Cams on a GN

[Boosted_One]

Would there be any merit in looking into what kind of cam profiles the GN run? They are 2V heads and turbo'd with a lot of information and proven years behind them.

 

Any GN guys out there?

[TainterRacing]

You are some what right there but the stroke it what makes us alot diff then most trubo cars and I dare say that there heads for the most part are higher flow heads as well. But they could help.

[Tim_C.]

There are 2 guys in our local car club that own GN's. My friend has done a lot of research on them too, but I know of no one who has experience modifying one that heavily. Most GN owners are the type to not want to touch the stock appeal of the car for fear of lowering its value. These guys both put a 3" stainless steel DP on theirs. They ordered them for like $380 ea. They were showing them off, so I popped the hood on the '87 to show'em what a real DP looks like! He He! No, actually theirs were sweet, and on a very nice car to boot. The one only has 15K miles on it. The other one 45K or so.

My grinder has quite a bit of experience grinding turbo cams. He does have 2 solid cams, and 2 hyd cams for our turbo engine. He says the most 2.6L engines he has sold cams for are in forklifts. He has a nasty torque monster for the N/A 2.6L. In the forklifts, it allows the forklift to lift much more weight. He put that same cam in a carberated Caravan. Before, he could not spin the tires at all, no matter how hard he tried. After the cam swap, he could roast them all the way up and down the street. It belonged to his brother, so they had fun testing it!

He looked at the 284F specs, and said the duration is too generic for Schneider to have put too much thought into it. Or, they save a set-up fee by not splitting the pattern. He splits the pattern on most all of his cams. His performance grind for a solid slip rocker raises the intake duration more, and the exhaust duration less than the Schneider. I wasn't going to put out any of his cam numbers until I tested my roller, but here are the numbers for his solid slip rocker performance cam:

INT: 292°  .454 Lift

EXH: 280°  .454 Lift

3000 - 6500 + RPM    

Lobe seperation is 2 degrees wider than stock.  Splitting the pattern like that does a lot to build and sustain boost levels. He didn't need to split the lift on that one.

Yes, they are available, so we can put that one in the mix of cams we have to choose from. He doesn't want to deal with the public since he enjoys grinding cams. He told me to take the phone calls, and e-mails. I will get pricing. He has some 2.6L cams he can grind to save on shipping to him, and time. Shipping to him is about $20. I got my roller cam back from him in 2 weeks, and that was one he spent about one entire day to come up with the grind design, and then grind it. I want to test it first to see what happens with performance, wear, etc.... His slip rocker cams are tested and being used on road race, and drag race cars.  He doesn't have any 2.6L Turbo customers any more, except for me! He does have a lot of 2.6L N/A racers who buy from him, but most of his sales are for the 2.0L DSM'ers and what is more popular now of course.

Anyway, his roller grind numbers make more sense than any cam I've come across as of yet. I really think it would do that MPI justice. I wish there were a solid roller rocker to design a cam for. That would be even better.

Tim C.

[scotty]

I was always told regrinds that arent treated will wear real quickly esp. if you have anykind of spring behind them  are these new blanks? regrinds?what if anything is done to harden the lobes ? Just curious, Im looking forn an upgrade again and there's so much funny out here right now, I cant make heads or tails of any of this stuff any more. Keep us posted and oh yeah prices/?Thanks Scotty .,

[Tim_C.]

Well, on American made cars, regrinds are junk. Japanese cars, regrinds are preferred due to the better metal used to make them than the aftermarket cams. Even a chill hardened Schneider is not as hard as a stock cam. We did a metal test to see what the turbo 2.6L cam is, and it is the same composition as what some new Jap cars are using on a roller lobe & roller rockers, so we are 95% sure it will work.

However, the roller puts more pressure in one spot to make the need for a tough cam greater. So, I am testing my roller regrind for a few hundred miles as soon as I get it on. Hopefully this week.(still waiting for kev to send the rockers! He's waiting for my M.O.))

As for the slip rocker solid/mechanical adjust cam, it is a better option than an aftermarket cast cam. To get better than stock, you need a steel billet, and blanks of those are outrageously expensive. But, that gives more possibility for a bigger cam, like .500+ lift. But then you need big money for special pistons like I did on my .510 lift roller Schneider.

So, a stock regrind for performance should last longer than an aftermarket chill hardened cam. But with slip rockers, they can't be worn on a different cam, and the majority of time, they must be replaced to get the cam to last, even on the stock regrinds. A worn slipper will cut into a new lobe. That's what makes break in so critical on a slip rocker cam set-up. It gets rid of the slight mismatch between a NEW cam, & NEW rockers, so they will last. If the break in isn't done right, the misalignment will still be in it, and it will wear the cam very fast. The wear on slip rockers is also in the center, at the shaft, so the rocker doesn't ride true on the cam lobe, thus the dig. There is no break in on a roller cam.  So, if they last 2 months, they'll last 10 years. That's what I need to test.

