Norpower

Was looking to get some more lift out of my 155/156 cams which are .435/ .395 int/exh . My local cam grinder says after analyzing these cams that we can get .473/ .434 lifts but has to remove .040in or so from the base circle. My question is can the stock hydraulic lifters compensate the bigger gap or are there any valve stem caps available somewhere? I tried doing a search in our forum but either I am doing something wrong but keep getting no search results no matter what I request.

RicerSchnitzzle

9mm valve lash caps will work. Some have used bigger cams with stock liters with 1mm or less base circle reduction. Problem is getting the oil fill hole on the lifter to be in the oil channel long enough to keep the lifter pumped up. You can modify the lifter hole with a small "channel" to help out. Since grinding cam base circles runs $125+ per cam, why not just buy a set of Euro S cams?

Also with a base circle you change the ramping rate for valve open and close, not just total lift. The lifters and springs have to work harder as they accelerate to full open/close quicker. I would recommend 944 Turbo springs with a base circle grind. With the Euro S cams available, I'd go that route first. Then if you want even more, base grinding is a cheap alternative to a true weld and regrind.

I should be able to tell the difference soon. My JE S+ cams were a weld and grind. I have a set of Euro S cams heading to Delta Cams for a base circle grind now. Should know in a couple weeks. I'm having the lift taken from stock to .511" About a 1mm reduction in base circle. I'm not expecting perfect results with a base circle grind only, it's a compromise for price. $250 total verse almost $1300.

hacker-pschorr

AFAIK all 16V 928's use the same lifters. The largest difference are:
80-82 US intake @.396 versus EuroS intake @ .472 = .076
80-82 US exhaust @ .350 versus EuroS exhaust @ .432 = .082

FWIW your new specs are damn close to EuroS. How much is this going to cost versus buying EuroS cams?

BC

I also have my 78 cams at Delta Cams in the NW for base circle cutting. They have yet to call me on what my options are. It seemed cheaper than finding euro S cams, and the overlap is too much for good boost. I just wanted more lift.

RicerSchnitzzle

Delta was recommended for good work and great prcing, however Johny Blaze (What a stage name) is slow to answer emails.

BC

Well for 125 a cam I can wait.

slate blue

I have three reground cams sets, I didn't get a power increase over the S cams when I increased the duration. I think the S cams are good but you need to increase the comp to get an increase in power over the S cams. This is what I will do when I build the next engine.

The big cams is are solid lifters and they have 0.542" net lift, this should make a big difference, I wish I had more lift. I had some luck and got some lifters made up courtesy of a member on this board and they were made for a reasonable price dlc coated too to reduce the friction.

When I did my heads I used part of the 944 turbo spring and part from another similar spring, I didn't want that much spring pressure for mainly wear reasons, you will need a very good/suitable oil with lots of ZDDP with that much spring pressure otherwise your cams will just get ground away.

When you guys say ground the base circle are you talking total regrind (which is what I have) or just a base circle reduction?

Greg

RicerSchnitzzle

Just a base circle reduction. A little bit is taken off the very lowest point of the cam, effectively making a new "zero" point and increasing lift. On my JE cams they welded new material on and then did a new grind so duration and lift rate remained closer to stock. With small base circle reductions the lifter can pick up the slack. More than 1mm and you need lash caps.

.542" Is HUGE by 928 standards. Love to see your results.

BC

Is the 1mm a sure thing? Is it not more like 2mm?

slate blue

Brendan I pretty sure Ricer is correct at 1 mm, you can sink your valves in deeper if you had to but there is limits to that too of course.

Greg

Norpower

I couldn't find any Euro S cams at the time so I had these from a 78 euro motor. Which are a little better than my 80. So it seems that I can just drop these in after a regrind since I will only remove .038 from the base circle. I understand the ramp angle will increase but wonder if I really have to run such high seat pressure if I replace the stock springs with 944 turbo springs?

RicerSchnitzzle

The specs you're after should not require new springs unless you're trying to up the redline. You're basically making Euro S cams wiith a little less duration.

BC

Thanks. So 1mm or .039" So call it .040. Doesn't seem like very much.

But I could tip the valves a bit, or get lash caps to make up another 1mm that could be cut from the cams? Maybe 2mm is too much, wrt the valve cuts in the pistons, etc.

Norpower

Great, that was the plan. Thanks again!! Now back in the garage

robot808

So, Norpower, did you ever get this done? Results?