hi. I have a few questions about heads to choose for my 305. I'm looking to lower compression for forced induction. I found these heads on ebay http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW
the seller claims the heads are 64cc, if im not mistaken stock heads on my 305 tbi are 54cc? are these heads a good choice to drop compression, or do you have any other suggestions. Thanks.

 

Probably 416s with a 58 cc combustion chamber. They will likely NEED a complete rebuild but they respond very well to a home port and polish, in addition to increasing the intake valve out to 1.94".

Follow the link at the end of my sig.

 

hey sitting bull is still here



Just curious, and i'll be the first one to say it: You want to supercharge your 305?
Care to explain your reasoning before this thread gets locked?

 

These heads appear to be 416 castings. They are 58cc's.
They can be opened up to about 65 cc's (unshrouding chamber) they can work well for ya on a supercharged 305 with full porting and larger 1.94" intake valves.

Depending on the compression ratio you want for you 305 and the pistons you'll be using you can also use a "350 head".

350 L-98 TPI heads "083" 64cc 1.94x 1.50 valves can be tweeked to 68 to 70 cc if nessessary.

350 "441" 920" 336 castings 76cc's 1.94x 1.50" valves.

any of the late 60's high perf heads with 64cc hi per chambers and accessory bolt holes. ("492",186 ,041, 370)
"Z28" "LT-1"

L-98 corvette aluminum heads (58cc) 1.94x 1.50" The chamber can be enlarged also to lower compression and improve flow . respond nicely to porting.

The small cc heads would/ could work well on a dished piston supercharged 305. The larger ones on a Flat top.
blown 305.
All these heads will respond well and make good power with a healthy dose of home porting.

Supercharged street motors like lower compression and more boost to make best power on pump gas. A 7.5:1 compression ratio will allow 10-12 psi ( non intercooled) with minimal boost retard.

Water/ alchohol injection will allow more compression and or more boost with less retard for a given fuel octane.
Avoid any of the TBI "swirl port heads" with the swirl ramp in the intake port.

What ever head you use your going to want to measure chamber size and calc the compression ratio youself.

Do you plan on using an existing 305 shortblock or are you building a new motor?

Crane HMV 278-2 # 113801

makes an excellent street blower cam in a moderate blown 305-350 motor.

 

its going to be an intercooled turbo. and i want compression to be around 8:1. i know the 305 is not the best platform for ANYTHING, but later on if I want to upgrade to a 350 or 400. I just want to learn on this one, since I already have it. to keep costs down I want to stay with the stock pistons and change out the heads.

the 350 heads you mentioned with 76cc chambers are probably my best bet. will it have fitment problems on a 305 because of the smaller bore?

oh. and this will be a blow through carb setup. to keep costs and headaches down, im staying away from fuel injection. 650 holley dp 4150.

 

No. I'm too broke to even dream of supercharging and since I use my car 365 days a year, I need the reliability of regular induction--especially when it is 20 or 30 degrees below zero

 

out of the heads you listed, what would you recommend I go with to get 7.5-8.0 compression with the stock flat top pistons? thank you.

 

how about these?
http://cgi.ebay.com/ebaymotors/ws/eB...MakeTrack=true
they should give me 7.8-8.0 compression, if they fit.

 

Pass they are pure crap.

 

well. i've just bought an lt1 from a 95 caprice, so i figure i may as well use the 305 as my lab rat. just looking for ideas. thanks.

 

oh no, you misunderstood me. I meant:

"oh, sitting bull is still around, haven't seen a post from him lately. How's it going?
.
.
.
91rs5.0 : Why do you want to supercharge your 305?"

like that. I just assumed supercharging when you said forced induction, my bad...

It's just usually if someone talks about souping up a 305 like forced induction, people will jump down your throat like crazy, so I thought i'd be the first person to politely ask why. you have good reasoning, build an essentially JY 305 with turbo and intercooler to learn on, if it wrecks, you didn't have a ton of $ into it, if it works, bolt on more displacement below it later.

My take would be bolt on nice large CC heads, to keep your compression low. If you port/polish them they should be good. (choose good heads of course..) Then when you bolt on a larger engine below it, you can probably keep the heads, just choose pistons to keep the compression where you want it...(rather then say 58cc heads on a 350, when boosted, you'd need some VERY dished pistons to keep your CR low enough...)
Well that's just my hope it works !

 

The 624 heads shown are the worst of the worst.
They fall into the same class as 882's ( light casting, crappy flow)

don't bother with Ebay, too much junk on there. find a heavy casting (pre 1974) 76cc head like the 441's or 920's

They are the best of the 76cc smog heads.

Assuming your flat top pistons are .025" down the bore at TDC.

76cc will get you about 7.7:1 with a .039" gasket

they can be milled to 71cc for 8:1

A 64cc camel back ( with bolt holes) (1969-1971) can be opened up to 70 cc's too. (492-186)
use 1.94 x 1.50 valves on a 305.

Same with a L-98 head (64cc)

A 64cc head will get you 8.5:1 ( less boost or intercooling or water injection.)

Any of these heads can work well for ya with porting.

The cam I mentioned would be for a blower like a B&M 144 or a Procharger or vortex.

Turbo cams are a little different.

A good "turbo cam" is a little milder, has less exhaust duration and wide 114-116 Lobe centers.

something around 218-212 @.050 .454" .440" on 114-115LSA

Comp cams 12-400-4 fits the bill

 

Will you be using a automatic or a manual trans?

 

manual

 

well. I'm currently bidding on the 441 heads you were talking about. but now I'm thinking if I should maybe just buy a 350 block and build that up instead of the 305. are these head good for pocket porting? what kind of compression ration should they get on a 400? what do you suggest? thanks.