Thought I should move this from the 'Journal' forum and update where the project is at. Wish I was at Coventry with everyone, but these things always take longer than anticipated, lol

 

20/01/2013

Having had the car for a few years now I have finally given in to the urge for more power.

 

The original engine in the car runs superbly only 66k miles with a proven Dyno run @ 357bhp, with boost jets and a uprated chip & air filter. Not bad at all for a 300ZX, but I was bitten by the bug and was set on going for more bhp and reliability, (I know why fiddle with it if it ain't broke). But having been lucky enough to have many nice high powered cars in recent years I wanted to keep the Zed long term and the engine is the first part of the project so it need's to be a good strong/reliable build.

 

After looking at various options of buying a part built engine form the US I decide to also keep my eyes peeled for the poteintial of purchasing an uncompleted project rebuild.

 

Back in March/April 2012 an ebay listing caught my eye regarding a nearly completed forged engine rebuild. The only problem with it was that the rebuild wasn't exactly completed by the most reputable of Zed engine builders known within the Zed world. In fact the seller had been caught up in horrific events where parts when missing, work was never finished and finally the garage was broken into and his engine was stolen. Retrieved from a nearby field 24 hours after going "missing". see here for a bit more http://www.300zx.co.uk/forums/showth...light=s+mochan

After talking with the seller for sometime we struck a deal and I waited for the day when the pallet with the engine would arrive.

 

It came with forged internals, Wiseco pistons, Eagle rods, ACL Duralite white metal bearings ARP main con rods and head bolts, Tomie 260 degree camshafts with solid lifters & harder springs, SARD 850cc injectors with a Border fuel rails/ new Turbo's, s/steel manifolds, new oil pump, heads polished, exhausts ports and valves shimed & lapped.

 

Didn't look all that great mind when it finally arrived to be honest, and I still had my doubts as to whether I had done the right thing in buying this.

 

 

 

After stripping down the engine as far I was prepared to take it anyway,

 

 

 

 

 

I wasn't going to attempt to go much further, so I thought it would be best to get this done properly!

 

So a call was made to Jim @ PowerZed to arrange a date to get everything to him in order for him to work his magic.

Effectively the surface needs to be ground rather then just milled to achieve that finish.

 

That's how your will be done then gaz? Angle grinder and some 60 grit discs :p

Nah I have an old ******* file in my lockup that'll do!

:lol:

Well Jim got the heads off the other day and you can see where the Cometic gasket failed

 

 

 

No detonation damage

 

 

That's rubbish from cometic, I'm using stock gaskets on mine.

Well Jim got the heads off the other day and you can see where the Cometic gasket failed

 

 

No detonation damage

 

 

Naturally:smartass:

Hopefully you won't have to see that view again! Looking at the spark plug projection into the combustion

chamber, what plugs are they?

so is cosmetic hg are not so good and you are having the head skimmed then wouldn't be be forced to use a after market hg or can you get away with a oem hg after a skim ?

so is cosmetic hg are not so good and you are having the head skimmed then wouldn't be be forced to use a after market hg or can you get away with a oem hg after a skim ?

 

you can use OEM, the overall compression ratio might change very slightly, but if the car is mapped accordingly that's not a problem

so what would be the limit on a skim when using a oem hg? my build am looking to hit around the 600bhp mark

Hopefully you won't have to see that view again! Looking at the spark plug projection into the combustion

chamber, what plugs are they?

 

I hope not to Andrew.

 

Re the plugs they are NGK I cannot remember the exact variant atm, will have to find the invoice.

so what would be the limit on a skim when using a oem hg? my build am looking to hit around the 600bhp mark

 

Taken from Z1 website;

 

If rebuilding and your block has been decked and heads have been surfaced with-in Nissan specifications, chances are that around 5-7 thousandths of material has been removed between the block and the heads (8 thousandths being the factory specified limit). In this case the .051" thickness (6 thousandths thicker) will closely compensate for the amount of material removed. Decking block and surfacing heads (especially past factory specifications) without increasing headgasket thickness results in higher compression ratios, affects timing due to distances between crank and cam timing sprockets changing, as well as can cause problems with valve to piston clearances in extreme circumstances.

hmmmmm interesting am not sure what road to take really with the heads and hg

hmmmmm interesting am not sure what road to take really with the heads and hg

 

Dan, Whatever you do don't use MLS (Cometic) I'm going with OEM HG

Howard - are you keeping your existing heads? don't see why you wouldn't

Howard - are you keeping your existing heads? don't see why you wouldn't

 

Yes Jim has confirmed they are good.

