LB9GTA

iTrader: (1)

I am thinking about putting L98 heads on my 305tpi.
I have headers, comp cam, ported plenum and 8.5mm MSD wires.

Has anyone tried this?(Please don't tell me I am wasting my time on a 305).
What gains can I expect in HP?
Will I lose driveability in anyway?
Will I have to do anything else?(Chip work obviously)

LB9GTA

DuronClocker

iTrader: (1)

You'll lose performance unless they are the aluminum L98s out of the Vettes. Those used 1.94 intake valves and flowed VERY nicely.

The L98 iron heads have the same sized valves (I thought) as the LB9 heads (1.84/1.5). They flow within 3cfm of each other last time I saw the tables, and those 3cfm were well within 2% of each other, and that's within margin of error.

You'll lose performance because compression will drop quite a bit. It will be mid-high 8s at best, from the 9.3 stock it should be on a 305TPI. Good for boost I suppose

1MeanZ

iTrader: (9)

the best 305 heads available are the ones you already have on the motor or aluminum L98 heads like i have. many guys on here have posted excellent 1/4 mile times and power numbers with ported stock 305 heads. there are also a small handfull of us running the aluminum heads, me included. these heads boosted my trap speed from 92mph to 97mph in the 1/4, and thats with my 2800 Vigilante converter. before the head swap my 305 had a 214/224 cam, ported intake, and edelbrock headers and went 92mph. i swapped the aluminum heads on with roller rockers, and using the same cam and intake listed above i gained 5mph which is about 50 horse, you decide what head is for you. but either ported stockers or the aluminum L98s are the way to go. see my sig for more details

Dr G

One of my best friends RMK (One of the mods here) put Corvette Aluminum L98 heads on his 305TPI. Although this was at the same time as other mods, so the difference the heads alone made is impossible to tell. The car runs very well indeed though.

LB9GTA

iTrader: (1)

Don't the LB9 heads have 1.84 valves?

The cast iron and aluminum L98 heads have 1.94 valves. So the only difference would be lower weight and a little better flow with the aluminums??

Now that I have an aftermarket cam and headers, don't I need more airflow, and won't the heads give me that?

Is everyone saying that is is a waste of money?

LB9GTA

LB9GTA

iTrader: (1)

Also, the heads I am looking at are L98 heads. They are polished and ported with a 5 angle valve job. With Manley race valves(1.94).

Will these be better that the current stock LB9 heads(1.84)?
Will I lose compression?

LB9GTA

DuronClocker

iTrader: (1)

My mistake, the L98 heads do have 1.94 valves. Didn't realize that.

Untouched, the aluminum L98 heads flow as good as "stage 2 ported" iron L98 heads if I remember right. I think they had smaller chambers too for increased compression as well.

I still think with those heads you'll lose more than you'll gain, and you'll get worse efficiency with the lower compression as well (decrease in gas mileage for a possible decrease in performance).

LB9GTA

iTrader: (1)

So what are my options now?

1. Port the LB9 heads, put 1.94 valves in them? What is that cost(the porting anyway)?

2. Get L98 aluminum heads?(What about $ for them)

Remember that I live in Canada.

Any input?

LB9GTA

DuronClocker

iTrader: (1)

Aluminum L98 heads are usually over $500/pair if you can find them. You're almost better off buying a set of used aftermarket heads, and the same goes with any type of porting unless you do it yourself. My plan was always to port my 305 heads and put 1.94 valves into them, but I picked up a set of LT1 heads a while back that I'm going to use. Quite a bit of work to get them to work though, its NOT a direct bolt-on, but they were cheap.

Dr G

I don't know how much they'd cost you used in Canada, like from a 'Vette owner who was upgrading to aftermarket heads.

Heres a link to Scoggin Dickey, they stock them from GM Performance Parts:-
http://www.sdpc2000.com/cart.asp?act...id=277&pid=147

Spefications as below:-
SDPC Part Number: 12556463
Manufacturer: GM Performance Parts
Valve Size : 1.940"/1.500"
Chamber Volume CC : 58cc
Intake Port CC : 163cc
Spark Plug Position : Angled
Spark Plug Size : 14mm
Spark Plug Reach : 0.750"
Spark Plug Number : RC12YC

They cost a whopping $469.25 each! Best of luck!!

LB9GTA

iTrader: (1)

Also, the heads are milled down and zero decked. Does this mean that they would put the compression back up??

Can anyone help with these phrases?

LB9GTA

RS Chris

Milled means the heads are cut down to raise compression, whether or not it will raise yours depends on the volume of your heads compared to those.

Decked I believe means they are checked to ensure they are completely flat on the bottom.

1MeanZ

iTrader: (9)

i got my heads from a Corvette owner. i got the heads, cast aluminum valve covers, roller rockers, valves, springs, locks and retiners, and screw in studs for $600. they were already cleaned, all i did was have a valve job done on them which cost me $40 or so. the composite factory head gaskets were $50. for $40 i bought the Standard Abrasives head porting kit and gasket matched and smoothed the intake ports and polished the chambers. so for a total investment of about $750, i swapped aluminum heads on my car and gained very little low end, but the increase in midrange power was amazing. from 3000 to 5500 rpm this thing goes. i think my quarter mile time with the stock chip and single 2.5 inch exhaust speak for themselves. (and yes i painted them black so they look like stock 305 heads except for the angled plugs )

8Mike9

Milled was explained before...the bottom of the head is milled for flatness, normally, somethims a little more to decrease the combustion chamber size.

Zero-decked has to do with the block...milling down the block so the pistons are sitting at the top, instead of down in the holes. Normally done to achieve proper/best desired quench area between the top of the piston and the flatspot in the combustion chamber of the heads.

LB9GTA

iTrader: (1)

I talked to the guy about the L98 heads I am looking at. He said that the compression on his engine with the heads milled and zero decked was 10.4:1.

So if I was to put a compressed head gasket on my 305, along with these heads, would I still lose compression??

Also, does my 305 engine have factory flat top pistons?

LB9GTA