Tim C.

[da_drgn]

i myself is a big fan of the GN,

         they were the first Turbo cars i fell in love with since 1985... there was one guy on the internet had one heavily modify, he posted that it was a 10 sec. car... looked sweet but wanted alot of money, hopefully in the future i'll purchase one.

[da_drgn]

http://www.gnttype.org/carofthemonth/archi...omdetails1.html

[jinx]

Doubt the GN cam grinds will help a starquest much because GNs top out around 5500rpm. Their .050 durations are relatively mild. If you check out their turbo sizing, you'll see the "rpm" issue reflected in the housing size choice also. Those motors make incredible torque at relatively low rpms... so much to the point that it'll tax the stock 3.8 bottom end in extreme cases.

The 2.3 fords may help a bit more, as they are a 2 valve motor, but they also top out around 6700 rpm. The stock ranger roller (junkyard) cam has proven as the most popular choice for the street turbo 2.3, by far.. not many folks look beyond that

 

Tim C.,

your grinder must be doing something right if his na versions are getting the job done. Maybe u can pass on those "hi rpm" motor build secrets so the starquest street motors will be bomb-proof.

Interesting u should show that kind of dual pattern cam design (more intake duration vs exhaust), as that is the way they were listed in all the older cam catalogs. It would be cool to see a mechanical and hydraulic version of his cam tested on starquests. Roller may be over the top for most starquesters.

 So many DSMs run staggered cams, but will have more duration on the *exhaust* cam. I wonder if the head design called for this, or if anyone tested it?? Most claims were BUTT DYNO saying how amazing the car picked up on top end, however, those who track tested admitted NO better et or trap... maybe the rpm pull distracts you from low end loss? Some showed a definite increase in MAS Hz, proving that the motor ingests more air... I think the overlap is just sending the boost straight out the tailpipe.

 

What intrigues me is that, with all these cam grinders in the USA, HKS still the only ones guarenteed to satsify across the board - look at DSMs for eg... crower and web get poor reviews.

 

My experience with imports; on a toyota 3tc, I had a crower regrind go flat on 2 lobes. I bought a *new* isky that claimed a powerband of 3700 to 7500rpm. Real world, it felt like I had vtec. That cam rocked!!

I'm curious as to why the schnieders don't "seem" to be working out for  turbo street starquesters, as they are a well respected. I've not frequented the bbs, so I may be off base, but thats the vibe I'm feeling. On the other hand, the isky I used tells me that u can get the "right stuff" at a good price if u keep looking for it

[Tim_C.]

jinx:

Yeah, the lower exhaust duration is better when there is a lot less overlap, so that is one reason this cam works. The roller set-up is cheaper if everything is done right on the mechanical swap. The reason so many people chew up cams is mostly because they don't use new rockers. A must for a new slipper lobe. Not all cases, but most for sure. Then comes lack of sufficient oil, and cam metal strength vs. spring pressure.

Used roller rockers are dirt cheap as kev and I found out.

The engine tricks are all posted pretty much. I just spent the bucks to get it done right. Line honing is most important. The rest is common sense lightening, and strengthening. We went closer/tight on the main journal tolerance, and dead middle of spec on rod oil clearance tolerances. That gives better oil pressure to the top of the engine.

There are others on here who really know more than I ever will. Mike K. is very knowledgeable, chiplee, kev, shelby117, and many others.

We did microhone the cylinder walls too, for a quicker seating time on the Total Seal Rings.

Tim C.

Tim C.

[kev]

Used roller rockers are dirt cheap as kev and I found out.

 

 

You can say that again.  I got 29 used roller rockers for the price of 1 new one!   And they all are in excellent condition.   There are tons of 3.0 caravans in the junkyards with these rockers.   However it can get frustrating because not all the 3.0 caravans have roller rockers.   I must have pulled a dozen valve covers only to find slappers.  

 

Tim, I may go back down there in a few weeks to pull the remaining few out of those engines where I couldn't get the alternators off.  That way I will have enough to set up two heads (1 for each of my cars).  

 

kev

[Tim_C.]

That sounds great! The cam works very well, but I just don't think the preload is quite enough, so we are going to not reduce the bas as much. He says he can get the same figures too. We had a slight miscommunitcation, so we are fixing that. I am keeping this cam in. It has slight ticking, but but not bad. Less than you hear with a performance solid. I am trying to come up with an inserrt for the rocker to extend the lifter out some. That may make it possible to do even the 284RH cam as a less expensive afair.

Tim C.