Compression test results

Post by **katanaman** » Mon Jan 28, 2008 2:30 pm

Sidecar where did you get your figures from for the typhoon? I think Kiwicar is more accurate as the typhoon isn't that hot a cam

sidecar · Post by **sidecar** » Mon Jan 28, 2008 3:06 pm

I think that I am getting my knickers in a total twist!!

The figures are at home but 220 does ring a bell!

Here's my final offer:-

270 at 6 thou,
220 at 50 thou,
320 seat to seat.

I actually measured the cam with a DTI and degree disk, I did not fit the cam, it was in the engine when I bought the car but was told that that it was a typhoon. when I got the spec sheet it did match up in terms of lift and duration with what I measured.

I spoke to V8 Delveopments today, they said that really a leakdown test is what I need to do, does anyone know where a can buy one that doesn't cost a bomb?

Thanks for your help!

(Paul sorry, to have semi hyjacked your post! I hope that the info coming back will help you out)

Pete

Post by **katanaman** » Mon Jan 28, 2008 5:18 pm

compressor, hollowed out sparkplug with an airline adapter welded on and a pressure gauge is all you really need. The good thing about doing a leak down test is you can actually hear where the air is leaking past. A good description can be found here http://www.xs11.com/tips/misc/misc3.shtml

Ian Anderson · Post by **Ian Anderson** » Tue Jan 29, 2008 4:30 pm

Just thinking out aloud here

Are you reading the scales correctly?
Is the pressure rwading in bars?

110 psi? could this be11.0 bar?

11.0bar *14 = 154psi

Just a thought!

Ian

sidecar · Post by **sidecar** » Tue Jan 29, 2008 6:09 pm

Ian Anderson wrote:Just thinking out aloud here

Are you reading the scales correctly?
Is the pressure rwading in bars?

110 psi? could this be11.0 bar?

11.0bar *14 = 154psi

Just a thought!

Ian

Hi Ian,

I wish I had made that cockup but no it was PSI!

I've cobbled up a leakdown tester, My compressor will compress the reservoir of compressed air to 100 psi, I then fed this into each cylinder in turn at TDC and read the pressure before it bled away. The best cylinder showed a 10 psi drop, the worst about 18 psi.

What I can't understand by the leakdown method is that surely a compressor with a high CFM must be able to pour so much air into a cylinder that the pressure would remain higher then if you were using a piddly little compressor.

I also slackened off the rocker shafts so there was no chance that the valves were open at all.

I noticed that some cylinders would bleed down to zero psi very quickly, maybe 2 seconds, the best maybe 4 seconds. (Bleed down with one injection of 100 psi air, not a constant supply of air!).

I've now decided that my home made tester is not that great (it only has one gauge and no restrictor in the middle of it) so I've ordered one off Demon Tweeks. If that one shows that the engine is duff then I'll be on the look out for a short engine! (I'm sure that the heads are OK as they are V8 development jobbies with only 2k miles on them).

Pete

stevieturbo · Post by **stevieturbo** » Tue Jan 29, 2008 9:21 pm

sidecar wrote:
Ian Anderson wrote:
What I can't understand by the leakdown method is that surely a compressor with a high CFM must be able to pour so much air into a cylinder that the pressure would remain higher then if you were using a piddly little compressor.
I would assume that factory supplied leakdown testers would have controlled orifices, rather than an open pipe from the compressor.

So I dont think a DIY leakdown tester can give usable results unless this was taken into consideration.

Ian Anderson · Post by **Ian Anderson** » Tue Jan 29, 2008 10:16 pm

Oh well I guess thinking aloud does not always work!

Ian

sidecar · Post by **sidecar** » Wed Jan 30, 2008 8:02 pm

Well I got a proper leakdown tester today and tested all 8 cylinders.

Two of them are border line OK, the rest are pretty well F%$ked!

My motor has a good set of heads on it, does anyone have a good short engine (of any capacity) that they want to sell?

There's a good looking 3.5 block on flea bay at the moment along with a slightly more dodgy looking 4.5 lump that has just been built by V8 Developments. (When I spoke to them they said that they had stopped doing the red rocker covers and 4.5 capacity ages ago, the seller reckons that it has only done 112 miles since the rebuild....it don't figure to me)

Pete

stevieturbo · Post by **stevieturbo** » Thu Jan 31, 2008 1:02 am

I think it would be worth stripping it down first, just in case it is an easy fix....

If you buy used, you could be buying another troublesome engine, when yours might be easily fixed.

Post by **katanaman** » Thu Jan 31, 2008 8:46 am

Like Stevie says strip it down first. It could be anything, Rover engines aren't renowned for wearing bores so new rings might be all you need.

sidecar · Post by **sidecar** » Thu Jan 31, 2008 12:48 pm

Hi Guys,

Thanks for you advice, I'm sure that it is the rings as I could hear the air leaking out when I used a tube as a stefascope and held it near the push rod holes.

The chance to by a BRAND NEW X drilled short 4.6 lump with high comp pistons has come up. (I think that it is a "red paint blob" block). Its not a top hat block but it has never been overheated as its brand new.

I know that it will cost more than rebuilding my 3.5 but a 4.6 would go quite nicely in my cob replica!

What do you guys think that its worth?

Cheers

Pete

Post by **katanaman** » Thu Jan 31, 2008 7:06 pm

if you can afford it then go for it but remember none of your old parts will fit so your looking at the cost of crank, rods, pistons, cam and all the other bits.

sidecar · Post by **sidecar** » Thu Jan 31, 2008 7:27 pm

katanaman wrote:if you can afford it then go for it but remember none of your old parts will fit so your looking at the cost of crank, rods, pistons, cam and all the other bits.

Hi Katanaman,

The block comes with a new crank, rods and pistons. (1400 quid)

I'm going to fit my stage III heads, typhoon cam, vernier timing gear, performer manifold and edelbrock 500 on it.

The liners are not top hat ones but the block is brand new, I hope that if I keep the temp down to 75-80 odd degrees it won't drop a liner on me.

I think that it is a "red paint" one.

Do you think that it is dodgy to build an engine round such a block?

Does everyone who has a large capacity RV8 suffer with liner problems?

Cheers,

Pete

stevieturbo · Post by **stevieturbo** » Thu Jan 31, 2008 7:40 pm

I never had any liner problems with my old 4.6 TT