Rover 3.5 build

[John Hamilton]

Hey everyone,

I'm slowly building an MGB GT V8 Sebring race car to SVRA regs and as usual, the budget is stretched very thin.  I've been looking at alternatives to stock Rover rods and custom pistons at about $1000 a set.  Would there be any advantages or disadvantages to using 6 inch 327 rods and Ford V6 pistons?  If my math is correct, it would yield about 11.4:1 compression ratio and the cost would be about half of custom pistons.  Plus, if I ever hurt the engine, replacement parts are cheap and readily available off the shelf.  If anyone has any ideas, pros or cons, please share with the group.  If you need specifics on lengths, sizes, clearances, etc. I can provide them from my research.

Thanks!

John

[WedgeWorks1]

My 3.5 bored .060 over has 327 h-beam rods with after market piston and an off set ground crank for the Chevy rods. It is a great set up and cheap too.

[tr8todd]

What are your displacement limitations in the class?  If your limited to 4 liter, just go with a 4.0 or 3.9.  Your cheapest end result will depend entirely on your displacement target.

[Moderator]

As I understand it, the SVRA rules are:
1) nominally 3.5L displacement,
2) stock (2.8") stroke,
3) an overbore of no more 0.047" on the stock bore (3.5")

To get down to that bore size, other racers in this class have used later model Rover (4.0/4.6) blocks with smaller diameter top-hat style cylinder liners installed to reduce bore. Jerry Richards is the exception. He has used Rover 3.5 or Buick 215 blocks, possibly motivated by economics, but he's very quick when he finishes.

SVRA regs for MGB GT V8:
http://www.svra.com/SVRA/SVRAHome.nsf/attachmentweb/EJEN-67XNGB/$file/MGB-GT+V8.pdf?OpenElement

[roverman]

John, Perhaps this worked for "Mike",(.060" overbore) in a 3.5L rover. I am skeptical about reliability, for your application. Stock sleeves are only pressed in place, not cast in place/ribbed like buick/olds. I would not bore .060 os. with them, either because of sleeve shifting, when cast. If the rover sleeves are too thin, they will "migrate". This then becmes a lose/lose situation. Good Luck, roverman.

[John Hamilton]

SVRA rules state that bore and stroke must remain standard (up to .047 overbore) no stroker motors.  Internals are free, so I started looking at alternatives to custom parts.  I have a couple of Buick blocks as well as a TR8 and a few SD1 and Range Rover blocks.  The overbore will be in the neighborhood of .030 - .040, depending on which piston works best.  Economics has a great deal to do with the parts gong into this car, since I'm still racing a 4 cylinder MGB while trying to finish this one.  Factory replacement 10.75 or 11:1 pistons are available, but they are all cast.  The Ford V6 pistons are hypereutectic flat tops with a thinner ring pack and probably weigh significantly less.  Just looking for ideas at this point since the engine build will come after the bodywork, and I've just gotten started on that.

Thanks everyone!

[roverman]

John, I suggest a "peep" on Icon pistons webb site, specifically # IC637C. Forged +.060" will give a 3.505" dia. Good Luck, roverman.

[WedgeWorks1]

Running a .040 over bore with custom pistons to compression up with offset ground Chevy 327 rods is a nice set up. The .060 over bore I have works well and was done professionally to assure the liners would not move. This was done back in the mid-90ies and gone through one rebuilt with numerous 1/4 mile runs. Ken Slagle ran in SCCA GT1  4.0 liter made from a 3.5 block. It was really dependable.

[John Hamilton]

Does anyone know if I can safely deck the Rover 3.5 block?  Can I take off .020 and still get my intake to fit, or do I need to mill the intake as well?

Thanks, John

[WedgeWorks1]

I know a few TR8 guys that decked the block removing the engine ID numbers and had no issues with the intake.

[BlownMGB-V8]

Your intake bolt holes are large enough to handle that with no problem. You could probably go. 040"

Jim

[roverman]

John, You "are" going port match the manifold, to the heads-yes ? What heads and manifold ?  Cheers, roverman.

[DiDueColpi]

John,
Milling the block is no problem at all.
Like Jim says .040" is probably not an issue (if you need that much, I tend to use the smallest cut possible to keep as much deck strength as I can)
This will do nothing but good things for your engine.
It lets you "zero deck" the engine and square the pistons to the deck.
You can also ''over deck" the block and machine the pistons to fit. Giving you your choice of deck height and eliminating the chamfered edge of most production pistons.  This removes the dead zone around the edge of the piston. And improves the quench area.  
Don't let the machine shop grind a chamfer at the top of the bore. Or all your work is wasted.
Another advantage of decked blocks and milled heads is that it raises the intake manifold on the cylinder head.
Properly port matched or ported (if allowed) gives you a better approach to the intake valve.
Angle milling the block and the heads is also an option if you are rule limited.
The compression advantage is minimal but the intake improvement is useful as well as the small change in valve geometry. This will require intake manifold machining for sure.
All of these improvements are small but we're racing and it all counts.
Cheers
Fred

[John Hamilton]

I'm using ported SD1 heads and an Edelbrock manifold.  I want to use the 6 inch Chevy rods and possibly Ford 3.0 liter V6 flat top pistons machined to zero deck to get about 12:1 compression.  Everything will be port matched when finished, but for now, I'll be using the block hugger headers.  This could change, but the budget can't absorb RV8 headers yet.

Thanks for the input, it's been very helpful.

John

[roverman]

FYI, There are some good sbf header designs,(non tri-y), that can be modded to fit the rover, ie. cut-off the Ford head flanges and add the Rovers. The (2) central primaries will need to be moved further apart by approx. an inch ? Good Luck, roverman.

[John Hamilton]

Do you have any details on the Ford headers?  I have a Rover V8 flange kit that could be used to make my RV8 style exhaust.

[roverman]

John, If you have one piece header flanges, compare them to prospective sbf headers. You will see what I mean. I find good used sbf headers at the swap for $20.-up. Bought "Hooker" for $40 Use 1 5/8" primaries, minimum dia.. Even though this is considerable work, it should prove much quicker, than from scratch.  Onward, roverman.