Drilling holes for cross bolting

Boosted LS1 · Post by **Boosted LS1** » Mon Jan 01, 2007 2:32 pm

ihatesissycars wrote:The last of the 3.9 rover blocks, about 95 onwards had the cross bolted caps and the bosses cast into the side of the block for cross bolting, they just weren't drilled to take the bolts.

I've seen the intermediate blocks with the bosses cast into them but iirc the caps didn't touch the side of the casing fully. They just touched at the bottom edge like earlier caps. Does your block take a 2.5" main bearing like a 4.0?

Boosted.

ian.stewart · Post by **ian.stewart** » Mon Jan 01, 2007 2:59 pm

My friend has just X bolted a block, drilled thru the bosses, etc, what he did say was there is a .006" gap between the edge of the block and the caps, he has had a question about this, the gaps do close, BUT I think it is relevent to the dimensional integrety of the block, if you can move the skirts of the block by this amount have no doubt the block is moving somwhere else, he has had real problems with piston slap, and I am begining to wonder if the X bolting of the block has aggrivated his situation
Gav possibly you are opening a can of worms, all for no real gain, , if you stud the block top and bottom not much seems to move about, my engine sits at 7k all day long on the rev limiter, and according to the ECU was buzzed to 8400!!! with a missed shift when I deleted the rev limiter by accident, so obviously there is strength in the older blocks if they are put together with the right parts, and mine is an early P6 flexiblock

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Ian

Boosted LS1 · Post by **Boosted LS1** » Mon Jan 01, 2007 3:06 pm

On my crossbolted block the caps were a snug fit in the casing. Same for all the lsx engines I build. They can be quite hard to extract from the casing.

The rover block sides do move when you tighten the side bolts. I remember the first one I built had a really hard to rotate crank and I thought my ARP studs had made the mains oval. It wasn't until I torqued up the cross bolts that the crank spun freely again. I was quite relieved to say the least!

Studs have always been fine with me.

Boosted.

Post by **Coops** » Mon Jan 01, 2007 3:18 pm

I'm the same as Ian mines studded top (ARP heads studs) and bottom (ARP main and big end studs) and mines seen revs of 6500 (datalog on ecu) and i have had no problems,
I did mention this to Gav when he came over, but he is determined to go this cross bolt route,
All we can say is good luck mate, and fingers crossed you dont get a fooked block at the end of it,

ian.stewart · Post by **ian.stewart** » Mon Jan 01, 2007 3:52 pm

Boosted LS1 wrote:On my crossbolted block the caps were a snug fit in the casing. Same for all the lsx engines I build. They can be quite hard to extract from the casing.

The rover block sides do move when you tighten the side bolts. I remember the first one I built had a really hard to rotate crank and I thought my ARP studs had made the mains oval. It wasn't until I torqued up the cross bolts that the crank spun freely again. I was quite relieved to say the least!

Studs have always been fine with me.

Boosted.

the thing about your block is it was meant to be cross bolted, and was machined WITH the extra bolts in place, twisting/torqueing the block into the "working position" what I was trying to say was the extra bolts will probably ruin the original dimensions of the block nessicitating the block to be machined back to base
Ian

Boosted LS1 · Post by **Boosted LS1** » Mon Jan 01, 2007 4:14 pm

ian.stewart wrote:
Boosted LS1 wrote:On my crossbolted block the caps were a snug fit in the casing. Same for all the lsx engines I build. They can be quite hard to extract from the casing.

The rover block sides do move when you tighten the side bolts. I remember the first one I built had a really hard to rotate crank and I thought my ARP studs had made the mains oval. It wasn't until I torqued up the cross bolts that the crank spun freely again. I was quite relieved to say the least!

Studs have always been fine with me.

Boosted.
the thing about your block is it was meant to be cross bolted, and was machined WITH the extra bolts in place, twisting/torqueing the block into the "working position" what I was trying to say was the extra bolts will probably ruin the original dimensions of the block nessicitating the block to be machined back to base
Ian

Agreed, they may pull the caps oval towards the side casing, or pull the casing towards the caps.

Boosted.

ihatesissycars · Post by **ihatesissycars** » Mon Jan 01, 2007 9:39 pm

Well i've jsut been doing some research.

I've checked for clearance on either side of the caps, ones side has the smallest amoutn, a few thou and the other has none.

The side with the gap is the side with the register. Refering to the "how to tune rover v8 engines" book it says that the 4.0 and 4.6 blocks had only only small register on one sie of eadh cap and the other side was plain from top to bottom. It also says that my block is identical to the later blocks except for the lack of bolts and smaller main bearing bore.

If the wording about the register is correct then the gap is supposed to be there and will close up when torqueing the side bolts.

As far as i can tell i will find out if i have a problem when i do up the cross bolts. If the crank no longer spins freely then further investigation is required probably leading to a line bore however if it spins freely then i'll leave it at that.

Watch this space and i will post up what i find.

ian.stewart · Post by **ian.stewart** » Mon Jan 01, 2007 9:58 pm

I would be doing a pre and post bore check as well, I am also wondering if the Xbolts will pull the bores out of line, I really do have mixed feelings about this, as I can see the machining costing more than it would cost to buy a genuine X bolted block, Does anyone have any torque plates for machining and checking the bores,

HairbearTE · Post by **HairbearTE** » Mon Jan 01, 2007 11:05 pm

If you only have one cap that is out by a small amount and all others are snug then perhaps some sort of a shim should be used on the one area? as Ian points out, ovality in the main bearing tunnel could be the least of your problems if your pulling in the skirt of the block when your torqing it up. A simple shim could cure this issue perhaps?

Boosted LS1 · Post by **Boosted LS1** » Mon Jan 01, 2007 11:31 pm

I doubt the bores will be pulled out of line if the caps are pretty close to spec as the skirts on a rover are below the parting line. The bores might not be that accurate in the first place, there will be a tolerence there as well.

May as well try it and see if the crank spins freely.

Boosted.

Wotland · Post by **Wotland** » Tue Jan 02, 2007 9:34 am

I know DJE offers this service to cross bolt last factory 3.9 block for 155GBP.

ihatesissycars · Post by **ihatesissycars** » Wed Jan 03, 2007 10:38 am

If i were to just stud one of my blocks for my next engine build which one would you use?

To recap one has the standard main caps and registers and one has the later main caps and register on one side. the other side of the cap and block is flat and plain so i suppose it registers on the whole surface.

Boosted LS1 · Post by **Boosted LS1** » Wed Jan 03, 2007 12:29 pm

ihatesissycars wrote:If i were to just stud one of my blocks for my next engine build which one would you use?

To recap one has the standard main caps and registers and one has the later main caps and register on one side. the other side of the cap and block is flat and plain so i suppose it registers on the whole surface.

Assuming all else is the same I'd use the block which has the tightest fitting caps. Once they're crushed down with some Arp's they won't move anywhere. You get extra crush when using rolled threads especially at arp torque values. Check out the other factors like wear in the bores etc.

ihatesissycars · Post by **ihatesissycars** » Wed Jan 03, 2007 2:40 pm

Well i'm thinking use the later one. It has the biggest registers, the caps are a complete sod to get out so very snug and bore wear doesn't matter as it'll get bore out a bit more plus it does have the plate that screws onto the front of the camshaft to stop it moving which is handy so that one i guess.

Phoned DJE, they reckon 1 in 5 blocks need a line bore after bolting so thanks for the heads up wotland