Rebuilt engine to the track?

notmytarga · notmytarga's Garage

I'm thinking of bringing my 2.7 engine back to Thunderhill where I dropped a valve on my 54K mile 1975 2.7 engine last December.

It has 650 miles on the rebuild that I did and has been running strong during this break in period. It will have 750 miles on the rebuild by the time I hit the track for some Hooked on Driving, Drivers Education track time.

Is it a mistake to track a newish rebuild engine? If I keep the revs below 5000would it be a problem or would the workout help with the break in?

I added an external cooler and it will be in the 70's.

engguy · 10-28-2008, 08:20 PM

Nascar engines do it all the time. So do drag race competitors. I don't think they get too many miles on an F1 engine before going to the track either.

Flieger · Flieger's Garage

Go for it!

What did you go through all the work of an engine rebuild for?

Enjoy the result of all your hard work

Eagledriver · 10-28-2008, 09:35 PM

No problem tracking a fresh motor. Do you know why you dropped a valve? Many times an over-rev will result in a bent valve and broken rocker arms.

-Andy

notmytarga · notmytarga's Garage

Eagledriver - The #1 exhaust valve stem fractured near the valve head. The valve guides were worn on tear down as one would expect from a 2.7, even at 55k miles. In pregrid before hitting the track for the last session I had significant smoke which wasn't a problem before. I remember a mis-shift sometime that day but it wasn't at the time of the compression loss and there was no evidence of valve/piston impact on the pistons that were left intact (any impact evidence on Piston #1 ws obliterated)

So the dropped valve was likely the result of poor valve cooling from valve guide wear. Thermal reactors were removed long ago.

I had the case timecerted, full head work with valve guides of course, oil bypass, 4 rib pump, shuffle pinned a center web, cooling tin modification, replaced all bearings, resized rods, crank polish, polished my CIS piston tops like I did my wheels, balanced everything out, replaced destroyed piston via EBay, new rings, engine tin - fan etc powder coated, new injector sleeves, vacuum and breather hoses replaced, full Elephant supplied lines to 28 tube brass oil cooler. SSI exhaust is on order and should be finished in another month or so.

The Stainless Systems Inc. in Novato had to shut down production until they had better stainless supplied, they are getting back on line now. I'll be interested to feel my power on the straights at Thunderhill with the rebuild and then again later with the SSI system.

notmytarga · notmytarga's Garage

The track day went well. The engine seemed stronger than before. I wasn't very good at keeping the revs below 5000 - I found myself at redline before going to brakes on some of my favorite turns. I was tempted to spend the $150 to jump on the dyno at the track, but I'll wait till I get the SSI's on.

The oil cooling was great. I never saw anything above 210 F.

I used an infrared pyrometer to check tires and also the cooling system exterior. The temp of the oil lines went from 170 to 110 during the long trip to the front and back. I did note that that the oil tank surface right behind the RR tire was 180 F which seems odd given that that is where the cooled oil ends up. I'm guessing the thermostat is still sending some of the hot stuff that way. Any insights on this?