Double hump heads

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dartfreak75

dartfreak75

Restore it, Dont part it!
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I'll be the first to admit that I know nothing about Chevrolet stuff. I know the common engine sizes and such but I have no clue on how to tell them apart. But ever since I was a kid I have always heard the term double hump heads for Chevrolet stuff you know them 300hp double hump heads on a tree fitty. But never knew what they was or how to tell them apart I always thought it had something to do with the port design or something. I just learned that its a casting mark on the end of the head. Seriously chevy? Why?? Now im gonna double roll my eyes everytime I hear someone say double hump heads. Why not just give them a number or something. Am I the only one that finds this ridiculously stupid? Lol
 
look at the Letter on a Mopar head and tell me why an X demands $200 more than a O or J.
 
Yep a double hump casting. Knew them well, great heads but if you put them on a later motor you had to get all the early brackets as there were no holes on them.
 
I bought a blown 327 out of a Blazer years ago because I noticed that it had double hump heads on it. It turned out to be originally out of a Corvette and it cost me 2 beers. I sold the short block got $100 and we used the heads on a roundy round car. We had to run flat top pistons in that class and angled milled the heads 100 thousandths. We ended up with something like 285 pounds of cranking compression which worked out to about a 15:1 compression ratio. It made one hell of a race motor.
 
pishta said:
look at the Letter on a Mopar head and tell me why an X demands $200 more than a O or J.
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At least its a letter and not a random made up shape lol. But I agree I haven't seen much difference other than the valve size
 
dartfreak75 said:
At least its a letter and not a random made up shape lol. But I agree I haven't seen much difference other than the valve size
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the 041 heads has a cheese wedge shape in the end of heads,.. bout best gen 1 sbc head, vortec heads are way better than any earlyer stock head long as thay ant cracked!
 
Got a little story about chevy's. I was tuning a customer's (friends) car a 64 Chevelle with a corvette 327/365 4 speed 4.11's. Went on a test run and just as I hit 4th gear, I was looking at a radar cop with someone pulled over and watched me go by. Well I just headed back to the shop via a different route, but he got me anyways. We still laugh about it today. O yes it was a 35 mph zone I don't remember what he wrote me for but it was heavy.
 
Ya got to say I love my 350 and 365 jobs but I had a 70 1/2 Z28 motor in a 65 Chevelle and loved that as much as my 340's.
 
pishta said:
There is a motor for you: a 327cid with 365/375HP....Id like to see that dyno....
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They were very fast, kick a 340's *** all day long. But the 375hp you better had a good tune on the injection.
 
MOPAROFFICIAL said:
461 and 462

I just did a valve job on some 462's "dbl hump" "camel hump" heads. They came 1.94 and 2.02.
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Yup, just like "X" heads you can not tell by looking at the "humps"

The heads before things went sideways ?? 69 ?? or so were a rectangle was everyday 283/ low performance, a rectangle with a "teepee" (triangle) in the middle of the top of the rectangle were "283 power pack" heads, and of course "double hump" or "camel hump" were "best" heads.

At least they were easy to see

What is NOT so easy is finding an engine number on an old SB because they were stamped into the protruding deck face and if you surfaced the deck, the number went away (or at least as i recall)

Lots of ways to "cheat." You could put an early 327 crank in a 283, and if you could bore that block to 4" you had a 301 (302) or 327 depending on what crank you put in there
 
67Dart273 said:
Yup, just like "X" heads you can not tell by looking at the "humps"

The heads before things went sideways ?? 69 ?? or so were a rectangle was everyday 283/ low performance, a rectangle with a "teepee" (triangle) in the middle of the top of the rectangle were "283 power pack" heads, and of course "double hump" or "camel hump" were "best" heads.

At least they were easy to see

What is NOT so easy is finding an engine number on an old SB because they were stamped into the protruding deck face and if you surfaced the deck, the number went away (or at least as i recall)

Lots of ways to "cheat." You could put an early 327 crank in a 283, and if you could bore that block to 4" you had a 301 (302) or 327 depending on what crank you put in there
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the 302 was a 283 crank in a 327/350 block...
 
