Bigport 4AGE Modification - Cams + Compression

[GeeEss]

I've ordered a set of 264 Tomei Poncams for a Bigport 4AGE and also ordered a 0.5mm TRD Headgasket.

I've been advised to be careful with how much I shave the head as I might run the risk of melting the (stock) pistons if I overdo it.

As far as I can tell, the head has never been off this car; I just want to remove the minimum amount of material necessary. . .

Can anyone advise machining specs and / or the maximum compression ratio the stock bigport pistons can handle?

PS: Engine has done 135000km; is running fine, not using oli etc. . .

[Sam_Q]

I am far from any expert but I have yet to hear of anyone having strength issues with the standard pistons without boost or N2O. Just don't shave the block with that gasket!

[GeeEss]

I am far from any expert but I have yet to hear of anyone having strength issues with the standard pistons without boost or N2O. Just don't shave the block with that gasket!

What do you mean; the head has to be shaved flat if removed anyway doesn't it?

[bohemian83]

usually yes or you may have sealing issues. when you remove the head you will find some indents in the head where the old headgasket had the steel rings to seal the cylinders. usually they just need to get all these indents machined out. usually about 6thou should do it. but that entireley depends how flat the head is, and how deep the indents are

are you sure its a 0.5mm gasket? I thought TRD ones were 0.8mm. stock ones are 1.2mm. I thought you lost about 0.5 when going the TRD gasket.

[hosking1991]

Not too hard man cc the chambers.and pistons ,measure piston heights , head gasket thickness, head gasket cc and work out your compression ratio

I reckon around 10.5:1 would be nice and easily achievable with your gasket

Luke

[hosking1991]

Also I can help with machine work and cc ing if your near Sydney

[oldeskewltoy]

I'm running stock "bigport" pistons(Euro/Singapore bluetop 10 to 1), I have 33.25cc chambers(head cut .039"/1mm), I had the deck/block cut .015", using a stock headgasket - my CR is 10.80 to 1 - I'm using a 264 type cam (Web Camshafts 577 grind)

I'm planting a bit over 145hp @ the wheels

[GeeEss]

I'm running stock "bigport" pistons(Euro/Singapore bluetop 10 to 1), I have 33.25cc chambers(head cut .039"/1mm), I had the deck/block cut .015", using a stock headgasket - my CR is 10.80 to 1 - I'm using a 264 type cam (Web Camshafts 577 grind)

I'm planting a bit over 145hp @ the wheels

That's not bad - I'd be quite happy with that output from 264's - to say the least. . . .

1. What exactly have you done to the Head?
2. What Induction set up are you using?

I know from your previous posts that you're a fan of the OEM Gasket Vs the Metal type. From what I've read so far it seems there are differing opinions on this. Some guys in South Africa are running the 0.5MM TRD gaskets w/o problems; I mentioned this to the guy servicing my Block & Head today & he said that as far as he was concerned; a properly installed Metal Gasket should be justy as durable as the OEM unit; I figure / hope he knbows his stuff as he races a 20V Blacktop Clubman which he says puts out 215 ATW HP. . . Having said this I know there are other factors that would influence the longevity of a Gasket. . .

He said that there's only a limited amount you can do to the Bigport Inlet (apart from raising the floor with Epoxy @ Motoman) so he's going to concentrate on the exhaust ports.
I was going to be a tight ass WRT induction but have been nudged into considering ITBs+ an aftermarket ECU (his mate has an Adaptronic available for $600).

Tomei adverttise their PonCams as Plug+Play; does this mean I can get away without spending another $X00 on Toda / etc Adjustable Cam pulleys?

[Duk]

I know from your previous posts that you're a fan of the OEM Gasket Vs the Metal type. From what I've read so far it seems there are differing opinions on this. Some guys in South Africa are running the 0.5MM TRD gaskets w/o problems; I mentioned this to the guy servicing my Block & Head today & he said that as far as he was concerned; a properly installed Metal Gasket should be justy as durable as the OEM unit; I figure / hope he knbows his stuff as he races a 20V Blacktop Clubman which he says puts out 215 ATW HP. . . Having said this I know there are other factors that would influence the longevity of a Gasket. . .

My twin charged 4AGZE has seen 18psi with a standard, 200000+km old head gasket. Pretty sure that a factory head gasket, ARP head studs and correctly torqued head will easily survive a little bit of compression and some mild cams.
Tuning will keep detonation at bay, rather than trying to resist it with metal head gaskets.

[oldeskewltoy]

first... I need to correct something, I'm running a smallport head (I'm sorry, I feel like a heel now ) I'm running a reversed plenum smallport intake



The porting work was done by Loynings Engine Service(has built quite a few Atlantic 4AGEs)

This engine was NOT ported to Atlantic specs!!! I SPECIFICALLY said that torque, and a wide torque band was the important thing in my build when I discussed this with Loynings. The torque band, and the 40/18 crank are part of why I chose 264 type cams... the earlier crank is good to about 8500. As I see it, there is no reason to run 272 cams or higher if I'm not going to twist it high enough to take full advantage...

[Sam_Q]

GeeEss: most people I hear of don't both shaving the head when replacing the gasket, I admit i didn't when I put my 0.8mm TRD gasket in. It's not what I meant though. I was refering to shaving the block as this reduces the piston to head clearence and with a 0.5mm gasket it's seriously close. If anyone is going to fit one of these gaskets I really suggest they measure evrything first to make sure it's going to work out, although I don't know how anyone would know how much to allow for rod and piston stretch

[oldeskewltoy]

I don't know how anyone would know how much to allow for rod and piston stretch

'sperience It's is why I chose Loynings

I know I'm always bringing them up, but I look @ Loynings, kinda like I look @ Toymods... there are always exceptions, but the knowledge available CONSIDERABLY outweighs the bullshit

[Sam_Q]

ah experience, the one thing I have little of but people think I do.

So this Loynings place is an engine builder?

[oldeskewltoy]

ah experience........ So this Loynings place is an engine builder?

One of the best in the USA... and they build quite a bit more than just 4AG... in fact they build quite a few different racing engines - having won 27 national championships in SCCA

http://www.google.com/search?q=Loyni...7d8e26231a088d - btw... there is a complaint thread - "BEWARE OF LOYNING ENGINE BUILDER" read it as well... it isn't often so many people respond in the positive to a thread like that

[GeeEss]

GeeEss: most people I hear of don't both shaving the head when replacing the gasket, I admit i didn't when I put my 0.8mm TRD gasket in. It's not what I meant though. I was refering to shaving the block as this reduces the piston to head clearence and with a 0.5mm gasket it's seriously close. If anyone is going to fit one of these gaskets I really suggest they measure evrything first to make sure it's going to work out, although I don't know how anyone would know how much to allow for rod and piston stretch

Thanks Sam; in this case maybe discretion is called for; I will ask him about using the O.5mm Gasket again - if he (the guy @ L.W. Parry) insists it's OK I will get him to screw the Head+Block together to cover my ass (Was going to p/u Head+Block & assemble) - have spent too much time & money on this thing for it to go bang. . . .