The V8 Owners Forum -

If you are pulling the heads off you can burette the chambers along with the volume above the pistons, you can get a cheap burette off ebay, this will give you the real static compression. Like you implied though the cam has an effect on the dynamic CR.
As your max PSI was 200 odd with the throttle closed it is going to be pretty high with the throttle open! especially if you are losing pressure at cranking speeds and low RPM due to a 'wild' cam.

Also if your increase in capacity is down to larger bores then the fire ring issue not being compressed is going to be worse than it is on a standard bore. MLS gaskets may need to be on your Christmas list!

What is your bore?

Bore is only 94mm with 90mm stroke. So standard elring gaskets have been always used. When it goes it is really quick! So am eager to keep the current setup. So i am all ears when it comes to opinions on how to make the gaskets last longer. 1) I will set the megajt for a restart when on gas. 2) will check flatness 3) want to keep the standard / current gasket thickness to keep the squish band as tight as possible. Copper spray was mentioned etc but any other tips ??? Sealant etc??

DaviesDJ wrote:Bore is only 94mm with 90mm stroke. So standard elring gaskets have been always used. When it goes it is really quick! So am eager to keep the current setup. So i am all ears when it comes to opinions on how to make the gaskets last longer. 1) I will set the megajt for a restart when on gas. 2) will check flatness 3) want to keep the standard / current gasket thickness to keep the squish band as tight as possible. Copper spray was mentioned etc but any other tips ??? Sealant etc??

If I was rebuilding my engine which I probably will at some point in time I would go for Cometic MLS gaskets, they come in various thicknesses and you can get them with 96mm bores, this means that the firing ring of the gaskets are not 'hanging in mid air in the combustion chambers due to the large chamfers at the top of the liners. (I'm assuming here that your top hat liners have a large chamfer). They are not cheap but then again pulling your heads off due to blown gaskets is a PITA!



http://www.ebay.co.uk/itm/Cometic-Head- ... 4d1519af90


How much NOS were you running and what sort of timing figures for you running for the ignition?

100 shot of nos but at an AFR of 10.2. 33-38 degrees of advance at 3000 + depending on load (I know that's a lot) but was running 100 octane all the time.

DaviesDJ wrote:Sorry !! Sorry!! Got them arse backwards!! It's cylinder 5 that's leaking (low comp) on the drivers side! Only driven 7 miles since the noise started and will not be driven again. Heads of, new composite gasket and check the head is flat- if not the smallest skim possible. Am quite please with the numbers on he others. Will also program the megajolt to retard when on NOS. never formally tested, but with a TVr 500 cam what sort of numbers for the static compression do you think 200psi indicates???

You mean number 6 eh?

sidecar wrote:

DaviesDJ wrote:Bore is only 94mm with 90mm stroke. So standard elring gaskets have been always used. When it goes it is really quick! So am eager to keep the current setup. So i am all ears when it comes to opinions on how to make the gaskets last longer. 1) I will set the megajt for a restart when on gas. 2) will check flatness 3) want to keep the standard / current gasket thickness to keep the squish band as tight as possible. Copper spray was mentioned etc but any other tips ??? Sealant etc??

If I was rebuilding my engine which I probably will at some point in time I would go for Cometic MLS gaskets, they come in various thicknesses and you can get them with 96mm bores, this means that the firing ring of the gaskets are not 'hanging in mid air in the combustion chambers due to the large chamfers at the top of the liners. (I'm assuming here that your top hat liners have a large chamfer). They are not cheap but then again pulling your heads off due to blown gaskets is a PITA!



http://www.ebay.co.uk/itm/Cometic-Head- ... 4d1519af90


How much NOS were you running and what sort of timing figures for you running for the ignition?

We are using Cometics on the Escort. I used them first when I broke then engine. Then swapped to the Escort. They are great items. Been used 3 times now and still fine. I'm sure I got mine from Passion Ford.

DaviesDJ wrote:100 shot of nos but at an AFR of 10.2. 33-38 degrees of advance at 3000 + depending on load (I know that's a lot) but was running 100 octane all the time.

It might behave better with a 100 shot at 33 degree's and the AFR at high 11's to mid 12.5's The 10.2 is safe but its costing you some power I reckon?

Copper gasket adhesive spray is bloody good stuff. Made by VHT. I get mine from USA automotive near Bedford. But it seems to be quite cheap here

http://www.amazon.co.uk/VHT-COPPER-GASKET-CEMENT-SP21/dp/B002NU4CFE

I reckon that you need to be running less advance at 3000 than what you are currently running. Of course the only real way to be sure is by running the engine on a dyno but having said that many large Rover lumps have been run on dynos and the figures quoted by many people are that the max advance needs to be 28-30 degrees. (I reckon that this is with bob weight dizzies, with programmable units you can be a bit more clever)

I've read loads on burn rates and ignition timing and have come up with my own idea on how to set my ignition up, you can take it or leave it but one thing seems to be common in all the text that I've read is that the peak cylinder pressure needs to occur when the piston is 14 degrees ATDC.
The idea of advancing the ignition to the point of detonation then backing it off a degree or two is old school and only works on engines that have been built with too much static CR. Too much advance will cause peak cylinder pressure to occur before the piston is at 14 degrees ATDC, the engine might not detonate but it won't be making maximum BHP either.


