For a wile now I have been battling with low vacuum at aprox 5 inch of vacuum. The vacuum wasn't checked before the engine was stripped down and the top end was freshened up so I am unsure if this is a new or old issue.
The cylinder head is an E88 and was checked over and was skimmed to make sure it was true, the valves were lapped and the ports were smoothed out but nothing to serious. It had an aprox 74 degree cam installed from Camtec camshafts and have included a picture of the specs sheet. The bottom end wasn't touched in the rebuild process.
On its first startup it bent a valve due to me not setting timing correctly, the bent valve was replaced and the head and engine checked for damage. Other than a little dent in the piston that was all the damage that I could see, since then the engine has been running and the timing issue was fixed.
- I have checked the compression and with the throttle CLOSED and received 140 / 145psi across all cylinders, I also did the oil check to check the rings and only noted a 5psi change on 1 cylinder. I know I should have done my compression check with the throttle open but completely forgot but to my understanding it will only increase the cylinder pressure.
- I have checked the valve clearances and they all check out.
- I have put all new gaskets on intake and carby's and checked all the bolts are tight, I have also checked over with aerostart and didn't find anything.
- The engine has no aircon or aircon gear all vacuum tank removed and aircon controls into the cab have been unplugged.
- I found the vacuum advance to be leaking so that was unplugged and just mechanical advance is being used.
- I have disconnected the charcoal canister and plugged the vac lines incase the diaphragm was split.
- I checked the brake booster check valve and its direction and that was all ok.
- All of the vacuum hoses and booster hoses are new but I checked them anyway
- All unused manifold ports have been plugged
Or could this be just the camshaft stealing all the vacuum? I searched and found an article on a zed that had low vacuum and a larger cam but the topic never stated if the issue was fixed. However another member said he had aprox 13inches of vacuum which is still low but not to bad for a larger cam. This makes me think 5 inches of vacuum is not right!
I have included pics of the cam spec sheet, timing gear, dissy/ ignition timing these pictures were all taken with the engine at TDC
hopefully this issue can be something reasonably simple help me fellas its almost got me beat.
Edited by blu260z, 16 October 2016 - 01:31 PM.