crazeinc

Hey guys...I was thinking about heads for the 350 this morning and I know a few of you like Stephen have used double hump heads that most likely have had porting done to them to help catch up with the past 30 or so years in head design. My question is with an advanced port job on a pair of 68cc double humps, how do they flow as compared to a pair of GM's new Vortecs?

Don't ask me what advanced is supposed to mean, lets just say that a lot of work has been put into them.

I assume that anything like new aluminum edelbrock heads or afr's would hands down out perform these old style heads, but Vortec's are so much cheaper.

Thanks.

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1982 Camaro Z28

trying to make it worthwhile for the spring....

Check the website for progress http://members.fbody.com/Pro82Z/

RB83L69

I'm not Stephen, but I have been using thse heads for decdes, since at one time they were basically all we had... I still have a set of them on my 400.

They could flow better than the Vortecs do out of the box depending on the work that has been done.

All of the "double-hump" heads had 64cc chambers. There are no 68cc ones.

What casting #? As to how much port work has been done, what do they look like? Do they match any gaskets? It's pretty hard to characterize port work over the Inernet I know, but if there's any physical features of the port work you can describe, it would help make an educated guess. What size valves are in them?

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"So many Mustangs, so little time..."
ICON Motorsports

crazeinc

RB, I appreciate your help. For some reason 68cc was stuck in my head. You kinda misunderstood what I said, but that's my fault.

I don't physically have a pair of double humps in front of me, but there are a pair for sale on the for sale board here for $600 that have had work done to them. Heck, I don't even know what valve sizes those come with.

All I really want to know is, if some some older heads like double humps are able to outflow even stock Vortec heads without a $1000 worth of porting done to them. I guess I'm talking 3 angle valve jobs, bowl work, maybe throwing some larger valves in there...

Any thoughts?

I also have some stock 350 heads from a late 70's camaro. I did a casting number check on them a while ago and they're the really bad version (small valves, big chambers), so I don't even want to bother with those.

[This message has been edited by crazeinc (edited January 25, 2001).]

Polecat

I had a set of ported #186 doublehumps on my 383. they were ported and had 2.02/1.60 valves. I liked them, but I was doing a new motor rebuild, and wanted better heads, so I chose the Sportsman's. For $600, I wouldn't do them. I sold mine complete for like $250. For a mild build smallblock, the Vortec's are great for the money, and you could have some port work done on them for what extra you would pay. For a little over the $600,look at the World S/R Torquers. They come in 67cc and can have 2.02's put in. They will be in the area of $750 complete, and be a waybetter head. I think you will like them alot better.

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350 4 bolt main, Speed-O-Motive 383 stroker kit, re-sized rods ground for clearance,TRW Forged pistons,10.7:1 compression,HPC Coated RPM intake, Speed Demon 750 cfm carb,World Products Sportsman II heads,2.02/1.60 valves, Comp Cam 1.6 roller rockers, Comp Xtreme 284 cam,240/246@.050 with .540 lift,Crane pushrods,Proform HEI and MSD6A box,HPC coated 1 5/8 headers, 2.5" exhaust with 40 series mufflers,TH350 with B&M 3000 stall, Powertrax NoSlip Locker, 4.11 gears.

crazeinc

If I spend $750 for some aluminum heads, I might as well spend the $860 or whatever for a pair of Edelbrock Victor Jr. 23*

RB83L69

For $600, sight unseen, I would pass.

Like so many of the other posts, yours included, point out: there are lots of head options out there now. There didn't used to be. Back in the early days of the SBC, about the only thing a street guy could do, was to get a set of double-humps and go to work on them. That was before CNC casting though. It has become possible to make new aluminum heads, with as good specs as bolt hole and pushrod placement will allow, for less money than it takes to work up a set of old cast-iron ones.

Also, don't forget that with the Vortecs, there's more expense than just the heads themselves. You'll have to buy an intake from a very limited selection, and probably have to do some valve spring and/or guide work. So their low sticker price is a little deceptive.

But it depends on your goals and your budget and what you've already got. In any case, I would not pay that kind of money for those heads unless I had a chance to look them over real carefully, and they came with flow #s for all 8 cylinders. Otherwise I would look elsewhere.

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"So many Mustangs, so little time..."
ICON Motorsports

crazeinc

I'm just trying to figure out the cheapest way to go fast, that's all...

Doesn't sound like double humps are the way to go, but I don't want to pass on vortec's yet because they do make a performance version that has provisions for screw-in studs and guidplates and springs that can handle more lift for under $600 a pair. The valves are still smaller, though, at 1.9/1.5 (something along those lines) compared to a 2.02/1.6 valve'd head. I'd also probably just get the Edelbrock Performer RPM Vortec version, so that's not really a problem as far as that's concerned.

