Patricknesmith88

Has anyone on here had first hand experience using 305 heads on the 350 block. I've searched but all i see are theory based answers. I'd really like to know how it turned out for those who have, especially the success stories.

ZONES89RS

iTrader: (25)

Yes, i have, works well for daily driving, not much on performance usually as they are factory with smaller valves, but the compression jump is great and a set of larger valves does wonders for the most part, the HO 305 heads of the 80s are some of the best for porting and polishing with the larger valves, like i said the smaller chambers bump compression a good deal when looking for more power.

azzsmasher69

iTrader: (2)

Had a 85 camaro with a 5-speed. put a 1980 350 4 bolt main out of a truck with 305 heads off a station wagon with a performer rpm intake,600 holley vac. sec., 3.23 gears, small tube shorty headers and had all the ac system,ducting removed. It was ok, had some torque and enough power to just barely beat a lt1 camaro. Good daily driver though but if i had a choice again id go find some better heads unless your budget is virgin tight.

Patricknesmith88

Thanks Guys Im going to look into it more I do have a tight budget but theres nothing wrong with saving for better. So far what im getting is that it has worked great for some and for others it was a turtle. Im playing with a game of chance here lol 50/50.

TooLateVTEC

iTrader: (2)

With the work they need to actually make power its stupid when you can buy some hopped up Vortec heads from Scoggin Dickey and a 218/224 cam and make 400HP pretty easily.

LilJayV10

iTrader: (39)

Homer Simpson voice....

Mmmmm virgin tight.

I would also second the vortec head option. They aren't as cheap as they were but still a great "bang" for your buck.

OK I'm done now.

1 FMF

iTrader: (1)

+3 on the vortec's,
i wouldn't go looking to purchase a set of 305 heads if that's what you're thinking, the only reason to do 305 heads is if you have them laying around or will cost you less than $100 and all you have to do is throw them on. If you have to sink any money or put work into them the forget it, just put the money and effort towards a set of vortec's or even aftermarket aluminum heads which can be reasonably priced.

geedub6893

1fmf is right. If u have them laying around then why not. If they dont have screw in studs and guide plates then u cant run a real big cam anyways. I have a built 355 with 305 heads in my nova and it runs 7.20s in an 1/8 mile, but they have more work done to them then they are worth. 305 heads dont breath worth crap so they run out of air on top end.

ky_black_ss

iTrader: (7)

ive put them on a 400 small block before

gosch383z

I have done this before also, but i have to agree with 1 FMF here, unless they are just laying around buy after market. They do bump up your final cr and add some hp though.

suicidal racing

iTrader: (14)

you would be better off going with just a vette head from 85-92 or a set of vortecs...the best 305 heads where the late 70s an early 80s ones..i forget the part number,but these are the heads the super stock guys would run..but they had a ton of mods done to them..most ive heard of anyone making is 52x hp..there are heat raisers in the exh port that killes the power on them..just blocking them out can ad 40hp from what i been told..

Patricknesmith88

Thanks Guys I actually had the Set of heads laying around. I will say this that they are good for burning tires but im not happy with the setup at all. My first time at the track I clocked a 9.7 first then second a 9.3 and thats dirt slow. I would like to be in the Low 8's, High 7s in the 1/8 and mid to high 12's in the 1/4th on my full bodied third gen camaro. Heres my setup 355 4bolt main with Forged flat top pistons, the stock crank, a Lunati Flat Tappet 480lift cam with a duration of 230 and a lsa of 109. 1.6 Full Roller Rockers. 416 Heads ofcourse and Air Gap Intake, and a Holley 750 Dp. What do you all recommend as long as It can Run off pump gas I'll be happy, and Also I would Like to change to a Hydraulic Roller Cam, but how big could I go without having Vacuum problembs. Any advice would be well appreciated Thanks.

brandoz28

iTrader: (3)

vortecs would work really well for you for sure


geedub....care to divulge anymore on that 7.20 combo? i've got these 305 heads coming out my ears and an extra short block and been thinking about trying something with them

Lucas_McCain

Not to get too off topic, but what about building a 305 headed 350 for a work truck? I just want a lot of low end torque on the cheap, and I already have a good set of 305 heads. It would probably never see higher than ~4000 rpms anyway.

