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Re: Too big of a cylinder head...
Posted: Tue Jan 30, 2018 9:32 am
by MadBill
Tighter LSA supports more overlap flow, which is important to feed the scavenging of a good header and exhaust system. With virtually all production systems of the era, such was not the case. However the early Z28 cam for one was optimized for open headers and with stock exhaust lost significant power compared to the later cam (which also had to be civilized enough for duty behind an automatic).
Bottom line, if the designers were targeting as-built vehicle performance, the overlap/LCA was likely to be wide, but if they were looking ahead to being competitive in various stock/near-stock race classes, not so much.
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 7:14 am
by bigpoppapreston
More head, less cam.....less cam all over. Look at a modern day LS engine. Huge heads, huge valves, baby camshaft.
[/quote]
No doubt. Look at the G5X3 camshaft for they use in stock bottom end 346 cid combinations. That cam specs at 234/242 @ .050 and I believe. 620/.620" lift on a 112+2°. With TFS 215 or AFR 215 heads, those little engines have made 500 rwhp through a m6. What's that...~570 hp at the flywheel? Very easy, cheap horsepower with only 11.5:1 compression.
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 8:25 am
by Orr89rocz
bigpoppapreston wrote: ↑Wed Jan 31, 2018 7:14 am
No doubt. Look at the G5X3 camshaft for they use in stock bottom end 346 cid combinations. That cam specs at 234/242 @ .050 and I believe. 620/.620" lift on a 112+2°. With TFS 215 or AFR 215 heads, those little engines have made 500 rwhp through a m6. What's that...~570 hp at the flywheel? Very easy, cheap horsepower with only 11.5:1 compression.
That is by no means a baby camshaft
I think Mr. Straub is refering to the later model gen iv ls stuff that has 376" with 2.165" valves and 350 cfm ports with cams in the 200-210 deg at .050 and mid .550 lift if that much, and make 430 hp with all factory restrictions and more so with simple bolt ons. I have a friend with a 2010 camaro ls3 that dyno'd 424 whp on a stockcam and heads ls3 with just headers dual exhaust and a tune
But i have to wonder how effective that recipe would be for a sbc for instance. Throw on a 2.08-2.10" valve afr 220-227 head on a street 355-383 with a 210 deg hyd roller. Will it be as snappy as the 6.2 ls stuff? 23 deg vs 15 deg stuff
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 8:29 am
by kimosabi
I quite like the big head small cam stuff. Better that than small head big cam. I''m building a street 355 now, looking for 220 heads for it. Smaller cams makes happier valvetrains is my theory.
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 9:46 am
by Frankshaft
No such thing as to big a cylinder head. If you find you have a cylinder head that is to big, you just didn't build a big enough short block under it.
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 10:19 am
by lekid
Frankshaft wrote: ↑Wed Jan 31, 2018 9:46 am
No such thing as to big a cylinder head. If you find you have a cylinder head that is to big, you just didn't build a big enough short block under it.
Ain't that the truth!!
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 10:20 am
by hoffman900
lekid wrote: ↑Wed Jan 31, 2018 10:19 am
Frankshaft wrote: ↑Wed Jan 31, 2018 9:46 am
No such thing as to big a cylinder head. If you find you have a cylinder head that is to big, you just didn't build a big enough short block under it.
Ain't that the truth!!
Or spin it higher.
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 10:56 am
by SRS_Chris
hoffman900 wrote: ↑Wed Jan 31, 2018 10:20 am
Or spin it higher.
My thought exactly.
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 12:17 pm
by Bos's5.0
I have a fun little 5.0 non racer with ported TW 170's that flow right at 299@.600 lift and a XE258HR-12. I love that thing except the cam/valvetrain is super noisy.
Anyways, that is almost 1cfm per cubic inch and it is fun, very streetable, revable motor. With that thinking, does the 1:1 scale up? Could a person do basically the same thing to a 454 BBC and run a 450cfm head with a tiny cam and end up with a killer, highly streetable combo? If that scale holds, it shows just how ungodly inadequate most big block heads really are.
Re: Too big of a cylinder head...
