Technical Game over for double hump heads?

I am having the same problem here. My uncle used to own a machine shop, so I always had the secret relative handshake working in my favor. He died and then his right hand man took over, then he died. I am thinking being a machinist may be dangerous…..

 

Or a good business to get into!

 

Roger that, I blew my shoulder out in 1988, eight surgeries (right and left), carpal tunnel surgery on both hands, cervical fusion, numerous other "mishaps" and I must agree with you.
Arthritis everywhere doesn't help either!

 

From what I’ve seen around other SBC talk, the old double hump heads are basically cool for period‑correct builds or stock restoration stuff, but for real everyday running they are getting pretty long in the tooth. Folks over on the SBC subs are saying Vortecs or modern castings flow better and cope with pump gas without straight‑seat issues. You can still run them if you get good hardened seats and guides installed, but plenty of people are just buying newer iron or aftermarket heads instead of pouring money into the old stuff these days.

 

Who cares what other folk say.
new heads are ugly and keeping old **** on the road is fun

 

Running a set of 186 now with non-hardened seats, throw a jug of lead additive in now and then.....I guess I'll see.

 

I had a set of camel humps built for my '32. Screw in studs and guideplates added, new valves, springs, guides, minor porting work etc. I have close to (and maybe more) into them than a budget set of aftermarket heads (not the point). But the machinist I had doing the work wouldn't add hardened seats. He said they've hit water jackets too often on these heads rendering them useless. They are a performance engine shop with a good reputation. Just wondering if others have had this problem?

 

I'm old and old school.
If I ever build something again it will be a nostalgia project like many builds are.
I grew up with 283's and 327's. I don't need big horsepower I want the look and sound.
It's a mental thing and that's ok. People have been questioning my mental abilities for years

 

Yep. No more than most hot rods get driven, you would be money ahead.

 

You know, we talk about our cars and parts and how much that world is changing on us. Last week my machine shop guy had time and felt like talking. We were admiring his old Sunnen hone.......if that disappeared it would put a real crimp in his setup. And that's just one machine.

 

Since last seeing this thread I’ve been collecting 283 stuff, and have 2 sets of power pack heads that I will be using. Same story as mentioned above, I’m after the nostalgia factor, not killer horsepower.

 

I think many over think the hardened valve seats.
There was unleaded gas back in the day don’t remember the brands, but didn’t seem to affect ohv engines.
I was a certified Waukesha Engine tech. On large Natural gas engines running 10.5:1 compression and turbo charged to 10 psi boost we used a medium ash oil, a light tan coating would form on the combustion chamber and helped valve life.
Valve seat wear is caused by a welding of the valve to the valve seat which is caused by high temp and loads. Over time the seat is eaten away. Lead produced a barrier.
Running a lead subs***ute or something like MMO does work. Also if the engine burns a little oil a barrier is produced.
Back to heat on the seat, under normal driving conditions the temps aren’t sufficient to cause rapid wear. Racing, pulling heavy loads for long distance definitely gets the seat hot.
There are several materials and hardnesses of hardened valve seals.
Talking with my machinist on my A engine build he recommended a middle of the road hardness if I went with new seats. I didn’t go with seats at this time. If I start to see recession I’ll pull the head and do seats. I’m running solid lifters so if the lash tightens up I have recession.
New seats are relatively inexpensive however getting into a water jacket is a possibility also. Under some conditions the seat can come loose - rare.
Last year at the Jefferson swap meet I saw several power pack and double hump heads for very good prices. Most didn’t have valve recession had good guides etc. a basic valve job would’ve been all that was needed. Many were at $100 and lees/ pair. They worked back in day don’t see why not now.
Dan

 

@anothercarguy I’ve seen an article where the insert is modified to avoid hitting water. The bottom OD of the insert is machined with a generous radius and the seat bored out to match, that way you don’t get into the water jacket. Also, they say you’re safe with 1.94 valves in camel humps, those inserts don’t hit water. True? No idea.
I have ‘186 2.02’s on my 350, haven’t seen any sunken seats.

 

Vortec heads are the ugly center bolt valve covers, and if I ran them I'd never open my frontend to let anyone see them. But beyond this, the high flow is restricted by the fact a Vortec head wont allow much over .490" lift on the cam lobes without spring bind. So they require machine work and high lift springs to really perform with a decent camshaft. Even entry level aftermarket aluminum heads flow better, and also handle fairly high lift cams without any mods to do so.
The old camel hump heads need a lot of porting and polishing work to flow as well as a Vortec, but they don't need any seat machining unless you go pretty high lift. Just a set of .550" valve springs to get enough lift to handle a bigger cam.

 

Sharpone, American/Amoco was the brand that was unleaded even in the '60s.

