Need some help building my engine.....

jwilson645 · Jan 15, 2015

I can fix a lot of stuff but all the calculations needed to get the right combination in my engine build is making my head explode. This is my first go at this alone. I am building an old school 350 for my 77 Silverado and here is what I have so far.

4 bolt 350 block
bored .040
crank journals are at .010 under
Standard deck height

I will be using Vortec heads and a 4L60E behind the engine. The truck is a 77 Silverado long bed. Not sure of the rear gear ratio off hand.

Goals:
9.0-9.5 CR
Run on easily available pump gas
Drive/Haul/Tow
Good low to mid range torque

Some Parts I'm looking at:
Edelbrock 2116 Vortec Intake- http://www.summitracing.com/parts/edl-2116
Lunati VoodDoo Cam: http://www.summitracing.com/parts/lun-10120701lk/overview/make/chevrolet

My main issue is deciding which pistons I need to use to get the right Quench, Squish and Compression Ratio with the Vortecs. I'd like to learn as I go so if you could give me some knowledge on why I should go with your recommendation, that'd be great.

Any help is greatly appreciated.

Elliott · Jan 15, 2015

L2256 forged pistons will get you where you want and they are very affordable, they've been making these for years

jwilson645 · Jan 15, 2015

Elliott said:
L2256 forged pistons will get you where you want and they are very affordable, they've been making these for years

You sure about that? Those only have 6.10cc dish. The vortecs are 65cc vs the stock heads at 76cc. By my calculation, I'd need a .040 compressed head gasket to get the CR down to 9.69:1.

Elliott · Jan 15, 2015

They should only be 9.5 or so with 64cc chambers. Unless youre deck on the block has been cut you will be fine on pump gas.

jwilson645 · Jan 15, 2015

Elliott said:
They should only be 9.5 or so with 64cc chambers. Unless youre deck on the block has been cut you will be fine on pump gas.

That's a $300 set of pistons and Summit doesn't show the L2256 as being available in a .040 oversize. I have flat tops with 4 valve reliefs in it now. By everything I've found, read, heard and calculated, the CR would be upwards of 11:1 by using flat tops.

jayphizzle · Jan 15, 2015

Better recalculate, there is no way you are getting 11.1:1 on a 350 with a stock deck height and a 3.48" stroke. You should be in the 9.8 to 10.2 range. Those engines came stock with around 8.5 or so with 76cc chambered heads. Just my .02

jwilson645 · Jan 15, 2015

Exactly why I'm asking around for explanations on this stuff. Can you take a look at the .doc I uploaded above and tell me what I may have done wrong?

jwilson645 · Jan 15, 2015

Ok, so I re-ran the numbers through the calculator.

Bore= 4.0425 (measured out at .002-.0025 wear by shop)
Stroke= 3.48
HG thickness= .015" (to get the correct quench )
Deck Height= +.022cc
Piston top volume= +6.00cc
Combustion Chamber= 65cc

Static Compression Ratio= 10.2

I would need to use a .040" gasket to get the CR down to 9.5 but that puts my quench at .065", which is waaaay too much.

Elliott · Jan 15, 2015

You have to run domes to get 11:1 in a 350. Flat tops with a 64 cc head a standard head gasket, and a undecked block is going to be around 9.5. It will burn pump gas no problem, And yes the pistons cost 300 but for forged pistons that's a deal.

Elliott · Jan 15, 2015

And why are you using plus numbers on your piston and deck height?

zukimaster · Jan 15, 2015

You don't need forged pistons in this build, and use the the flat tops for sure! Just keep the total advance timing to about 32 degrees and you will be fine.

throttlejunkie · Jan 15, 2015

Shave those heads a smidge, or just run the thinest gasket, upgrade the valve springs, throw some non forged flat tops in it and rock out!

Hucklebuggy · Jan 16, 2015

I would agree that there is no need to spend the extra $$ on forged pistons for this. I would rather spend a little to have the bottom end balanced than on the high dollars pistons. That cam and intake should work well together also. Keep the lobe separation to 112 or above, for low end grunt and driveability. Not sure if your gonna run a carb or tbi. If carbureted, don't go too big. The vortecs breath good, but I would still stay in the 600-650cfm range. 750 would be max only if you already have one sitting there or get a good deal. You will be fine with flat tops I think too. Like mentioned above just don't add a bunch of timing. The vortec combustion chamber burns more efficiently and evenly than the older heads, if I'm remembering correctly, which helps limit detonation.

jwilson645 · Jan 16, 2015

Elliott said:
And why are you using plus numbers on your piston and deck height?

Deck Height- + for below deck/ - for above deck
Piston- + for dish/- for dome

jwilson645 · Jan 16, 2015

I've definitely got more research to do. If I can use the flat tops, that'll save me cash because I can just re-use what I have now.

jayphizzle · Jan 16, 2015

Ive personally used .200" dome pistons in a 377, which is nothing more than a .125 bored 350, with 76cc heads, 0.00 deck and used 93 octane just fine. Definitely keep your ignition timing in the 32-34 degree range total. Use your flat-tops!