Marin

What's the CR for the stock '89-'92 305 LO3? 8.5?

I'd like to mill the heads so CR is in high 9s... I don't think my engine is going to live to see a blower or N2O. While I am at it, I'll probably do some porting to. I'd use 305 HOs as a baseline..

Will the stock bottom end be able to handle it? $$$ for machinework?

New rockers and springs are a must in this case, as is probably a different cam while I am at it...

How much will milling the heads affect the valvetrain geometry? How hard (expensive) is it to change the pushrod length, if that is the case?

I know I have a TBI, but don't worry about that, I am in the process of building a custom computer based on Megasquirt from diy-efi.org...

Marin

Anyone? This is a Tech/General engine board, there has to be someone who did engine buildups who is merciful enough to respond...

Mark305TBI

I think LO3s run 9.3 cr. I wouldn't bother.

Marin

Hm...
OK. Before I quit, what's max VE for a 305?

I am thinking it's dynamic CR might be low enough so pump gas can tolerate higher comp.

Besides, I am really interested in machinework pricing, I want to see how viable is it to get some of those things done...

Like, how much $$$ is milling?
boring&honing?
extrude-hone porting of intakes?

And basically I need detailed specs for 305 LO3 (I am going to try & find them online)..
bore, stroke, connecting rod length, piston type (flat, domed,..)..

Is it cheap to get longer connecting rods? Perhaps I should be trying to decrease ILF to tolerate higher RPMs..

I am just looking for cheapest that can be done on a 305 bottom end to gain some power, whether torque or hp , it's not really cruical right now, as long as torque loss in bottom end is not outrageous, because i'd use it mostly for street. I don't know if I can afford a 350 right now, and at this point I am not even sure a Chevy 350 is the best base for a good street motor (yeah, I know, it's better than a 305, but still..)

Mark305TBI

If it were me, I wouldn't do anything to the 305 bottom end. I've got pretty much the entire top end redone on my 305, but I'm just gonna swap out shortblocks.

The crank in a 305 has a 3.48" stroke.
The bore is ~3.75 odd inches.
Don't know about rod length...
I think that the pistons were slightly dished (it's been a long time since the heads were off, and I can't remember now).

Mark A Shields

From what I hear the L03 swirl port heads are total junk.

AJ_92RS

The rod length is 5.7"

The bore is 3.735
Stroke 3.484"

Pistons are dished to 12cc's. They are cast aluminum.

Here......

Gen.I, "Small Journal"
265...Mains-2.30"-Rods-2.00"
283...Mains-2.30"-Rods-2.00"
302...Mains-2.30"-Rods-2.00"
327...Mains-2.30"-Rods-2.00"

Gen.I, "Medium Journal", includes "Vortec" 305 and 350 thru '98
262...Mains-2.45"-Rods-2.10"
267...Mains-2.45"-Rods-2.10"
302...Mains-2.45"-Rods-2.10"
305...Mains-2.45"-Rods-2.10"
307...Mains-2.45"-Rods-2.10"
327...Mains-2.45"-Rods-2.10"
350...Mains-2.45"-Rods-2.10"

Gen.I, "Large Journal"
400...Mains-2.65"-rods-2.10"

CHEVY SMALLBLOCK V-8 BORE AND STROKE LIST
262 = 3.671" x 3.10" (Gen. I, 5.7" rod)
265 = 3.750" x 3.00" ('55-'57 Gen.I, 5.7" rod)
265 = 3.750" x 3.00" ('94-'96 Gen.II, 4.3 liter V-8 "L99", 5.94" rod)
267 = 3.500" x 3.48" (Gen.I, 5.7" rod)
283 = 3.875" x 3.00" (Gen.I, 5.7" rod)
293 = 3.780" x 3.27" ('99-later, Gen.III, "LR4" 4.8 Liter Vortec, 6.278" rod)
302 = 4.000" x 3.00" (Gen.I, 5.7" rod)
305 = 3.740" x 3.48" (Gen.I, 5.7" rod)
307 = 3.875" x 3.25" (Gen.I, 5.7" rod)
325 = 3.780" x 3.62" ('99-later, Gen.III, "LM7" 5.3 Liter Vortec, 6.098" rod)
327 = 4.000" x 3.25" (Gen.I, 5.7" rod)
346 = 3.900" x 3.62" ('97-later, Gen.III, "LS1", 6.098" rod)
350 = 4.000" x 3.48" (Gen.I, 5.7" rod)
350 = 4.000" x 3.48" ('96-'01, Gen. I, Vortec, 5.7" rod)
350 = 3.900" x 3.66" ('89-'95, "LT5", in "ZR1" Corvette 32-valve DOHC, 5.74" rod)
364 = 4.000" x 3.62" ('99-later, Gen.III, "LQ4" 6.0 Liter Vortec, 6.098" rod)
383 = 4.000" x 3.80" ('00, "HT 383", Gen.I truck crate motor) (5.7" rod)
400 = 4.125" x 3.75" (Gen.I, 5.565" rod)

There's plenty more at WWW.MORTEC.COM

AJ

Mark305TBI

Yes, sir. You are correct, sir.

Marin

Thanks for the link, AJ.. Looks very oldschool. I was trying to figure out the approximate VE of my 305 setup. Here's one link I found:

http://www.ac427.com/html/tech_airflow.htm

I'm thinking 80% with a bone-stock intake manifold I have and a ported throttle body...

Are HO "swirl port?" I know my stock heads are junk, but I think decent gains can be reaped from porting the HOs? As a matter of fact, there was one guy doing it over this summer and he posted all the pics on the board.. Sitting Bull, I believe?

Could I fit 6" rods into my otherwise stock 305 bottom end? Why? So my engine tolerates higher RPMs better...

89gta383

iTrader: (5)

Hand porting will improve the flow of any head. It's always worth it to me to get heads ported, no matter how crappy they start out at.

I had my AFR's milled from 79 cc to 63 cc. You check valvetrain geometry by marking the valve stem tip with a magic marker and looking at the marks left by the rocker arm on the valve.

The problem with using 6" rods in the 305 is trying to find a piston for it. If you can't find any off the shelf pistons, then Ross will make a custom piston for anything you can think of for about $550.