if you're leaning more towards the mileage/driver characteristics, I think the 268 may be a bit big for a 305...I've got an XE268/pro-action heads and an RPM intake in a mild 350 that's on the rough side of perfect for the street. I really like how it runs but I think it'd be a bit much for the little engine. of course I went kinda crazy the other way on my near stock TPI 305 with a Crane PwrMax 2011 with a whopping 246 advertised duration! that's mainly because the stock TPI manifolds/unported heads do well with a small cam, it's 19mpg of stump pulling fun but dies out around 4500rpm...you'd want quite a bit more with a carb I've bought a vortec head 'kit' through Scoggin****ey, for an engine I built for someone else a few years ago, made it really nice...comes with complete heads, intake, bolts, gaskets and rockers in the $800's. it's worth a little extra money to have brand new castings that aren't going to crack for a very long time!
I also think a 268 degree cam is a bit too much for what you want. I've got one in a 350, with a th350 and 3.40 gears, and it's okay. But you said that you were worried about economy, running an auto with o/d, and having to move a hefty rig, all of which points to a shorter duration cam to keep the bottom end power up, and a bit less lift for keeping the velocity up too. Likewise don't go nuts in the induction department, if you aren't going to crank the snot out of it. Like they said, porting is the key on your heads. If you take a long hard look at how poorly the intake ports match up with the gasket, you will see that is one place that needs attention. Likewise the exhaust valve guides jut out into the flow path, and should be contoured. The stock valves should be adiquate for what you want to do too. These engines will do very well if you give them a little tlc, and a few aftermarket parts.
Oh.. Not intended to be a 1/4 runner or any type of speed racer. I DO intend to drive it on the interstate,.. and run around town and to shows... but nothing radical. BUddy of mine has a ch***is dyno... I'll probbaly have it up on that when I get it built just to see what it'll do and that will be the extent of the hard running it'll see.<!-- / message -->
ive always wanted to take a 305 and make one into a 335 with one of those stroker kits. would be different and kinda neat to see. really throw people off.
what a good point, so putting a good top end and valvetrain on a 305 is a bad idea because they're not good stock. that leaves me scratching my head AND balls in dumbfounded wonderment. if you had a stock 80's carb'd 350 it would have ****ed just as much while making a tiny bit more power. and this thread was started with a performance street engine in mind, not a race car. I think there are enough knowledgeable people that have posted their own positive personal experiences modifying a 305 to disprove it being the most worthless build platform ever (notice I did say platform, which implies potential for building it CORRECTLY).
kind a late comment here, but my experiences with 3 different 305's. first 2 were in 81 and 84 short/short Chevy pickups. scored a nother 305 out of a burned up z-28 (didn't even know about the HO) stuck a Comp 260 cam in it and with true duals it ran like a ****d ape. 3rd one was in a full sized extended cab 94 GMS with a 5-speed and got 20 mpg and could easily pull a dual axle trailer, since there wasn't all the power lost through an automatic. my 40 pickup build will have a 305 with a torque cam, 5-speed and a single 4 barrel (carter WCFB or early rochester for looks)
it gets the piston velocity up pretty high but I've always thought it'd be fun to do, you can get rotating ***emblies to do this SO cheap. I think a well balanced, light rotating ***embly and coated pistons would be my main efforts.
305, 600 edelbrock and intake, Isky cam, 700r4, chevell posi. I installed the 305 as a temporary motor untill I could build a 350. It's been 4 years now and still running strong. Gets good gas milage too. I think wait untill it wears out before I replace it. I may just rebuild it.
NEVER too late to throw in your 2 cents worth. Love to hear all sorts of opinions, and it's interesting. I'm learning all the time.
Do you happen to know the part number for the 305 Vortec heads? I found a #12558059 but I can't find anyone who actually sells the heads. Also the part number doesn't come up on GM Performance Parts website. I am very interested in them if anyone happens to know where to get a hold of them.
All right you guys pickin on the 305, you've aggravated me so much I think I'll build the lowly 267 V-8 i got for nothing into a evil little screamer. I'm not really aggravated, but you can make decent power and gas mileage with a 305 even though the bore to stroke ratio is less than ideal. As far as small motors go I prefer the 283 any day of the week. If you are interested in stroking your 305 to a 335 go to enginekits.com. HR magazine has done stories on their inexpensive stroker kits in the past and have shown very good power gains.
haha, yeah, it's made me want to put a little more effort into my 305 just to catch people off guard! btw, my favorite thing that people don't realize about the *HORRIBLE* bore:stroke ratio that I so commonly hear about and how the 350 is so much better because you can stroke it out: 305: 1.072 350: 1.148 383: 1.066 seriously, it's a small inch 383. let it breath good.
I'll have to give my local GM dealership a call(or have my co-worker look at his truck). I've only been able to come up with a PN for the replacement longblock, the L30 (pn 12530284); L31 is the 350(pn 12530282). the PN for the 305 heads isn't ever listed because they're not a '350' performance part.
juswt a note on the 305 vortec's, i've got a friend with a 97 1/2 ton 4x4 with the 305 vortec engine, gets 19-20 mpg regularly. runs good too..
Does GM Performance Parts produce "aftermarket" 305 Vortec heads like they do for the 350 or will I need to find some on a truck in the junk yard?
what do you mean by 'aftermarket'? I know there are GM dealerships, like Scoggin-****ey, that do their own performance upgrades and custom engine work, like springs and valves. that gives me one more thing to ask my dealership about...valve springs, I want to have them look up valve springs for both heads to see if it's the same p/n or not. to my knowledge GMPP doesn't really have a 'performance' or modified version of the vortec heads, they're just good performance heads outa the box. either way, the most you'd want to do to a 305 vortec head, if anything, is upgrade the valve springs. they're already setup to run a hydraulic roller cam, so a mild aftermarket roller shouldn't be too much for the stock springs. really any higher performance efforts/higher RPM (even on a small bore engine) would warrant just using the 350 vortecs.
What I meant was can you buy 305 Vortec Heads from GM? Do they sell new ones like the sell the 350 Vortec heads (p/n 12558060) or will I need to find ones from a 96 and up 350 in the junk yard? Thank you for your help!
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