[eatonde]

Hey guys I know the L31 350 vortecs are the most desirable ones like the 062 and 906 castings, But I was just wundering what the majoe difference is between those and the ones one the vortec 5000 305's.
I know the 305's have 58cc chambers... But what else is there?? One of the guys that I buy my core engines from for rebuild has several of the vortec 5000's... He wants 200 for the 350's and 150 for the 305's.
I don't have much use for the blocks, but he says 150 for the whole motor or 75 each for the heads, which is $150 anyway. So I might as well get the whole thing.
Do the vortec 305's have the forged powdered metal rods like the 350??

I have also heard that the vortec's cranks are steel rather then nodular???? Is this true.

My main concern is the heads, I'd like to know the runner sizes and chamber/valve sizes. Does anyone have this info?? My logic is that if the runners and valves are the same, and the only difference is the 58cc chamber then they should perform just as good providing you use the right dish pistons.

[curtis73]

I'm 90% sure that the 305 vortecs have the typical, tiny valves. They flow a lot less, but not sure if its because the ports are different, or if its just the valves.

For the extra 50 bucks it is SO worth it to get the 350 heads. To get 305 heads modified for larger valves and get them to flow like the 350s, you'll spend thousands. Plus, the small 305 chambers means you'll have to run dished pistons which will ruin efficiency and quench.

Edit: Nevermind... I just noticed you're looking at a 5.0 engine... I was replying as if it were a 350.

[GMC boogie]

The 305 vortec heads do not have the same (desirable) style combustion chambers as the 350 versions.

Get the 350.

[eatonde]

I agree completely theat the 350's are the better ones by far... The trouble is that he's outta them right now but he has 4 96-99 vortec 5000's (cores), and also 2 LS1's I just got another 400 SBC today, with the deepest dish top in the pistons I've ever seen... I was told the motor had 47000 miles on it and dropped a valve in the # 1 hole. You can see the piston is all dinged up and a piece of the ring lad in broke off. I was just thinkin of builtin a mild torque motor outta this one to pu in my dually.... just basic cam prolly 254 or 268, or mabey one of the extreme 4x4 lines. I'd like to re-used the stock pistons and sdt bore cuz the cyl walls are in great shape, just put a set of rings and bearings in it with that cam...
This is where the trouble comes in The new 400 i got was a short block(no heads, balance or flexplate). So I need heads, and even thought the one a asked about are 305 heads, thier still "VORTECS", Whick will definitely make more power then some old smoggers I got laying around..
When it comes to the heads, I thing theyr'e listed on mortec as 58cc chamber with 194/150 valves, but it doesn't say runner size... Anybody know??? ALSO I was brousing through ebay the other day and a guy had a set of an Astrovan 305 for sale, 059 casting.... What baffled me was that they had the traditional chamber style.... The plug boss was out to the middle as it should be, but the chamber wasn't "heart/kidney shaped"... you guys know any thing of this?? I thought all vortecs had the heart shaped chamber???

One last thing... I'd say the pistons in this motor are atleast 30cc dish, what kinda CR would that give me on a 400 with 58cc chamber heads???

[SSedan64]

Here's a good CR chart for the factory style 400 piston.
http://www.northernautoparts.com/Pro...tModelId=15104

[Hogg]

L30
230hp
285 lb/ft torque

L31
255hp
330 lb/ft torque

The L30 still uses a raised runner port, and I have been told that they are THE Stock 305 head to have.
The L31's do flow more.


peace
Hog

[406 ss monte]

have you ever been in a truck with the L30 305? i must say their pretty damn stout for what they are. on a 305 those heads do fine, they have 1.84-1.5 valves & 58cc chambers. i don't know what they would do on a 400.

[D. Newland]

Related thread with photos.

305 vortec heads

[oldbogie]

Originally Posted by eatonde

Hey guys I know the L31 350 vortecs are the most desirable ones like the 062 and 906 castings, But I was just wundering what the majoe difference is between those and the ones one the vortec 5000 305's.
I know the 305's have 58cc chambers... But what else is there?? One of the guys that I buy my core engines from for rebuild has several of the vortec 5000's... He wants 200 for the 350's and 150 for the 305's.
I don't have much use for the blocks, but he says 150 for the whole motor or 75 each for the heads, which is $150 anyway. So I might as well get the whole thing.
Do the vortec 305's have the forged powdered metal rods like the 350??

I have also heard that the vortec's cranks are steel rather then nodular???? Is this true.

My main concern is the heads, I'd like to know the runner sizes and chamber/valve sizes. Does anyone have this info?? My logic is that if the runners and valves are the same, and the only difference is the 58cc chamber then they should perform just as good providing you use the right dish pistons.

The 305 does not use the L31 Vortec head. While it's called "Vortec" it is in fact the same old 305 head. Reason being that the smaller bore and overall displacement of the 305 does not show a significant gain with a 350 Vortec head. Simply put the relocated sparkplug and reconfigured chamber doesn't change the swirl pattern nor burn time sufficiently on the smaller bore sized engine. It is hard to build a 305 head that will supply sufficient flow for a 350 or larger engine, it's done but it's always problematic. The ports of 305 heads are smaller as are the valves. They require careful porting and larger valves to support bigger engines, often the pursuit of a sufficiently larger port results in the discovery of water. The intake runner size of 305 heads is about 135 to 150 ccs, 350's run from 150 to 170. Valve sizes for the 305 are typically 1.84/1,5 for 350s typically run 1.94 to 2.02 for intakes, and 1.55 to 1.6 exhausts. Chamber sizes for 305s run from 53 to 60 ccs, 350s run from 55 to 76 ccs. The Vortec hangs at around 64ccs. Compression is also controlled by a dish in the piston, so you also have to know what piston is being used to compute compression. Be aware that many rebuilder pistons are short by .020 to .030 inch between the pin hole and crown compared to OEM pistons. This is done to lower the piston in blocks that have beed decked.

Bogie

All "modern" small blocks use powdered metal rods and cast hypereutectic pistons. I'm not aware of any factory forged cranks being used with one piece seals, that includes the LT1 and LT4.

Vortec blocks from mid 95 to end of production have at least the provisions for a roller cam. This makes them attractive from the stand point that they are a lot less expensive to build as a roller engine even if they originally had a flat tappet cam than are blocks never made for a roller cam. This makes them attractive to engine builders.

Bogie

[red65mustang]

"Vortec" is just a trademarked "marketing" name for a GM motor....
that last/latest inline SUV 4.2L six is a "Vortec" motor....
the very early inline six was named a "Blue Flame" motor in the 54' vette to make it sound more sexy since a V8 wasn't offered....
LOL,
Ford "Cobrajet" motor, I'm thinking a snake with a flame shooting out of his butt hole?????

only the spec's of a particular head model # can tell you the good/bad/ugly