will 1997 Chevy Silverado 350 Vortec Heads with casting #906.fit on my lo3? i know id need the intake as well. tnx
Doug

 

You can put 350 heads on a 305? I thought that the area where the valve seals are different sizes due to diff bore sizes, no? Did I just make myself look realy dumb?

 

im not sure, i know there is a bore size difference on the block but unsure of the heads :/ Im guessing they wont but i want a guru's opinion

 

That would be great. Id imagine 350 heads would flow more than our 305s would ever need. Now some other threads, I think, make some since...

 

bump

 

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From what ive read it will lower compression to much :/ so ive been searching for 305 heads, not easy to find for cheap :/ Vortec would be nice

 

Dont most head swaps require them to be milled down anyway? Maybe they can be milled to 58cc?

Quoting robertfrank;

There are many different cylinder heads that can be used in your TBI controlled vehicle. Here are the most popular choices.

Ported stock "187" heads
ZZ4 or "113" heads
"059" or 305 vortec heads
Standard "062" or "906" vortec heads
Ported "081" TPI heads
Trickflow 53cc aluminum heads
World Products S/R Torquers

It all depends on how much money you have to spend. With the 059 or 305 vortecs you still have a 58cc combustion chamber, no real milling involved. But you need an intake to match because your stock one WILL NOT bolt-up.
With the 062 or 906 heads they will need to be milled down a bit to get the proper combustion chamber size or you'll lose compression and like the 059 heads a new intake will be needed.

The ZZ4 heads will need to be milled down even though they are 58cc due to the aluminum dissipating heat faster and thus a loss in power will result IIRC. Also with the ZZ4 heads your intake will need the two middle bolt holes elongated due to the angle being off between the 87-88 model years.

The Trickflows seem to be a good choice for a head but at a price of almost 1200 dollars it's not really a "budget" head. The S/R torquers from what I understand aren't that great of a head and they also weigh a ton due to the extra meat left for porting.

So this leaves our stock heads. In recent years the stock 187 or Swirl port head have been shown to have great gains when ported. If you don't want an engine that breathes hard above maybe 5200 rpms and you want more torque through out the powerband stick with a set of ported 187's. Stock TPI heads don't flow that well in stock form but ported they flow pretty well.

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So 059 is an option. I know its not what you asked but thought it may help...

 

I would like the 081 TPI heads and get those worked on, im sure they would put down more power, besides id lke a little bit more rpms.

would the TPI heads be better then my current setup with lets say port/valve job, guides, push rods, springs, rockers or rollers dont remember which one?

 

The 350 heads will definitly kill the compression. Since the 305 has less cylinder volume it needs a smaller combustion chamber in the heads. I had a Monza once that had a 262 V8. I modded it some but I got my hands on some closed chamber 350 heads (300 horse heads as they were called) and I figured they would make it scream. I bolted them on there and the car was real weak. The 305 would not be as affected like the 262 was but it will still run like poop.

 

if that's the only problem, imho you can still mill the compression chamber down to keep CR up?
e.g. take a set of ZZ4 heads, stock they have a chamber of 58cc. now if you mill them down say ~.031" and you get maybe 53.5 (i'm taking these numbers from some other thread). keep in mind that this is an aluminium head and therefore has to be milled down although 58cc is already small!

google is telling me that the 350 heads you got there have a chamber volume of 64cc. you also want to include piston type into your considerations!

hope some else is going to chime in on this to give you some reliable information!
greetz

edit: this link could be helpful: http://www.hotrodders.com/forum/906-...at-106666.html

 

Dart sells a 49cc iron head. Is that too much compression? maybe not with a cam to bleed off.

 

i think we would need to stay in the 58-64cc

 

You can use those heads but you will lose your compression since they are larger 64cc heads. You can have them milled down so they are around 58cc (smaller may be better) and you will not lose your compression and can get great performance gains. You should also be concerned with the thickness of the head gaskets you use as they can also affect the compression ratio. You will also need the vortec intake and some tuning to go with it. Vortec heads in the stock form have 1.94 / 1.50 valves which are the largest a 305 can use without the valve hitting the cylinder wall due to the small bore size. EGR will need to be plumbed externally if you still need it to pass smog. If not, then you will need to remove the EGR stuff from the computer as well. I have researched this extensively as this is what I plan to do in the future along with an LT1 cam upgrade at the same time. With the right Vortec head and cam you can easily take your 170hp L03 up to around the 300hp range.

 

Also, to add. Ronny I think those 49cc dart heads will not only add too much compression but they have too large of valves to work with the 305's bore. They are really not an option.

In my opinion after surfing this board for several years the best bolt on head options for a 305 are the Vortec, Corvette Aluminum, or the World Products Torquer 305 heads.

 

!hanks for the incite blue . So get those heads milled down, port and polish, 3 angle job, get new valves, springs, rockers, push rods.


What would you need to externally run the EGR valve? i will have emissions to deal with crappy cali laws.