1985IrocZ

Hey everybody...
I am puzzled here. I have an 1985 Z-28 with an LG4 305 carbed. When I bought the car from the previous owner, he told me some of the bolt-ons that he put. And as far as the heads are concerned, I took his word for it, but he told me that they were Vortec heads. I noticed that they are cast iron, and after changing header gaskets this week end, I've also noticed that they have round ports. But the big question is the following.....where is the identification number?????????
I've always thought that they were located on the driver side, at the rear of the head.....but no. I've looked absolutely everywhere and nothing. So how do I figure out what heads I really have???????

Thanks for the help!!!!!
Jon

Stephen

iTrader: (12)

Vortec heads have a totally different intake pattern, so they'd need a different (than 3rd gen stock) intake.

Either he lied (most likely) or it has a truck/aftermarket Vortec intake too. Does the intake look factory or aftermarket?

1985IrocZ

he said that he changed the intake for one that's called a Cyclone. Never heard of it...have you??? So how woud I identify what I got on there, wether it's a Vortec or something else???

Stephen

iTrader: (12)

Closest I'd know of is the V6 Syclone S15.

As for casting #s.....I've always seen them under the valve covers, near the springs. As for what #s you'd need to be looking for, I dunno.

1985IrocZ

oh really??????? under the valve covers???? I will check tomorrow, I was thinking of changing them anyways. Thanks for the help!!!!

mcbchild

iTrader: (1)

On a 305 engine, the last three numbers are usually the important numbers you need to know. Also, I thnk vortec heads are only for the 350 engines. Putting vortec heads on a 305 will lose alot of compression since 305 heads are around 58 cc and 350 heads range from 64 to 76 cc.

Sonix

iTrader: (1)

There are 305 vortec heads, but are not as popular.
Vortec 350 heads are 62cc. They will drop the compression marginally, but the superior flow makes up for any loss of compression.

Yes, casting number is under the valve covers. 8 digits or so, ending in 416 is your factory head. Ending in 062 or 096 are Vortec heads. (did I get that right?)

187, 193, 993, 882 are all junk garbage that would have me running over to the bastards house with a baseball bat...

the zander

As far as i know, Cyclone is what professional products calls their entry level manifolds.

http://www.professional-products.com...tmanifold.html

-Z

five7kid

iTrader: (14)

Dollars to donuts they are swirlport heads. Since they have centerbolt valve covers, people think that means "Vortec" since Vortec heads have centerbolt valve covers.

Professional Products does make a Vortec Cyclone manifold.

Standard SBC and Vortec intakes are easy to tell apart. If there are only 4 bolts on each side and they are straight up & down, that's Vortec. If there are 6 bolts one each side that are (mostly) at the angle of the mount flange, that's standard SBC.

1985IrocZ

WOW!!!!
Thanks Sonix for all of those part numbers......when I will remove the valve covers, I will be able to use them to identify my heads...thanks again!!!
Thanks Five 7Kid, I appreciate the info. But when you were talking about the differences between Vortec and SBC heads, the bolts you were reffering to, are they the bolts bolying the hedders down, or the ones from the valve covers>?????? Because, my valvecover bolts are centered, on top of the valve covers themselves.


Jon

1985IrocZ

OK everybody, here's an update. I removed the valve covers. The number engraved on my heads is the following: 12558062. So according to Sonix, they are actually Vortecs. So my next question is how do I know if they are Vortecs for a 305, or Vortecs for a 350???????

Thanks again!!!

BloodyBlueBird

iTrader: (1)

What five7kid was referring to was the number of bolts your intake has. if it has 8 bolts you probably have a vortec setup. If it has 12 their only standard sbc heads. lets hope there vortec huh!

Sonix

iTrader: (1)

062 are 350 vortec heads.

1985IrocZ

So Sonix, if you are certain that they are Vortecs for a 350 (which I'm sure you are), well, my engine is definitely a 305.....so is that much of a problem???? Is it still better to have a 305 with Vortecs for a 350, than to have stock SBC heads on a 305????

jagass

Take it to a dealer...I'm sure they know...lol

1985IrocZ

Thanks BloodyBlueBird for that clarification, well....I've checked. They have an 8 bolt pattern which should confirm that they are Vortecs.

Sonix

iTrader: (1)

Yes, a 305 with 350 vortec heads will be fine. You'll lose a bit of compression, but it won't be a show stopper.
Do the math on the CR, but i'm sure you'll be able to run 87 octane, and you'll gain HP over what you had before. It'll be great.
Keep the cam mild to build up cylinder pressure.

Damon

If your 305 underneath those Vortec heads is the original 1985 engine it will have flattop pistons in it and a factory compression ratio of 9.5:1. 84 and earlier LG4 engines got dished pistons and a lower 8.5:1 compression ratio.

The larger Vortec chambers would drop your compression by about half a point from 9.5 to 9.0:1. Like was said above- their better flow should more than make up for the modest drop in compression, power wise.

Stephen

iTrader: (12)

Don't forget though.....
The 350 headers will have a bigger (larger diameter) combustion chamber, so there may be "ledge" of the cylinders creating hot spots (the edges) & bad air mixture flow.

Bowtiebruiser

So then out of curiosity what wouldn happen if you have a mildly buil 350 with 305 headers?

Stephen

iTrader: (12)

Stick a straw in your mouth, go run a mile at full speed, while trying to breathe through it. Pretty much the same thing will happen to your engine.....

Sonix

iTrader: (1)

305 headers? what the hell are 305 headers?
There are small block headers, and big block headers. Lots of different headers, but they are specific to the engine.

Stephen

iTrader: (12)

I assumed he meant small tube headers, sized for a 305.

Sonix

iTrader: (1)

ok, I re-read, he got it from you Stephen!

He meant to say 350 HEADS.
That ledge is theoretical, it doesn't really exist. 305 and 350 and 400cid heads all have very similar chambers. 58cc, 64cc and 76cc heads can be used on any bore SBC.

Stephen

iTrader: (12)

TYPO!!

But I was referring to the top edges of the block cylinders, not the edges of the combustion chambers of the heads.

1985IrocZ

so were getting side tracked here. To sum up, my Vortec heads casting number 12558062.......keep or no keep?

Sonix

iTrader: (1)

As I said before;

Keep!

Damon

Keep.

You're not the first person on this board (and elsewhere) to use 350 Vortecs successfully on top of a 305 block.