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Old 08-15-2011, 01:09 AM   #1
metricmania
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Default Best stock SBC head?

OK, for my class of racing, I have to use stock, unported heads. I can change valve size. I can't use Vortec heads, but can use any thing else. Right now, I have camel hump heads. I find that they can rev up to about 6000 RPM and after that, they start to fall flat though RPM does still increase, just not as much as 3000-6000.

My engine is a 355. Stock intake and exhaust.

What could I expect if I put some 305 heads on there with big valves? I can do machine work 1/2" above the intake seat, not sure if that would help with making a 305 head work or not.

I heard 305 heads fall flat after 4000 RPM is that true? What about if they have bigger valves? The reason I'm considering 305 heads is for more compression. I heard the 601 casting is a good head, and it would bump my compression up by 1 full point. But it won't help unless they rev up to 6000 RPM (I'm hitting 6500 RPM at the end of the straight).
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Old 08-15-2011, 01:45 AM   #2
JeffB2
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Default Re: Best stock SBC head?

It could be your valve springs and lifters causing your problem,in your class it is common to use "cheater" valve springs like these: http://cgi.ebay.com/ebaymotors/SBC-C...#ht_3510wt_951 they are stock diameter and you will be able to use the stock retainers and look "stock" if you are using a hydraulic cam OEM type lifter they will "float" at the RPM you are running,solution is swap to the Rhoads RHL-8178 lifters these are anti-pump-up and have a little extra advantage below 3500 RPM they increase torque which will pull you off the corners faster.Do not swap to the 305 head to use the larger valves it requires "bowl hogging" to unshroud the valves to do this is a waste of money for the gains you might get from it and some 305 heads being a thinner casting are prone to cracking.
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Old 08-15-2011, 02:02 AM   #3
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Default Re: Best stock SBC head?

Is Extrune honing legal? Tappered valve stems? Sodium filled valve's? Roller rocker or tipped ones?
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Old 08-15-2011, 05:33 AM   #4
big duece
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Default Re: Best stock SBC head?

1960-63 "461X" castings have a larger than normal intake runner
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Old 08-15-2011, 10:15 AM   #5
Homespun91
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Default Re: Best stock SBC head?

The old school solution to those class rules was, as big duece noted, 461X heads; their intake runner volume is 10cc + larger than the 461 (no "X") heads. They are relatively hard to find, but still out there.

The first place I would start is to use 2.02 or 2.05 valves on the intake, and 1.6 on the exhaust, if you aren't already. These won't have much effect unless you have the port throat opened up to roughly 90-95% of the actual seat diameter; fortunately you can work with that 1/2".

If you are allowed to modify the chamber, by all means have the chamber "swept" with a side mill around the intake valve. Though you will slightly increase the chamber size, you'll get greater benefits by unshrouding the intake valve. If you are running 4 valve relief pistons, get rid of them and use 2 relief pistons; you'll compensate for the sweep and you'll increase your compression even more as a result.

If permitted, I would use reduced diameter ("necked down") stems, or even go to a smaller diameter stem & guide. If allowed, have the bowl end of the guides shortened so they don't protrude from the guide boss- though be aware that you may get much shorter guide life as a result. Set the guide clearance as tight as you can reasonably get it to help this.

I agree with Jeff about the 305 heads...

If they don't have to be "production heads"...just "Chevy heads"...you can switch to Bow Tie heads or even the old 292 "Turbo" heads and pick up some gains, though for a claimer engine it may not be cost effective.

Lastly...if you're sneaky as Dick Cheney...peruse this: http://www.castheads.com/

And yes...they are that good.
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Old 08-15-2011, 12:28 PM   #6
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Default Re: Best stock SBC head?

If things are falling flat at whatever rpm, perhaps you should consider switching cams to find one that better suits the rpm range that you are trying to run in? The same thing applies to everything else too. Manafold design, carb sizing, exhaust restrictions, etc. If you are stuck using stock heads then you are probably limited on what intake you should use too. The cast iron Z28 style is suposed to be as good as it gets for a "limited" engine.
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Old 08-15-2011, 12:41 PM   #7
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Default Re: Best stock SBC head?

Post up what valve springs you are running, maybe your springs at done at 6k. Then again, post the cam too.
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Old 08-15-2011, 01:47 PM   #8
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Default Re: Best stock SBC head?

Quote:
Originally Posted by Pro Stock John View Post
Post up what valve springs you are running, maybe your springs at done at 6k. Then again, post the cam too.
I was actually thinking that I may not be the heads that are done @ 6K it could be the engine.
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Old 08-15-2011, 01:57 PM   #9
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Default Re: Best stock SBC head?

Quote:
Originally Posted by porknbeaner View Post
I was actually thinking that I may not be the heads that are done @ 6K it could be the engine.
Exactly, we know nothing about this deal. Lippy
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Old 08-15-2011, 02:08 PM   #10
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Default Re: Best stock SBC head?

