building up my 305...suggestions welcome

[dudeman]

So first things first...I know most would tell me to take my time and carefully remove the 305 then throw it away and get a 350.  But I found a build for my 305 and wanted to get some tips and pointers for this massive knowledge pool.  I have a 1983 GMC k1500 pickup high sierra 4x4 long bed with everything stock. And here's what I am looking to replace...
Holly 750 hp Carb
XM270HR cam
Trick flow Super 23 175 heads
Fel Pro head gaskets
ARP head bolts
1.5 ratio roller rockers from ProComp
dual-plane, aluminum intake ProComp
Hooker long tube headers
Flowmaster 40 series Exhaust
Cold air induction undecided

Any suggestions, tips, or info I might need would be awesome.  It doesn't seem to need any fabricating or machining but my knowledge is limited. Appreciate it...

[nlauffer]

I have decided to build my 305 as well.  Just a couple things I noticed on your list.  1.  Watch out you don't overcarb the 305.  2. the 270 cam seems sized well, but remember the 305 will react differently than a 350 will.  3.  I don't about the Trick Flow, but you should look at the Torquer 305's. 

There is a pretty good article on a 305 build, but I can't find it.  When I do, I'll let you know.  It is what i am basing my 305 on. 

[nlauffer]

My build is going to be:

1. My 305 pickup block with flat top pistons (previous owner build)
2. World Products S/R 305 heads ( I believe it will put it at 9.5:1 compression)
3.  Comp cams XE262H in the k-kit
4. start with iron manifolds, maybe headers later
5. Quadrajet rebuild, mine performs great now
6. Edelbrock RPM manifold

This should put out in the neighborhood of 325hp and comparable torque and have excellent driveability.  With my rebuilt TH350 and stock 3.73 gears.  I should be in it for less than $1500

[dudeman]

I will definitely look into the torquer 305's thanks for that.  What Carb would you suggest if that ones too big?  Yeah I would appreciate that build if you come across it again...thanks for the response brother

[nlauffer]

I really want to try the new Speed Demon 625.  It looks like a perfevt choice carb.  It sells for 350 at Speedway,not sure where else.

[dudeman]

Good deal I'll look into that too...checked out the torquer like you suggested and think that's the route I will take.  Will I need any mods or machining with the build I got including the demon and torquer?

[nlauffer]

Others might have a better answer than me, but if you use the heads and that carb, they should both be bolt on items.  And I was wrong on the heads. 

World Products sells a Torquer and S/R, but only the S/R has the combustion chamber for the 305.  Just double check that before you buy.

I'm not sure on the cam you chose.  I know it will act like a more radical cam in the 305, you might be looking at losing vacuum or the possible need for a more than stock converter.

Other than that, anytime you stray from stock configuration it can lead to fitment issues or compatibility problems, between parts. 

[78 Chevyrado]

Looks like from your parts list above, you want an engine whose RPM range is 3500RPM and above?  Whats the redline going to be?

If you are wanting it to be streetable and have power off the line it will need some adjustment in the parts list.  Just be forewarned, the setup your looking at now will have to be 2-footed at redlights and won't idle well.  but it will sounds super awesome. 

For the carb with a high winding engine, I wouldn't go over 650CFM.  Though to have more throttle respone I'd probably go with a 500cfm.

[nlauffer]

Through planning my 305 build, I have read alot on the 305 Chevy heads.  Not so much the H.O., but stock run of the mill, every pickup had them, heads.  What I have read tells me the 305 heads were never meant for max flow and performance, but a way to keep emissions compatable with standards.  Also, with any design, there can be improvements somewhere.  With that said, I have had a hard time deciding on aftermarket (better flow, more cost) or stock rebuild (with me porting and polishing).  I still want to go with the World Products, but there are a few others out there.  Engine Quest sells a set also. 

So I guess the main question remains, high horsepower or better daily driver.  And by high horsepower, I mean relative to the 305.  There is nothing wrong with maxing out the potential of a 305.  That is a whole nother discussion.  Just as Chevyrado stated, if you go too far with the 305, you probably won't like it.  A 350 can handle upgrades better.   But that doesn't mean the 305 can't be brought into the performance level.  It takes the right parts and more planning.

Here is another option for you instead of aftermarket heads.  If yours are in good shape, do some research, and try your hand at a port and polish job.  Keep the cam within the 305's driveable range and maybe add the aftermarket heads later if you don't like the polish job. 

[nlauffer]

On your list, from Fel Pro gaskest down, those items would be nice upgrades.  Just watch out for those first few items on your list.  that's where the money pit is, and a bigger potential for disappointment.

[nlauffer]

I believe the 305 build that Car Craft did was where I got some of my information.  They used the Comp Cams XE262H cam.  The stock cam numbers are:  .350int/.385exh & 178int/194 @.050 vs the Comp Cams: .462int/.469exh & 218int/224exh @ .050.  Read the whole article.  It will show you that there is some power in the 305.

[gto109]

here is a build a guy did on a 77 grand prix with a Chevy 305.  It doesn't say hp ratings but the times tell me that it was gaining hp.

Baseline: Stock 1977 305 2v................17.30s and 12mpg
Performer intake w/ Holley 600 carb........16.50s and 17mpg
Recurved stock HEI and added Supercoil.....16.30s and 17mpg
Headers w/ turbo mufflers dumped at axle...15.70s and 20mpg
Mufflers removed, 3ft tubes on headers.....15.50s and 21mpg
TRW #274 cam, new chain, flex fan..........15.00s and 23mpg
Full duals from headers Dynomax mufflers...15.10a and 23mpg
K$N stub stack, softer secondary spring....14.90s and 22mpg
Magnum roller tip rockers, 1.52 ratio......14.80s and 24mpg
Magnum 1.6 rockers on exhaust side.........14.80s and 25mpg