I wish more people would sell heads on ebay...or I knew of a place that sold them used locally.

[This message has been edited by crazeinc (edited January 25, 2001).]

crazeinc

did some browsing on ebay and found a few prospective pairs:

$385 for a pair of #441 with 2.06/1.60 valves. It's an actual company that is selling these so I guess I can sleep easy if I buy these. It doesn't say anything about porting though, so I can imagine the flow number aren't that great.
http://cgi.ebay.com/ebaymotors/aw-cg...916673&r=0&t=0

$295 for a pair of #993 with 1.94/1.60 valves. The springs can handle up to .575 lift. 3 angle valve job. They've been professionally done, are rather cheap, and seem like nice heads.
http://cgi.ebay.com/ebaymotors/aw-cg...429903&r=0&t=0

Am I on the right track, should I jump on one of those, should I just buy aftermarket? I've read a few of David Vizard's books on small blocks and the combustion chamber shape on those heads aren't the greatest so I'm still not sure about them, especially since they 76cc's, so my compression ratio is still going to be low.

[This message has been edited by crazeinc (edited January 25, 2001).]

jms

iTrader: (1)

Back in my 'younger' days, the double-hump heads were the hot set-up. Then, as now, most people thought all double-hump heads were '375 horse' heads. Probably 90% were not. Most came off 275 and 300 horse 327s. These heads were 64cc heads. Double-hump heads that had casting numbers of 461, and 462 could be had with 1.94 intake/1.50 exhaust OR 2.02 in/1.60 ex. as did other heads with other casting numbers. The heads that were 'true' 375 horse heads (even though they came on many lesser rated engines-such as 340 horse, 350 horse, 360 horse 327s, 290 horse 302s, 295 horse 350 in '67, etc.) were machined out, in the combustion chamber, around the intake valve to make the head breathe better on the intake side. The machined area increased the cc's to about 68cc (even though I've talked with people who say 67cc). There were also some very early (mostly 1962, I believe) 461x heads with larger imtake runners that 'seemed' to have smaller combustion chambers. Most of these heads I've seen had been surfaced during their lives, but compared to later double-hump heads they did look noticeably smaller. After all these years, I have some problems remembering the exact cc numbers but I do remember that not all double-hump heads had the same cc's.
jms

AlkyIROC

The trouble with the old double hump heads is that the castings in all of them is very limited. Mine are 370 castings (041 replacements). I had the spring pockets enlarged for bigger springs. It's possible that when the pockets are machined out that you can hit a water jacket. Mine didn't however I'd like them a little deeper to get more spring install height and I know I can't get them machined deeper. The deck face casting is also thin. If you mill the heads down you risk hitting water again. 2.02/1.60 is about the maximum you can go but 2.06 intakes are possible on some heads.

After market heads have much thicker castings where its needed. They'll already have larger spring pockets. Most of them you can go to 2.08/1.60 valves or larger.

I don't know what my flow ratings are after I finished porting the heads. Factory volume was around 160. I never even checked mine but I would take a guess at around 220 (I removed a lot of metal). If I wanted to spend more time, I could have increased the volume even more. There's a lot of tricks on how to get more porting done past obsticles such as head bolts and push rods. I saw some extensivly ported brodix heads that had something close to 400cc.

Those 993's are good heads even with the 76cc chambers. A set of 2.02/1.60 valves will make them even better and the valves will be unshrouded with the larger chambers. You don't have to use flat top pistons even though they are the best way to build a SBC. If you use a pop-up (dome) piston, the 993's can be used to get 10.x:1 compression ratios.

Really compare prices on what all will be required. For the extra cost I'd go with the Victor Jr's myself.

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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block almost ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

crazeinc

Thanks for the input Stephen. Here's what I gather from that last paragraph you wrote:

The price difference between the $300 #993's and the $850 Victor Jr's is the fact that I'll need some new pistons with the 76cc chamber heads to make up for the difference in compression ratio which will ultimately make more HP?

But let's say I'm going to be really cheap and just go with the 993's and the pistons I have now...will the extra $550 I saved cost me over 100 horsepower? or how much are we talking here?

The problem with those Victor Jr's is that they flow so well unless I run a 12:1 CR, they really don't come into their own and I'm not willing to buy race gas every weekend to drive my camaro.

Sounds like I just answered my own question. I think I should grab a book in SBC head porting and think about upgrading the intake valves to a 2.02 and get them to flow better and then I will have a very cost effective way to make power.

Any idea how much I could mill the heads and not run into problems to try to lower the chamber size?

Thanks for your help guys...The info in this post is killer. We should save it somewhere, or maybe I'll post it on my site.