Tomei Poncam 'b' Install In Rb26- Exhaust Cam Does Not Rotate

[Andrw Le Lievre]

I recently took my BNR32 to my local shop to install turbos (2530s), manifolds, dumps and cams and a D-JETRO Power FC. Everything went smoothly except for the cam swap. During the install the exhaust cam would not turn. A litlle too energic coaxing ended up in it snapping. Suspecting it was a problem with that cam they ordered a replacement but still no joy. The intake Poncam rotated smoothly but not the exhaust cam, even after some wet & dry work on the caps. In the end they reinstalled the original cams which rotate fine. Dissapointing as the 2530's could really do with the extra airflow to get them on boost.

Has anyone encountered a situation like this before? Are there any solutions other than line boring the head?

Andrew

[BHDave]

were they obviously fouling on anything?

It's a long shot but did you check the diameter of the new cam where it sits in the head compared to the stocker?

[Andrw Le Lievre]

Yes checked that out. No appreciable difference. The shop thought that perhaps the head had warped or something.

Andrew

[Beer Baron]

my first guess would be incorrect installation. as if the cam caps are not torqued down properly and in order then this can happen. it does seem strange though that it would happen twice, and not at all on the stock cams.

[Andrw Le Lievre]

The question I face is to take it to another shop in Sydney, pay for the install only to find that the first shop was right and there is a major problem that requires the head to be pulled. I will then face paying for the labour to pull and remove the standard cams a second time...

Andrew

[DVS JEZ]

my first guess would be incorrect installation. as if the cam caps are not torqued down properly and in order then this can happen. it does seem strange though that it would happen twice, and not at all on the stock cams.

sounds like they have swappedthe cam caps around, my machine shop did it about 4 weeks ago to mine, they snapped my cam when they bolted it in but, they swapped the cam caps around and its all good now

[Beer Baron]

sounds like they have swappedthe cam caps around, my machine shop did it about 4 weeks ago to mine, they snapped my cam when they bolted it in but, they swapped the cam caps around and its all good now

yes that can happen too. as the surfaces have worn unevenly when the mix up the caps one of them is suddenly now gripping the cam. you really just need somone cluey to have a look at see where it's grabbing the cam. it's unlikely that it's a major problem with your head as if it were your stock cam wouldn't work either. the reason the stock cam is ok is that it's most likely worn down in the spots where the new one is being grabbed.

[rev210]

cam caps as suggested sounds like the issue.

[2rismo]

Agreed. Just cos they look the same doesn't mean they can go back on differently.

[Blitz]

Unfortunately this isnt the first time I have heard of Poncam's snapping.

I know of around 3 other cases where this has occured, and each time the cams have been installed by experienced workshops

[BHDave]

Thats intersting, it's usually the hks cams that get bagged for snapping.

On the cam caps idea, They're numbered so easy enough to check

[Andrw Le Lievre]

They actually said they tried different caps with the same result, but I cannot be sure they got them in the right order in both cases. They did go at the caps with wet and dry which suggests they were onto the issue though. No one has had a case where it was impossible to get the caps/cams to work together with a little TLC?

If so who in Sydney do you think I could take it to troubleshoot the install? I was thinking CRD this time around but am already down $800 on the first failed attempt to put these in...

Andrew

[mattymagoo22]

did the cams snap at the same point both times?

[Fitzpatrick Speed Works]

Ok heres a post to help you sort the BS from the info you need.

-You MUST keep the bearing caps with the corresponding spot or this will happen everytime.

- with GTR's you must be ULTRA attentive when pulling down the caps, you must take it slowly and do it correctly otherwise bang, snapped cam.

- You DEFINATELY can't use different bearing caps without tunnel boring otherwise, SNAP.

-You need to ensure correct torque settings are addhered to.

GTR cams are cast forgings, majority of them are not true billets, actually I have not used any true billets in any of my engines, and they are very brittle items that will snap if mis-managed.

I highly doubt you head is warped however this is easy to check, run a deck hight measurer on you head and measure the heights of the cam caps relative to the cylinder deck.

Cheers

[Andrw Le Lievre]

After it snapped the first time, they ordered the replacement, fitting it. Found it was still binding. Played around trying to get it to work and then gave me the call. Pull the head and line bore the exhuast cam ($1500) or put the standard ones back in ($800).

[DVS JEZ]

After it snapped the first time, they ordered the replacement, fitting it. Found it was still binding. Played around trying to get it to work and then gave me the call. Pull the head and line bore the exhuast cam ($1500) or put the standard ones back in ($800).

plastigauge it to see which cap is binding?

[rev210]

the fact they tried different caps says ' oops forgot to which one goes where...' thats where the problem starts.

Edited February 6, 2007 by rev210

[sky30]

The caps have numbers on them (1- 7) so i cant see how anyone could get them mixed up?

What lift in mm did the cams have?

[mattymagoo22]

just wondering (again) at which cylinder/lobe did the cam snap/shear?

[Andrw Le Lievre]

Thanks for all advice so far. The cams are standard Poncam 'B's so lift is 8.5mm@ 256 duration. Did not see the snapped cam so not sure where it broke.