CMac,s 1971 Datsun 510

[Cmac]

Well I went to go on the NorCal Delta run Last weekend and had some issues on the way to the meet up point. I thought i had blown a intercooler pipe line the car just was not running well and sounded like a 1200cc VW. Its too bad the run attracted about 25+ cars and can be seen on Ratsun's events section.

I limped the car over to Phil Lee's Shop Speed of Sound here in Sacramento. He did a leak down test and compression test as well as the Radiator bubble test etc. checked the injectors and coil packs. With no clear results as to WTF and the fact that my daughter was in the car with me I limped the car home and parked it thinking I did something really bad. Wednesday night I was able to pull the valve cover off and found that i had broken a rocker arm into 3 pieces. Come to find out that this is a common problem if you miss shift / over rev I am not admitting to either of the two. Solution is to run solid lifters 130lb springs etc. The other option that people are talking about is using the VVL roller rockers on the standard head. Issues are the rocker is 3mm larger so the spring and valves need to be shorter I hope someone figures this one out. Mazworks you listening.

[PoorMtnKid]

Ahhh man that sucks. I has a guy from a shop trying to sell me upgraded rockers for this reason. It's actually good to know he was not BS'n.

[510wizard]

So, if you don't miss shift / over rev then this is not a high fail item or is it just a poor design on Nissan's part? I wonder if the rocker gets at an angle (cock eyed) at valve float, then when the cam lobe comes around it wipes it out.

[okayfine]

http://www.ebay.com/itm/Tomei-Rocker-Ar ... c0&vxp=mtr

[johnbureezu]

Looks like he has those installed already^^. I have heard varying arguments about using rocker arm stoppers too. One being that if you use them, the rocker arms snaps since they have nowhere to go. Usually they would pop out but still be intact so you can pop them back in with out the RAS. I personally use them myself since I rarely go past 7.5k. Usually when you take SRs to 8k is when those problems become more evident. But yeah, sorry that happened to you Cmac.

[S15DET]

Roller rockers, nice, we need a solution for this swap. Bad luck but at least nothing else was damaged.

[Byron510]

My shop mate "chipped" his E30 with a claimed 15HP increase. Prior to the chip the car had about 10 track days on it. With the chip,there was actually absolutely no change in the map, it just moved the redline up 500 RPM. Same result as above, one longer pull and he passed the factory redline and bang - that's all she wrote!
Those engineers get paid the big bucks for a reason, and it makes me laugh when some tuner in some back alley shop figures he knows better. Don't get me wrong, there are lots of guys out there who do know better, but they are not the ones panning this newfound knowledge.

I hope the repair isn't too bad. Do you think you may have tagged the valve? Might it be worth checking? A valve head breaking off is not a failure the motor will recover from. Dealing with industrial engines on a daily basis, we see the result of broken valves often in the turbo business - pretty messy stuff.

Good luck with the repair.

Byron

[Cmac]

digging some more and found these

NAPREC Strengthened Rocker Arms SR20DE(T) at 700.00 id hope they did not break.

[Cmac]

Well on friday the new rocker arms were supposed to show up but they Nissan sent the Roller rockers instead of the Std ones. There just happened to be a new kill at the Pick and pull a 1999 G20. I was able to pull all of the rockers, lifters and shims for $30. Given I was not sure if there was any other damage to the valve train I said WTF. Installed the parts and it ticked for about 5 min and then became quiet. Such a relief because it was a long 5min let me tell you. I need to re time it and all should be good for now right.

While digging around on the net I found a Dual Guide modification for the rockers that is supposed to help retain the rockers. Mazworks performs the rocker modification. That is going to be plan B along with some solid lifters if this happens again.

[Sleepys-14]

9 times out of 10, its the harshness of the rev limiter. It is very common to use a fuel cut to soften the rev limiter. If you keep the revs to 7500 and have a soft cut rev limiter, you should be golden showers.

[Boy Blunder]

Cmac,

As a former fwd SR20 guy ( SE-R owner)... I can tell you this. Revving the piss out of an SR20, especially a non VVL engine can get you these results. More strain on the mechanicals can do this as well. I do not know what camshaft/valvspring etc combination you are running at the moment.. But I will warn you that you should NOT run rocker arm stoppers. These are the engine killers. It is a well known fact in the FWD SR20 community that you are better off popping a rocker rather than turning one into shrapnel.