He says that it will turn 6500 at the end of the straights, and that it will still rev at 6000, just not as easily. If he was having serious spring issues, i.e. spring harmonics or valve bounce, it probably wouldn't be capable of turning 6500...or at least not very many times.

Factory SBC heads have fairly weak intake port flow and this is a fairly common symptom. A different cam might help, depending on what he has now...but then again it might not.

I'd like to see more details of the cam, intake manifold, and exhaust system...if he cares to share...he asked specifically about cylinder heads.
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Old 08-15-2011, 02:51 PM   #11
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Default Re: Best stock SBC head?

There are other heads that will flow but those heads will run well over 6 grand. Carb, intake, cam, etc as posted earlier would be a big help. If you don't have the components to support bigger valves they won't help.
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Old 08-15-2011, 05:53 PM   #12
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Default Re: Best stock SBC head?

I've run OT LS1 engines to 7200 with a hydraulic cam, and we ran spring pressures that traditional SBC guys said were too much. I'd be curious to hear the spring package, there are lot of really good springs out there.
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Old 08-15-2011, 06:03 PM   #13
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Default Re: Best stock SBC head?

my vote would be
1970-73 LT-1, Z-28 and ANGLE PLUG CYLINDER HEADS
(Chevy Part No. 3965742)

if I remember correctly they used the same head on the 302 engine that would rev forever
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Old 08-15-2011, 06:48 PM   #14
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Default Re: Best stock SBC head?

I like the "492" and "292" angle plug heads...
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Old 08-15-2011, 06:56 PM   #15
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Default Re: Best stock SBC head?

I like the 39711 heads good for uper RPM
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Old 08-15-2011, 07:20 PM   #16
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Default Re: Best stock SBC head?

Quote:
Originally Posted by Deuces View Post
I like the "492" and "292" angle plug heads...
turbo heads....old school over the counter race castings. big thing about finding a stock casting ....old heads are out there , finding a pair of virgin castings might be possible , and probably costly.....used castings are probably on the 4th or 5th life cycle by now.....a pair of 186 or 041's might be another vintage possiblitly

how much work would be involved in trying to use a set of steel late model lt1's.... supposed to be where the vortec evolved from.
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Old 08-15-2011, 07:26 PM   #17
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Default Re: Best stock SBC head?

We had a class limited to 360ci and stock heads with no porting. They would allow larger valves and milling. We ran 2.02-1.6 valves, I unshrouded the chambers like Homespun91 explained, and anglemilled the heads .125 to get the chamber volume down. The angle mill also tips the intake runner a little in the right direction for better flow. I'll take 12 to 1 with a flattop over 13 to 1 with a dome any day!! Lightweight 2 valve releif pistons are a must both for durability, and the lightweight helps the engine rev quicker on starts and comming out of the turns.

Maybe I missed it, but what are you running for a carb?
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Old 08-15-2011, 07:45 PM   #18
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Default

186 camel humps came on the DZ 302's and have the advantage of accessory bolt holes in the end if you need them. There were some different varieties of 186's though so watch for them. Some had screw in studs, & 2.02's while others had press in studs and 194's. Later
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Old 08-15-2011, 08:42 PM   #19
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Default Re: Best stock SBC head?

I swiped this from his other thread.....
"I have the following:
462 camel hump heads
355 C.I. small block chevy
flat top pistons, 10:1 compresion ratio
camshaft: 106 degree LSA, 250 degree duration at .050"
165-180 cranking PSI in all cylinders.
Quadrajet, stock intake, exhaust and heads, no porting (it is on a circle track street stock and those are the rules)."


This is just my .02 from 20 years of turning left on dirt..... I have won in hobby stocks with smog heads, I have won with 305 heads. Have never used double humps. The 305 heads were awesome (casting 14014416) and Z28 springs (no port work, stock valves) with a 355 flat top solid or hyd cam. Solid cam was a pretty big cam (Speedway Motors' 2 barrel grind) with QJ and open tube headers...would turn 6800 rpms all day. Hyd cam was was Lunati Voodoo and also would pull 6800 rpms with no probs, but was more a torque cam and was run with a holley 500 and stock log manifolds and flowmaster mufflers. The lunati had a ton more lift and duration on the exhaust side. I always ran 38 degress total advance autolite 26 and HEI. Its racing remember...good cooling is a must, free flowing exhaust and plenty of maintenance and attention to detail. Make sure your ignition system (that means every part of it) is in perfect working order. Have your carb guy tell you how to tune the secondary butterflies and the importance of your secondary metering rods and hangers.....ask him he will know...at least he better. I dont think your heads are your problem, I think its a tuning or valve train issue.
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Old 08-15-2011, 08:45 PM   #20
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Default Re: Best stock SBC head?

oh and remember to check this site.....http://www.thedirtforum.com/
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Old 08-15-2011, 08:58 PM   #21
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Default Re: Best stock SBC head?

