[buzz1961]

I have a 350 that has a set of 305 heads( #376450)with 350 valves.It also has a ultradyne 276 cam 454 lift,and trw 2256 forged pistons.I have a performer intake.I plan on headers and probably a 650 carb. Any ideas about what my compression would be? Will the 305 setup be OK? What kind of hp ?I'm not going to race or rev above 5000rpm. Just cruise.I bought the engine with little time on rebuild.Going to put it in a 68 Camaro

[6426yy]

I just put 305 heads on my 350 this spring for my pickup, real tight budget!!
I had the dished stock pistons though, and a GMPP cam 212/222 @ .050 435/460 lift, edelbrock streetmaster intake and a 600 holley with headers and 2.25 duals with flowmasters. The single plane intake is surely hurting low end torque but all in all the engine runs better than I had expected.

Make sure you have the 350 head gaskets on it and you'll be fine. As for power I couldn't tell you some one on here mentioned I'm porbably making around 300 lb/fts. You're probably a little shy of 10 to 1 with the flattops according to Flatlander Racing's website they claim with your pistons and 58cc heads 10.27:1. Let us know how it works out. For a budget these arn't bad engines.

[1FST4DR]

My dad has a 65 Pontiac Acadian Canso with a 350 quite done up, dont know the specs but its over 450hp for sure, he told me that back in the day he tried 305 heads on his 350 and it kicked *****, he said it would go through head gaskets every couple months though. that was a while ago though, maybe gaskets have changed since then, but if anyone knows if 305 heads on a 350 is possible without going through gaskets id like to know too thx, Tim

[WakBordr7387]

Ive used 305 heads on a 350 for my truck before.
Ran good for the budget I was on. I was using the stock flatop pistons. Only time I had any pinging or detonation was from timing being off. Of course I also had a big cam to bleed some of the pressure off to.
I never thought about the head gaskets blowing out on an engine like this being a problem for other people to. Mine blew a head gasket before, I thought I fixed the problem. Until a few months later when it blew again and had quite a bit of compression in the radiator (like the overflow tank looking like ol' faithful )
Personally I wouldn't do it again. I only did it because I was on a budget and the 350 heads I had were crap to begin with, and the 305 heads were in great shape.



Brad

[lanierledford]

I had a .040 350 with flat top pistons with 305 heads with 1.94 valves. pinged bad with 93 Oct. gas. Run about 100 mi. and started skipping bad. Tore it down and the first two pistons ( 1 and 3) were cracked from the top of the piston down to the top ring ( broken off in spots). I was told that the comp. was to high (heads were 58 cc) also used shim head gaskets. Changed to new flat top pistons and went to 73 cc 350 heads with 1.94 intake valves with a lunati hyd. cam 00016 with 1.6 rockers and it barks the tire when it shifts( 700r). Alum (chevy ) intake with qua. carb. and headers with 2.5 exhaust pipes ( flow masters) .

[Mustangsaly]

what about the 305 votec heads ? what are they like on a 350 ? any advice from someone that has used them would be great.......



Thanks




Mustangsaly

[1FST4DR]

Lanierledford, sorry to hear about your problems with the pistons i have a 350 also bored.040, i run 87 octane, I have hyper eutectic pistons, stock 882 350 heads with 1.5 roller rockers, i have a hydraulic cam thats rated at 300 hp from a corvette, performer intake and a crappy old 6sumthin holley carb and headers also, if you look in my pictures youll see that i drive an old Grand LeMans 4 door Grandpa car! it barks the tires too, just thought id share that info with ya..id say keep 350 parts with 350s and 305's with 305's, cant go wrong...happy motoring

[modelawoody]

Hey Buzz, I've heard all kinds of myths about putting 305 heads on a 350. I build engines professionally. Untill I moved about a year ago I was building up to two 350s with 305 heads a month. Never had a problem with any of them. With a standard replacement type flat top piston a 350 with 305 heads will have 10.22 to 1 compression. Thats about as high as you want to go on a street motor. 305 heads are cheap horsepower and work great on a 350. I guarantee you it will blow the doors off a 350 with open chamber 194s. As for you guys who had problems, could it possibly have been something else?

[jimchevy]

I've always heard 305 heads don't flow well at all and weren't worth the trouble on a 350.

[Rhansen]

Friend of mine did an 86 Monte SS with a set of late model camaro (1987 305) heads on a 350. It made all the right sounds (chirp tires on a gear change, slight lope at idle) but would lay down bad at around 4000 rpm. I got the stopwatch out and timed it 0-60, took a little over 9 seconds - not too impressive in my book.
My understanding is that the 416 casting is the best 305 head to use, but I would rather use vortecs or aftermarket heads any day.

[buzz1961]

What would be a good option instead of the 305's. Would like to keep cr down some. What are advantages of aluminum heads?

[bigbadbowtie]

advantages are.....
easier to repair when it comes apart at 7k.
usually can run 1 more point of compression on pump gas.
lighter by quite a bit.

[machine shop tom]

The head gasket problem is from detonation and/or pre-ignition.

Putting 350 intake valves (1.94") into the small chamber (55cc) 305 heads will not increase breathing because the intake valves are extremely shrouded. The 1.84" valves probably breathe as well or better.

Putting 305 small chamber heads on a flat-top 350 (L2256F-30) yields a comression ratio around 11:1 compression.

Putting 305 larger chamber heads (62.5cc) on a flat-top 350 (L2256F-30) yields a compression of 10.1 compression.

The biggest problem I see with using 305 heads on a 350 is the compression ratio being too high for the application and the fuel/timing combination. Also, too many guys run a "torque" type cam with this combo and run into head gasket and/or broken pistons, etc. (sound familiar?).

Putting 305 heads on a 350 is a quick way to increase compression, but there are better heads for getting decent power from a 350.

tom

[modelawoody]

Machine Shop Tom, I'm the only one who mentioned the word "myth" so I'm assuming your comment was directed at me. I have heard all of the same things about 305 headed 350s. Exactly how many 305 headed 350s have you built? Have you experienced these problems personally? I built one that ran 13.20s at Mission Raceway, Mission B.C.in a '70 Nova with, flat tops, mild cam, dual plane intake and headers. Ran a full season before I lost contact with the customer, No Problems. Also built one that I personally ran in a '78 Regal which went 13.60s, at Eagle Motorplex, Ashcroft, B.C., then installed the motor in a customers '87 S15 Jimmy, again no problems. I built and installed these motors in too many cars list, No Problems. Maybe I hallusinated the last 10 years of my life. Oh by the way, have you heard of a little company called Summit? I used get their catalogues. All of their lower budget engines ran 305 heads on 350s. Also the compression ratio I gave in my last thread was calculated by cc ing the head, measuring the deck height, gasket thickness, cc ing the valve reliefs, with a replacement type flat top piston and 58cc heads, composite head gasket, this was not a guesstimate or something I read somewhere. modelawoody.

[xntrik]

Big valves should be unshrouded .200 minimum or to the cylinder wall, whichever comes first. This will remove a little metal for lowering the compression also.

The right 305 head massaged gently works well on 350s.

Qustion is..... at what point do the Scoggins-Dickey modified Vortecs for $ 620 pair ready to run start to sound like a bargain?