I want to know if i could put 350 heads(TBI) ON A 305TBI engine? Also would it help the performance of my engine and would i need to do anything else to the engine?

 

You'd probably not gain much performance wise if you do that. The reason being that you'd lose a lot of compression since you are going from a 58cc combustion chamber to a 64cc. This lowers your static compression and hurts performance. If you got some corvette aluminum L98 heads though, that'd be a good swap since the combustion chambers on those are 58cc as well.

 

It isn't really worth it to put those heads on. You may want to look for set of 305TPI heads. I have seen them here go for as little as $100 a pair.

 

some wont even fit.

the valves have to fit in the bores... if they do, and you can keep compression up, go ahead and put em on.

 

ok THANK I guess i wont swap heads. how much more of a power gain would i get from the 305 TPI heads?

 

the 081 305 tpi heads will bolt right up and should be worth 10-20 hp stock. as shifty said, you can pick them up for around a hundred bucks. watch the classifieds on here and set up a search in ebay for:

("305 tpi",lb9,081) include the parenthesis in the search. that'll find any heads with 305 tpi, lb9 or 081 in it.

if you're going to run any kind of camwith those heads, though you'll need to upgrade the springs. figure another 1-200 to have the heads redone and springs upgraded. i believe it'd be worth it to put another 4-600 into those heads having them ported and polished. i've said it before and i'll say it again ... if there's one place to splurge, it's the heads. they're the heart and soul of the engine.

i was going to go that way, but found a set of world products s/r torquer 305 heads on ebay for 250. 50 for shipping, 2-250 for valves, springs, etc, 5-600 for some serious porting and polishing and i believe i'll have the best heads you can reasonably get for a 305 that still have 58cc chambers and functional egr.

if egr isn't an issue, you can go with vortecs. you can find the pro topline vortecs, which are an improved design over the chevy vortecs, flow better and have springs good for cams up to .550 lift for around 700 shipped to your door. you'll have to get them milled, they have 64cc chambers and you'll have to buy another intake as they use a unique design. total cost for vortecs (with the intake) would be about a grand, same as the s/r torquer 305s i have.

if i were going in that direction, i believe i'd spend another 300 bucks and go with the edelbrock etec 170s. they're a fast burn design and flow significantly better than the vortecs. they're also cheaper than the gm fast burn heads, and their 170cc intake runners vs the 200cc intake runners on the gm fast burns makes them a much better head for a street car.

 

you can't go bigger than a 1.94 intake valve on a 305 because of the bore. any head with a 2.02 intake valve won't work. even if you clearanced the tops of the pistons and the sides of the cylinder bores so they don't hit, they'd be so badly shrouded there'd be no performance gain.

 

False info you can use 2.02/1.60 valves on a 305 with no other work done to the block

 

nope.


i can go home and prove it with a hammer.

as some of you know, im making a intake manifold to mount my eaton M112 on... i went to the local machine shop and picked up a junk 305 block and some junk heads for free... the intake valves dont fit in the bore..... i can tap the valve spring assmblies with a hammer... tap the exaust, it goes in, tap the intake it goes "ting" and doesnt move..... hehe.

i REALLY REALLY REALLY wish i had a digital camera... id spray some paint down the bore from undernieth, and take the head off to SHOW people they dont fit.

 

btw, i went to your website just now
schweet motor



but you say you're running thoes valves on that 305!? what casting are you using????

 

Well then I guess the last 4 yrs ive been driving with them on my 305 dont count

 

or you got screwed and they machinest lied about the size.. *shrug*

what casting?

 

LOL you posted to fast sorry bout that I have to pull a cover to be sure lost my part list and I am to old to remember that far back but the are a set of mid 70's heads that were opened up to 2.02/1.60

 

no I am positive they are 2.02

 

mmk, well if you pull the valve covers off anytime soon, post the casting number up...

the overhang isnt much, so if the casting has them just slightly closer or towards the exaust side, they'll clear.

 

I will get that casting # and take a pic. I had heard they would not fit when I bought these but I got them cheap, did the same as you but without the springs and both valves went in just fine so i figured someone had lied to me, but now I wonder if G.M. had slightly differnt valve locations between castings

 

as far as i know, they didnt. theres a "standard" SBC valve layout....

otherwise a stud girdle wouldnt fit between all the heads..... athough now that i think about it, thats the only part that would be really adversly effected. a minor sideways deflection wouldnt really effect everything else... from a production engine standpoint atleast.

i know 882s, iron eagles, pro toplines and whatever heads i have in the garage dont fit with thoes valves. be intresting to find some that do...


athough valve shrouding would still be a problem.

 

one more reason to run a blower dished blower pistons

 

when i first began researching heads, i spoke with tech people at edelbrock, afr, trick flow and brodix. i've checked my notes and they all said 2.02 valves would have clearance issues. they said the biggest valves that would work would be a 2.00, but that shrouding would create problems and i'd be better off with 1.94 intake valves. they also said clearance problems would be made worse if i milled their 64cc heads to get the compression back up.

i see your car is blown. i wonder if the heads you have might be 76cc chambers? low compression wouldn't be an issue for you and i'd think there'd be a little more room.

anyway, i could be wrong on the 2.02 valves, i don't have direct experience, i've never tried running 2.02 valves on a 305

 

seanof30306 it looks like you might have hit it on the head almost didnt mean to get this thread off subject started a new post about this under 2.02's on a 305
https://www.thirdgen.org/techbb2/sho...hreadid=221370

 

I tried 3 different sets of heads with 2.02"in valves on my '84 305 HO and none fit.

The 2.00"in is as big as you can go. But I've never tried a 305 bored .060 over. My '84 was only bored .040 over. Also the 1.60ex valve is to much shorued. The 1.55ex or 1.50ex is the best.