I'm just lookin to go low 13s with new heads, and higher compressoin heads are what I want.

 

Dude, that freakin thing in your sig scared the **** out of me too.

 

like my avitar

 

NOOO!!!! Take that down now!!!!!

I'm serious. The first time I saw that thing, I had just woke up. I strolled in here to check my email, and a friend had sent me one saying "To funny".

I about whizzed all over the computer!!! Now I can't stand to look at that pic. I'm too old to be scared like a little kid, but I am!!!!

Please take it down.

 

They're 492's?? And how much do they want for them? Grab em asap. Are they angle or straight plug? 492's are from the Vette and Camaro LT-1's and I would snap them up asap.

 

Mark :

The 492's are probabily the best of the "camel back" class heads.

As long as they are not cracked, I say go for it.
If they need new valves, go for the 2.02's and 1.60"'s
There is no difference in the price.

Either port them your self or get some one to do it.
Even a simple pocket port job will do, but the more effort you put into them the better they will work.

Yes you can get good flow out of ported 305 heads
but again it depends on the amount of effort your willing to invest.

By a Book by david Vizard called " How to build Chevy Small Blocks on a Budget" It explains what to do to these heads
and the results In a straight forward manor. It also covers the Vortecs and Corvette l98's
the kind of stuff in this book is what makes or breaks a good hp motor. Some you can do your self, some it's better to pay someone else to do.

Again as long as they are not cracked, go for it.
You can have them checked for cracks by "Magnafluxing" them.

Ask your machinist.......

 

how much would 305 heads raise the compression?? say i did the same hting sittingbull did, but to my LG4 416 heads, then bolted them onto my 8.5 compression 350?

 

I'm pretty sure the 305 heads have smaller combustion chambers. The 305 also has 3.736" bores, while a 350 has 4" bores.

 

Well, they already have all the hardware with em including 2.02/1.6s. But, now his dad is saying he may not part with them or that he might keep the hardware, I already have matching valve springs.

So, considering their in working order, how much should I offer for the heads? With hardware and without.

 

If by harware he means the valves springs locks retainers
screw in studs and guide plates, tell him to include them in the deal or no deal. These are not the only set of heads in town.
Like I said you'll have to weight out the total cost of the project.
If you have to buy all this hard ware in addition and have some work done, You may as well buy some vortecs and the manifold
and do the mods to them. It will be about the same $'s
and the vortecs will probabily work better for you.

There are lots of good heads floating around for sale.

 

OK, so what would be a fair price if they're in good condition, I have no clue. Remember they've been decked to 62cc already, I forget if they were ported or not.

 

If the motor is infact 8.5 with the 76 cc heads
the new cr would be 10.25:1 with 58cc heads.

Most motors like Marks Good wrench motor are not even close to 8.5:1 actual cr because the pistons are way down the bore at TDC.

Usually these motors are 7.8/8.2:1 as delivered.

thats why 58cc's heads do not result in exessive cr
when you swap them on. Your actual cr will be between 9.24
and 9.65 depending on your actual measured deck clearance.

By the time you've swept out the chamber for some bigger 1.94x 1.6 valves your chamber will be closer to 60cc's
finished. A little deck milling can bring the final cc's to what ever you want.
You can down load a good working compression ratio calc
for windows from performance trends

www.performancetrends.com

You can find typical piston specs ( dish vol's) etc from
http://www.kb-silvolite.com/

Lots of info here....

 

yikes, that is horrible. for a non blower car.

 

I would pay $500 to $700 (canadian) for a set of 492's
that are ready to go but unported. And not cracked!
thats $300 to $500US.

really depends on the condition, Why does he want to keep the "hardware" ? Is he trying to dump the heads?
Questions you need to ask.

I have a set of fully ported 305 heads with new 1.94x 1.50
valves 3 angle valve job hi perf springs pinned studs etc
Painted bagged ready to go for $600 canadian.
They are for sale......
thats what??..... $375+/- US money.

There are lots of good deals out there.

 

thanks for the help, guess I'll see if he'll take $300 if my other deals fall thru.

 

305 heads have 58 cc combustion chambers, so if you were going from the typical 76 cc 350 chambers you would definitely raise the ratio over 9:1 on a 350. You would be in the really good street performance range.

 

Hee Hee Heee!!! wait till you pull those heads off.
And measure the deck cleareance on your motor.....


You'll see what I mean......

 

Gm is horrible when it comes to thier standard crate engines. If you do yank the heads the dish portion of the piston is much deeper then a standard GM production line engine. The compression ratio is still in the 8:X range but it is lower then production engines.

Mark, I was doing mid 13's with the old camaro uncorrected, 355/TH400, 270H cam, double springs 58cc heads 1.94 intakes, 3.42's and dual 2.5 exh.

 

What kind of springs are you gonna run Mark? you'll have a fun time tryin to open the spring pockets for larger springs on these heads because of revised and enlarged water core on these heads. Running a 1.25" spring poses no problem though.

 

would running nitrous on these heads be ok? also, what is the typical hp/tq increases from compression alone. is 1.0 good for 10, 20, 30, 40hp?

 

You can run Nitrous with any head, and any compression ratio.

there are 3 rules
1. supply enough extra fuel to burn with the nitrous. And
help in cooling the chamber and fuel charge.

2. use a fuel with a octane high enough to prevent detonation
due to the increased cylinder pressures and temp while under nos boost.

3. Only give it just enough spark advance to match the increased burn rate of the Nitrous/fuel mix. (retard the spark)

Heads that have good exhaust flow relative to intake flow,
work especially well on Nitrous.

each 1 ratio increase is worth about 2/4 % more torque and hp.

this is not linear but a general statement.

going from 7:1 to 8:1 is worth more gain than going from 12:1 to 13:1

 

Well, if I need springs for my heads, I have the matching comp ones for my 268xe.