 

Jaffa any idea how SpecialtyZ run OEM HG ( 87mm)with 87.5mm and 88mm bores? Surely the 88mm piston would foul on the 87mm OEM gasket?

 

I am awaiting an answer from Gregg, just wondering if you could shed any light on it?

Yes Jim has confirmed they are good.

 

Jaffa any idea how SpecialtyZ run OEM HG ( 87mm)with 87.5mm and 88mm bores? Surely the 88mm piston would foul on the 87mm OEM gasket?

 

I am awaiting an answer from Gregg, just wondering if you could shed any light on it?

 

OEM are oversized to allow for the larger pistons

Thanks Jaffa

That's rubbish from cometic, I'm using stock gaskets on mine.

 

Cometic are well known for being lower quality when it comes to sealing compared to other brands, or even OEM items.

 

Unfortunately, U.S. companies still sell the sub-standard product knowlingly, even admitting they use other brands for big power builds.

I still don't get this! During the last few years I had the Zed and reading up on builds and ads for car's frequently quoting cometic as de-rigueur for performance builds, the consensus of this thread it's Cometic are s##t!!

 

I guess the ones I bought on the forum believing them to be the way to go for a build! May as well be ditched!

 

There seems to be little evidence of people using OEM gaskets for big builds, so given the info here, it seems many have missed a trick!

One of the highest powered Zeds in the UK uses Cometic gaskets.

 

I'm aware of 3 high powered Zeds with Cometic gaskets that have failed.

 

It's a gamble for a high-powered build.

 

OEM gaskets have long been well known for being very strong.

I still don't get this! During the last few years I had the Zed and reading up on builds and ads for car's frequently quoting cometic as de-rigueur for performance builds, the consensus of this thread it's Cometic are s##t!!

 

I guess the ones I bought on the forum believing them to be the way to go for a build! May as well be ditched!

 

There seems to be little evidence of people using OEM gaskets for big builds, so given the info here, it seems many have missed a trick!

 

SteveE, I'm afraid your right, it seems that in the USA the consensus seems to be to me that the Cometic gaskets are pretty bad.

 

Just to quote Greg Dupree from SpecialtyZ again incase anyone missed it earlier:

 

Hi Howard,

 

The OEM head gaskets seal the best, I run stock head gaskets on my

1000 HP drag Z.

We also do all our builds with OEM gaskets.

We have never had a gasket failure with factory gaskets.

 

The only reason to go metal is for bore sizes over 88mm, or if the

heads and block have been surfaced too far.

 

Cometic gaskets are the worst available, I know lots of people that

have had issues with those gaskets.

Tomei are the best Metal gaskets, but it requires an extremely fine

surface that most machine shops are not capable of providing.

Most surfacing machines cut too coarse, they will still seal fine

with a OEM gasket.

 

And more from Greg

 

Again I highly recommend FACTORY head gaskets as they are hands down

the least likely to have issues.

 

and finally regarding larger bore sizes

The stock bore size is 87mm

The factory head gaskets fit 87, 87.5, and 88mm

 

We only use factory gaskets and bore 87.5 and 88mm all the time.

 

I hope that this helps with anyone contemplating future rebuilds

Edited November 7, 201411 yr by bigh

That's interesting on the bore size using stock gaskets.

 

I have 87.5mm Wiseco Pistons to fit and a stock gasket will obviously suffice, however I bought the Cometic type as I don't know if or by how much the Heads have been skimmed on a previous owners repair! I don't know how to measure this yet or even know the original height stock 40P's are, but it looks like the stock gasket is the way to go.

 

Sorry for any perceived Hijack of this thread BigH but it's been enlightening, despite your unfortunate situation.

 

Sorry for any perceived Hijack of this thread BigH but it's been enlightening, despite your unfortunate situation.

 

SteveE, no problem at all. All this information/discussion is good for all of us.

do all head need to be skimmed once removed before refitting ? is that a must