Top Hat liners

mgbloke · Post by **mgbloke** » Mon Sep 22, 2008 3:42 pm

These guys did my top hats.
http://www.automotivecomp.com/index.html
They made a very good job.
Cost £800 +VAT about 4 years ago.
Might be worth giving them a ring.

Mark

CastleMGBV8 · Post by **CastleMGBV8** » Mon Sep 22, 2008 9:29 pm

http://www.powerstores.co.uk/?t=si&item=286

£999.00 + VAT

They are not top hat linered because the don't need to be and I seem to remember that they have a long guarantee.

Kevin.

ppyvabw · Post by **ppyvabw** » Mon Jan 19, 2009 5:37 am

How do the cosworth blocks get around the cracking problem? Is it simply better casting methods or is it a fundementally different design around the water jacket?

Anyone know? I'm umming and rrr-ing still about a 5 litre conversion I want to do and I'm looking for cross bolt blocks on fleabay and they are going for 500/600/700 quid plus top hatting , may aswell start with a new block.

chodjinn · Post by **chodjinn** » Mon Jan 19, 2009 8:20 am

CastleMGBV8 wrote:http://www.powerstores.co.uk/?t=si&item=286

£999.00 + VAT

They are not top hat linered because the don't need to be and I seem to remember that they have a long guarantee.

Kevin.

Dont need to be? Why is that? Is that a 'cos-cast' block?

ppyvabw; I've asked that and the 'answer' i get is better casting methods. Fair enough, but it still doesn't change the design flaws in the block. As the cos-cast blocks haven't been around too long i dont think anyone has done enough miles in them yet for an accurate comparison.

I'm just waiting for the first on to have a slipped liner, closely followed with guffaws of "told ya so" from me lol.

I stand by my route; seasoned 4.6 block with top hats - same price as one of those new blocks but with a much higher guarantee of not to fail.

ChrisJC · Post by **ChrisJC** » Mon Jan 19, 2009 9:13 am

I wonder about this top-hat liner business. Yes you end up with a block that doesn't leak water. However it can still crack, and I wonder if that affects block rigidity. Cracks spread - maybe ultimately the block will fall in half???

Chris.

ppyvabw · Post by **ppyvabw** » Mon Jan 19, 2009 9:30 am

The cracks are only in the thin part of the parent metal, around the water jacket aren't they? Hardly structural?

The water jacket surrounds the top part of the bore doesn't it, whereas the lower part is solid? Am I right?

That's the way I see things anyway.

mgbv8 · Post by **mgbv8** » Mon Jan 19, 2009 9:15 pm

Sorry!!

I'm still confused by all this "early weak Block" "top hats required" "4.6 engines are trouble" stuff.

Or am I just lucky??

I rebuilt my first ever RV8 about 7 years ago. A stock 3500 pre SD1 Factory MGB V8 134hp lump. I tweaked that V8 up to 187 bhp NASP from the stock 134 bhp. I added Nitrous and took it to 257bhp on the rollers with a 50 shot of gas. I then added another 100 shot of nitrous for the best part of two years with no problems apart from the 1/4 mile times were maxxed out for that old engine. This old weak block engine made 12.4 seconds on the strip.

I've now fitted a late model 4.6 engine which is all stock bar the cam and lifters. Its not even been rebored. Which was a bit pricey when it came to finding stock 4.6 pistons. She has had a slight hone and has new stock 4.6 pistons and rings.

I have been running this stock lump for over a year now at the track with a 200hp shot of Nitrous and the worst that has happened is a couple of melted pistons. But these were weak pistons with the valve cutouts ground in. I swapped these out for stock 4.6 pistons and shimmed the the rocker pedestals up a bit and she has been fine for the last 9 months running mid 11's on the 1/4 mile.

My oil and water systems are spotless and have good flow at all times.
I use comp head gaskets.
The heads and block are all stock with no skimming done.
And I shall be adding a total of 250hp of Nitrous in 2009 to see if I can get a 10 second pass on the 1/4 mile.

