this was originally a aluminum head motor with 58cc chambers, what will my compression ratio be after putting on 64cc 89 350 f-body heads on the motor. I am also pondering with the idea of rebuilding it without having it bored, what would be a good piston that would make 9.0 - 9.5 to 1 compression using these 64cc heads.

Also what kind of pistons did this motor come with originally cast, forged, hyper ? This motor is being built as a daily driver motor so not looking for 500hp out of it. Just around the stock 245hp, I am also adding slp runners, edelbrock lower, stock throttle body, I am undecided between stock tpi exhaust and edelbrock TES.

So tell me whats a good combination for this engine for pistons, rings, etc.

 

Why are you changing the heads? Or, did you only get the shortblock?

The pistons were the same between iron and aluminum headed engines. With the aluminum heads, the chambers were made smaller to increase the compression to make up for the increased heat loss and therefore power loss through the aluminum material.

You should get 9.3:1 compression with the stock pistons. If you aren't going to bore the cylinders, reuse the pistons (cast, by the way). If you get flat-top pistons with 4 valve reliefs, you'll get about 9.5:1 compression.

 

The heads are being changed due to EGR related reasons.

So I would just need stock bore say TRW flat top pistons then or just use the original pistons that are in the engine. The reason I'm considering rebuilding this motor in in the past it always fouled the number 6 plug out with oil, however compression was never a issue so I don't know if it's ring related or if it had a valve seal/guide problem, and it's number 1 intake valve lifter has issues so I'de just as soon freshen the whole motor up before it goes into my trans am

 

If the engine has some miles on it you're probably going to want to overbore it anyway. Ring seal problems and worn out cylinder bores go hand in hand quite often. And getting fresh rings to seal up on a worn out bore has a good chance of being worse than in you had just left it alone to begin with (barring any mechanical damage to the current pistons/rings, of course).

Tear it down, see if you're got a ridge in the bore right where the top ring stops at TDC. If so, it's definitely time to bore it out. In which case you'll be taking it out to 30-over and buying 30-over pistons to match. Then, of course, a set of flattops would be the cheap and obvious choice.

 

I'll catch some heat for this one but what the heck. I'm a big proponent of not boring a block with negligable wear. Measuring the wear is the first step. You can do it with a disposable feeler gauge and a piston. Most people have a bad experience with a re-ring or ring&piston change because they fail to scuff the bore. You don't need a cylinder hone to do it either. Just your hand and some 400 grit paper. You remove the mirror finish on the cylinders with a diagonal motion. Not up and down or round&round but both. I have done several engines with no blowby or oil consumption.
Everyone will chime in about now that boring an engine is cheap. And it is a bargain, but the bottom end must now be rebalanced because the larger pistons are heavier. This isn't cheap and opens the opportunity for error. Once the engine is together follow the break-in procedure. This frequently doessn't happen as the engine usually spends it's first critical hours idling while people sort out fuel and timing problems.

The first thing you must do either way you go is to diagnose the #6 oil consumption. If you don't have the original heads this could be a problem. While I'm on the soapbox, everyone checks piston ring gap, very few follow the instructions for ring placement. This is what "o'clock" the ring gap is placed on the pistons. Each ring gap goes towards a specific different direction, (ie: top ring, 4 o'clock) on the piston and the right bank and left are set up different. This REALLY does make a difference and is usually the reason that someone has new "everything" and tons of blowby. He never notices the ring gaps all in a straight line on one side of the piston. Oh yeah, blowby is created on the compression stroke, not the power stroke like most people think.
(exiting soapbox and donning asbestos underware)

 

Please explain how one does this...and why the original heads would need to be involved. I reckon you must be talking about "before a rebuild"...but still, please explain.
Thanks.

 

Sure thing. I was talking about rebuilding the engine without reboring it. If the intake or exhaust valve guide was the source of the oil consumption this would only be found by checking the heads. If the piston and rings look fine in #6 the problem could be in the heads or the cylinder bore and the block would need to be bored. You'd need the heads to be sure.

 

Makes sense. One thing I forgot to ask, is why the #6 cylinder? I don't recall ever reading or hearing to specifically look at the #6 first or anything of the sort.

 

For function or visual inspection?

EGR can be fed externally from the exhaust manifold to the intake manifold. That's how the Vette system worked. If that won't cut it for a visual inspection, that's one thing (but you could just have it inspected as a Vette system). Seems like an insignificant reason to make a significant change.

 

smithtc: This was his second post in the thread. This should answer your question. #6 was in reference to his particular engine.

 

well I've pulled the 350 apart and cant see anything out of the normal with the rings or pistons so I believe my problem is in the topend of the motor. I should have said this earlier but this 350 didn't have aluminum heads on it they were sold sometime ago. The heads that are on it are 157,000 mile LO-3 heads but lets not get into why they are on there or start a LO-3 uggggghhh thing.

I am going to top the motor off with a 305 TBI for a little while till it gets through emmisions and pondered with settling the TBI verses TPI debate and dyno the motor with both setups.

I've chosen to run a stock 90 vette L-98 cam in it, 30 over flat top forged pistons and might drop a steel crank if I can find one thats not too expensive. I don't know much about connecting rods so I have to do a little more research on this. I'de like to build the motor to have a very strong bottom end for future turbo/supercharger but for now if it puts out around 250 horsepower I'm sure I will be very happy with it considering my stock LG-4 can't even make 150 LOL.

My goal with this car is to have a very streetable car that can at will be daily driven. The body and interior are near show condition so I hope this power transplant won't kill the cars value but if it does oh well. It will be much funner to drive and be more reliable than the feedback quadra-jet ever was.

I will try and post sme pictures of the car here soon but can't figure out how to change the size yet.

 

The TPI would most likely make more torque below 4500 RPMs, the TBI might win out with HP above that. That assumes the right things are done with each system.

Building the bottom end stout is a good idea, regardless. However, blaming the LG4 for low HP has nothing to do with the induction system. It has everything to do with a lame cam and soda straw air cleaner and exhaust.

Delusion is a powerful drug. I'm putting down more than 250 rear wheel HP with an LG4 induction/control system in a daily driver car (including Colorado winters). Neither TBI nor TPI would have a prayer of touching that without significant, expensive upgrades, and the additional economy that could be assumed would take years of daily driving to pay back.