticking out in the exhaust ports on my heads and finished porting the inlet and outlet on my supercharger. gotta hook up the heads and waiting for a set of rotors and then it goes back together!!
 
pictures of the cracks between the valve seats?

those are fairly common and usually don't mean a thing for the performance of the heads unless they are really bad.
 
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