3/4 race cam ? - Page 2 - Chevelle Tech
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post #16 of 30 (permalink) Old Dec 1st, 01, 9:41 AM
 
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Vettefella:

I keep telling myself I'm not getting old. You guys keep bringing up subjects that prove me wrong.

I say AMEN to that!!!
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post #17 of 30 (permalink) Old Dec 1st, 01, 10:09 AM
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<BLOCKQUOTE>quote:</font><HR>Originally posted by Argus:
Vettefella:

I keep telling myself I'm not getting old. You guys keep bringing up subjects that prove me wrong.

I say AMEN to that!!!
<HR></BLOCKQUOTE>

TC forums tend to do that, don't they Anyone remember Clay Smith Cams w/the Woodpecker logo? I remember "3/4" and "full race" cam-talk back in high school (early 60's). To most of us then 3/4 meant any cam other than stock that wasn't in a full out race car. I always wondered though, 3/4 of what? I think Mytmouse and vettefella have about the best explanation...just an old racers term.



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post #18 of 30 (permalink) Old Dec 1st, 01, 1:31 PM
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<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Block Dave:
Crane still has cams that are marketed as 3/4 race cams<HR></BLOCKQUOTE>

Dave's right. When I rebuilt my 355 in the summer of 2000, I got a Crane with the rebuild kit. The specs are .470/.470, 226* @ .050. On the end of the box, it says "3/4 Race Cam"...


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post #19 of 30 (permalink) Old Dec 1st, 01, 3:19 PM
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Nick, I put that same cam into an L69....a 305 Z28 motor.....ran pretty funny!
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post #20 of 30 (permalink) Old Dec 2nd, 01, 12:38 AM
 
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Some day (years from now) someone may ask, "What is an RV cam?" I want to put it in my car, not the motor home!!
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post #21 of 30 (permalink) Old Dec 2nd, 01, 9:17 AM Thread Starter
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Here's the scoop. (I think) Back in the olden days about the only place to get speed parts was the Chevy dealer. There were three cams available, a stocker and two high perf grinds. The middle cam was the Duntov 350hp/350cid cam. The other high perf was another very lumpy solid lift Duntov job. You walked up to the dealer parts counter in your cool buckskin jacket and shades and announced "Gimme a 3/4 race cam." What you got was a 350/350. I'm still looking for the PN's.
It's history. Cool history.

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post #22 of 30 (permalink) Old Dec 2nd, 01, 11:03 AM
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The terms 3/4 race and full race predate the sbc by a quite a few years. I remember hearing the term "full race" around 1950 relating to a built up flathead in a '35 Ford coupe.

Cam grinders only made a few different cams. They were handmade, and the grinder reset for each lobe. Just a few cams per day. Ed Winfield actually ground different profiles for some lobes on the flathead Ford cams to make up for differences of flow from port to port. This would have been his "full race" cam. It was meant for nothing but competition. High compression, ported and relieved [flatheads], multi carbs, open exhaust stuff.

The 3/4 race cam would be a hot compromise cam. Sort of "hot street" in todays terms. It would work best with higher compression ratios and multi-carb manifolds, but could get you away from a stoplight ok.

As the market for hot cams got better, cam grinders would have more "full race" cams available designed for different kinds of racing, but all without compromise for street use. They added more street cam profiles under the 3/4 label. Even Sears had cams listed in their Catalogs, and I bought a 3/4 cam from them for my first car. There was no real science to our choices. Pretty much pot luck. I decided I needed a 3/4 cam, and Sears sold one for 10 bucks.

Things change. When the "Duntov" cam was released in '56, it was a "full race" cam in our eyes. With .400 lift, it allowed us to crank a 265 or the new 283 over 6 grand with ease.
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post #23 of 30 (permalink) Old Dec 2nd, 01, 11:40 AM
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Hoffman, the old Duntov stuff preceeded the 350/350 camshafts by well over a decade. There were at least a couple of different solid lifter profiles available from GM for the SBC before the 350/350 which was a hydraulic first delivered in 68. I always thought the 3/4 designation was a loose description for comparison, probably coined in the 50's, but maybe earlier since I never fooled with flatheads which were before my time. I know that the old mail order hot rod houses like Honest Charley and JC Whitney widely used the descriptions 3/4 and full race in their catalogue to loosely describe the comparisons. Now days there are so many possiblilities I'm surprised that Crane would still use the designation on one of their boxes.

Mr. 4 Speed, maybe I've just been lucky, but I've been using Crane repro, or blue printed camshafts in all my old Chevy restos for over 25 years and I've never lost a lobe or had a problem. I've got Cranes in both my LS6's, 4 435 cars and a number of solid lifter high perf small blocks with the 30 30's. I've also got a fairly radical solid lifter Crane in the 540 in my boat and even though it is prone to sitting for long periods without being started, and I don't prime it each season, it's been trouble free for 5 years now.