Tomei solved this problem by converting to a solid mechanical lifter type that requires shims etc.. in a way you would be taking a step back in engine theory and would deal with tolerances like an L series... but from what I know the system is bullet proof. FYI – NIssan actually used a mechanical solid type lifter valvetrain in the 54C SR20DET.. the "Homoligated" rally SR20 from the Pulsar GTi-R.

Most important point though... Do not run Rocker Arm Stoppers.

Mazworx knows their stuff quite well and have helped the US SR20 community a great deal.

However... if you really want to dig into some SR20 dirt.. head over to the www.sr20-forum.com ( the dash) and search for some of the Andreas Miko posts on the valvetrain. The guy knows his stuff, have met him personally, and I would recommend his advice to anyone with an SR, no matter what variant.

[Cmac]

Thanks for the ideas. I have read many of Andreas Miko posts on the sr20 forum and have found them to be very informative. The times I have popped off the rocker the revs had not been over 6500 rpm. however I can say that this started to happen the day after I miss shifted bounced off the rev limiter.
Current set up as follows:
-BC Springs
-BC Retainers
-256 Cams - damaged the exh cam on last go around
-Rocker arm stoppers

I have come to find out that 256 cams can be run with stock springs and retainers - this could be the issue there just might be to much spring for the application. I have also read in many posts now not to mix and match cams and springs from different companies. So much for listening to the shop that I purchased these from.

The car as it sits right now is motor stripped head is off and trying to figure out what my plan of attack is going to be. So far the set up is going to be tomei solids, tomei springs, with 260 cams. double guide shim conversion. Id love to go to the VVL head conversion but I dont think it will fit under the hood.

[Boy Blunder]

The VVL head should not be any taller. The 20V ( not a 20 valve, commonly mistaken) head may be just a slight bit taller. Mostly because of the valve cover.

If you were wanting to go with a VE head, Mazworx is the only shop I would listen to. They make parts specific for this swap and are the go to source for most things commercial SR20 stateside now. They used to run SuperTech valvetrain components and thus far I have not heard of any failures to do components. You cant fix stupid, and sometimes people shouldn't build an engine in a backyard so you have to have that as an X factor.

BC cams is the low end of camshafts in the SR20 market. JWT would be one of the better ones to get, if not Tomei. I would only choose between the two on a street driven engine anymore. JUN had some nice grinds but they are old news anymore.

If i were to build a RWD DET setup, I would run the Tomei Pro Cam solid lifter setup with the 270 degree 11.5mm lift cam. One thing to really pay attention to between the brands on the SR20 cams is the lift. ( Hint, Look at JWT and you will see the R&D). We would always joke how the cars with the JWT S4s would do the "Harley Shake". SR20's eat up the lift on a camshaft. I am not sure what turbocharger you are running, but with a smaller T3 turbo this would be a insanely fun street setup.

Get rid of those damned rocker arm stoppers!

[Cmac]

Cams were the Tomei 256 poncams good all around cam undersized however for the GTX3071 turbo. I have been talking to Mazworx tech support the last few days to see if the VVL head will fit in the Car. The Head on my s15 with Valve cover is 8 1/4 inches tall at the front and 9 1/4 inches at the highest point in the rear. From what I have found out the VVL head is 9 inches tall with valve cover. In order to make it work you have to modify the hood at the front by 3/4 of an inch in my case. Now in order to do this and make it look right is another issue all together. Thinking about this last night I came up with a couple of options 1. graft a 240 z center section into the 510 hood. 2 graft a roadster hood section in and lastly the new M3 hood has a raised section in it now that might work. The last thing I want to have it look like a mail box or an attic fan.

The P11 head is easy to find the p12 head is not so easy. In order to build a solid Det head the cost is almost the same as doing the VVL head swap. Yes the other factors that I am not including will put the over all cost of the swap well over the rebuild cost but at this point I am just thinking out loud.

[Super X]

CMac, what c/m and mounts are you using? The vvl head will clear the 510 hood w/o any modification on a flipped c/m and 510 mounts. The only problem would be firewall clearance with the vvl solenoids but there are many ways to go about this issue.