1970 454 Corvette Stingray
Visitors Since May 2000Updated January 2008From a Time When COOL Was Measured in Cubic Inches!
Blowing Smoke! The First Sign of an Engine Problem Since the Rebuild.
September 2005... Almost 1 year to the date I put this 454 in my Vette, the first engine problem arose. I last ran my '70 Vette about 2 weeks prior to this event. We attended a local car cruise. It ran great, came home and put her in the garage. Uneventful day....
Today we planned to go to another cruise, so I go start her up and back her out of the garage and after a few minutes there's blue-ish smoke coming from the drivers side exhaust. Nothing from the passenger side. I mean a lot of smoke. Yeah, I think I'm burning oil.
There's no difference in idle, it's not missing or struggling. Nothing! Everthing else seems fine. Still pulls strong.
I'm thinking maybe it's the valve lash. Could it be comething that simple? My worst nightmare would be the piston rings that I laboriously installed. I really wasn't looking forward to the diagnosis on this one.
The only other clue/symptom - I noticed what looks like oil/grease dripping onto the exhaust manifold. Don't think the smoke was caused by this because the smoke was definetly comming from the exhaust tip and it was blue.
Over the course of the next 2 months I have very little time to spend with the Vette. I started a new job in August with a new project go-live coming up.
When I finally have time to diagnose the source of the oil, people have told me everything from head gasket to intake gasket to rings to you name it. Except a couple seasoned guys simply told me not to panic and look for clues and DON'T start tearing into the engine until you've checked all the simple things first.
My first step was to remove the Holley carb to see if there was any oil in the intake. That could mean a blown intake gasket. As you can see in the picture above the intake is sparkling clean, a good sign.
Well, I had oil seeping from between the exhaust manifold and the head. It also looked like there was oil coming from the bolt! So I began there and removed the exhaust manifold bolt. Above is what I found. The top bolt has oil in the thread! The threads should look like the lower bolt. When I assembled the engine, I used anti-sieze on the exhaust manifold bolts because they were going into aluminum heads and manifold bolts are notorious for seizing in the head over time.
A few guys told me that there could be a flaw in the head and that oil might be seeping down thru the bolt hole during compression. I used some Permatex thread sealer and re-installed the bolt. I fired the engine up and there was a little less smoke but not much. That wasn't the problem but part of it.
At this point I didn't know where to look next for the simple things that could have gone wrong. It was time to do a compression test and leak down test. I ran the compression test and found cylinder #1 @125psi and #3, #5 and #7 to be around 170-180. So something was definetly going on and wrong with #1. Something I didn't want to accept either.
I removed the valve covers once and hadn't noticed anything unusual with the rocker arms-pushrods and springs. But this time I took a real close look at things. I was trying to look between the springs to see if I could see the valve seals in place. I couldn't.
But, while I had my head real close to the spring, I noticed tiny shiney silver specs on intake #1 spring! I grab the rocker arm to see if it's tight or loose and it's real loose. So loose in fact that I could loosen the rocker arm nut with my fingers.
Valve lash? I evidently had about 0.5" of valve lash on intake valve #1. I slid the rocker arm to the side and the above picture is what I found. The pushrod tip was smashed.
My take on what happened? I think my rocker arm nut on intake #1 had backed off and continued to do so until symptoms presented. The symptoms being oil sucked through past the piston rings and out the exhaust. With the valve lash so large the push rod was just mashing into the rockerarm. Eventually the pushrod tip caved in.
My take on what happened? I think my rocker arm nut on intake #1 had backed off and continued to do so until symptoms presented. The symptoms being oil sucked through past the piston rings and out the exhaust. With the valve lash so large the push rod was just mashing into the rockerarm. Eventually the pushrod tip caved in.
When I pulled the pushrod out I inspected the lifter end. Fortunately it was ok and didn't indicated any lifter involvement.
I removed the rocker arm to inspect the underside and found that it had taken a little beating too. And these rocker arm are Severe Duty rockers.
The solution? I replaced the pushrod and rocker arm with these in the picture above. The rockers are "roller-tip." There's much controversy over these rocker arms as to whether they add any or how much additional horsepower. I just don't want them beating up my valve stems.
I also plan to install these rocker arm locks once the weather warms a bit. This should prevent the rocker arm nuts from backing out and preserve the lash on the solid lifter cam. I just hop they fit under the stock valve covers with the drippers.
In the mean time, I double nutted cylinder #1 with two rocker arm nuts.
In the mean time, I double nutted cylinder #1 with two rocker arm nuts.
May 2000-----This is a reprint of the actual road test for a 1968 327-350HP 4sp Corvette. Its HP and engine is a close match to my original L-46. Its interesting to view some of the specifications, and not just dwell on the performance stats. One item that caught my eye was the tire size...F70-15!! But remember back in 1968 this was the Wide Oval performance tire. The performance figures are somewhat misleading though, since R&T's figures were nortoriously slow.
May 2000----------These are a couple of scanned photos shortly after we purchased our Corvette. The wheels are 15 x 8 Cragar Wires. I'm not real crazy about them, but they're starting to grow on me. I remember reading years ago that wire wheels were esentially for show due to possible flexing under torque. I really have my eye on the American Racing 200S's Below is a picture of the front grille, before I restored it. Quite a difference when compared to the grille on page one!
May 2000----------The body color is Cortez Silver with a Charcoal belt line which then covers the tail light area and then proceeds up over the gas tank area in the form of a racing stripe, atop the roof and ends in a point on the hood. Its sort of a combination of the ZL-1 Mule Cars, the Baldwin Motion Racing Stripe and the 1978 Anniversary Edition paint scheme. Mindy though, wants to paint it Mille Miglia Red, or Torch Red. We'll see.
Visitors Since May 2000