problem with decomp plate

[hass]

hi guys

after 2 days of building my turbo engine

i had the top hose blow on me on the m25 junction 5 at 10.pm in the evening

anyway got her home £120 later
and thought ok just a simple job change the hose. got a new hose fitted it was lovely for half hour then the gauge went a bit over half and thought maybe a bit of air in the system

wen i took the nipple off i had loads oil cream pouring out.
now my engine is freshly built so i assumed it could be a bit of shit in it.

flushed i throu and re-started her
half hour its fine but wen i undone the nipple again the same stuff came out.

i did a sniffer test (cyclinder leakage test) and came up with headgasket

now my engines only been running 2 days
and the gauge hardly touched the red wen the hose blew

so it carnt be the headgasket
ripped the head off today
and the headgasket is perfect its so good that i can reuse it but i wont

the head got skimmed and pressure test too before wen i was building the engine so thats fine

but i bought the decomp plate second hand and the previous owner had a fucked thread and it was leaking so i think the decomp plate is wrapt

but i i only used 1 headgasket which went on the block
and used curl t paste to stick the head to the decomp plate

now from my experience as a mechanic i carnt see that working but i gave it the benift of the doubt

im gonna go with the overseized headgasket now and see what happens

what do you guys think of the decomp plate?
have you had a similar problem?
or any problem?
are you using a decomp plate?

thanks hass

[gareth]

what's the plate made of?

unless it's something soft like copper, it'll have a job sealing properly won't it? i've aleays assumed you need 2 head gaskets (one either side) with these things as otherwise there's no sacrificial crush gasket to seal properly.

[hass]

see gareth the plate is made of ali
i thought the same as you that you'll need to thin headgaskets
cos it wont seal properly

[Colonel Sanders]

im running only an mls gaket, had it runninwith no issues, no need for a decomp plate IMHO as long as you aint goin stupid boost..
il be runnin a bar everyday on stock cr

[hass]

gonna go with the oversized head gasket for now
running my engine in
then start running some boost(carnt wait)

then wen she blows gonna go with the mls

how much are one of those mls gaskets

and rossle did you sort out the tread on your block?
did you use the same mls again?

[Colonel Sanders]

i managed to get a longer bolt in there mate,
it cost me 140 delivered in 5 days from the us
www.vacmotorsports.com
but i live in guernsey so dont pay no import dutys.
but yeah you can use them a few tmes unless you blow a hole through it, which is highly unlikely unless you are running big boost on a really bad tune causing det.

[hass]

glad to hear that its fine now

like i said im gonna use an overseized headgasket for now then im gonna go for the mls

thanks for the link to

[Colonel Sanders]

glad to hear that its fine now

like i said im gonna use an overseized headgasket for now then im gonna go for the mls

thanks for the link to

loads of nice e30 stuff for big power its very usefull site..

[hass]

i could spend all my life savings on that store

[isTURBO]

From what Ive been given to understand the decomp works with a single gasket and a special sealant, however the head should at least be cleaned and skimmed a bit to provide a flat surface in order to seal correctly. Apparently 2 gaskets with one set of head bolts wont provide a proper seal.

hope this helps

[Demlotcrew]

The proper way to use a decomp plate is to chemically weld it to the block then sleeve the cylinders

You will never have a reliable car with a turbo attached the way you are going. I would suggest you get a custom multi layered metal head gasket to bring the dynamic compression down.

Andrew

[Colonel Sanders]

if i blow my motor and it comes to me lowering the cr, wich i will...
il go down the piston route, personally i dont trust docomp plates

[Andyboy]

Decomp plates are just horrible - what a bodge up. An oversize gasket is the way to go. I'd be wary of taking meat out of the piston crown on a Turbo engine, better to take it out of the combustion chamber.

[gareth]

agreed. anyone heard of 'squish' in the combustion chamber? remove it at your peril... unless you like detonation and burnt rings

[RowdyBurns]

The proper way to use a decomp plate is to chemically weld it to the block then sleeve the cylinders

You will never have a reliable car with a turbo attached the way you are going. I would suggest you get a custom multi layered metal head gasket to bring the dynamic compression down.

Andrew

What a load of crap!

...and why on earth would you go to all the trouble/cost of re sleeving a block to lower CR when you could just slot in some forged slugs for a third of the price???