882 &993 Heads have as good flow as the 292 heads
but the chambers are not good at 76cc's. If angle milling is legal
that would get your compression back up to where it would be with
With the 64cc's of the double humps. They are cheap, plentiful,
and some had 2.02, 1.6 valves. Most had 1.94, 1.5.
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Old 08-15-2011, 08:59 PM   #22
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Default Re: Best stock SBC head?

Anderegg just said everything I couldn't remember from racing circle track, 305, bombers. Sounds exactly like our set-up. Stock bore, 305, factory heads, HEI, tweaked-out 2-Jet, same timing, stock manifolds, no mufflers, .420 lift cam.... Would turn 6500-6800 RPM at the end of the straights, no problem. One engine I built lasted nearly 5 seasons and it only broke after a hard hit.
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Old 08-15-2011, 09:09 PM   #23
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Default Re: Best stock SBC head?

[Heres your answer.
QUOTE=Deuces;6859032]I like the "492" and "292" angle plug heads...[/QUOTE]
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Old 08-15-2011, 09:17 PM   #24
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Default Re: Best stock SBC head?

Stock bore? A 355? LOL. You already bumped the comp when you bored it ,030. Lippy
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Old 08-29-2011, 01:22 AM   #25
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Default Re: Best stock SBC head?

Sorry guys, I wasn't keeping up with this post.

Cam is: Howards 110812
Basic Operating RPM Range2,500-6,500
Intake Duration at 050 inch Lift248
Exhaust Duration at 050 inch Lift252
Duration at 050 inch Lift248 int./252 exh.
Advertised Intake Duration286
Advertised Exhaust Duration294
Advertised Duration286 int./294 exh



I've used a few carburetors from different builders-car acts exactly the same. HEI ignition with pertronix flame thrower coil and module. 36 degrees total timing.

Valve springs are: Isky 8205, seat pressure is 160 lbs and it's close to 390 on the nose. My machinist picked out these springs and I didn't reealize I was running that much spring pressure.

Pushrods are supposed to be good up to 500 lbs.
screw in studs and guideplates. stock stamped rockers.


Well, right now, I have my motor half apart because I was told by numerous people, I'm running way too much cam for my car. I'm going to put Comp # 12-646-5 in there now with matching valve springs.

Valves are 1.94/1.60
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Old 08-29-2011, 01:58 AM   #26
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Thumbs up Re: Best stock SBC head?

Quote:
Originally Posted by man-a-fre View Post
[Heres your answer.
QUOTE=Deuces;6859032]I like the "492" and "292" angle plug heads...
[/QUOTE]
Thanks Man!!
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Old 08-29-2011, 07:59 AM   #27
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Default Re: Best stock SBC head?

How about the early cast aluminum "recall" heads from the early '60's... Those were recalled because of porosity issues...
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Old 08-29-2011, 08:04 AM   #28
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Default Re: Best stock SBC head?

Quote:
Originally Posted by Deuces View Post
How about the early cast aluminum "recall" heads from the early '60's... Those were recalled because of porosity issues...
All right if you really luck into a set, but the only ones I've ever seen came with an asking price in the $2500 range.
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Old 08-29-2011, 08:24 AM   #29
Deuces
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Default Re: Best stock SBC head?

.....Yikes!!

Does anyone have pictures of those??? I think I read an article once that people were bolting those on the 283/315 hp fuelie Vettes back in the day... Or, they were a factory installed option..
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Old 08-29-2011, 08:37 AM   #30
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Default Re: Best stock SBC head?

Quote:
Originally Posted by derbydad276 View Post
my vote would be
1970-73 LT-1, Z-28 and ANGLE PLUG CYLINDER HEADS
(Chevy Part No. 3965742)

if I remember correctly they used the same head on the 302 engine that would rev forever
LT-1's came from the factory with straight plug heads. The angle plug 492's were over the counter heads only.

292's were over the counter heads too.

If these are legal, the "bow-tie" head will be too, and would be a better head.

But all this depends on if the spec is "stock production head" or "OEM casting numbers".
Larry T

BTW, all production 2.02 heads had the chambers milled around the valve as suggested above. The smaller valve "camel hump" heads didn't.
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Last edited by Larry T; 08-29-2011 at 08:43 AM.
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Old 08-30-2011, 08:55 AM   #31
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Default Re: Best stock SBC head?

Quote:
Originally Posted by Deuces View Post
.....Yikes!!

Does anyone have pictures of those??? I think I read an article once that people were bolting those on the 283/315 hp fuelie Vettes back in the day... Or, they were a factory installed option..
They were installed on the assembly line, but so many of them had coolant leakage problems that they recalled them very early in the model year and switched to cast iron. Given that fact, I certainly wouldn't pay the price for them just to try to use them in a non-stock application. The same money will buy you lots better performance elsewhere.
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