Question: Your buddy just gives you a 350 to replace your stock 305. Sounds good so far. The 350 has 305 heads (58cc) then he gives you a set of 350 heads (76cc). Since the whole outfit is free which way do you go. I was thinking keep the 305 heads and polish the s**t out of them to get the biggest bang out of them. What to do?

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"It's not about going fast all the time; It's knowing you can, anytime"

 

I'd use the 350 heads. I don't think you'd ever get the 305 heads to flow as well, and if you were going to make that much of an effort, you might as well do it on a better-flowing head.

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1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles

 

I'd stick with the 350 heads too. The 305's have a smaller combustion chamber, and this will give you a higher compression ratio, but the smaller valves and more restrictive flow rates will do more harm than good.

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Rob
'86 TA 305 TPI

 

I've corresponded with one individual who saw my website and my efforts to port the 305 head. He too, has ported 305 heads (416 casting). In addition, he has flow data! What his email shows is something sorely lacking in most internet postings on this site: Quantifiable data. Based on his comments, there are good gains to be made on those 305 heads. You will, however, probably require a flow bench to find them. I, myself, have 25 hours of time into my heads, and my 305 is now knocking really close on 13's at 101 MPH. I have a lot of tuning to do until then!

Another case in point: Mr. Ken Dye, an A/Stock racer in Chicago, is running a 305 engine with solid roller cam, and 305 heads. His 305 dynos at 380 horsepower! Now, to be able to build that kind of power means that his cylinder heads MUST be flowing good air, regardless of displacement. I think you can run the 305 heads; however you again will need to port them.

Lastly, in the early nineties, Summit Racing Equipment used to offer their own Summit crate engines. They sold a 300 and 325 horsepower 350 engine that used a 2-bolt main, hydraulic flat tappet cam, and SUMMIT prepped 305 heads! These bargain basement priced motors were selling for less than $2K. They used the 305 heads probably in an effort to boost compression ratio and keep port velocity high.


Check out this email excerpt by Eric Hodges(mailto:hodgesel@yahoo.com):


Hi Dan,

Finally, someone interested in 305 heads. I have a friend that built a flow bench in his garage and was willing to measure for me. I replaced the 2-barrel heads on my antique 283 (bored to 292) with casting no. 416 305 heads. The 283 heads flowed 145 cfm and the stock 305's flowed 165 cfm.

I have enough grinding time in the heads that my wife accuses me of grinding just to pass the time. I'd guess 60-80 hours. I would grind, have them flowed, grind more, flow, grind, flow..... My buddy's patience wore out. The big hitters for flow were the floor and short side radius, and the wall against the other intake port. The floor got lowered a bunch and the radius flattened as much as I dared. The common wall got straightened - there was a bump. When the grinding dust
settled, I got 195 cfm out of them. Whew!

Just for reference, stock camel hump heads with 2.02 valves only flowed 205 cfm on his bench. I was very pleased because my 305's still have the stock 1.84 valves and 165 cc intake ports (small). The camel humps were
195 cc, I think.



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Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Turbine Technologies 2500 stall converter, underdrive pulleys, Crane Hi-6 & more.
1.05g skidpad verified.
New best E/T! 14.039 at 100.82 MPH in 41 degree air at Stanton, Michigan.

 

My friend has an Elcamino with a 350 with 305 heads and it didn't do 11's 'till he put the 305 heads on.

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...

 

IMARK, from what I've read about the 305 heads on a 350 they will cause your compression ratio to go well over 10:1. For street use this is bad. You will have to use higher than 93 octane or your engine will have detonation (pinging) and may cause overheating. I'd stay with the 350 heads or if you can find a pair of 64cc heads thats even better. Old vettes may have them. If your gonna race this engine then go with the 305 heads if you have access to VP racing fuel (usually over 100 octane)

 

How about putting the 350 heads on the 305? Is it doable?

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Mods:Hooker Aerochamber 3" exhaust, gutted kitty,
March 2 piece underdrive pullies, smog pump gone,
14x4 K&N, 3.42 gears,
Eibach springs with KYB's all around.
Appearance: Harwood cowl hood, Z-28 wing, painted black(7/20/00)-original color was light blue
*All these mods were made this year
Stock Options:120,000 miles on motor, 5spd, TBI, 305, T-tops
Run a best of 16.7 @85mph before gears

 

NO!, the compression would go down far to much, it will be a good 9.4 or so on the 350 so you can imagine what it will do to the 305s compresion. You would have to mill them to hell then correct the incredible amount of milling(which will never correct the compresion, being that they are 76cc/you can only go so far) then you have to mill the intake manifold. So no not possible.

 

Thanks guys for all the replies, although you were about evenly split on the 350 w/305 heads issue.
Guess I'll try the 350 (624) heads and see if I can get the deck near zero and pump the compression up a little and mabye take advantage of the better flow.
Now what to do with the 416's?
Thanks again

 

go with the 350 heads besides 624 are pretty good flowing heads. far better than any CRAPY 305 head could flow.

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when the green flag drops the bull$hit stops

350,performer RPM intake ,650dp, 700r4, headers, 3inch exhast

 

it is possible to get the 305 heads to flow OK, but why bother??

If you want high compression and using stock pistons just shave the heads a few thousands and/or use a very thin head gasket. I believe a .022 thick head gasket can raise your CR almost .3 points...you'll have to get shortened pushrods, but it should be worth it.

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1982 Camaro Z28

trying to make it worthwhile for the spring....

Check the website for progress http://members.fbody.com/Pro82Z/