I hear this is fine expcept for the compression. I'll have to check the heads again but I believe the chambers are 60cc. Aside from lowering the compression as much as possible, would running a colder plug and less timing help much with possible detonation on 87 octane?

Here's my plan on the build:
-355 shortblock
-stock cam
-305 heads (I'll get the casting #'s soon enough)
-performer intake (or stay w/ stock 305 intake?)
-edelbrock 1406 carb (or stay w/ stock quadrajet?)

Any opinions?

Patricknesmith88

I know Less Time and a colder plug would help with detonation, but everyone I've talked to including myself runs 93 octane with the time already backed off because its such a thin line. Let me research it and get back to you on it.

Lucas_McCain

I appreciate the help! Are are you running a stock cam? I'm not that familiar with chevies but I've heard the stock cam raises the dynamic compression with this setup. I don't know much about dynamic compression to begin with but maybe I can degree the cam slightly to help it out?

Patricknesmith88

I myself am not that familiar with dynamic compression, but know I dont have a factory cam. I have a Lunati Hydraulic Flat Tappet Cam. part number 00010Lk it has .480 Lift with an rpm range of 2000-6000 with a duration @ .050 of 230. All In all If its properly done you can have a good setup but I still need to get headers and a Y pipe to finish it

1 FMF

iTrader: (1)

regarding the work truck application yeah that's generally what the 305 on a 350 head is used for per the reason you said. It doesn't need to flow a lot of air and make hp at high rpm, all you want is the low end torque which comes from increased cylinder pressure from increased compression.
I don't know about 87 octane, it would obviously be much safer with 93
but with that in mine you'll need to do the measurements and math and first figure out the static compression ratio to see where you stand. If you're very close or over 10:1 then I'd say there's a good chance 87 octane will be a problem. To handle the detonation problem, you want piston to head clearance as close as possible (a.k.a. quench). This is a catch-22 because in doing so generally increases static compression ratio which is bad if you already have too much of, on the other hand using a thicker head gasket decreases static compression ratio but also reduces quench and reducing quench makes it more detonation prone. The good news is since you don't plan on high rpms is you can more safely run tighter quench and you want to shoot for 0.035" or better.
regarding dynamic compression ratio, that is determined by what cam you run. I have some cam/valvetrain books which detailed builds and how retarding/advancing the cam affected cylinder pressures and i'm pretty sure if you described your build and goals to whoever cam company they will know what grind helps not give excessive cylinder pressures in the mid range which is what causes detonation, i believe it's mostly related to intake valve closing point and what amount of valve overlap there is or isn't. Ignition timing is a big player in detonation however i would argue that the spark plug heat range is more of a "pre-ignition" problem which is different, and in this situation unrelated, to detonation so a colder plug wouldn't help anything.

Lucas_McCain

Hey sorry about that, I just noticed you already posted what cam your running. But yeah, I hope this all works out. And good luck to you running those times. Wish I could help you out.

Lucas_McCain

If I end up having to run to 93 then that's no big deal.

That's interesting about the quench. Now when you say 0.035" or better, I take it you mean run a quench 0.035" or less?

I was originally wanting to run a thick head gasket to lower compression, but you agree that a tighter quench is more important in dealing with detonation?

I brought up the colder plug because I ran fresh 350 spark plugs on my 305 (didn't know any better) and no matter how much timing I pulled, it would ping under load. I switched to the colder heat range meant for a 305 and no more pinging. Now there could be some other explanation for this, but that's just my guess.

Thanks for all the pointers. There's a lot more research I need to do!