pistons
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pistons
Hi,mg project coming along,bodyshell all blasted etc,as i previously posted was looking at n/a 4.6 with headwork and cam,however a jag xjr has fallen into my my grubby little hands,and now obsessed with supercharging,want use as much of jag system as poss ie m112 with chargecoolers,i know it's loads of work but childishly i like the idea and here is the prob,engine build in progress block tested ok and bored +20,new pistons,rings etc bought however i guess for s/c i need forged pistons are 4.6 +20 available,have checked real steel,v8 tuner etc but +10 seems to be all there is,help,but i guess it's reliner back to standard,any thoughts,thanks
Talk to John Eales about Omega Forged pistons for your application.
I'm sure he will be able to help.
It really depends on how much boost you inted to run with the blower.
If I can run a 200hp shot of nitrous on my 4.6 with cast pistons then I'm sure you can run a good chunk of boost on stock pistons.
I only started to crack stock pistons when i added a 300 shot of nos...
What compression ratio have you had the 4.6 built to ??
Are you going to run EFI or a carb with the blower??
And it also depends on if this is going to be a daily driver or just a track car...
For our DIY application the only head work you will need with the blower is basic cleaning up of the runners as per John Eales drawings.
The 4.6 valves are plenty big enough for what you will want I'm sure.
Example:
I have a stock 4.6 engine in my MGB. I do have forged pistons at standard size though. My block has over 100,000 miles on it. I fitted the forged pistons because I intended to run up to 500hp of nitrous. So I bit the bullet and bought them.
The engine has all stock original internals apart from the Real Steel Blower cam which I run 2 degreee's retarded. It runs a Weber carb and makes 200hp on the dyno. With 8psi of boost from my 4/71 blower it makes 350hp and a torque figure that is fantastic.
Your base 4.6 engine has so much potential in an MGB. If you intend to blow the engine then I would be thinking more about the gearbox and clutch troubles that you may be about to unleash than engine problems ???
Let us know what the build spec is going to be??
If its going to be EFI then John Eales does a nice belt driven Pro charger setup ????
Perry
I'm sure he will be able to help.
It really depends on how much boost you inted to run with the blower.
If I can run a 200hp shot of nitrous on my 4.6 with cast pistons then I'm sure you can run a good chunk of boost on stock pistons.
I only started to crack stock pistons when i added a 300 shot of nos...
What compression ratio have you had the 4.6 built to ??
Are you going to run EFI or a carb with the blower??
And it also depends on if this is going to be a daily driver or just a track car...
For our DIY application the only head work you will need with the blower is basic cleaning up of the runners as per John Eales drawings.
The 4.6 valves are plenty big enough for what you will want I'm sure.
Example:
I have a stock 4.6 engine in my MGB. I do have forged pistons at standard size though. My block has over 100,000 miles on it. I fitted the forged pistons because I intended to run up to 500hp of nitrous. So I bit the bullet and bought them.
The engine has all stock original internals apart from the Real Steel Blower cam which I run 2 degreee's retarded. It runs a Weber carb and makes 200hp on the dyno. With 8psi of boost from my 4/71 blower it makes 350hp and a torque figure that is fantastic.
Your base 4.6 engine has so much potential in an MGB. If you intend to blow the engine then I would be thinking more about the gearbox and clutch troubles that you may be about to unleash than engine problems ???
Let us know what the build spec is going to be??
If its going to be EFI then John Eales does a nice belt driven Pro charger setup ????
Perry
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
mgb spec
Thanks for reply,i have tvr t5 gearbox and clutch assy,Hoyle front and back end,need propshaft,as you can see have spent a fair bit so far and don't really want it to go bang.
