Information wanted on 265,283 HP ratings

[F-BIRD'88]

Rumor has it that the 140 cam is a copy of a Mercedes cam.

it is the same cam as (one of the the) BBC 427 L-88 cams (first design) was but on a SBC core.

But you may be right about the cam lobe)s) design origin.

[maxracesoftware]

GM-Chevy had at least 4 different versions of the 461X Heads
a few versions of the plain 461's

the largest Intake Port Volume CC 461X version actually CC's larger than NHRA Legal Specs
so i'm guessing NHRA never saw or measured that ultra rare version ???

this 461X version has as cast unmachined very large Exhaust Valve guide bosses
a Fin in the middle of Head in valve cover area , coming off a Pad .

Lower + wider Floor at Apex , with a maxed out Roof height at the Short Turn
and the widest Pushrod Pinch width of all the cast-iron OEM SBC Heads produced.

[fdicrasto]

GM-Chevy had at least 4 different versions of the 461X Heads
a few versions of the plain 461's

the largest Intake Port Volume CC 461X version actually CC's larger than NHRA Legal Specs
so i'm guessing NHRA never saw or measured that ultra rare version ???

this 461X version has as cast unmachined very large Exhaust Valve guide bosses
a Fin in the middle of Head in valve cover area , coming off a Pad .

Lower + wider Floor at Apex , with a maxed out Roof height at the Short Turn
and the widest Pushrod Pinch width of all the cast-iron OEM SBC Heads produced.

I was not aware of 4 versions but on 300 hp engines( hyd. cam- iron intake) the 461X heads only difference were the cheaper 1.94" and 1.5" valves were not swirl polished as the sp.hp. stuff was equipped with. Nhra used to have the cc #s in National Dragster that did show that the 461X heads were at least 4-6 cc's larger intake port volume but I have not seen that info for years so my memory might be off. One thing for sure, as you have stated, the 461X intake port pinch was wider than any sbc iron production head chevy produced. We could easily identify the good ones with the old thumb down the port measurement. Worked every time.

[wwmtlineman]

classracerinfo.com has the complete legal NHRA specs on all the engines but you do have to join it to see them. Excellent info though in this post though, learned something

[maxracesoftware]

I was not aware of 4 versions but on 300 hp engines( hyd. cam- iron intake) the 461X heads only difference were the cheaper 1.94" and 1.5" valves were not swirl polished as the sp.hp. stuff was equipped with. Nhra used to have the cc #s in National Dragster that did show that the 461X heads were at least 4-6 cc's larger intake port volume but I have not seen that info for years so my memory might be off. One thing for sure, as you have stated, the 461X intake port pinch was wider than any sbc iron production head chevy produced. We could easily identify the good ones with the old thumb down the port measurement. Worked every time.

at one time , i had 4 different 461X versions in my Shop
so it was very easy to see + measure the differences

there might be more than 4 versions???

one of the #461X versions had no Fin in the valve cover area
and was not as wide at the Pushrod Pinch as the other #461X versions

so the Fin is always the better version ... but the the very best is the Fin + as cast very large/tall unmachined exhaust guide boss + Pinch width

i kept that rare #461X version ...cherry original , its in my Shop, i'll take a Pic + Post it later on

i just remembered i have another #461x version in my Shop , maxed out Angle Milled, Screwin studs , Bronze Liners , no Porting or Valve Job yet

used the 2nd best version on Bob Fordyce's NHRA SS Car "Mother's Olds"
http://www.maxracesoftwares.com/forum/v ... p?f=3&t=80

the other 461x's , to other SuperStock Racers

Also if anyone interested , have Dyno test results near Stock 283cid engine i built or warmed over stock 283cid

and Corvette Blue Flame 6 Cyl ( 1953 ) Dyno Data ... that basically matched GM Chevy Dyno numbers
but we ended up make a few more HP than Chevy claimed at end of Dyno session
scarificed welding + modifying the spare original style Bell Housing to mount it on the Dyno
but the Customer also had actual real original Bell Housing left.

[novadude]

I'd love to see the pic of the 461x (the rare one). Not sure I've ever seen the fin that you mentioned.

[Old School]

I am interested in the 283 engines.

