187 swirl port or 601 305 heads

[keith nohner]

Just got laid off, in the process of building a 400 with 305 heads because I have them. Should I run the 601 casting no. or the 187 swirl ports. Which head flows better. The only reason I am running them is because I have them. Both head have 1.84 1.50 valve sizes. The motor will have a solid lifter cam, 248. 251. at .050 .531., .542 lift, 106. degree lobe separation, 279, 282 advertised duration, .016 lash . Will run a single plane intake with plenum divider inserted. I know this engine will not breath as good as it would with good heads, but it is what I have laying around. It should have monster torque to 5000 rpm. Any input would be appreciated. How much does a stripped out short box weigh with no bumpers? 3500 pounds would be my guestimate.

[Beefcake]

im certainly not an expert. But i had an interesting conversation with one a few weeks back. I told him i was running trick flows on my 350 looking for more low end torque. He said i would have done better with 1.94s than the 2.02s.

So what im learning is, when your a truck owner, looking for low end torque, you need to go against the grain and bigger isnt better. this makes me wonder if 305 heads are indeed a better choice.

I dont really understand why this is the case. U'd think bigger valves just mean bigger air/fuel= more power....

can someone enlighten us further??

[BossHogg69]

you planning on running pump gas?? that won't happen with 53cc chambers on a 400 SB. The 601's may flow better (only my GUESS), only because the swirl ports have that big hunk of iron sitting in the intake tract, but only a flowbench will be able to tell you for sure. As you know, neither are ideal, and the cam is way to big for those tiny valves & ports. I'm not sure you'll be very happy if you bolt this combo together. A cam that big is just waking up at 5000rpm, and those heads will be strangling that motor by 3500rpm, not to mention using a single plane intake. I know you gotta work with what you have, but selling both those sets of heads to finance a set that may work better with that cam and intake might make you happier in the end.

[D.PASSMORE]

I ran a 350 ci with stock 305 heads for about 8 years. I bought the truck with the motor set up that way. I know the CAM wasn't to erratical because I ran A/c on the engine. Ran / looked like a stock motor until hooked a trailer or load on it. That mouse would pull. I never knew it until I blew a head gasket and took the heads down to have the checked and rebuilt. The machinest said they had a crack in one of them and sold me a set of 882's heads. Never had the reach down power after that. Pulled the the motor and put in a 400 CI.
If you want tourqe, its a good idea, mild cam and a stock intake with Q-Jet. I ran 89 octane and put in 92 when I hauled a load, If not, it would ping a little. Thats my story - Good Luck

[BossHogg69]

Originally Posted by D.PASSMORE

If you want tourqe, its a good idea, mild cam and a stock intake with Q-Jet. I ran 89 octane and put in 92 when I hauled a load, If not, it would ping a little. Thats my story - Good Luck

Thats good advice, but he's got a 248 @ .050" solid lifter cam and a single plane intake, which is not mild by any means. with flattops a 4.125 bore 400 with 53cc 305 heads would be well over 13:1 comp ratio, and that will detonate with any pump gas. no mention has been made to what pistons are being used yet.

[keith nohner]

Pistons are dished production gm, I know I will be hi on compression with the small chamber, I will cc heads on the motor. I will first try 100low lead , and if this doesnt keep it from detonation I will try e-85. This will more or less be a stress reliever, kind of toy, built out of junk I have laying around. Do you think a stripped out short box half ton, No bed floor, no bumpers, no heater core, no inner fenders, basically everything removed from truck that isnt necessary, i can get it to weigh 3200 lbs. It will have 1 3/4 headers, and three inch exhaust. Basically, I had a big block in the works, but due to the lack of a job that will have to wait till this winter. I had purchased the mufflers and tubing for the exhaust for the big block. I know the single plane is probably is the wrong choice, but I am going to make a plenum divider, that I can remove, just to try it. Just finished welding up center holes of the 187 swirl ports. Will re drill straight so I can run a carbureted intake. I think it will be interesting to see how good or bad it runs. Any input is greatly appreciated. Sooner or later I would like to try iron eagle 200cc intake runners with this combo, when times are better. I think it will have tons of torque but sign off by 4500-5000 rpm.

[BCOWANWHEELS]

Can you say hi-compression and alot of spark knock.

[Longhorn Man]

i had 305 heads on a 350 and it needed 93 octain, timed way low, jumped out of the hole OK, but started wheezing by 3200 RPM... which sucked with 4.10 gears since that was my cruise speed.

Smaller valves can help with low end torque by maintaining high port velosity. Kinda like a smaller carb giving you better throttle responce over a big 1000 CFM piece.

[jorgensensc]

I recently installed in a truck for someon a 350 .60 over, with an "RV" cam and 305 heads. She already had the engine, it wasn't my choice. I had a lot of greif trying to get the darn thing to run right. It had high octane gas, way retarded timing, and I still had to run some more octane booster to get it to stop knocking. I definitely would caution against this combo. JMHO.
SHawn