Posted: Wed Jan 31, 2018 4:22 pm
by Frankshaft
hoffman900 wrote: ↑Wed Jan 31, 2018 10:20 am
lekid wrote: ↑Wed Jan 31, 2018 10:19 am
Frankshaft wrote: ↑Wed Jan 31, 2018 9:46 am
No such thing as to big a cylinder head. If you find you have a cylinder head that is to big, you just didn't build a big enough short block under it.
Ain't that the truth!!
Or spin it higher.
That too!! Lol. I was just teasing really, but it's true
Re: Too big of a cylinder head...
Posted: Sun Feb 04, 2018 8:20 am
by racin69z
Orr89rocz wrote: ↑Wed Jan 31, 2018 8:25 am
bigpoppapreston wrote: ↑Wed Jan 31, 2018 7:14 am
No doubt. Look at the G5X3 camshaft for they use in stock bottom end 346 cid combinations. That cam specs at 234/242 @ .050 and I believe. 620/.620" lift on a 112+2°. With TFS 215 or AFR 215 heads, those little engines have made 500 rwhp through a m6. What's that...~570 hp at the flywheel? Very easy, cheap horsepower with only 11.5:1 compression.
That is by no means a baby camshaft
I think Mr. Straub is refering to the later model gen iv ls stuff that has 376" with 2.165" valves and 350 cfm ports with cams in the 200-210 deg at .050 and mid .550 lift if that much, and make 430 hp with all factory restrictions and more so with simple bolt ons. I have a friend with a 2010 camaro ls3 that dyno'd 424 whp on a stockcam and heads ls3 with just headers dual exhaust and a tune
But i have to wonder how effective that recipe would be for a sbc for instance. Throw on a 2.08-2.10" valve afr 220-227 head on a street 355-383 with a 210 deg hyd roller. Will it be as snappy as the 6.2 ls stuff? 23 deg vs 15 deg stuff
I have wondered the same thing. My .060 350 engine for my blazer is apart now and i really want to try my pro action 220s on it. Ive about talked myself back into the vortec heads. My cam is going to be a hyd roller in the 200s-2teens @.050 on the intake depending on which one i use.
Lynn
Re: Too big of a cylinder head...
Posted: Tue Feb 06, 2018 12:34 pm
by cv67
kimosabi wrote: ↑Wed Jan 31, 2018 8:29 am
I quite like the big head small cam stuff. Better that than small head big cam. I''m building a street 355 now, looking for 220 heads for it. Smaller cams makes happier valvetrains is my theory.
Not sure i would....unless theres no other head to use
Ran one a hair bigger on a solid roller 350 and wasnt happy at all. Course the cam wasnt small either still it was the slowest sbc I ever put together.
Re: Too big of a cylinder head...
Posted: Tue Feb 06, 2018 1:29 pm
by Bos's5.0
cuisinartvette wrote: ↑Tue Feb 06, 2018 12:34 pm
kimosabi wrote: ↑Wed Jan 31, 2018 8:29 am
I quite like the big head small cam stuff. Better that than small head big cam. I''m building a street 355 now, looking for 220 heads for it. Smaller cams makes happier valvetrains is my theory.
Not sure i would....unless theres no other head to use
Ran one a hair bigger on a solid roller 350 and wasnt happy at all. Course the cam wasnt small either still it was the slowest sbc I ever put together.
So basically the half of the puzzle that is the heart of the idea (small cam), you ran the exact opposite and now are recommending somebody NOT do something because you did the exact opposite and got the exact poor results anybody would expect?
It's like not recommending a 2 barrel carb because you couldn't get your hilborn 8 stack mechanical injection to idle on the street.
Re: Too big of a cylinder head...
Posted: Tue Feb 06, 2018 2:08 pm
by cv67
How many buy a head that big and really plan on a small cam, not many that was my point.
Re: Too big of a cylinder head...
Posted: Tue Feb 06, 2018 4:58 pm
by kimosabi
200-220cc head on a 350+ci sbc isn't really that big. We see a whole lot of people running 195-200cc port volume on 350's running well these days but not that many years ago you'd be ridiculed if you did that. Head development, and not to forget engine building, have evolved. It's not the small GM castings with a huge cam anymore. With the older heads you had to run a big cam, help the cylinder fill any way you can. Bigger ports pretty much all you have to worry about is to keep the speed up and that's where a good cam grinder comes in. Major benefit is the valvetrain happiness.