first, I need to make it clear this engine is not my final engine build. It is just a bandaid for between 1-4 years to keep me happy. It probably/definitely will not see more than 10,000-15,000 miles. Probably more likely in the 5,000 mi range. I just want something to keep me happy until my 383 is built.


I currently have both a 16,000 mi 98' 4 bolt 350 Vortec block (out of a van), and a 166,000 mi 88' L98 out of a GTA. Regardless of which block I use (leaning towards the 4-bolt because i want to splay the L98 for the 383), I was looking to raise the compression slightly along with a few other cheap things to make it alittle warmer on the cheap (cam I have laying around, some home work on the heads, Intake that I plan on using again later etc).

So, assuming the engine is in balance to start with (they both are), would changing just the pistons to something just alittle warmer mess up the balance enough to warrent a rebalance? I was just looking for like 10:1 ish, which cant be achieved with what I have right now (the L98 needs bored, and the vortec's compression comes from the heads, which i am not using).

any tips? I was just going to throw cheap cast or hyper pistons in place of the used ones. Something from summit.

note: I have deep discounts on GM and GMPP due to my dad. If it would be price effective, I would be more than happy to stick to GM parts.

Thanks
~LMSkyliner

 

technically, you are disturbing the balance of your engine. the counterweights are designed to offset the weight of the components attached to them (the their respective journals) such as rods, pistons, wrist pins, rings, bearings, and a thin film of oil. here is an article that has some info (yes i know its about small block fords, but it works)

http://www.carcraft.com/howto/ccrp_0...ing/index.html

 

dollar for dollar, I wouldn't upgrade the pistons as a performance addon.

Look elsewhere, especially for a short term build.

and yes, it would need re-balancing.

Look at parts that you can re-use on your future 383 - eg exhaust... suspension, etc etc. Don't put internal engine parts into an engine you may not keep for that long.

 

yea I had already considered that. It's just that currently the best i could get out of either of these engines is probably in the 9:1 area if i had a guess. Not good for power, but i guess it will have to do.


The other upgrades i planned on doing were essentially free. using parts I had around (cam, rockers, lifters, springs), some home jobs (porting), and then, like you said, stuff I was going to use on any engine, like the FIRST system, and full exhaust (Don's headers/Y-pipe hooked up to Magnaflow cat-back). Along with CAI and stuff like that. The cost to rebuild would be the biggest actually cost going into this engine.

I was hoping that if i could buy appropriately matched pistons cheap, it would be a good way to raise the compression for a few hundred and still not need balancing.. Doesn't seem to be that way.

 

Only if you can get a set that weigh the same as the old ones.

 

If pistons weigh same, no need to balance.

 

Pistons would probably net the least real gains of anything else you could change. That being said, you dont really need to rebalance it. Most of the engines that we have rebuilt with a "kit" (read northern auto parts 159 dollar wonder) we would weight match the pistons.

It stands to mention though, just as in the last thread on balancing a week or so ago, that countless people over the years have pulled apart near stock engines, bored and honed and stuck on the rebuilder pistons and a mild cam. They virtually never have problems. THough it will happen eventually.

Get a good digital scale and some patience. Weight match the pistons. Or spend the money in a better place.

 

Personally I wouldn't even waste my cash on balancing such a motor... Money could be better spent elsewhere.

 

I suppose i was simply over-estimating the power loss from that extra compression point. Plus, the L98, despite its 166k miles, is still in very good condition. There is barely even a miniscule ridge in the cylinder wall.


I guess I'll wait till the big boy to break into bottom ends. That one will be done right. Fully forged, with all block prep, machining, and assembly done by a shop that spits out consistent 9 second NA cars.


The more you know! Thanks for helping guys. I'm still learning all this stuff as i go (barely 18).

 

What I meant before was that I wouldn't spend the money on pistons to make you go faster. Dollar for dollar, it's better spent elsewhere.

on a (what I consider seperate matter) - you don't need to balance. As a (bad) example, I rebuilt my engine by turning the crank, new rods, new hyper pistons, and I never balanced it. See the cam in my sig? Not exactly mild.... I didn't even weigh the pistons or anything... I like to take chances