Kevs79, This would be a great time for you to experience some very easy to do pocket porting. It will give a decent increase to the stock heads, and as long as you are careful it will not hurt at all. The bowl areas in the stock heads you have are very rough as cast. If you can take the valve springs off, and pull out the valves then this would be an easy "porting" job with decent rewards. Then when you are done, you can put on new valve seals as well!! This will be a benefit with you adding a performer intake and better carb. If you want some detailed instructions send me a pm and I'll walk you through it. Al.
We were planning on taking them apart and cleaning them up and replacing the valve stem seals while they were apart. I might take you up on that when I get to that point.......if I get brave enough....thanks, Kevin.
Well I was doing some more research online and found a reference to an article in HOT ROD March 1999 and I just happen to have that exact magazine in the bottom of my end table(what a coincidence!!). It actually talks about the 305 heads w/ the 1.74/1.5 valves and recommends them for a boost in CR and torque to a 350. They also said it was "necessary" to smooth the ridge in the heads that outline the 305 cylinder wall since the obviously the 350 cylinder bore is bigger. They also recommended smoothing the ridge around the edge of the valve openings. Any thoughts on this??
Here are some photos of the article. Not very good quality, but you get the idea of what they suggest on the heads.
Any idea on HP estimate on this set up: Stock 1984 350 from GMC van w/stock cam and internals Performer intake Holley 650 w/vac secondaries Headers Dual 2.5 inch exhaust 305 heads (1.72/1.5 60cc) Thanks for all the help you all have provided us!!
How's this; I disagree with about everything posted so far, but was hoping a real engine builder(which I don't claim to be) would chime in an set you straight. Put as much valve in your engine(any engine) as you can get w/o it being shrouded by the side of the combustion chamber. A cylinder gets it "****" when the valve first leaves the seat. Good low lift numbers are esp important when you're trying to build low-end torque. Look at a modern cam design. Something with aggressive ramp angles. Get the valve open fast, don't have to open it as far as long. Here again, low-end torque. Spend money on a good mult-angle valve job. Break all the sharp edges in the heads. The flow restriction in a sbc is the bowl area and valveguide boss. Don't go hoggin' on the ports. Get some of David Vizard's books, "How to Build Horsepower", "SBC Cylinder Heads". Should be able to find an engine builder w/a Desktop Dyno program. Run your previously stated engine combination, I'm guessing 275-300 hp.
I actually did get a copy of DD and ran the numbers, but not sure how accurate they are. Stock 350 w/stock heads(1.72/1.50) 191 hp @3500rpm, 337 torque @2000 rpm Stock 350 w/stock heads(1.72/1.50), headers, intake/carb 224 hp @3500, 399 torque @2000 rpm Stock 350 w/305 heads(1.72/1.50),headers, intake/carb 242 hp @3500, 425 torque @2000 rpm
This gave me a great Idea for the motor in my panel truck I Thought i kinda got the shaft on the deal for the truck (long story). The guy had thrown in a strong running 305 since the 350 in the trucks needs head gaskets. Well the 305 was out of his boat and is reverse rotation so i was kinda pissed and thought it was worthless to me. Threw it in the corner. So tonight i pulled the valve covers and i have the same heads on the 305 as you do. I have to pull the heads off the 350 anyway to replace the head gaskets so i'm going to put the 305 heads on when i'm done. thanks for the idea.
Please give an example of the cam specs that illustrate what you are talking about using a 305 head on a 350. Thanks
Built a 355 flat top with 305 heads (416 castings) z28 springs, performer intake, QJ carb and Lunati Voodoo cam (1000 - 5300 rpm grind). Would roast 9 1/2" wide autocross tires with a Tru-trac unit in a 82 camaro with 5 speed at will! A totally awesome motor and was very happy on mid-grade pump gas. Louie
I am still on the fence about doing this, but probably will......I am pulling the heads on the 350 to chk it out anyway so might as well stick my 305's on for a little boost in power.
No prob, glad to be of help. Just to brag, took the motor out of the camaro, put it into a Monte Carlo hobby stock on dirt without doing a thing to it and won 2 main events....gave the guys with 383s fits!!! Also, this motor is going to end up in our roadster, but with the Speedway motors solid lifter 2 barrel cam for some old skool tappet noise and a really lopey idle. Not too shabby for a motor with less than 800 bucks in it. Louie
I have them on an O/T truck of mine. They were ported mildly and port matched, also had the intakes opened up to 1.94 in. valves. They are the older open chamber ones, but I am running flat topped pistons, and they work very well with a Comp 268 high energy cam, and stock manafolds.
ttt one more time. Just hoping to hear from some more w/experience on the topic. Thanks for all the input so far!!!
