Lee Ivatt

iTrader: (1)

Hi all

Im looking for some information for a 1971 Aston DBS

its the straight 6 Vantage 4.0L
compression ratio is 9.4:1 and has tripple webber 45's

should have 325bhp. but has far less at the mo. The head gasket has given up, but this has also affectet the vacum circuit, so we need to do a compression test on the cylinders to try and eliminate a few things, before the head come off.

Heres a link to the dbs on the wiki-thingy

http://en.wikipedia.org/wiki/Aston_Martin_DBS

Any info would be much appreciated as i cant seem to find anything with the compression test fiqures noted

a few pics

GUZZLER

iTrader: (3)

get a cylinder leak down test aswell, tells a lot more than a compression test.

cjwood555

what would you glean from a compression test when you know the headgasket has failed??

Chris

Lee Ivatt

iTrader: (1)

sorry yes we intend to do this aswell, our machine guy performs this as part of the job when he checks/skims a head anyway

The brakes have really reduced in perfermance latley and after creating a false vacum its clear that both brake servos are knackered.

but also we know the vacum it not as strong as it should be. this is one reason for testing the compression.
unlike modern cars which pull from the inlet manifold (i.e all 4 cylinders)
the aston takes its vacum from one of the 3 carb bodies. so buy checking a 6 cylinders we should be able to see if its the head gasket causing most of the loss or wether its a combination of this and the fact it draws from one carb.
im guessing 1-4 should be about the same. and possible 5. and 6 should be less as this is where the oil is weaping from the gasket down the block.
also with the comp test as well, we should be able to gauge a rough idea of the state of the piston rings across the 6 cylinders, and compare this to the leak test results.

basically for the sake of a few tests, its worth it. it should give us an insight into whats going on inside, before we rip it open.
Also when we build it back up and do a second test we then have fiqures to compare it to.

Dont forget its an aston engine, its bad enough when u say the word cosworth when ordering parts. when u say aston the price tripples.

So can anyone help me then, i need to know what the compression test fiqures should be please.

StephTell

Lovely car! Not too keen on red cars but still: stunning!

GUZZLER

iTrader: (3)

Lee, just spoke to a friend who has a collection of Astons, he thinks from memory the comp should be around 130-140.
He said theres a garage in stoke on trent who are very helpfull, FOUR ASH, they do a lot of work with Astons, if you can find a number for them they will be able to tell you.

Lee Ivatt

iTrader: (1)

The car was blue last year, and after doing some work on the car i realised it had been resprayed. so after a quick call to some sexy receptionist at newport pagnell, it turns out it left the factory in "Fiesta Red" So we returned it back to red just in time for the wedding last christmas.


thanks mate i will look into that.

my mates got a special machine which does a full leak test. it it can tell u is its loosing from inlet/ exhaust or through the rings.

My thoughts are its a few valves, probably to do with the change over from leaded all them years ago. anyway the test will show all.

nice to have an idea before we pull it apart.

The engine should be 325bhp, so im almost certain the block/bottom end is fine. as it should be near bullet proof.

anyway i'll let you know how i get on.