[maxracesoftware]

I'd love to see the pic of the 461x (the rare one). Not sure I've ever seen the fin that you mentioned.

i'll bet you saw that Fin before ... it just didn't click it was different than other castings

NHRA Specs for 461X are :
Intake Port Volume CC's = 172.0
Exhaust Port Volume CC's = 64.0

the 2 Intake Ports i measured with "Kimax brand Class A Buret " purchased from Mr. Red Anderson, then Div 4 Tech Director
one = 173.5 CC other = 175.0 CC
did not CC the other Head , nor any Exhaust Ports, but i measured the width of the Exhaust Port + wrote all the info ontop the Heads
20+ years ago ... a little faded to read, but still can make out the text

will start a separate Thread on SBC Rare Heads + Post Pics later tonite
its taking me way longer than i thought to move stuff out the way to get to these Heads
but i found a whole bunch of various Heads i forgot i had .

found a weird plain #461 casting ... will Post Pics

found (2) pairs of PowerPack #520's with Diamond Emblem + T in valve cover

found another pair of #041x's ( there were many versions of #041x too , and same thing with #441's open chambers )

1 #292 Turbo Head ... i already had 1 spare ... now i have a pair

SS 426 Hemi Heads w/blue anodized Spark Plug tubes

pair of #781 BBC Heads

bunch more to get to

[maxracesoftware]

found a Total of (4) Pairs of #520 Power Pack 283cid Cyl Heads
(3) pairs with Diamond Emblem + large capital T
(1) pair plain #520 just casting numbers ( without = Diamond Emblem + large capital T )

long time ago i rebuilt a 1955 265cid Chevy engine for a local Guy ,
i did all the machine work and he later assembled everything

it did not have an Oil Filter , no side motor mounts ,
and i vaguely remember 2 other things -->
something different about the Connecting Rods ??? maybe the bottom Caps ???
and something different about the Cylinder Head's ... maybe the valve cover bolt hole layout
was not exactly like later years up to today ... it was close but maybe off on the top or bottom holes by .050 or .100 ??
or maybe it had a wide pad at the upper valve cover bolt holes ???
and something else about those particular Heads ??

i'm sure someone here reading might know what i'm talking about
or have Pics of maybe a very early production run 1955 265cid ???

is there any evidence of any 265cid Chevy V8 earlier than 1955 ??

there was something different i saw about those Heads , just can't exactly remember what stood out so much to me at the time .

[kirkwoodken]

Darn, Paul beat me to it. The 327 340/365 Corvettes had the 2 1/2" pipes coming off the larger rams horns, maybe. The later 327 365/375 engines had them for sure. We are going back a lot of years, but I know I had those ram horns on my 340 HP 327 in my 55 Chevy, but don't remember exactly when I put them on. (Engine went in April of 1962. Exhausts mods came later.) Those had a MUCH larger volume than the earlier models. Didn't take much longer before they were exchanged for 1 3/4" fender well headers.

[kirkwoodken]

The 1955 heads had valve cover bolts in line with each other. Different spacing came about in later years. I still have a pair of 55's in the garage attic. One has the little tab that holds the temp sensor wire.

[fdicrasto]

The 1955 heads had valve cover bolts in line with each other. Different spacing came about in later years. I still have a pair of 55's in the garage attic. One has the little tab that holds the temp sensor wire.

I respectfully disagree. The '55-mid '57 v/8 heads had the upper valve cover bolt holes closer together than the lower vc bolt holes. They then were exactly even spaced top and bottom row. For years you could purchase vc gaskets with 6 holes so they would work on all sbc heads.

[maxracesoftware]

any thing different about the Connecting Rods ??? maybe the bottom Caps ??? on earliest 265cid

what else was different on the Cyl Heads ... there was something else
besides the Valve Cover bolt holes .

[fdicrasto]

Trivia on the SBC staggered valve cover bolt holes:

They were used until early 1959 in the U.S. but early 1962 in Canada.

Thanks
Randy

Your right Randy, my bad.

[novadude]

Darn, Paul beat me to it. The 327 340/365 Corvettes had the 2 1/2" pipes coming off the larger rams horns, maybe. The later 327 365/375 engines had them for sure. We are going back a lot of years, but I know I had those ram horns on my 340 HP 327 in my 55 Chevy, but don't remember exactly when I put them on. (Engine went in April of 1962. Exhausts mods came later.) Those had a MUCH larger volume than the earlier models. Didn't take much longer before they were exchanged for 1 3/4" fender well headers.

62-64 300 hp 327s used the 2.5" Ramshorn manifolds too.

In those years, 250 hp had the "power pack" heads with 1.72/1.50 valves, small Rochester 4gc, and 2" manifolds.

300hp 327s had the same compression ratio and cam (198/198 @ 0.050, .398/.398), but had a larger AFB, "camel hump" (461?) heads w/ 1.94/1.50 valves, and 2.5" manifolds.

The 50hp came from intake/heads/exhaust. I'd say it's a believable number, as the small 4gc and 1.72 valves probably really choked the 250hp engine.