3/4 camshaft designation
 

I got interested in automotive things in the mid-fities and was hands on in the mid-sixties with drag race victories going 13.02 109.73mph on street tires in 3rd gear with a Sunbeam Tiger with 289 in late sixties. I was surprised to read another post that said 3/4 camshaft profile was not used as a term for other cams other than flathead engines. I can remember a Duntov Chevy cam for 283 cubes, dual quads 270 hp that was a stock chevy part #, came in that engine originally and was available at the parts counter. It was referred as a 3/4 cam. A cam that could be driven on the street daily and yet rev to 6000 rpm when performance was desired. When the 327 engine was made with fuel injection and rated 375 hp the cam in that engine was referred to as the 30-30 cam in reference to the valve lash. It had near .500 lift and long duration. That cam was not called a 3/4. The cam in my Tiger 289 was a $17 Ford cam that won Lemans in the Cobras. It had over .510 lift and 312 degrees of duration. That was a full cam. I just thought 3/4 cam could be said of any dual purpose cam because there were hotter cams that were not mean't for dual purpose. Sorta like getting a whisky over ice and soda istead of drinking it straight. I would not call a RV cam a 3/4 because their purpose is to make low end torque and towing power but seldom have anything going past 4000-4500 rpm similar to stock hydraulic cams. The three cams I mentioned previously were flat tappet solid lifter. The redline on the LeMans cam was 8250 rpm.

The last time I looked you could not run with 1/2 or 3/4 of a cam. You needed all it.:p

I do remember those years. I had a 289 with 13:1 comp ratio that I drove on the street, with 310 duration, hyd lifters. Personally these days all the new mechanics do is plug in a scan tool. replace the part. done.

Cam technology today is a lot different than it was in the 60's. With the use of technology there able to make cams idle smooth that you could not do 30-40 yrs ago. Advancement in hydraulic lifter make this happen as well as roller cams. On another thread a user was looking for a different cam for his 428. He needed a min vacuum of 15 at 1200rpm. I had a hotter cam in a 360, that had more vacuum than his setup. The differents being variable lift lifters, gave a better vacuum than his did.

We actully need to look at grinds and the whole picture. The cam is just 1 piece of the picture.

I agree with your assessment of the situation. CAD is improving the camshaft profile that just was not possible back then. I never used varible lifters but did hear of Rhoads lifters. That was the complaint of those, that they had an audible tick at idle.:rolleyes: I also understand they could turn 7000 rpm as a hydraulic lifter but then you had to run a little more spring pressure which in turn tried to defeat the lifter. You bet I wish I had some of the tech of today back then from cams,aluminum heads, carbs, ignition and tires and synthetic oil to better tolerances on most everything. I imagine I'd be even faster.:cool: That engine had 10 to 1 compression

67 PUstomp,

I run a "RV" style, low end high torque cam. I run mid 12'ET's at 120 +/- Mph TE with my 385 series engine in a 3000#, F-100. I never get over 5K RPM. So cams are just a piece of the package today. 50's - 60's terminologies are no longer the bee's knee's or the cat's pajamas. Just like the 60's & it's technology, time had passed all that by. :-X22

There are guys in my circle now who run in the 10's with street driven cars today. In the 60s, the early 60s anyway, 10's were rail & AA/F Dragster territory, by late 60's it was A & B Gasser realm. But all of that has been long gone. :cool:

The problem is with the newer jargon upgrade, only older guys have a clue what you are trying to state, or say, because contemporary guys don't use the old termimology any longer. Performance field is full of younger guys today. What was it that Bob Dylan said? :rolleyes: . . . . oh yeah, I remember what it was, "The Times They Are A-Changin' "

So when I say 3/4 race was Flat Head speak, that is my point reference. One can go into a Flathead Vendor & they still use that jargon. However out here in the real world it's all running by it's own updated rules. Here in the 21st century it's a faster pace among many more participants, at many more venues, with much advanced technology, and quite different thinking than we used in the middle of the past, last, century of the last, past millennium. . . . Like my signature says, change is the only constant.