Below is what I've found...

1. The engine will 'tell you' how much advance it needs at idle if you listen to it very carefully, the revs will rise as the ignition is advance from a retarded start but the rate of increase in RPM will slow down at some point even if the revs still continue to rise, this is the idle figure that the engine wants. The cam has a big effect on the idle timing, I run a Piper 285.

2. When the engine is running in the RPM range where the engine is in the 'plateau of torque' the rate of ignition advance needs to back right off, this is because the VE of the engine is at its best and therefore the burn rate is high (The cylinder pressure BEFORE the plug fires is high). As the revs rise the turbulence in the chamber rises which increases the burn rate which compensates for the fact that the rising revs means that there is less time for the burn to complete.

3. As the VE starts to fall at high revs the engine may well respond to more advance, this could be around at 4500 RPM for a road based lump depending on the cam, manifold and how well the heads flow.


So with the above in mind I have set my engine up as follows:-

Idle RPM 18 degrees advance
1000 to 2200 the timing climbs to 25 degrees
2200 to 3700 the timing climbs at a lower rate to 28 degrees
3700 to 4400 the timing flat lines at 28 degrees
4400 to 5400 the timing climbs to 32 degrees (32 at high RPM only where the VE is poor)
5400 to 6000 the timing flat lines at 32 degrees


I must stress that none of the above has been backed up with dyno runs and as your engine has a non-standard stroke the conrod ratio may also be non-standard, this effects how the piston dwells around TDC and this could change the timing requirements to a small 'degree'

I also run a lot more timing at high manifold vacuum levels, from 10" of mercury my system starts to add an extra 14 degrees of timing with all the extra timing being in at 15" (This is not added at idle because I use the timed port on my carb). My engine pulls 15" at idle on the non-timed port.

Whenever my NOS is running it knocks off 4 degrees from the ignition

Your 100 octane fuel may well stop the engine detonating but your timing could still be too far advanced.

Like I said take it or leave it!

At last someone who understands what I have been telling folk for ages about how to try and tune on nitrous and or boost

I have tried to explain to folk that too much timing will slow the engine down as peak cylinder pressure occurs too early and tries to stop the piston rising to get over TDC !!

Your comments are spot on Sidecar

My settings at the moment are:
Idle 11 degree's
2000rpm with 4psi boost approx 18 degree's
Then the boost ramps up to 8psi and the nitrous hits at 100hp 23 degree's
Then to full boost at 12psi and nitrous at 175hp 27 degree's

This is my safe setting for the 9 second runs with AFR running rich at high 10's / low 11's

This is a low comp engine though. Approx 7.5:1

Next season I will be keeping fuel, boost and nitrous the same and adding timing only.

Cheers Perry!

Thank. You guys, I do believe that my engine is one of those with too much static compression, built at an earlier part of the learning curve. I will post my map once I am home from this bloody wedding I am at (my wife's friend - forum keeping me sane ) the way I drive is keeping the timing in the middle of the right hand column so to speak, and 28 degrees is used at higher load. But I will post this later. Many thanks for your comments guys, and it think I need a dyno session, but it may not be in time for the end of January. Thanks for your advice guys. I have a lot to learn, but considers these numbers as my con rod is short and the piston is long (tvr 500), and I have a lot of static CR so I wanted to bring things forward to catch the sweet spot etc. thanks for your advice on,the nos perry, shortened the route to 5.5 feet and thought the cabin, my fuel pressure in 6-8 psi and I am yet to fully test the new AFR settings and tweak fuel pressure to suit. May get a chance to do this at the pod . Dreaming of 14s - what is the best a road going landy has run???

DaviesDJ wrote:what is the best a road going landy has run???

Mine has run 16.5. So you should easily be able to beat thet!

Chris.

Don't be so sure Chris mate!! Still untested!! Will you
Be at Santa pod in the new year?? Would be great to see a couple of landies head to head. I am going to take the opertunity to coat my chambers an inlet valves with ceramic coat (have a load of it). Does anybody rate this? And perhaps invest in a minimax controller?? So I can safely push up to 150 shot?? Or should I save the 300 quid and stick with a fixed hit?? I have the capacity to switch maps on the megajolt- so will put in a 3 or 4 degree offset for nos use.

I won't be at the pod this year - the Landie leaks too much oil to be allowed anywhere near the strip!

Give me a few years to rebuild the engine (there are a few things need doing), then I'll be back.

Chris.

Hi guys, so the heads are on their way off- and apart from scraping off the stupid insulation foam I put over my manifold I am thinking of other mods to do while I am there. Thinking of these

1) ceramic coat inlet valve and and combustion chamber
2) back cut the valves at the point at which the 45 degree seat finishes
3) possibly roller rockers???

Have been offered a set of roller rockers at a reasonable but still significant price, and am toying with the idea of these, for my track project the use is obvious - but for the Landy- revving to 6500??? Griffith cam (uncertain of duration) - realise they increase the life of your valve train- but am not sure of the way manufacturers state a useable power gain as an isolated upgrade - cant imaging the frictional advantages give that much back??? Or should I just leave it as is, they look very acceptable and have alloy outriggers to support he rocker shaft. Cheers

Dave