So why has my stock 4.6 not suffered all the problems that I have been told I should expect re liner issues etc??

I'm no expert on these engines as most of you know. But I have taken a stock pre SD1 3500, a stock 3500 SD1, and a stock 4.6 and made them all go pretty quick with nitrous and one of them have suffered more than piston failures. My pre SD1 Block is now happliy residing in a Morgan replica and the new owner is very impressed with the performance and tells me she is a smooth non smoker. That engine lost 7 pistons in two years and all I did was to scrape the ally from the bores. Run a glazebuster across the bores and fit new +10 rings.

From what info I can gather it seems that most of the RV8 engine failure issues stem from poor maintenance to the cooling system and the oil system. I may be wrong of course.

As I've said before. I'm no expert. I just rely on my own field testing.

Perry

ppyvabw · Post by **ppyvabw** » Mon Jan 19, 2009 9:41 pm

mgbv8 wrote:Sorry!!
From what info I can gather it seems that most of the RV8 engine failure issues stem from poor maintenance to the cooling system and the oil system.
Perry

Well you're probably right. The 3.5 aside which never had the issue no matter how much abuse it recieved, the later ones that were ran by joe public would have been poorly maintained.

It's a combination of a marginal design running emmisions choked fuel restrictions and temperature , and poor maintenance I reckon.

Also, because of the nature of modded cars it only takes a blown hose or something and the temperature starts rising and it's possibly fucked before it comes up on the temperature gauge.

I'd say with your 4.6 you've been lucky sourcing a decent block, and looked after it.

The problem to me is spending money on blocks until I find one that isn't donald ducked

ChrisJC · Post by **ChrisJC** » Tue Jan 20, 2009 8:25 am

There is a difference:

Perry is running the engine at over 100% of it's design rating for 12 seconds.

In a Range Rover, it can run at 90% of it's design rating for hours on end. It's clearly this that causes problems....

Some new engines have this 'overboost' facility to run the engine at over it's max rating for a brief time to allow overtaking for example.

Chris.

mgbv8 · Post by **mgbv8** » Tue Jan 20, 2009 8:39 am

Out of curiosity!
Has anyone got any pics of a failed liner as its something I've often hear of but never seen.
Cheers
Perry

chodjinn · Post by **chodjinn** » Tue Jan 20, 2009 8:53 am

Not really much to see Perry. I had a 4.6 block last year that apparently had 3 slipped liners, I could only find two! They only move in the block a very small amount, but enough to matter.

Not every 4.6 block is guaranteed to fail, but with 75% failure or something there's a high chance of it. From your experiences Perry, you really look after the engine in terms of cooling/maintenance and the way you run the engine makes failure very unlikely.

Post by **katanaman** » Tue Jan 20, 2009 5:46 pm

I think there was a pic on the old forum where the liner had been taken out and you could see the crack. Have a search and see if you can find it.

mgbv8 · Post by **mgbv8** » Tue Jan 20, 2009 9:05 pm

So, with the heads off, you can actually move the liner by hand?? Holy crap!!!

ian.stewart · Post by **ian.stewart** » Tue Jan 20, 2009 9:30 pm

is the slipped liner thing more commom with the 4.6 than the 4.0???
If this is the case, as it seems to be, could it be caused my the p-ss poor rod to stroke ratio in the 4.6, caused by rod angularity side loadings, look at the stroke/rod length in the 4.6 then compare the 4.0. which has a shorter stroke and longer rods than the 4.6

Post by **katanaman** » Tue Jan 20, 2009 10:38 pm

mgbv8 wrote:So, with the heads off, you can actually move the liner by hand?? Holy crap!!!

If your on about my post no the liner had been bored out if I remember right.
I thought it was supposed to be the 4.0 that was worse because the blocks were basically rejects from the 4.6?