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RaticalRods 08-23-2010 11:35 AM

305 build help
Ive used this site for ages to look at already asked questions but it is now time that i ask my own, so any help would be appreciated.

I just bought a 305 w/ flat top pistons, said to be about 10:1 compression, stock heads, no cam, clean crank,etc. i bought this for a 1986, c10 truck. I am starting with the motor and working my way back as needed.

My question is, i am building this motor for street/strip, mostly street but i do tend to find my self at the track on weekends. It is a chevy 85' 305 block standard bore with the stock crank. I was looking at a cam that will give me good performance street and track as well as allow me to upgrade my heads without buying a new cam when i eventually do so. I played with that Comp cam program and found 12-246-3 to be to my liking...Duration @ 0.006": 274 / 286 Duration @ 0.050": 230 / 236
Max Lift w/ 1.5RR: .487" / .490" Lobe Separation: 110

First, is that a cam for me and how much do you think i need to do to my stock heads to make it work- springs/retainers... ect...?

I also have a buddy with Trick Flow Heads TFS-31400001 that i can get cheap. Should i just go with those since they already have the needed springs, lift clearence, milling etc.

And if so should i stick to this cam choice?

I know its alot of questions but any help is appreciated. thanks

my87Z 08-23-2010 12:07 PM

that is a whole lot of cam for a 305, i would say that would be a healthy street/strip cam in a 350. what heads are on the 305 if they aren't th 4416 HO 305 heads then they are pretty much garbage and need to be scrapped. i know that you should already know this but the 305 is certainly not the engine you want to start out with as a street/strip motor, they are a efficent low end light weight tow motor, they make next to no power above 4000-4500rpm. pretty much all the non 4.000"+ bore sbc's are not a good motor to start with when wanting to build a performance engine.

about the largest valve's you could go with would be 1.94 intake and a 1.5 exhaust as you will still have to have about a combined .060" clearnace between the two valves and the valves and the cylinder walls. so you would have to see what all is in your friends heads

how about this you find out what are all the specs on your friends TF heads and let us know and we'll tell you if it's a good idea or not.

RaticalRods 08-23-2010 12:21 PM

thanks, yeah i realize that a 305 is not an ideal motor to build for this but it was cheap, free for some work i did.

the specs on the heads are; 180cc intake port, 64cc chambers, 2.02"/1.60" valves, 13* intake / 23* exhaust valve angles, angled sparkplugs, 50 state legal, Has steamholes for 400" engine, heads flow 240cfm intake @ .600" lift & 200cfm exhaust @ .600" lift.

thanks for the help

GTXKen 08-23-2010 12:41 PM

Keep in mind that any money you put into that block in the way of parts and machine work is throw away money because you will want to move up to a 350 some day.

Do yourself a favor and at least check around and see what a 350 will cost you before you start.

my87Z 08-23-2010 01:00 PM


Originally Posted by GTXKen
Keep in mind that any money you put into that block in the way of parts and machine work is throw away money because you will want to move up to a 350 some day.

Do yourself a favor and at least check around and see what a 350 will cost you before you start.

i certainly agree with this!

with those heads you will have problems with the valve size and wall clearance, as well as you will loose about .5 of a compression point so if you have "10:1" now you will end up with about 9.5:1 and limit your choice of cams all due to the 58-60cc heads you have on there and the additonal 6-4cc's in the TF 64cc combustion chambers.

if your goal is to make a 300hp 305 then i would say find a set of 4416 305 HO heads, and use a cam around 210-216 duration @ 050 with about .450 lift. you may want to look into a cam with a later intake closure or more LSA to compliment the cam selections you will be looking at and the supposed 10:1 CR

RaticalRods 08-23-2010 01:02 PM

Ive seen builds done that make 325hp with vortec heads, i just figured these trick flow heads would help open her up alittle more. A 350 is ideal but as for now i am gonna try to see what i can get out of this 305. If i was really concerned about times i would choose a different car too but iam just trying to build something fun, my other projects are for the other half of me trying to turn times. thanks for the idea tho

my87Z 08-23-2010 01:13 PM

like i mentioned the 2.02/1.6 valves will be too much/close to the 305 cylinder walls, you wont be able to go over 1.94/1.5 and that is what the vortecs have. the TF heads are pretty much out of the question, now a set of vortecs may work but you will spend 500.00 to get a set that have been rebuilt and worked the way you want then vs you can find a set of 4416 heads for 50-100.00 and have them rebuilt for 200ish and it wouldn't be too hard to make 300hp with them just dont expect to turn the 305 up much past 5000rpm

RaticalRods 08-23-2010 01:31 PM

thanks for that information, iam going to look into that. Now what about a cam set up? if i run those style heads. Is that cam i mentioned going to be to much? thanks again.

RaticalRods 08-23-2010 01:52 PM

Also this block is a 85' 305, what years did the 4416 heads come on. i dont have them around me to look at the casting numbers, thanks.

cobalt327 08-23-2010 03:53 PM

The TFS TW heads you are talking about are the "G2" version that has a few of the problems sorted out that the first heads had. Keep the lift below 0.520" unless you flycut the pistons for valve clearance. The usual eyebrow or trough valve slots will not do- the TW G2 head has 16/18 valve angles and the(intake only?) valve isn't in the same location as OEM, IIRC. P to V clearances have to be verified for all cams to be safe, including both sides of the ICL where it is to be installed.

Using the TW heads, the CR will be low- about 8.2 w/the usual stock bore, stroke, deck and piston volume specs and a 0.041" head gasket thickness. You can bring this up by using 0.028" composite gaskets ~8.6 CR), even more by zero decking the block (~9.0). More yet w/milling the heads.

The 416 heads were used on '80 to '84 or '86 (depending on where you look) 305's.

Another option is to use the Vortec 5.0L "059" head from a '96-up L30 engine.

Vortec L30 "059" casting:
.100" 68 47
.200" 128 103
.300" 179 138
.400" 205 152
.500" 221 163

L30 305 head info- POST #487.

V8 Super Beetle 08-23-2010 04:21 PM

Here's how these guys got 372 hp out of their 305.

RaticalRods 08-23-2010 07:19 PM

ok well i think iam sticking with the heads that came with it, they held a .480 lift cam before it was torn down, the springs were replaced to hold that much lift and the heads are 68cc. So a little for information for my build.

That being said, with those heads and a 5.0l Edelbrock rpm II with 600cfm carb.

Any suggestions on a cam... i would like a rougher idle, good torque but also hp for a little track time (i know its not going to be turning stunning times, but id like it to do as well as possible)

Thanks again

American Muscle 08-23-2010 08:02 PM

I have an 86 chevy C-10 with a nice little 305 in her. Not a street/strip but fun to drive and turn a few heads. All i have is headers, edlebrock performer intake, edlebrock 600 carb, 700r4, and most inportant i got a set of gears(3:42) and this thing flies. I wouldnt do anything internally to a 305. Now I have seen some pretty wicked sounding cammed up 305's but that same cam would do lots more in a 350. If thats all you have then roll it.

RaticalRods 08-23-2010 08:55 PM

Yeah sounds like fun, i cant wait. I am only looking for a cam because i need to buy one anyways, so i figured id go as big as possible with this set-up because honestly there isnt really a money difference between a stock cam and a little beefier cam.

RaticalRods 08-23-2010 10:18 PM

i think i am leaning towards a comp cam magnum:

Magnum 270H Hydraulic Flat Tappet Camshaft & Lifter Kit
Lift: .470''
Duration: 270
RPM Range: 1800-5800

any thoughts?

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