 

Thanks
Dan

 

Me , I like to mess with people see scratch , shake head wondering ,
Big tube of JB ,
Internally balanced 400 with a 283 balancer, Tunnel ram with 2 barrel carbs. Use like IAC to increase cfm,
One engine with beat up stamp steel Valve covers with Jesel under ,
One old rodder thought I was B$ing until I pulled cover off after I knew there was not going to be a race in a parking lot of 1/8 run & 1/8th shut down because he said he would not make p*** on street , typical S-R argument.
Take a set of Vortec on mill , add threads
for older valve covers .

 

I’ve thought about that with the early L98 aluminum heads, add old style valve covers, profile the ends to look like power pack heads. The early ones had 1.94 intake valves, and should clear on a 283. But then I got the two sets of real power pack heads, and said well I’m not going for big power, so good enough…

 

19eddy: What, specifically, is the big tube of JB for?

 

OK, this isn't the best way, but it worked for me! Spent a few hours with my grinder, fabbed double hump plates. Fill the holes with cut off bolts, and finished off with high temp epoxy. Glued the hump plates and finished them off. Sanded, primed and painted. No worries about seats, and such things! These are the heads from my crate 350. So far so good!

 

Built this engine back in 1998, cloned Hot Rod Magazines Junkyard Jewel 350 Chevy Vortec head build, they had claimed 396 hp
Started with a 1970 truck 4 bolt main block, had it bored, 0 decked, balanced with forged flattop pistons, the 64 cc Vortec heads came machined for .600 lift and screw in rocker studs, installed the 268 Compe***ion cams extreme energy with .480 lift Hyd cam and the Vortec super victor intake as in the Junkyard Jewel build.

Wanted to have a more stock look when bolting it in the 64 and the super victor was too tall for an air filter under the stock hood, couldn't find a Vortec intake with an oil fill tube so drilled this Summit brand Vortec intake and used some JB weld to seal/retain the oil fill tube, also drilled and tapped it for a pcv valve under the distributor.
Then could put on my favorite, 327 valve covers using Vortec to early style cover adaptors, the Vortec raised rail with the adapter height + gaskets makes the 327 covers tall enough to fit over rocker arm stud girdles along with Compe***ion Cam magnum roller tipped rocker arms.

During the last 27 years, bolted it in 4 different vehicles lol

1st Broke it in, 4 speed 1978 G.M.C. pick up, pulled my car trailer like a big block
Best 1/4 ET in 3700 lb 78 Camaro, .373 gears- 4 speed, "had traction problems" was 14.7
3140 lb 67 Chevelle drag car, .456 gears, 5500 stall, trans brake, power glide and the super victor intake was 11.97
3600 lb 64 Chevelle street/strip car with .373 gears, 700r4 still with the super victor intake was 13.29
in the same 64 Chevelle with the intake change to a low-rise dual plane is 13.80, seems it really likes the single plane intake
We will find out more this year, made a couple of changes to improve the 60 ft time.

 

Yes, had hardened exhaust seats put is some 292 heads, the legendary, over the counter GM turbo head...leaked through 4 of the seats.

 

A ideal for the JB,
Pics from @Utahvette build , he carved ,
I started see this in late 70's ,
Street
Drags
Round D round .

Local Lee Edwards one of pioneers of
Moutan Motor would stack head gaskets to get more Cid by rules of stock p***enger block @ the time

 

The perimeter area on a center bolt head isn't wide enough to drill and tap to make them into old style perimeter bolt valve covers. Need adapters and then those are about 3/8" thick aluminum that shows around the edge.
I wouldn't waste the time or money to make Vortec heads look like old heads, and still need more work to allow taller valve springs to get some lift. Buy some aftermarket aluminum heads and paint them orange.

 

@1971BB427
With mill you half moon valve cover lip
On Vortec & bottom tap down in floor of head ,
Longer bolt , stud's is better
& those adapters need modification if they're bigger than the valve cover on the inside it creates a shelf oil lays there and will leak between Valve cover and spacer /adapter.
I balled milled a channel / gutter half way up each side & full length the bottom with holes was one way I solved the issue

 

One benefit of using the L98 aluminum heads, a boss could be tigged to the valve cover rails and drilled for either bolt pattern, straight across or staggered. With effort they could be made to look like power packs. But like stated above, I got two sets, and I’m not after killer power. I’m too old to have reaction time to respond to problems… heck, my DD has 300 horsepower and it’s got awd and can scare me!

 

Having owned a machine shop for over 30 years I have to say that the Dart head is superior in every aspect other than nostalgia. Both the double hump and vortec are prone to cracking, nothing to do with installing hardened seats.They just do! My shop did far and away more sbc than everything else combined.

 

Then I won the lottery with my NOS 67 dated "291's".

 

I see no reason I'd ever want to go through all that, or pay someone to mill a Vortec style head to make it perimeter bolt. And then have such a narrow mating surface, plus still need to mill the valve spring seats to allow those heads to actually use a decent lift camshaft. Not worth all that extra time and money to me.

 

I have Dart SHP heads on one 350, and old 291's on another. The difference in HP is huge for the Dart head motor!