[DeTomaso] Got the shakes?

[Thomas Tornblom]

Yesterday I took my GT5 out for the first drive after the engine 
rebuild, and I am happy to report that the vibrations are gone.

When I had the engine rebuilt in 2005 I had the rotating assembly 
balanced, just to make sure everything was optimal. Turned out the guy 
do the balancing must have had a bad day. I was surprised to see the 
amount of material they had removed from the bob weights on the crank, 
but assumed it was necessary.

I noticed already on the first drive that there was quite a lot of 
vibrations at certain rpms, ~1200 - 2000 rpm, and the images in the 
mirrors was just a blur, and I could not attach a GPS to the windscreen 
as it would just jump around.

Over the years I have tried a lot of things, including pulling the 
transaxle to check that the correct weight had been installed on the 
flywheel, and I installed a new clutch, to no avail.

This winter I thought enough is enough and out came the engine. When the 
local machinist checked the balance he said it was about the worst he 
had seen, and he engaged some other machinists to check that he hadn't 
made any mistake setting the crank up. The crank was missing about 180 
grams of mass in one end and 160 grams in the other end, and it would 
have taken a lot of expensive heavy metal inserts to fix. Luckily I had 
the crank from the original engine on a shelf and we used that one 
instead, and it took very little work to get balanced.

He said he was surprised that the bearings looked good even after 12 
years of beating with this severe imbalance.

I'm just cursing myself for not having the energy to pull the engine out 
again back in 2005. The shop that did that job has since moved and the 
guy that did the machining has retired, and it wasn't even them that did 
the balancing, they used someone else as they did not have the equipment.

I also swapped the cam on this rebuild for a Dan Jones speced Bullet 
hydraulic roller, which should work better with my heads and the EFI 
than the staggered Crane hyd roller I've been running, and I can once 
again putter around town in 5:th :)

I followed http://www.mototuneusa.com/break_in_secrets.htm on the 
initial run and did a first oil change after about 20 miles, and I was 
surprised to see how discolored the oil had gotten. Not from soot, but 
from what appears to be metal from the rings and bores, so changing the 
oil should be done soon after break in.

Now I need to put some miles into it before we leave for this summers 
trip to Austria.

Cheers,
Thomas

-- 
Real life:   Thomas Törnblom             Email:    thomas at hax.se
Snail mail:  Banvallsvägen 14            Phone:    +46 18 32 31 18
              S - 754 40 Uppsala, Sweden  Mobile:   +46 76 209 8320