[cobalt327]

Originally Posted by 1968chevy

Would a set a 305 head work on a 350 with flat top piston stock piston the 350 came with I was just wondering and can you run pumped gas the motor has a edelbrock manifold and 600 cfm and would I get more power

You need to know the piston to deck height, the dish volume of the pistons and the combustion chamber volume.

If the pistons are the common dished 350 pistons, they're around 11cc. The piston will reside about 0.025" down the hole if the block is stock, undecked. Now the heads are usually somewhere around 58cc. That leaves the head gasket thickness as the final factor. The thinnest is about 0.015 steel shim. That gasket gives a good 0.040" quench and a CR of 10.4:1. Using a common 0.041" composite gasket gives you a 9.75:1 CR w/a wide quench of 0.066".

To use those heads the right way, they'd need to be ported and the pistons should be reverse dome, D-shaped dished pistons w/a dish volume of about 22cc and a 0.041" quench to give you a 9.2:1 CR- which is the max I personally would try to run w/iron heads and today's gasoline.

[smallblock383]

hey guys dont mean to butt in i have a pair of 14101081 H.O heads off a 1988 monte carlo ss will these work good on my 350 3970010

[F-BIRD'88]

Originally Posted by smallblock383

hey guys dont mean to butt in i have a pair of 14101081 H.O heads off a 1988 monte carlo ss will these work good on my 350 3970010

You jumped onto a old thread with a lot of disinformation.
Here is the scoop on the 081 heads.
In stock as cast form they are pretty lame.
If you just bolt them on stock on your 350 keep you expectations modest.

If you are willing to do generous home port work to wake then up they can work very well.
See my post on porting 305 heads.
The 081 heads have a very shrouded combustion chamber and will
need some extra hand deshrouding work to allow larger 1.94x 1.60 valves and lots of flow.
The chamber will be bigger when you are all done.
Look at the similar 083 casting cousin to this head for inspiration.
Look at the vortec chamber and the chamber on other hi perf SBC heads too.

with generous hand porting and chamber rework and larger 1.94x 1.60 valves you can make this head into a good head for a street motor.
Its up to you to do the dirty work.

They flow about 185cfm and 130ex cfm stock.

easy 230++cfm 180-190ex when done.

The small chamber allows and requires you to get creative with deshrouding and resshaping
and end up with a decent finished result around 62-64cc.
If you just throw them on stock all you will get is the benefit from the compression ratio raise. (more low and midrange torque)

Sort of a diamond in the rough depending on how you see things.
If you are allergic to work, just go buy a aftermarket head.
if you are not willing to do the porting work yourself its not going to be very cost effective.
not worth paying someone else to do the port work.

A 58cc chamber head on a flat top piston 350 does not create excessive compression ratio.
But will need 92 octane gas. cheap 87 octane gas is not going to work.
They will end up around 62-65cc when all done unless you mill them back down.
On a 383 you will want a dished piston (Approx -12cc)
You want to keep the true measured compression ratio under 11:1 for 92+pump gas
on a high perf street motor.
Its up to you to measure and calculate the compression ratio accurately.
You cannot determine the finished compression ratio by asking people on the internet.
I find a finished compression ratio of between 9.8 and 10.5:1 works real well.

Its all about how much effort you are willing to invest. A half baked lazy effort will get you a half baked lazy motor.
This is true when working with any of the stock SBC heads.

[smallblock383]

Originally Posted by f-bird'88

you jumped onto a old thread with a lot of disinformation.
Here is the scoop on the 081 heads.
In stock as cast form they are pretty lame.
If you just bolt them on stock on your 350 keep you expectations modest.

If you are willing to do generous home port work to wake then up they can work very well.
See my post on porting 305 heads.
The 081 heads have a very shrouded combustion chamber and will
need some extra hand deshrouding work to allow larger 1.94x 1.60 valves and lots of flow.
The chamber will be bigger when you are all done.
Look at the similar 083 casting cousin to this head for inspiration.
Look at the vortec chamber and the chamber on other hi perf sbc heads too.

With generous hand porting and chamber rework and larger 1.94x 1.60 valves you can make this head into a good head for a street motor.
Its up to you to do the dirty work.

They flow about 185cfm and 130ex cfm stock.

Easy 230++cfm 180-190ex when done.

The small chamber allows and requires you to get creative with deshrouding and resshaping
and end up with a decent finished result around 62-64cc.
If you just throw them on stock all you will get is the benefit from the compression ratio raise. (more low and midrange torque)

sort of a diamond in the rough depending on how you see things.
If you are allergic to work, just go buy a aftermarket head.
If you are not willing to do the porting work yourself its not going to be very cost effective.
Not worth paying someone else to do the port work.

A 58cc chamber head on a flat top piston 350 does not create excessive compression ratio.
But will need 92 octane gas. Cheap 87 octane gas is not going to work.
They will end up around 62-65cc when all done unless you mill them back down.
On a 383 you will want a dished piston (approx -12cc)
you want to keep the true measured compression ratio under 11:1 for 92+pump gas
on a high perf street motor.
Its up to you to measure and calculate the compression ratio accurately.
You cannot determine the finished compression ratio by asking people on the internet.
I find a finished compression ratio of between 9.8 and 10.5:1 works real well.