My concern is that as i said i want to use the jag system as far as poss,complete with chargecoolers,the jag runs 12psi,don't know what that boost level will give on 4.6 rover,i would be hoping for300- 350 max,going to have custom manifolds made to mate with jag chargecoolers and use AVT pre rad behind front valance,have put golf mk1 flared arches on to give a bit more tyre width,car is going to be mostly road but few trackdays and maybe brighton speed trials just for a laugh,crank and clutch assy are balanced,i'm not hung up on hp but would like car to be tractable,hence one of reasons i like eaton blower,the other is i've already got it
nigel
My concern is that as i said i want to use the jag system as far as poss,complete with chargecoolers,the jag runs 12psi,don't know what that boost level will give on 4.6 rover,i would be hoping for300- 350 max,going to have custom manifolds made to mate with jag chargecoolers and use AVT pre rad behind front valance,have put golf mk1 flared arches on to give a bit more tyre width,car is going to be mostly road but few trackdays and maybe brighton speed trials just for a laugh,crank and clutch assy are balanced,i'm not hung up on hp but would like car to be tractable,hence one of reasons i like eaton blower,the other is i've already got it
nigel
At 12 psi on a 4.6 you should easily make your target HP, I would look at around 8psi if it was me, you will have a hard time keeping the head gaskets intact otherwise. 8 psi should make 350 HP easily, get the blower cam it will make a difference, look at Toncats Mazda build, he ran more boost but made nearly 400 HP on a 4.0, on methanol with 11-1 compression we are making around 400 HP on 11 lbs of boost, that is forged pistons though. Previously we ran Volvo cast pistons at 17 psi on a 3.5 for the same numbers. I believe the 4.6 pistons are pretty good though.
Alan
Alan
bigaldart wrote:At 12 psi on a 4.6 you should easily make your target HP, I would look at around 8psi if it was me, you will have a hard time keeping the head gaskets intact otherwise. 8 psi should make 350 HP easily, get the blower cam it will make a difference, look at Toncats Mazda build, he ran more boost but made nearly 400 HP on a 4.0, on methanol with 11-1 compression we are making around 400 HP on 11 lbs of boost, that is forged pistons though. Previously we ran Volvo cast pistons at 17 psi on a 3.5 for the same numbers. I believe the 4.6 pistons are pretty good though.
Alan
Those are my numbers Alan!!!
8psi takes me from 202hp to 351hp.
I havent done much with the other pulley for 13psi yet but I have been sticking a 120 shot of gas into the top of the blower. Hence the air under the front tyres and the new PB a few weeks back
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
Hi,am now in process of ordering JE pistons from usa,they have uk agent,cost is about £900 for complete set with rings to whatever c/r you want.
Question,The xjr that i have broken for parts runs at 13psi boost,(checked with jaguar),with a cr of 8.5,this makes about 390hp on 4.0 v8,as i want to use as much of jag stuff as possible(inc existing top pulley,crank pulley will be custom) purely because i expect that jaguar had a whole lot of resources that i don't,i don't expect my manifold to be as efficient as the xjr one purely because it will be home made and probably more restrictive.
I assume then the advice will be for a smaller crank pulley,however from previous stuff read on here by stevieturbo i think,run it as fast as it will go seems to be advised,confused.Perry do blow head gaskets regularly?
nigel
Question,The xjr that i have broken for parts runs at 13psi boost,(checked with jaguar),with a cr of 8.5,this makes about 390hp on 4.0 v8,as i want to use as much of jag stuff as possible(inc existing top pulley,crank pulley will be custom) purely because i expect that jaguar had a whole lot of resources that i don't,i don't expect my manifold to be as efficient as the xjr one purely because it will be home made and probably more restrictive.
I assume then the advice will be for a smaller crank pulley,however from previous stuff read on here by stevieturbo i think,run it as fast as it will go seems to be advised,confused.Perry do blow head gaskets regularly?
nigel
I dont blow head gaskets on the 8psi + 120 of nitrous setup.
Its when I experiment with more nitrous that things leak
This is with ign advance dropped by 13 degree's.
Perry
Its when I experiment with more nitrous that things leak
This is with ign advance dropped by 13 degree's.
Perry
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
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topcatcustom
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If an XJR has fallen into your hands, why not use the whole engine assembly and ECU etc, then you will get a reliable 375bhp ish (IIRC) that is easily increased, no fabrication and machining costs, no cooling or piston issues, more fuel efficient, still a V8...