Could you expand on this chemical welding process???

The only reason i have seen people extend blocks and re sleeve was an experiment to run a longer rod ratio.

You state to lower the "dynamic" compression ratio! Could you explain to us the difference between the dynamic CR and the static CR please? I would say that a thicker MLS HG would in fact be a mod that is more related to the static CR.

More home work needed. D-

[RowdyBurns]

agreed. anyone heard of 'squish' in the combustion chamber? remove it at your peril... unless you like detonation and burnt rings

Crap!! So you have mapped a car with no squish? Experienced early detonation?

Squish can be beneficial and has an effect on burn speeds but remove at your peril????

For f*ck sake just about every big power cosworth YB engine runs with naff all squish.

[RowdyBurns]

Decomp plates are just horrible - what a bodge up. An oversize gasket is the way to go. I'd be wary of taking meat out of the piston crown on a Turbo engine, better to take it out of the combustion chamber.

Interesting comments but probably crap again!

Can you explain the mechanical advantages of a 2.5 mm HG over 1.5 mm decomp plate and a 1mm HG??

[e30_Turbo]

Just to throw a complete spanner in the works....

Dimmy's car has a decomp plate, done thousands of miles now, now blow ups, issues at all and it'll quite happily destroy most cars on the road at 12 psi.

I would not suggest a thicker head gasket at all, go steel all the way if you want it too hold over 1 bar. ( I have some first hand experiance too )

And the REAL way to do it is using proper pistons but as we all know this is where money issue comes in, if I knew then what I know now I would have bought steel gasket, arp bolts, low comp pistons, rods and a crank spec'd for the job.

I've wasted hundreds on parts that I hoped would do the job when I could have spent half that originally and saved hundreds over the whole project.

The main issue with decomp plates is getting them to seal, you only need to speak to ferriday engineering to confirm this, they sell them all with a warning that they will only work if sealed and fitted perfectly.

@ Rowdy, the new lump is going in this weekend, I'll be round for those det cans and your help soon dude!

I suppose I should book a slot with LPS then

Ow and steel head gasket and arp head studs this time! ( and a HUGE intercooler just for good measure )

[RowdyBurns]

Fozzy,

You are welcome to pop round mate. I'm in the workshop pretty much all day every saturday. Will be firing up my latest creation this weekend too.

Prob best get a power run in sooner rather than latter with LPS. I think you will find they are not going to be around much longer.

Neasrest RR after that is EA @ Witham (dyno is set way off to please customers) or APT @ Norwich.

[e30_Turbo]

EA mapped James meastro to 326bhp! then it shit brick on the A12 as the gudeon pin slipped on no 3 and cut a lovely grove in the cylinder wall

I'll call you later dude, gotta go, one of my staff just shot himself in the leg with a 4 inch nail gun off to hospital I go!

[RowdyBurns]

Messy!

[Ant]

Hi Doug long time dude

whats the coup with LPS then ?? going under ???? for sale ( Idea ! )

On topic again for a sec......

Decomp plates are no worse than any H/G , the key to success is preperation and cleanliness, oh and some flat surface help too.

an MLS is effectivly a decomp plate in any case, only the construction changes, the function is the same

Agreed on the squish comment too, nice thing to have N/A and will net gains if massaged correctly, less of an issue with an FI motor.

[RowdyBurns]

Going under apparently. I have sewn some seeds to see if they want to do a cash deal out the back door on their RR before the liquidators get their mits on it but i doubt anything will come of it!

Their overheads were massive and they only had one guy on the spanners to earn the bucks. Was easy to see it as never going to add up.

So there is a space in suffolk for a well run performance tuning shop. Fancy a move out into the stix?

[d6dph]

Do it Ant, Be closer to me! (Ooh, That's probably not a good selling point is it? )

[Turbo-Brown]

Hmm, surely having a good charge density as a means of speeding up the burn and thereby reducing the chance of detonation is a good idea in any engine guys?

[gareth]

agreed. anyone heard of 'squish' in the combustion chamber? remove it at your peril... unless you like detonation and burnt rings

Crap!! So you have mapped a car with no squish? Experienced early detonation?

Squish can be beneficial and has an effect on burn speeds but remove at your peril????

For f*ck sake just about every big power cosworth YB engine runs with naff all squish.

ok then, i'll shut up and say nothing.
feel free to botch it if you like, no point in doing things properly is there?

