Old terminology to New terminology

[d240zx2]

I was discussing cams this morning with my Z guru. I have a BRE 3/4 race cam (old terminology) and was discussing a brief hesitation on launch at below 2000 rpm. I was curious as to whether the cam could cause or contribute to it.

Saying that he'd need to know the lift and duration of the cam to reply intelligently, I asked if he might know the equivalent in the new terminology, i.e. Stage I, Stage II, etc.

He doesn't. Would any of you?

BTW, I installed a Pertronix electronic ignition package and the hesitation almost disappeared. I think a slight timing adjustment would smooth that out pretty nicely. But I'd still like to know where the 3/4 race cam fits with today's terminology.

Thanks,

Frank

[Arne]

The problem is that terms like "3/4 race" and 'stage 1" are both undefined, and can mean anything the sales people say it means. In other words, not all 'stage 2' cams will have the same specs. If you want to compare cams, you really need the true specs, not undefined terms.

[240ZX]

I believe one would have to either contact the cam manufacture or get ahold of the correct spec sheet, in order to find out lift/duration.....beyond that, it would be a SWAG!

Tom

[Walter Moore]

I have often wondered about those terms myself. For example the cam that I put in my car has an advertised lift of 0.460 inches and a duration of 0.222 somethings (duration units were not specified.

Does that make it a stage I, II, or 3/4, 1/4, I don't know.

[d240zx2]

Back when dirt was new, a 3/4 cam meant 3/4 from stock to full race grind. I've got 3/4 of a full race grind cam....or at least that's what I was led to believe at the time. Now we come to the meaning of "full race," don't we?

Does that mean the cam grind that's used on really fast Z L-xx race engines or is it merely another marketing term with tenuous definitions anchored in whimsy? If a Stage V is "full race," does that mean a Stage I is a 1/5 race cam? Lordy, it's gettin' way too complicated for this old brain to figger out.

Someone needs to modify Wikipedia to settle this thing.

Frank

[Walter Moore]

Ok, How about if we try to apply some logic to this? (A dangerous proposition when talking about marketing...)

The Haynes manual lists the cam lobe lift at 7mm which for the sake of this discussion is about .276 inches. Motorsport auto lists their "Stage VI" performance camshaft at .620/.624 inch lift. A difference of .344 inches

(Which is more than the stock lift?) The Stage V is shown at .560 lift. (.284 higher lift) Both of those cams are listed as intended for racing use.

If a 3/4 race cam is 75% of the way from stock to stage V that would make it .489, which is what Motorsport calls a Stage II cam. On the other hand, if they actually meant it was 3/4 of the lift of a Stage VI cam that puts it at .465, which is a Stage I cam.

In either case, both of those are said to have good to moderate idle with a power range for the Stage I of 1500-5000 RPM, and the Stage II of 2000-6000 RPM.

I doubt the cam is causing your hesitation. More likely it is somewhere else.

Just my opinion however...

[Nigel1943]

As for stage1, stage 2 etc, this means different things to different people dependent on who you buy the cam off. Only safe way is to get details of the lift/duration.

Regarding the hesitation L series engines are well known for having a flat spot around 3500-4000rpm, which can be eliminated to a certain extent by fitting a proper header with a the longest collector you can get on. I suspect your hesitation is something else at 2000rpm, maybe carburation.

[26th-Z]

The only cam listed in the "BRE" Interpart catalog is 329 degree duration and 0.463 inches lift. It is described as: "BRE / Power Lobe Camshaft" with a 6000 rpm power peak. I have both the '73 and '74 Interpart catalog and that is the only cam listed. I don't think there is such a thing as a BRE 3/4 cam.

By comparison, Datsun competition sold camshafts described in my 1971 Datsun USA Competition catalog as "slalom" and "rally". No specifications and the part # is 99996-E1031. Datsun Japan sold two types of cams listed in their competition catalogs 1970, 1973, and 1976. In 1970, the part #s were 13020-A0220 (310 degrees) and 13020-A0221 (300 degrees). In 1973, the cams were listed as 13001-E4620 and E4650. In 1976 they were listed as 13001-E4621 and E4651.

FYI, Motorsport Auto sells Schneider cams http://www.schneidercams.com/cams/50.htm

[d240zx2]

Thanks, fellas. That cam information is invaluable.

I finally solved the problem....I think. But may have created another. I advanced the timing sufficiently to eliminate the sub-2000 rpm hesitation. But by doing so, I think I am compromising the rest of the timing advance. The Mikuni manifold has only one available port for vacuum, and it's going to the MasterVac. Does anyone know of a source for a vacuum fitting that will allow the MasterVac to continue to operate properly while permitting a vacuum hose to go to the distributor? The fitting into the manifold is 1/4" NPT.

I hate to think of pulling the manifold to drill and tap another, single-purpose hole.

[240dkw]

26th-Z

I have a 1979 Datsun Factory Competition Parts book and it lists the Slalom Cam 99996-E1031 as a .475" lift/275 Degree duration. As well it shows a Racing Cam 99996-E1052 .595/306 and a Racing Cam 99996-E1053 .530/306.

in this book it lists three IECO Racing cams .420/250, .450/270 and .480/284.

BTW the 1979 list prices for these cams where $54.95,$59.95 & $64.95.

[Tony D]

If you have the proper Mikuini on the first position (nearest distributor) it will have a small vacuum advance port for the distributor to hook to...this was available on the Mikuini Kits, and was the reason the part number was different for the first carburettor than the other two. The Toyota Mikuinis used on 2TG and 18RG DOHC Fours also had this brass tube right in the carburettor as well. It is one of the reasons the Mikuinis are superior for daily use compared to Webers.

As for 3/4 Race, the rationale was always explained to me that duration was at least 270 degrees of EFFECTIVE lift to get '3/4 Race' as in the old days, if you have a V8 with duration like that, it was pretty radical, but not a 308 or 310 duration cam. Incidentally, most of those 308 and 310 degree cams when checked at 0.050" will come in around 260-270 degrees effective duration...coincidence? I think not.

As for "Stage 1" and the rest, it's all marketing gibberish. Nothing more. There is no standard, it's a made up set of criteria from whoever packaged the stuff in the first place, and is a ploy to sell you more stuff in a lump rather than piecemeal. Hopefully they have done their homework and packaged compatible peices...but that may be a stretch.

To get to it, stick with standard engineering terminology with all it's specifications and qualifications and you won't be steered wrong. The first thing Engineers do is DEFINE TERMS so there is no question what is meant. If people can't explain what they are selling you, and why you need it (other than to say something like 'it's the Stage One Upgrade Package) then you should really consider going someplace else for your parts and performance upgrades!

BTW, it is possible to add the vacuum tube to a Mikuini, but you need a good drill press (Bridgeport Mill ideally), steady hands, some precision reamers, and microdrills for the actual wall penetration at the throttle plate area. It's been done, but if you are running 40's, there are tons of Toyota Carb Bodies out there you can swap your guts into and run like that.

Heck, I may even have a spare...

[d240zx2]

Thanks, Tony and everybody.

I checked the carbs/manifold. Nothing except the vacuum port for the brakes. As this set-up was bought and installed more than 30 years back, no memory of purchase details remain.

I'll try to find the parts I'll want to make a clean installation of an additional vacuum port, teed off the existing port. I'll post photos when it's done to get opinions on what I could change or do better.

As for the cam...it runs scary fast now, what does a 63 year-old guy need with anything more?

Thanks again.

Frank