£900 is a lot to spend on pistons that will also need fitting, balancing, rings (if not supplied), then will you use standard conrods etc and is the block safe or would you want to top hat liner it?
Not meaning to sound pesamistic but the Jag lump seems much easier and more reliable to me!
£900 is a lot to spend on pistons that will also need fitting, balancing, rings (if not supplied), then will you use standard conrods etc and is the block safe or would you want to top hat liner it?
Not meaning to sound pesamistic but the Jag lump seems much easier and more reliable to me!
TC
Hi,i can think of a few reasons not to try xjr lump,
1/I have t5 g/box to fit rover
2/ have had block rebored,pressure tested etc
3/if rv8 goes bang top hat block from turners £1200.00,have you seen price of jag parts?
4/rv8 fits mgb without that much hassle,with megasquirt or emerald ecu diagnostics can be done at home,jag ecu would require our w/shop dignostic computer
5/never heard of anyone using xjr lumpbut appreciate that it can probably be done
6/xjr that i have has done over 100k
7/suspect major surgery to mgb required,engine is wider and taller
have to admit it was one of my thoughts but more i think about less i like idea
8/car is being built purely for fun so fuel consumption not major issue
Any suggestions to save money on piston costs eagerly awaited
nigel
1/I have t5 g/box to fit rover
2/ have had block rebored,pressure tested etc
3/if rv8 goes bang top hat block from turners £1200.00,have you seen price of jag parts?
4/rv8 fits mgb without that much hassle,with megasquirt or emerald ecu diagnostics can be done at home,jag ecu would require our w/shop dignostic computer
5/never heard of anyone using xjr lumpbut appreciate that it can probably be done
6/xjr that i have has done over 100k
7/suspect major surgery to mgb required,engine is wider and taller
have to admit it was one of my thoughts but more i think about less i like idea
8/car is being built purely for fun so fuel consumption not major issue
Any suggestions to save money on piston costs eagerly awaited
nigel
Hi
Pistons
1/ chevy 305 pistons with chevy rods with the sides of the rods relieved by .02" i think, ask Kevin (castleMGB) /Mike (boosted LS1) they will know, it is also posted up here several times, you have to bore the block to 3.736" but still forged pistons are about £220 imported and the rods are £275 (for H beam I beam from about £75 plus shipping and they are plenty strong enough), with the rebore work you will be below £600.
2/ chevy 305 pistons, use rebushed rover rods (cheeper but less choice of rod lengths)
3/ ford mod forged pistons, 3.7" bore (I think you can get 3.72" aswell) from JE they are $660 so about £550 to £600 imported.
BUT these are the expensive ones, they come down to about £175 a set of forged ones if you hunt for them again. You use either chevy 2" big end rods or rebushed rover, they come with different dish sizesto alter your compression or use flat toppers and buick 300 heads and skim them for CR.
There are a few others, but these are the common ones.
Best regards
Mike
Pistons
1/ chevy 305 pistons with chevy rods with the sides of the rods relieved by .02" i think, ask Kevin (castleMGB) /Mike (boosted LS1) they will know, it is also posted up here several times, you have to bore the block to 3.736" but still forged pistons are about £220 imported and the rods are £275 (for H beam I beam from about £75 plus shipping and they are plenty strong enough), with the rebore work you will be below £600.
2/ chevy 305 pistons, use rebushed rover rods (cheeper but less choice of rod lengths)
3/ ford mod forged pistons, 3.7" bore (I think you can get 3.72" aswell) from JE they are $660 so about £550 to £600 imported.
BUT these are the expensive ones, they come down to about £175 a set of forged ones if you hunt for them again. You use either chevy 2" big end rods or rebushed rover, they come with different dish sizesto alter your compression or use flat toppers and buick 300 heads and skim them for CR.
There are a few others, but these are the common ones.
Best regards
Mike
poppet valves rule!