Someone at GM told me a long time ago that they use a variety of suppliers including Melling and TRW for their parts and that the cam specs could vary a good bit within a given part # as to specs.
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post #24 of 30 (permalink) Old Dec 2nd, 01, 11:48 AM
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<BLOCKQUOTE>quote:</font><HR>Originally posted by 2BlueLS6's:


Mr. 4 Speed, maybe I've just been lucky, but I've been using Crane repro, or blue printed camshafts in all my old Chevy restos for over 25 years and I've never lost a lobe or had a problem.
<HR></BLOCKQUOTE>

My comment said Comp Cams,NOT Crane.Just wanted to clear that up
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post #25 of 30 (permalink) Old Nov 6th, 03, 1:50 PM
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Quote:
Originally posted by imdarren:
Some day (years from now) someone may ask, "What is an RV cam?"
Easy... it's a 3/4 Truck cam. [img]smile.gif[/img]

Reid
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post #26 of 30 (permalink) Old Nov 6th, 03, 2:20 PM
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Quote:
Originally posted by vettefella:
For example: Most of you think of a fax as sticking a sheet of paper into a machine and a few seconds later it's gone. My introduction to facsimile was back when it took 4-5 minutes to transmit a single page. If it was a picture, it took much longer. The PC you use to make these posts has a memory capacity measured in gigabytes. I was teaching computer related stuff in the 60s when the memory capacity was measured in single bits...several years before the term "byte" came into common usage.
I'm just wondering what kind of dinosaur you had as a pet when you were a kid.........

JUST KIDDING !!!! [img]graemlins/waving.gif[/img]

My 11 year old daughter askes me questions like that..... drives me nuts [img]graemlins/clonk.gif[/img]

I remember all of us BIG BAD RACERS in high school throwing that 3/4 cam term around all the time (early '70's) and I just now realize that NONE of us had any clue as to what we were talking about.

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post #27 of 30 (permalink) Old Nov 6th, 03, 2:32 PM
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Quote:
Originally posted by mr 4 speed:
I know Comp Cams makes 3/4 cams..that's what you end up with after a few miles with the way their grinds wear out! &lt;IMG SRC="https://www.chevelles.com/forum/wink.gif"&gt;
I have a 280H Magnum Comp cam that I plan to put in my 454 pretty soon. Am I to believe that my Comp cam is junk ? and that my engine will run like crap after I have driven it a short distance.
I have read several posts related to this and have to wonder how Comp cams has been so successful for so long by selling junk that wears out before it's time. Please fill me in. If I need a different cam, please tell me why and provide some suggestion. I appreciate the info. [img]smile.gif[/img]

John Austin
Katy, Texas
'70 SS454 Chevelle "clone" project
My combo:496 BBC (454 +.060), Muncie 4 spd, Centerforce dual fric clutch, "781" heads 2.19/1.88, 12-bolt 3.73 Eaton posi, Scat forged rot assm (21cc Wiseco slugs for 10.4:1 CR), Lunati Voodoo billet 60213 hyd roller, Lunati hyd roller lifters, Scorpion 1.7 #SCP1014 roller rockers, Edelbrock Performer RPM, Holly 850 Dbl Pmpr (1" spa), Carter 172 GPH mech fuel pump, MSD R2R dist. #8360, O'reilly Master Pro coil, Weiand high volume mech water pump, 772 stock 7 blade fan, Hayden clutch, fan shroud & Hi-flow 160 deg T-stat, Doug's 2" x 3 1/2" headers
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post #28 of 30 (permalink) Old Nov 6th, 03, 3:23 PM
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I seem to recall back in the early 80's looking at a "3/4 race cam" in a JC Whitney catalog. Me and my high school friends were talking big about what we were going to put in our cars . . .

That was the same year I built my first 350 Chevy in my basement - took like 6 of us to get the assembled engine back up the stairs! but it was soooo easy to get down the stairs . . . LOL

But JC Whitney has always been a little behind the times IMO.

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post #29 of 30 (permalink) Old Nov 6th, 03, 4:37 PM
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Quote:
Originally posted by hoffman7476 - posted 11-30-2001:
to be continued 12-01-2006

[img]smile.gif[/img]

just kidding
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post #30 of 30 (permalink) Old May 19th, 07, 4:06 PM
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Re: 3/4 race cam ?

A full race cam was a cam with the maxim duration useable, Around 340-360 degrees. The idle was 1500 to 2000 and was drag race only, not useable on the street. A stock cam was 230-250 degree on most engines of the era. The 1/4 cam was a mild street unit around 260, a half race cam was somewhere around half the difference 280-290 degrees and the 3/4 was around 305 degrees. Hope this helps, this was what I grew up with and believe it or not a lot of us still use this terminology and know exactly what is meant
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