My engine build list so far

[Dean80Z28]

For anyone following my progress, I've started looking through a lot of options to build up a motor and gotten a LOT of advice from different sources. Unfortunately I couldn't use it all, but I've decided that I'll probably go with Upgraded Vortec heads (bigger springs, roller kit etc from Scoggin Dickey), Edelbrock Performer RPM Air Gap Vortec intake, XE274 (Comp Cams Xtreme Energy) Cam, Forged rods and pistons, not JE/Eagle quality but something a little bit cheaper like SCAT ICR rods and some TRW forged aluminum pistons.. 650cfm carb, and a moderate shot of nitrous for the track and rare street ocassions. Purge kit is a must for showing off. LOL

Now a couple of questions. For a 350, should I be looking at 5.700" or 6.000" Rod length? And for pistons, 3.750" or 3.480".

Also I'm new to the v8 world and there are some things I don't understand yet, like Pressed or Floated style Pins, Flat or Dish pistons, Overbore, 4 valve relief, 2 valve relief... Is there any site that has explanations for this kind of stuff? I'm trying to learn as much as possible in the process of building this motor! Thanks guys.

-Dean

[Injuneer]

Some basics....

Your "350" started its life with a 3.48" stroke, a 4.000" bore, and 5.7" rods. If you "rebuild" it, it is likely you will need to bore the cylinders to clean them up, get them back to round, etc. You can "overbore" by anything up to 0.060", but the most popular bore is 0.030" over, for a 4.030" bore. Your "350" is now a "355" cubic engine. If you are happy with this displacement, you buy a 3.48" forged crank, or you have your stock 3.48" crank cleaned up, honed, radiused, etc.

Then you pick your rod length. With a 3.48" bore, you have a choice of 5.70", 5.85" or 6.00" rod length. Although there is a lot of theory on the "optimum" rod length, and rod/stroke ratio, it has very little to do with the "daily driver". In theory, the 6.00" rod will produce the best results, but it isn't critical. Point is, you need to select your rod length before you select the piston.

For the piston, you need to determine the ultimate purpose of the engine to select the compression ratio. With iron heads (Vortec) you are looking at compression ratios about "1" less than you would be with aluminum heads. You are probably not going to go over 10.0:1 with pump gas on a normally aspirated or nitrous motor. With a S/C you would be looking at something under 9.0:1. Once you determine the required compression ratio, you have to look at all the factors that get you that compression ratio, and that would include the volume of the combustion chamber in the head, the thickness and bore diameter of the gasket, how "deep" the piston sits below the top of the block (deck height) and the volume displaced by a dome on the piston, or added by a "dish" in the piston and any valve reliefs.

So.... rod length determines where the wrist pin goes in the piston, the compression ratio calculation dictates the shape of the top of the piston, and the "overbore" determines the required diameter of the piston. When you ask "for pistons, 3.750" or 3.480" " it appears you are looking at a spec table that reflects the "stroke" of the crankshaft. 3.48" + rod length determines which piston you want for a 350/355. The 3.75" + rod length piston would be applicable to an engine running a "stroker" crank to increase displacement to the 381-385ci range, and you haven't indicated an interest in that.

Doesn't come close to answering all your questions, but perhaps will get you pointed in the right direction. One answer might be a "short block".... an engine combination where a builder provides everything you need in the way of the block, crank, rods, pistons, bearing caps, etc. Then you put the heads, valve train, intake, exhaust, etc. on it.

You will also need to consider the issue of "internal" balance vs. "external" balance.

A lot of the answers will be dictated by the size of your budget.