Really low vac with 274 cams

[dsmgsx98]

So I installed some Dsm graveyard 274 reground cams strait up and trying to figure out why the my vacuum is at -8 at 900rpm. I thought they would still have a vac of around -12 to -14 can someone that has these cams help me out

 

[dsmgsx98]

But. I should see like -14 because I adjusted them for less overlap

 

[dsmgsx98]

OK so Saturday before I pull the cams I am going to pull the shims out and see if that changes anything because I think some or all the valves are staying open causing vacuum problems ... If anyone's has any suggestions on what to try I am interested in hearing them.

 

[dsmgsx98]

Guess what ppl, I pulled those shims guess what I got all my vacuum back. My cams are see a 0ex+2in and I have -17 vacuum but my lifters are a little noise bit I think if I find the loose roller rockers an add a shim I bet I will quiet it down, still lopes at 1000 rp. Wonder if I have to use shims? ??


Edit: I pulled the valve cover back off seems that about 8 or 9 valves need shims so I am going to add them and post back shortly...



Update: all but 2 rockers needed shims. So I installed the shims and now I am back with low vacuum, well around -10 so I guess ill have to find shims that arent #10 SS. Washers but some thing a little thinner. Anybody know if its safe to run with out shims

 

[dsmgsx98]

Does anyone know if I can run these cams with out shims and them still perform like they are suppose to?????

 

[Boomdeeze]

I have heard that you dont want to run cams without shims that require shims. You might lose a rocker arm because there isn't as much pressure on it.

 

[dsmgsx98]

I wonder if I went back to my stock 2g lifters if that would help because these 3g lifters are a little bit bigger so I guess I am going to try stock lifters with shims. Even thou I think I will yeild the same out come

 

[Sandman817]

isn't the point of running the shims with the regrind cam is so make up for the material that was ground off from the cam? running no shim would act like an even less agressive cam than the oem one...if it works that way.

 

[dsmgsx98]

Well it still loped pretty hard and had a vac of -15 and .60 shims it was -9 and with .30 shims in it has a -11 to -12 vac and I adjusted the gears and it did nothing for vac

 

[viperlp01]

A hell of alot of work you are doing here man and by removing the shims you are changing the geometry of the rocker. You are getting alot of lifter tick which tells me your loosing some of the duration when the cam lobe looses contact with the rocker and that is what is giving you the vacumm back. Seriously I would stop trying. Just drive the car or switch cams. You are spending half the spring trying to get your car to have more vacumm.

 

[dsmgsx98]

Just trying to get to the bottom of why these cams suck. I am not trying to argue with you but I would be losing lift not duration, and I am sure my vacuum problem is due to vavles being stuck open.

 

[viperlp01]

You would be loosing both now you mention lift.. How do you gain vacumm by just lowering lift?
The duration is what is hurting your vacumm(overlap). You bought cam gears to adjust when the valve opens and closes. If you did a compression test you would know for a FACT if you valves were open. You loose an extreme amount of compression if one is stuck open even a little. You can also pressurize the cylinder and slowly try to turn the engine over and see if you hear leaking coming from the exhaust or intake.

If you look at the profile of the 274 regrind the lobe looks to be off center. It is done on purpose as my kelford have the same basic profile but one thing I brought up last time I was over at The Graveyard shooting the shit with Jon was how noticable it is. My Kelfords cam lobe is noticable larger than the regrinds cam lobe. Mainly because material had to be taken out. But the Kelford has a smoother transition in and out of lobe center while the regrind seems to just kind of fall off. I am not a cam expert by any means but these are things I noticed.

 

[Boomdeeze]

So are you saying these cams are junk?

 

[viperlp01]

I don't know guys. If they make power there not junk. It seems they are asking alot out the stock cam lobe don't you think?

With that said, all the labor and time and add ons like the cam gears, are the 250 dollar set of custom cams worth it. We have had good results from the 275s we offer which have an extremely similar cam profile to the graveyard 274s and have never had a complaint. So you would have to get a set of both in your hands and start measuring the differences.

 

[dsmgsx98]

Do you wanna send me some ill test them out for you!?!?!?!?!

 

[johnmarines]

I currently run there 275 cams in my 2g. The lobe sounds great. My vac is about -8 at idle in park. I do have adjustable cam gears but I am hesitant to start messing with it due to being worried about piston slap. viperlp01 would you have any recomodations on what degrees I should try ?

 

[rocafellafw]

I'm ready to ask Jonn if he can take the cams back + some $ and return me 272's like I originally wanted, plus these cams do not suit my 16g well at all in the first place. The multiple negative side effects definitely out way the power these cams make up top.