Its all about how much effort you are willing to invest. A half baked lazy effort will get you a half baked lazy motor.
This is true when working with any of the stock sbc heads.

i dont mind working on them i spend alot time working on cars but what will i need to port them i never ported heads before i'm shore i can do it im knot a dumb *** and my buddy has a pair or 92 350 heads with mild port would them be better

[machine shop tom]

From what I have seen over the last 30 years or so:

Very few people outside of machine shops have the capability to replace guides, pull press-in studs and machine for and install screw-in studs, and grind and seat valves. In my shop, the labor for the stud work, guide replacement, and valve job would run around at least 400 bucks, less parts. Add to that valves, springs, studs, retainers, etc., etc., and you are getting close to the price of a set of far better heads.

Without these capabilities, saying that it is cost-effective to take a set of 305 heads and make them as capable as a good set of aftermarket heads is ignoring the fact that it costs money to do half the job.

Which brings me to the other half. Most guys haven't a clue as to how to or how much work is actually involved in properly and effectively doing the port and bowl work, and unshrouding, that is needed to make 305 heads work as desired. I have seen way too many botched or half-done port jobs that ruined the heads or had to be completed (at additional cost) to make the heads "work".

By all means, if one is has the equipment and ability to take on the task, go ahead. But you will still have, at best, a set of dated, thin-wall heads that are not what knowledgeable people would consider worth messing around with.

tom

[machine shop tom]

Originally Posted by smallblock383

i dont mind working on them i spend alot time working on cars but what will i need to port them i never ported heads before i'm shore i can do it im knot a dumb *** and my buddy has a pair or 92 350 heads with mild port would them be better

92 heads are swirl-port heads that aren't worth monkeying around with, plus the intake manifold side is different.

tom

[cobalt327]

Good points IMHO, machine shop tom. Something that also sometimes bites first-time/novice heat porters is that just because it looks good does not mean squat about how the port may flow. Members have posted some photos of ported heads and they can look very impressive. Unfortunately that means nothing for the most part, unless the work was done by a seasoned porter and/or there was access to a flow bench- along w/the knowledge needed to digest the bench's results and turn the data into viable, meaningful, positive changes.

Doing a full-on porting job is very labor intensive and is a dirty, time consuming project- made doubly so when working w/cast iron. To bring a set of 305 heads up to what even a set of stock untouched L31 Vortec heads can do is hard to do regardless of who you are, let alone someone w/no experience. Just doing one port is a chore. By the time all 16 ports are done along w/the cost of the machine shop and parts, most guys will see that buying aftermarket or using a better production casting to start with (like the Vortec) is the better way to go.

If the decision has been made to use the 305 heads regardless, staying w/the "low hanging fruit" like removing/blending the lip that's almost always present where the bowl meets the bottom seat cut (red arrows on swirl port head below), and removing casting flash and irregularities, and careful port matching (NOT gasket matching) can result in an improvement of several percent w/only moderate time and effort. Often backcutting the valves gives an improvement for little cost. A true quality valve job can be worth a few percent more and should be considered a 'must-do' on any production head- even aftermarket heads need to be checked over carefully.

As has been said already, the difference between a properly rebuilt and prepped set of production heads and a set of aftermarket heads becomes less the more parts, time and work they consume. But if a production head is going to be used, it makes more sense to me to start out w/the best performing head available rather than using a head because it's cheap (or even free). Remember- the same machine shop time and money will be spent regardless if you're starting w/a Vortec head or a 305 head.

On the '92 heads, check the casting number to see if they're swirl port (SP) heads. If they are, proceed w/caution- while they have 64cc chambers and a relatively big intake port volume, the swirl inducing vane (seen circled below) costs flow at mid to upper rpm. If you're interested in researching the SP heads, there are several sites that have info on them.


Casting number 14102193

[cobalt327]

Here is a page w/some info on porting.

[crazy_boy43ontario]

i ran 305 heads from 1990 to 2002 on my 350 with flat top 4v pistons trw
i ported the heads my self had the shop cut 194 and 160 in them shaved 10tho off heads intake i tried where torker 2 the old one weiand xpert is what i end up on the engine i had it in a camaro with 4 speed 456 gears car was around 3400
i ran 1215 at 114mph shifting at 6500 car pulled just fine i think the key is cutting the 194 and 160 vs in if you want them to work i won alot of races even maid alot of pp think wow one of the best race i ever had was a 1981 camaro with a 383 dart geads roller everything money money in to this car first race i won by one fender he came back said lets go again i was thinking ok how did i win this i told him to go get his slicks on so away he went he came back we went he one by one fender i went back to the startin line i had spon one car langht he about one foot i know if i heated up the tires i would have him he said you want to go again i said na in happy with what we have he said how fast is your car with the nos i said you wouldnt have been close at all yap i had 100 of nos on my car if ever needed cuse u just never know when a big block will pull up and yes we took the nos out before we raced that nite he helped on hook it

[vinniekq2]

welcome to the forum crazyboy
the thread you are posting on is very old
maybe introduce yourself on a new thread and post some pictures?

[DoubleVision]

nos? Is that the same thing as saying "Nauce" like they do in the movies?
Hey crazy,, was it a 350 Rocket by some chance? Or was it a Vette engine?

[gcamp]

can you put 1.94 or 2.02 valves in the heads to get past the 5000 rpm wall

[gcamp]

oh well should of read all of the post

[F-BIRD'88]

The key to making it all work is generous full effort home brewed porting and 1.94x 1.60 valves.
2.02's are not optimum in these heads.