Not just valves. Chamber size is 62 or 64 I think. Don’t quote that. They are / were a great head to provide performance back then if you got the big valves. But today working any iron head is almost not worth it as you all know. I have 69 humps in my Nova. :)

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4F9F5A50-C6F4-406C-99C8-29518CE8BFE0.jpeg
 
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Chevy L84: 2 year only, corvette only....fuelie 375HP, 1324 made? Was more $ than the 396 motor.
"The carbed L76 327 (0.484-inch lift, 254-degree duration, 114-degree lobe separation) produced peak numbers of 355 hp at 5,700 rpm and 366 lb-ft of torque at 4,100 rpm, the L84 EFI version produced exactly 10 more, 365 HP with headers on a dyno with no accessories"

Mopar 340 "355.9hp at 5500 rpm, and 483.6 lbs/ft at 4400 rpm...Headers on the dyno STOCK CAM (268/276-degrees duration; 210/220-degrees duration at .050-inch; and .429/.444-inch lift on the intake/exhaust respectively. Lobe separation 114 degrees), stage 2 springs, Air-Gap intake STOCK HEADS!

Cam up the 340 with a L84 like Comp 268 cam (224/230 duration at .050 inch, .477/.480-inch lift) and the 340 puts out 391.6hp at 5700 rpm and a tire melting 412 lbs/ft at 3800 rpm.

340 was no chump against a L76/L84 but what did a corvette weigh in 64? ~3425 lbs
70 Dart 340 ~3065 lbs.....grudge race?

1970 340 High Performance Mill Dyno - Mopar Muscle Magazine

L84 Fuelie Motor On Engine Dyno - Vette Magazine
 
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67Dart273 said:
Yup, just like "X" heads you can not tell by looking at the "humps"

The heads before things went sideways ?? 69 ?? or so were a rectangle was everyday 283/ low performance, a rectangle with a "teepee" (triangle) in the middle of the top of the rectangle were "283 power pack" heads, and of course "double hump" or "camel hump" were "best" heads.

At least they were easy to see

What is NOT so easy is finding an engine number on an old SB because they were stamped into the protruding deck face and if you surfaced the deck, the number went away (or at least as i recall)

Lots of ways to "cheat." You could put an early 327 crank in a 283, and if you could bore that block to 4" you had a 301 (302) or 327 depending on what crank you put in there
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I remember hearing about the power pack heads, lol and those ram horn manifolds.
Yep Chevy had designations on the ends of their heads and the other day I was thinking about how Chrysler did that too.

On the ends of the heads as follows..
894 X's have 2 vertical lines/distinct submarine shaped bulge along bottom deck edge

915 J's have 1 vertical line

974/596 have an L

587 also have 2 vertical lines, no distinct bulge on deck edge and sharp core plug flashing

308 nothing, Smooth.

Shhhh dont tell no body :D

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Screenshot_20220131-202132_Gallery.jpg
 
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Also the diff between j and x, x's have the artistic curvature along the outside deck edge/outer head bolts
J's are blocked out , for strength/rigidity I assume.
Later heads have crowns around the head bolt lands...etc..

If someone puts this on YouTube they better give me credit for how they found out. Lol
 
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pishta said:
Chevy L84: 2 year only, corvette only....fuelie 375HP, 1324 made? Was more $ than the 396 motor.
"The carbed L76 327 (0.484-inch lift, 254-degree duration, 114-degree lobe separation) produced peak numbers of 355 hp at 5,700 rpm and 366 lb-ft of torque at 4,100 rpm, the L84 EFI version produced exactly 10 more, 365 HP with headers on a dyno with no accessories"

Mopar 340 "355.9hp at 5500 rpm, and 483.6 lbs/ft at 4400 rpm...Headers on the dyno STOCK CAM (268/276-degrees duration; 210/220-degrees duration at .050-inch; and .429/.444-inch lift on the intake/exhaust respectively. Lobe separation 114 degrees), stage 2 springs, Air-Gap intake STOCK HEADS!

Cam up the 340 with a L84 like Comp 268 cam (224/230 duration at .050 inch, .477/.480-inch lift) and the 340 puts out 391.6hp at 5700 rpm and a tire melting 412 lbs/ft at 3800 rpm.

340 was no chump against a L76/L84 but what did a corvette weigh in 64? ~3425 lbs
70 Dart 340 ~3065 lbs.....grudge race?

1970 340 High Performance Mill Dyno - Mopar Muscle Magazine

L84 Fuelie Motor On Engine Dyno - Vette Magazine
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Did you mean to say the 340 had 355hp and 383tq with headers and air gap?
A factory stock 340 never had 483tq even with bolt-ons.
 
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pishta said:
look at the Letter on a Mopar head and tell me why an X demands $200 more than a O or J.
Click to expand...
Absolutely! My Friend Tom ( Old School Mopar Racer) looked at some J heads I had for sale at Garlits. He looked at me, and said, " why are you selling these? They'r Better than X Heads.... they are in the Duster.....
 
Double hump. Original fuel injected heads . I believe someone else mentioned that. those 302 motors were early Z/28 engines DZ code . They only came with solid lifter cams, 4 bolt mains.
 
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