[Demlotcrew]

The proper way to use a decomp plate is to chemically weld it to the block then sleeve the cylinders

You will never have a reliable car with a turbo attached the way you are going. I would suggest you get a custom multi layered metal head gasket to bring the dynamic compression down.

Andrew

What a load of crap!

...and why on earth would you go to all the trouble/cost of re sleeving a block to lower CR when you could just slot in some forged slugs for a third of the price???

Could you expand on this chemical welding process???

The only reason i have seen people extend blocks and re sleeve was an experiment to run a longer rod ratio.

You state to lower the "dynamic" compression ratio! Could you explain to us the difference between the dynamic CR and the static CR please? I would say that a thicker MLS HG would in fact be a mod that is more related to the static CR.

More home work needed. D-

Sorry and you are?

Why on earth? Well if one wanted to build a 380bhp S50B35 maybe? Or if someone wanted to turbo a car which you couldnt buy custom pistons for

Maybe your customers are penny pinching scrapyard merchants mines are certainly not

So tell me why would anyone run a longer rod ratio? Then extend the block? Because all the engines ive seen with longer rod ratio setups (as they have their own advantages) had a piston set which brought the wrist pin closer to the crown and there was no need for 'extending blocks'

In regards to static vs dynamic i think its you that needs to do the homework, as any 'half decent' (that does not extend to you) engine builder knows that bore, stroke, rod length, cam timing, compression ratio, boost pressure (if you run a turdbo) and altitude have an affect at the dynamic compression ratio, which at the end of the day is what i need to know before i even consider mocking the engine up.

And finally, drop the attitude mate read what the original thread is about and stay on track, If you cant dont come back, simple really.

Andrew

[Andyboy]

Decomp plates are just horrible - what a bodge up. An oversize gasket is the way to go. I'd be wary of taking meat out of the piston crown on a Turbo engine, better to take it out of the combustion chamber.

Interesting comments but probably crap again!

Can you explain the mechanical advantages of a 2.5 mm HG over 1.5 mm decomp plate and a 1mm HG??

Mate, if you don't know the difference between static and dynamic CR, you should go back to Kwik Fit fitting exhausts.

[Andyboy]

Maybe your customers are penny pinching scrapyard merchants mines are certainly not

Hmmm, the comment about Cosworth YB's says it all really.

[Demlotcrew]

Hmmm, the comment about Cosworth YB's says it all really.

[Andyboy]

'I say old chap, one would be delighted if one could procure a decomp plate for one's Cosworth? And not to impune your good work Sir...

.....'ow much for back box for me S plate Omega mate. Innit? Got any plasters for me knuckles?"

[RowdyBurns]

Maybe your customers are penny pinching scrapyard merchants mines are certainly not

Hmmm, the comment about Cosworth YB's says it all really.

Does it say that I helped build, and mapped the fastest BMW engined E30 at a the PBMW brunters thrash a few years ago???

Not that cost is everything but i think you will find cosworth owners spend far more money on tuning their cars than most other marques.

[RowdyBurns]

Decomp plates are just horrible - what a bodge up. An oversize gasket is the way to go. I'd be wary of taking meat out of the piston crown on a Turbo engine, better to take it out of the combustion chamber.

Interesting comments but probably crap again!

Can you explain the mechanical advantages of a 2.5 mm HG over 1.5 mm decomp plate and a 1mm HG??

Mate, if you don't know the difference between static and dynamic CR, you should go back to Kwik Fit fitting exhausts.

..and if you can't get the quote feature right on a forum you should go back to surfing for porn!

[Andyboy]

Maybe your customers are penny pinching scrapyard merchants mines are certainly not

Hmmm, the comment about Cosworth YB's says it all really.

Does it say that I helped build, and mapped the fastest BMW engined E30 at a the PBMW brunters thrash a few years ago???

Mate, I helped build an engine for an Audi Quattro that won the 1/4 mile at GTi International. Yes, I washed the block in a parts washer and took all the bits to and from the machine shop. Doesn't give me the right to come here full of 'know it all' attitude.
As in most things, those who shout the loudest know the least and I'm surprised a chap of your undoubted expertise hasn't made himself a big name by now.

As for decomp plates - please show me a standard production turbo car that has one.......

[RowdyBurns]