I dont think it's worth the swap unless your 350 heads are junk. if youre replacing the cam and just bumped up the numbers a little bit youd probably see the same results if not better than the head swap. good luck and keep us posted
The search function is your best friend. Haven't we beat this horse enough???? Look and ye shall find ! Hit the search ****on and type.... 305 heads on a 350.........guys I thing we've gone past rigor and its startin to smell bad.........anybody got the febreeze???
How about a 350 block with a 307 crank/327 piston ***embly and the 305 4 barrel heads?? Just kidding! I have 2 sets of the 305 4V heads. 1 set are from '76 and the other from '77. Not sure on the casting # though.. I gotta look those up. As for around town driving, I'd go with a smaller carb than a 650... I think a 575-600 cfm carb would be much better for more torque on the low end. But, that's just my belly ****on opinion.
I'll just throw in my $.02 before you break out the coffee grounds ( learned that one from CSI ). If done correctly a 350 with the right 305 heads makes a great TQ engine below 5,000 RPM. I haven't built one YET but I've been behind the loud pedal on one, throttle response and low end launch was off the chart. It was a lot of fun and it got pretty decent mileage. It was so much fun I'm rounding up the parts to build one right now for my '66 C10. I'm using a 350 roller cam block and I was going to use the '416 HO heads with some port work and the 1.84 valves but I have a 305 Vortec I bought for parts and after looking over the heads on it I'm using those. They have the same chambers and valves as the '416s, no they don't have the heart shaped chambers like the L31 Vortecs and the runners aren't "as good" as the REAL Vortec heads. They have that little "bump" above the intake valve to help induce swirl "blah, blah, blah" but when compared to most stock 350 heads they look pretty damn good to me. I'm using 21cc D-cup forged pistons, quench distance should average about .046", static compression will be about 9.1. I'm using the '395 Marine/Ramjet/HT383 factory roller cam and.... you'll love this...... a cast iron copy of the old Chevy Q-Jet intake manifold made specifically for Vortec engines used in industrial equipment like generators and forklifts. It will be topped with a Q-Jet and I'll be using small tube headers. I ran it through DD2000 with conservative inputs and fudging the numbers down a bit more it should make an easy 300+ HP at 5,000 RPM and 380+ FtLbs. from 2000 through 4000 RPM. Actual DD2K numbers were 336 FWHP and 405-409 FWTQ. Even with conservative inputs I think DD is "optmistic" so I scrub a little off the top. Based on the one I drove which had just plain old **** heads with 1.72's, full dish pistons and a generic flat tappet RV cam I think DD is pretty darn close. I'll have an NV3500 and 3.73 or 4.10's behind it to help TQ but it shouldn't need much help. I finally landed a new job after being a "national statistic" for the past 5 months (5 mos. to the day) so I'm hoping to have this on the road this summer. If it's a squarebore I'd go even smaller, but a 650 spreadbore would be fine. But that's a "dead horse" of a different color.
Thats sounds like a duplicate to our possible set up. Where did the power curve seem to end on that one?? Congrats on the new job BTW!!! It is a spread bore Holley 650.......this one http://www.summitracing.com/parts/HLY-0-9895/.
Thanks, my UI runs out in 4 weeks so the timing was pretty good. Been awhile and it didn't have a tach but I'm going to say it pulled hard to at least 4800, it was right off an idle where it really shined though. Throttle response was right there, right now. It was in a mid-70's El Camino with a TH350 and 2.73 gears. He patched it together from left overs he begged and borrowed from friends but it worked. He had to run Premium in it because it only had 12cc dishes in the pistons and the cam was pretty mild. You'd have basically the same setup but with a bigger cam like a Summit 1103 and standard Fel-Pro head gaskets it would probably do OK on 89 Octane. Sealed Power makes a set of inexpensive set of 22cc full dish pistons to keep compression down when using 305 heads. They are PN H580P, I have a new set of them in .030" over but decided to step it up with D-cups ( Pistons! I'm talking about "PISTONS"! ) so I can get decent quench.
Based on the advise from Groucho earlier in the thread, we were actually thinking about leaving the stock 350 cam in it and see how it runs that way first.
The bad thing is we won't really know the difference between stock and the different heads because never will drive it before engine installed. I guess if we are happy w/it we will leave it and may upgrade the cam if needed later on.
I have some kind of Super Chevy book about random Small Block Build-ups. They actually found the compression on one of the Goodwrench 350's with dished pistons and 76cc heads was around 7.6:1. A local guy has a 70's 350 with stock 305 heads, headers, Performer intake and edelbrock carb with a stock cam. Its his daily in a 70 Chevy pickup, and he runs cheap pump gas in it and drives it everywhere.
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