Carburetion is also obsolete, IMHO because it flies in the face of Bernule's principles of fluid dynamics , MAFS-TP/ EFI is a half a century ahead of anything they even thought of in the 60's or 70's, as are disc brakes, progressive suspension, envelope and drag coefficient aerodynamic design etc etc etc. But all that change has made what we tried to do "back in the day" an achievable goal at the street level today.

BTW so called "Fuel Injection" GM/ Blowtie came out with in the 50's & 60s wasn't fuel injection, it was port induction. It had no injectors no spray or spray pattern and it relied on engine intake dynamics to induct the gasoline.
I believe the cam you refer to was Blowtie P/N 3736096, I might be wrong, it's been a while doncha see?

FBp :-X22

:-wink FordBoyPete that was as good as answer as I wanted just to stir up the conversation stew...thanks for replying

Roger That "67" :)

In my Screen Name, don't let the Boy part fool ya' I may be 19 but I have 48 years experience at being 19, so I'm good at it, doncha see?

I was at Allentown PA, in the Lehigh Valley behind the Allentown Diner off Rt US22 at a old WWII airbase there, back when Wally Parks brought his newly founded NHRA east to hold the 1st sanctioned Drag Race on the East Coast in the spring of '56. Been at it ever since. :rolleyes:

FBp :-X22

Back in '84 my '70 F100 302 had a 3/4 race cam!! Back then things were a bit different, as anyone will remember the Summit ads for cams with "be the baddest sounding car at the drive-in".

Yup, "race cars" had full race cams, street cars had "3/4" race cams LOL! You only raced 3/4 of the time on the street(the other 1/4 you did the speed limit).

Tiger
 

I knew a guy about 15 years ago that would consistently run low 11's with his 289 Sunbeam Tiger. It ran like a motorcycle. He would take it easy off the line and then it would go like lightening once he had some traction. He moved to CA to work for Ford. Haven't seen him or his Tiger in a long time. It was fun watching him line up with BB chebbies running drag slicks, etc.

hate to go on and on but I dug that last Tiger story of course and just had to say that I live about 1/2 hour from Allentown, Pa. Was cool to hear that story also. MapleGrove Raceway is about 40 minutes from my location. Sometimes it does be a small world.

Funny you should mention Tigers...my moniker sure doesn't refer to jungle cats!

The way my first auto shop teacher explained it back in the early '70s, a 3/4-race cam was so called because the grind was 3/4 as hot as a full-race cam. Pretty simplistic. He had a '39 Chebbie Sedan De-Lux with a built 235 with twin Strombergs, electronic ignition and...a 3/4-race cam!

nice image...very explainatory for those who think its another MG}>

Except that you can't see the Ford V8 under the hood...perhaps this one explains that particular feature a bit better:

http://www.users.globalnet.co.uk/~ga...gine%20bay.jpg

Sweet, Very nicely done.

I went to the Yellow Rose All-Ford car show in Fort Worth a couple of weeks ago and there must have been 20-25 of the old Sumbeam Tigers with the appropriate 289's. I'll be 61 next month and had damn near forgotten about those old Tigers. They were some very cool old cars and you didn't see that many of them on the streets. This has been a good thread.

Most Tigers that you see had the 260 from the factory, not that you can easily tell it externally from a 289. Of approximately 7000 Tigers built, only the last 533 (or maybe a few more, no one knows for sure) had the 289. Mine already had a 302 in it when I got it but it had some problems, I built a 289 for it and ran that for about 40K miles and right now it's in pieces awaiting its new aluminum head long-rod 302. Hopefully I'll get it together this winter. (The yellow one in the above pic isn't mine, I just found that pic on the 'net to show what they typically look like under the hood. The drawing I first posted is an artist's rendering of what mine will look like when it's finished.)