Smokey exhausts off throttle. TVR Chimaera V8

dbv8 · Post by **dbv8** » Thu May 14, 2015 11:15 am

Been seeing a lot of smoke in the mirrors at the top end of the drags strip when backing off and braking.

I did think it may have been tyre smoke from the drag radials touching the chassis and arches under heavy breaking but a witness says it looks to be coming from the exhaust but only at the top end of the run not on gearchanges.

My engine was recently rebuilt with refurbed heads including new valave seals. The engine is clean on the outside still. I did a compression test and all 8 were between 200 and 225. The rocker breather feeds to a catch tank and that used to feed to the plenum but this was changed and the inlets to the plenum were plugged. The catch tank now feeds to air.

Any ideas?

kiwicar · Post by **kiwicar** » Thu May 14, 2015 2:22 pm

Hi
could be sucking oil in from the valley past the gasket/valley cover as you lift off at high speed, by the top of the run there is probably quite a bit of oil built up in the valley area and with no crank case vacuum oil mist is getting pulled into the inlet.
The slingshot did this early on but because the Chevy has a paper gasket that is a bit thicker is sucked the bottom bit of the gasket through the engine then wouldn't run properly!
best regards
Mike

dbv8 · Post by **dbv8** » Thu May 14, 2015 5:50 pm

not sure where you mean?
Can you explain further please?
There is no feed into my inlet now so i cant see any oil vapour entering there

kiwicar · Post by **kiwicar** » Thu May 14, 2015 7:54 pm

Hi
where the bottom of the head joins the block the gasket face between the head and the inlet manifold is very narrow, the gasket/valley cover forms the top of the valley however it also tends to lift gasket away from the head surface at the corner this offers an area for the inlet vacuum to draw air from the valley into the inlet tract. On my Chevy this is bad enough to draw the (admittedly thin) bottom of the gasket into the inlet port and through the engine.
Best regards
Mike

DEVONMAN · Post by **DEVONMAN** » Thu May 14, 2015 10:28 pm

Could be too much oil in the sump surging when you brake and it's getting whipped up by the crank onto the bores. I had this happen on a 4.6 with a 3.9 sump.
OR your rings are not yet bedded in and high vacuum when on overrun is sucking oil up into the combustion zone.

Regards Denis