I bought a 69 302, & when I tore it down, one head had shorter valve seals than the other. I realize someone must have re-done one of the heads. So when I bought new seals, I Got the long style. I'm fixin to go to the shop to hand lap the valves, & reassemble them. Before I do, I just wanted to know is there a differance between the two? besides the obvious. These are stock heads. 58cc combustion chambers, 1.78 intake, 1.6 ratio rockers. I'm going with a lunatti Bracket Master 2 cam. 284 Adv. Duration, .488 gross lift, 1000 to 5000 rpm window. I want a street car that sounds real good. also what was with 3/4 race cams? I can only remember what they sounded like, were they a fad? I know to get good horsepower I need aftermarket heads, but I remember riding in some fast fords, before they were so popular. tanks for any help, this is a tottally cool site.
I am of the opinion that people who use the term "three-quarter race cam" don't really know anything about cams or cars (I'm not talking about you here). It is an extremely vague description of what I guess is supposed to be a performance cam. No one ever seems to know the specs of a "3/4 race" cam. Personally, I wouldn't worry about it. Today's cam manufacturers specify the lift, duration, intake centerline, lobe separation angle, and RPM range of their cams. Stick with that. ...
The "3/4 racing cam", I believe, described the magnitude of the cam compared to a "full racing cam". I don't believe it had any actual numbers (lift/duration, etc.). It defined a street/strip friendly cam. As far as the seals go, there are more than a few types to chose from - in size and in material. The main thing is to make sure the O.D. of the seals do not interfere with the I.D. of the springs. This is only a consideration if you have a set of "two springs/valve" setup - which I doubt you have - but there's no way of me knowing what yours has for sure. You can go with Nitrile (rubber) or PTFE (Teflon) type materials. The PTFE is typically smaller in diameter and hold up against heat better than the Nitrile. It sounds like, for your application, you can get standard "behind the counter" replacements and be fine. Some seals have multiple ridges (or 'seal lips'). I'd get those if practical. If not, I'd just get the standard seals.
HEy Rick, are the FelPro seals Teflon? I just used what came in the FelPro engine gasket kit I got. How do I know what they are made of?...
Just to clear up the term "3/4 race cam" : I comes from the beginnings of the hot rod scene in the late 40's and early 50's. cam grinding or regrinding was just coming into it's own and you would have your cam ground on a 3/4 base circle - using your worn out cam to make a new one. The ramps and lift would begin in the same place as before so the duration was longer and the lift was a bit higher. The duration was very near 3/4 of a circle - 270 degrees and the lift was close to .450" about 3/4 of .6 lift. The term came from the duration though and they were pretty mild cams by todays standards - J.C.Whitney sold a "3/4 race cam" into the 60's but the usage of the term has died.
"full race" cams were not something that was purchased - your racing team included a cam grinder and they did a lot of "playing with things until it was what worked best. The cams that were 3/4 race cams were 3/4 of the circle not 3/4 of a full race cam. Think of it this way it was a race cam with 3/4 circle of duration. it was a "3/4" --"race cam". It was no reflection of what a race cam was. You should keep in mind that this was before you could order a cam with a certain duration and lift. It was back when Isky was a custom cam grinder for racers only.
I guess "full racing cam" meant different things in different parts of the country. Where I growed up, a "full racing cam" meant it was a strip-only cam (kinda humorous to think about the jargon now ).
I think Paul had the very beginning term,, (thinking might have been 3/4 horseshoe back then,,sorry,had to throw that in there) It was a general term in my school days 3/4 cam, pretty streetable, but they knew you were in it,,,,full race cam,,stay away,,ain't gonna beat him and he runs airplane gas!!! Anybody want to comment on RV cam? Should be out with a SUV cam soon!
Well, Thanks guy's on the info. Guess the term 3/4 race cam is politically incorect nowday's. Which I understand. It's like spaghetti sauce. back in the day, you could go to the store & grab a can. nowadays when i go I have to search for an hour to find the traditional kind. I know it's a good thing, but I'm trying to find the perfect cam,intake,carb combo. & when I open my Jegs or Summit catalog There's literally 5 pages worth of parts. I know, they make package deals on these combo's, but I never have the money at one time for that. (little lady always seems to know) Plus I like to do things a piece at a time, this isn't my daily driver, so I'm having fun with it. Wish I could get my photos on this, but Im pretty much computer iliterate. thanks for all comments good or bad. that's what it's about
