where to go from here, 77 esprint

[poncho88]

my cousin has a 77 firebird that was cloned into a trans am, it has a 1969 Pontiac 350, headers edelbrock intake (not sure what kind) edelbrock 600 carb, and who know how many miles, it has quite a bit of valve chatter (already set rockers to factory spec) and alot of blow by. it does ok but he wants more power, my question is what route to take, rebuild the 350 and stroke it out, find a 400 or a 455 and build that, or go with a chevrolet engine, being that i have a couple laying around along with a TH350, he isent looking for a 500hp engine but a nice street engine, say around 350-400 flywheel hp and matching tq way down low. just need some input from you guys. thanks

 

[melsg5]

What do you mean you set rockers to factory spec. ? Pontiac rockers are not adjustable, you torque the nut to 20 ft/lbs of torque, is that what you did? You are sure it is a Pontiac 350 and not a Chevy 350? What is the rear end ratio? If it's in the real low 3's ,3:08 or less in the 2's you should correct that first. After that it depends on your cousins budget. Raising the compression and improving air flow by installing a set of Edelbrock heads and a performance cam would be two things to do. How did you determine the engine has blow by as opposed to needs new seals on the valve guides? Did you do a wet and dry compression test?

 

[poncho88]

i torqued the rocker arms, some chatters others keep the valves hung open (IE they are too tight), i know its a pontiac 350, ran casting numbers and im a huge chevrolet guy, its hard to confuse them. it has 2.73's but he wants to keep them. i did a compression test and all cyl's are between 135-130psi, and after driving it hard, we come back and the dip stick is pushed up, and smoke is coming out of the crank case breather and the dip stick tube. i think the engine is worn out. he really wants to keep it all pontiac but is it economical to do so?

 

[melsg5]

you have a low compression engine so what numbers did you expect, higher then 135 to 130? Was there more than a 10% variation between cylinders and if you squirt oil in the cylinder did you get a change in readings? Is the PCV system hooked up? There is no reason to expect a Pontiac to be more expensive than a Chevy so back to what your budget is. I would suspect the clatter can be signs of a cam/lifters on there way out. Did you notice if there were grooves worn in the sides of the rocker arm studs? You are not going to get much performance out of that car with a 2.73 no performance cam will work with that kind of gearing. He cannt have it both ways more performance and an economy ratio. You could go with a larger engine and just get the power from the cubes.

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[poncho88]

i dident know what numbers to expect, i just go by the 10% rule as well, and yes the PCV system is hooked up, one from the lifter valley pan to the intake and another from the PCV hook up on the front of the carb going to the valve cover. i still cannot explain the reason it would be blowing the dipstick and smoking after you shut it off unless it was blow by.

 

[melsg5]

Not sure what you mean by two PCV systems. A Pontiac should have the PCV in the valley pan with a hose going to the intake. Tpyically there is a tube in the passenger side cover with a connection to the air cleaner to allow fresh air to come in to the crankcase and then the PCV valve in the valley controls the air flow back into the intake.

 

[Too Fast]

My vote is stay with the Pontiac. Get a 400 and build it, or the 455 for massive torque off idle. You already have the exhaust/intake for the Pontiac motor.


And, lose the 2.73s! If you don't have this as the dailey driver, put some 3.55s in and watch the car wake up.