[Barry H]

Looking for some input everyone. Putting together a 355, 10-1 compression, 280H cam. my question is how much higher compression would I get by decking the block to zero? Also I've read articles about placing small chamber 305 heads on a 350, how does this work, and what advantage would that give (if any) over a normal 64cc chamber (2.02/1.6)? Any suggestions will be appreciated. Remaining powertrain is PG w/2500 stall and 4.10 gearing in RS/SS convertible 67. Thanks

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[Crash]

I've got a 350 with the 305 heads(cast#601).The buider who put my engine together said they would give me 10.3 to 1 with flat tops and a ton of torque right off the line. He was true on both counts. The problem is that the small valves run out of flow starting around 4000RPM.Of course by then your probably speeding anyways.I'm considering going to a larger aftermarket head that flows well at low AND high RPM.I've read many articles on cams and the best all round cam is Comp Cams 268H or Extreme Energy 268. Best combo of HP and Torque that tops out at 5500RPM. You'll only get the benefit of a bigger cam if you're going to take it to 6000RPM or higher. You'll have to decide how often you're going to go up there and build your engine to suit.Again the bottom line on the 305 heads, cheap way of raising compreesion and torque.

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74 Camaro

[BillK]

Barry,
Crash has described it right on the money. We tried a set on a dirt track 355 that has to use stock heads. It made a bunch more power coming off the turns but was out of breath about 3/4 of the way down the straight. Stick to the 350 heads so you can use the larger valves.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

[tom3]

Decking the block is a little better than cutting the heads since a portion of the head surface is flat anyway. Figure your deck height is now about .025 so going to 0 would give about a quarter point on the compression ratio I'd guess. Have to calculate it all out to be sure.

[68'camaroguy]

What casting number are you guys talking
about on thse 305 heads?
Do you mean the "601" castings? I just
wanted to know.

[68'camaroguy]

are you running pump gas with the modified "601" heads or are you using any fuel additives? I am concerned with pinging and/or detonation.


[This message has been edited by 68'camaroguy (edited 02-07-2000).]

[68'camaroguy]

[JimM]

I'd stay far away from the 305 heads on a 350. If you need something cheap, think about late model truck or camaro junkyard heads. The chambers are small to give you lots of compression, but the chambers are a better fit to the bore and the ports and valves are a lot bigger than 305 heads.

[Barry H]

Thanks everyone, I think I'll stay away from these small chamber heads. Barry

[Crash]

Well, this just in. I was just about convinced of the complete unsuitability of the 601 heads when lo and behold, an article in a new magazine. It's got a greenish cover and it's a compilation of several magazines.The last article in the book talks about these exact heads.Just to give you a digest version.Cheap compression,plentiful in boneyards and flow really well even with the small valves if they are ported and gasket matched to the HEAD gasket. Great heads under 5000 RPM with gobs of torque for stoplight to stoplight motoring.Very interesting article!

[Go69]

Crash,
I was running these very heads on a 355 with a Performer RPM, Holley 650 DP, 224 @ .050"
cam w/443 intake, 465 exhaust. I switched to the 305 heads while I was porting, polishing, and rebuilding my #186 fuelies. When I put the 305 heads on I was blown away by the difference! I took these heads from the junkyard, cleaned them up and bolted them on with no mods and they stomp my fuelies up until 4500-5000 rpm's. How often do I run over 5000rpm? Not often. I am considering selling my #186 right now and continuing to use the #601's. Really strange how switching heads can pull out that much torque.

[Crash]

GO69, sounds like you can help with a small dilemma I'm having. Same old, Same old, which cam.I'm down to 218 @ 050 or 224 @050?How do you like the 224 for performance and idle? Were you running a manual; or auto.I'd already chosen the rest of your combo pieces already. Thanx in advance.

[MarkTaylor618]

I have been reading your old posts on the 305 chevy "601" castings, I have done a lot of dyno and flow bench testing on these heads, and I can say that these heads work well on any 350 if done right. the best combo for the street is to install a 1.94 intake valve (a 2.02 wont go, the chambers are too thin when unshrouded) and a 1.60 exaust valve. the exaust valve should be set lower than the intake to promote scavenging, and help to keep fresh mixture from blowing into the exaust port during overlap. the Exaust ports seem to be the problem on these heads, it is very restrictive. bowl blend the intake and exaust under the valve seat,also narrow & raise the exaust guide boss, and raise the roof in the exaust port....for the street the intake port needs nothing more than port matching at the entrance. the bigger valves need unshrouding on the chamber side of the valve, you will gain a few cc's chamber cutting for this, but you can still keep it down to 60 to 61 cc's, and if milled, you can get them back to 58 cc's. the intake port will have high velocity for good mixture, and low end torque, and these heads have great quench, and great port swirl for the street, or mildly modified race engines. since the quench is so good, it is possible to bump the compression up a little higher on the street with pump gas. it is possible to run as much as 10.9:1 compression on pump gas if you keep the timing at a manageable level,and run flat top pistons......although I really dont recommend this, but it is possible.
with a fully ported and modified set of 601's,I have built a 355 chevy that produced 434 HP., and 490 lb. torque at 5300 rpm, and made no less than 350 HP up to 7000 rpm. these heads produce a broad tourqe & HP curve throughout the rpm range. And as for dirt track cars....I have won 4 track championships with these heads. so I must be doing somthing right! hope this helps some.

Matk T.

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Mark's Racing Engines
7700 cr3522
Quinlan,TX,75474
(903)883-0196