jax78v

I have a 78 that had its motor done over years ago. Put in a 3/4 racing cam and double eyebrow pistons when bored out. Sellers says it now 333 HP? . With this work being done on the engine what type oil should I use ? Synthetic or Regular ? Also 30w or 40 w? I asked owner but his memory is going and he has no answer.

71 Vert LS1

Oil wise I would start with a zinc type 10-30 dino oil. Run it a bit to break in the cam. Then drop the oil and filter adding more zinc 10-30 dino oil. Then maybe after 500? miles go to Mobil 1 or something similar.
Man it's been many moons I have heard of a 3/4 race cam. LOL.

randallsteel

Many opinions on oils here, you’ll get answers supporting both. I prefer regular oil on older motors.
for breaking in motors, I use Lucas break in oil 30 weight.
After break in I run Lucas hot rod and classic oil, 10-30. Great for flat tappets without a catalytic converter.

I wonder if Europeans say things like, Im running a 19mm cam? Lol

4-vettes

3/4 race cam? Is that like muffler bearings?
At any rate, what oil you need depends on wheather that only 3/4 of a race cam is flat tappet or roller. And the climate you live in.

DWAVette

AMSOIL Z-Rod is another example of an oil that has the zinc you need.
There are other good oils out there also.

Rescue Rogers

3/4 race cams is jargon from the 70s and early 80s...so ya its been a while. As for oil I use Mobil1 20-50 for the High ZDDP which is zinc and phosphates. Without them your 3/4 cam will be a 1/4 cam in no time. The lobes will get ground right off. As for the pistons they are probably flat tops which could be the stock style by the description but there is no way of knowing the cam specs without the numbers or the compression without the heads combustion chamber size. You could go through the trouble of actually measuring the valve travel and dividing the travel by 1.5 to get the cam lift but you wont get the duration or the lobe seperation. 330 hp is not unreasonable at all, the stock 327s had 300 hp so a 350 could easily be 330hp with flat tops and decent heads with good compression and an aftermarket cam

Mdbirk

The term originated from the hot-rod industry who were modifying engines. The legendary Ed Winfield was one of the early pioneers in grinding camshafts with more aggressive lobe profiles, and the cams were often labeled as full race for promotional purposes. “And then some guys wanted a milder cam that could also be used on the street, so you could get three-quarter race cams because it didn’t have as much duration and lift,” "John MacKichan of the Speedway Motors Museum of American Speed".

Isky cams back in the old days offered 1/2,3/4 and full race cams. Ohhhh and the great isky mega cam!

Tech141

How much valve lift are the Top Fuel NHRA guys running? .900?

4-vettes

I remember hearing that 3/4 race cam jargon back when I was in High school. And that's a long time ago now gentlemen. And I thought it was horse **** then.
Thus my comment on muffler bearings.
If I purchased a car and the seller gave me silly information like that I would question it. At the very least I would assume the engine is bone stock and the guy is full of it.
The history of how this terminology came about back in the day is interesting nonetheless. I can appreciate marketing.
So, is my Xtream Energy 268 a 3/4 race? Maybe a 5/8ths? Sounds kinda silly doesn't it.
But marketing back in the 60's. Yup, I get it.

Bikespace

Yup! If I had purchased a car like that, I'd take pictures of the engine compartment, of the engine with the air cleaner assembly removed, and of the engine stamp pad (under the AC compressor), and them post them all here.

But perhaps the OP can do all of that!

Mdbirk

It wasn't just advertising these were actually grinds.... without these 1/2 and 3/4 race cams and the likes of Elgin, pinky, Winfield and iskadarian we wouldn't have these street/strip cams we have now. They messed around with duration and exhaust overlap etc to make cams more efficient ie this cam is good for all out rpm or this cam is good for low end torque etc... it was actually a very important time for engineering and the hot rod/ car culture.

F4Gary

I put Valvoline VR-1 10w30 dino oil in my 72 LT-1. They also make a synthetic 20w40.

Rescue Rogers

I remember them in the old PAW catalogs

doorgunner

Rookie question......

Do "modern" engines have what would be considered high compression (compared to a '68 327/300)?

I ask because the synthetic "oil" I went to did not make it to the 5,000 oil change in an older engine...
also there was noticeably more engine "noise" after 2,000 miles of driving with the synthetic oil.
I went back to 30wt dino oil.

Bikespace

Diesel engines certainly do. 20:1 and higher. And certain diesel oil, like Shell Rotella, has lots of ZDDP.

Rescue Rogers

Regular synthetic oils don't have the zinc and phosphorus that are needed in a flat tappet engine. All the engines were basically roller cams after 87 and the oils lacked enough zddp after 93. So you may have lost a little metal off your cam or hopefully your lifters just weren't pumping up....
Compression has nothing to do with it but yes, the naturally aspirated v8s that are running around above 400 hp have atleat 10:1 compression. If you start wondering about octane ratios, 10:1 motors can still run 87 with knock sensors and variable timing easily

Mdbirk

Shell rotella t4 is great $16.95 a gallon in my area! Lots of zddp and more than enough anti froth agents! Great cheap choice! Valvoline vr1 $39.95 for 5 qts in my area and is a good but more expensive option and amsoil zrod is a good synthetic that has enough zddp but for 5qts is around $100 for me in my area.

69XR7

Mobil 1 20w-50 from Walmart

srs244

it used to be that you could also buy ZDDT additive at one time, not sure if it is still available however. as another alternative (and if cost is of only slight concern) would be to look at the joe gibbs line of oils with sufficient levels of ZDDT etc already in them.

LT1M21Vette