 

[ziggo0]

I'm ready to ask Jonn if he can take the cams back + some $ and return me 272's like I originally wanted, plus these cams do not suit my 16g well at all in the first place. The multiple negative side effects definitely out way the power these cams make up top.

I've thought the same exact thing to be honest - but since I'm moving to a HX40 from my 20g maybe they will be put to better use. The vac doesn't bother me that much, just keeps things interesting when the car is off in the drive way and you go to start it .

 

[Odin]

Sorry if this is too off-topic,
Ive got a stock bottom end 4g64 DOHC swapped and I just recently installed Delta 272 regrinds, but I have stock cam gears hence -8in vac at idle haha.

How much of a PITA would it be to install Adjustable gears with the motor in the car? The low vac doesn't bother me too much, the car doesn't die at 900rpm idle, and the brakes still work, the low rpm bucking gets annoying though. Plus some vac would help with gas mileage haha

 

[dsmgsx98]

The gears will not help your problem. I bought some and i adjusted them all over the place and never gained any vac back.... I now have the adjusted to 0 and 0, it runs the best at this setting!!!

 

[rocafellafw]

Man that's disappointing..I thought we were on to the something with these cam gears I'd love to find someone willing to trade cams.

 

[Delta Cam]

The lobes don't actually get taller on a re-grind cam, they get smaller because you're taking material off. So to compensate, shims are used to effectively gain lift. Thats why on re-grind camshafts you have to use the recommended shims for that particular cam.

INCORRECT !

Take a minute and watch this video....... YouTube - ‪Aaron's 4g63 Mitsubishi Eclipse Turbo 272 cam grind‬‏

Shows that when we regrind the lobes, we remove MORE off the bottom than the top this creates more lobe height = more valve lift.

The shims are only used to properly preload the HLA because we removed material from the bottom of the lobe ( basecircle ) this lifts the HLA back to the proper location to get preload.

 

[rocafellafw]

INCORRECT !

Take a minute and watch this video....... YouTube - ‪Aaron's 4g63 Mitsubishi Eclipse Turbo 272 cam grind‬‏

Shows that when we regrind the lobes, we remove MORE off the bottom than the top this creates more lobe height = more valve lift.

The shims are only used to properly preload the HLA because we removed material from the bottom of the lobe ( basecircle ) this lifts the HLA back to the proper location to get preload.

So what is your guys recommendation for these problems we are having ? I would have never purchased these cams if I knew it would make it me not be able to idle below 1k, not be able to drive under 1.5k without bucking, and pull such little vac it actually affects my braking.

 

[EclipticalGS]

This low vac reading you guys are seeing is the sacrifice your going to make when your running a reground cam with a drag strip duration that needs shims.

A better set-up, (although costs more up front), would be a cam that is cut from a fresh core. Delta's K272's, Kelford 272's, etc, in which there are no need for shims.

I personally run Kelford 272's, stock cam gears, 900rpm idle, and am shooting for 14.5afr at idle with a set of 1350cc injectors. My car pulls -14 vacuum and literally idles perfect with a "gentle but firm" lope.

When my car was stock it pulled -21 vacuum so I wasn't surprised to see that reading drop 6-7 points.

Maybe you all should have made a better choice of purchase.. Meaning, there's a whole thread with people in it complaining about a 'certain' set/duration of cams from one or two company's and they all have the same issues.

The cam degreeing for less overlap formentioned in the previous pages is correct to a point, but I highly doubt retarding Exh. 2*, and advancing Int. 2* is going to take someones vacuum from -8 to -17....It's not even logical.

I recently have been working with/ designing a lot of CNC-machined heads (just for a measurement base, and a flow study) at work and their "variable-cam timing" for a big-name car corporation, and I can tell you that you are all just seeing the belly of the beast when upping the cam duration and lift.

Lastly, most of you still running the 16g are wasting it's potential. The 16g drops off well before redline with 272's so the cams you just bought to make power in the upper rpm's, wont make it because the turbo falls on it's face at the same time.

264/264 is probably the best cam set-up for a linear power-band with the 16g, as well as being daily driveable, and will all get your vacuum within -14 to -17.

Everything must coincide when you start modding a car. Everything is purchased to accomodate a certain power level you want to achieve.

 

[Boomdeeze]

Thought I would report back on this thread about my findings. I finally got my car started after doing the cam swap from the 274's to the fp2 cams and my vacuum went from -4 to -16!!! All I did was swap the cams and that was IT!!! I am amazed with these cams and love how they sound. DO NOT BUY THE 274 CAMS FOR ANY TYPE OF STREET CAR.

 

[19BLACKGST98]

Congrats on figuring it out...I was subscribed so Im glad to see you got it fixed.