Effect of a 38mm restrictor on an LS7

[C Lee Farquar]

I may have misunderstood what he was saying to me. This was to increase the bore by 10 thou from standard. He mentioned something about a diamond cutter.

I'm taking the block, crank and pistons to be measured at Performance Unlimited next week. That should put me in a better position to decide what I can get away with.

[C Lee Farquar]

Hi Stan.

I can't help with the math, but the restrictor size was increased to 42mm in 2014.

I calculated, hopefully correctly, that this gave a 30% bigger orifice.

I would be interested to see how this affects the other figures calculated.

[C Lee Farquar]

Hi Stan, thank you for your time.

It has never been dynoed. I bought in new in 2006 with an E38 ecu. Initially I ran without a restrictor.

I did one race with the 38mm restrictor, quite a few with the 42mm.

Once I get the engine sorted I plan to get the ecu better set up for the restrictor.

[C Lee Farquar]

Update for anyone who's interested.

I took the block to Dave and he's taken the worst cylinder out to +10 thou and he feels it needs another 7 thou to take the lip out. From most sources +5 is the recommended max oversize although +10 has been done successfully.

I took the crank to be crack tested and it is significantly cracked and scrap.

My current thinking is to try and sell as is and buy a new one when I've saved some money. I think the cost or liners or a block, crank, pistons, rings, couple of con rods, bearings etc. will be too high.

[C Lee Farquar]

Thanks, I have been looking at short engines but I think they will work out more expensive. Assuming it would be £5k landed.

There seems to be differences of opinion as to whether the LS7 heads will fit an LS3 block. TBH, the compatibility of bits concerns me, I don't have much knowledge, most advice is contradictory. I'm building an unusual house without detailed plans, I'm finding this challenging enough without learning how to be an LS expert.

The LS7 sump has worked perfectly, the oil light never came on when it had enough oil in the tank. The consumption caught me out, a gallon in 200 miles. The other reason I need the sump is clearance, I have a propshaft running about 10mm under the sump and block. I could possibly have a custom sump made to saddle the shaft but I still have to deal with surge. Time consuming and expensive, and if the oil pick up needs modifying even more hassle.

Then I have the loom and ecu to sort out, gaskets, new bolts.

Finally, the engine wasn't running right before I spun the shells and I'm not sure why. With a new engine with new injectors and sensors I would hope the problem would be cured or at least easier to solve.

Also, an LS7 comes run in which is handy for a car you don't want to drive on the road.

[C Lee Farquar]

If it would fit I'd have an LS3 over a new LS7 and save £4k less ecu and loom costs.



the problem with fitment is that the valve covers only just fit in the inverted v of the roll cage. The hand made ali transmission tunnel also fits snugly. I really can't lift the engine.

I've had to grind the bottom of the block to clear the propshaft that runs to the rear diff. It's possible to lower the centre bearing of propshaft a little but then I lose my flat floor and it's running out of line.

This shot is looking forwards. The shaft runs 10mm below the transmission sump and about the same below the starter ring.

An aftermarket dry sump would be OK but I don't like belt driven oil pumps for off road work.



ERL stuff looks good, core charges kill it though.

[C Lee Farquar]

I raced against an interesting V16

here

[C Lee Farquar]

PhillipM said:

So, when's the Jag engine conversion then?
I hear there's a load going cheap...

Wouldn't be the first time! I expect you remember all those new supercharged engines at £2k a decade ago?

Been having off thread conversations considering the options.

My current preference is to sell mine on ebay as a complete lump for someone else to fix and buy a new one. Then buy a new one. Mrs CLF seems to think a new (house) roof is more urgent.

Considering building to a smaller capacity so we can run lighter in France but I don't think the weight lose will make up for the loss in power.

Work and house build is quite mentally draining at the moment. I rather like the idea of saving up and getting a direct replacement. Plug and play in a day. Not too bothered if I don't race until October.

[C Lee Farquar]

I've stuck it on ebay, after long and careful deliberation it doesn't make sense for me to rebuild it.

Thanks for the advice, particularly Mike & Stevie off forum.

[C Lee Farquar]

Update time

I sold the LS7 and, unfortunately, the price of new ones has gone up by £2000.

I've been looking at the viability of buying a base spec LS3 for £6k less and fitting a cam that is more suited to running with the restrictor.

I've been recommended this spec by Cam Motion

Duration at .050": 216/224
116 Lobe Center Angle with a 113 Intake Centerline
Lift with 1.7 Rocker Arm Ratio: .595"/.587.
Double spring kit with titanium retainers.
Severe duty timing chain using stock gears

Google tells me standard is 204/211 .551/.525 117

The other issues I have are sump clearance, a standard sump will foul my propshaft and the risk of oil starvation

I'm thinking of importing this sump which is shallow enough, has baffles and trapdoors.

They also do a bolt on adapter so that I could easily fit an Accusump. I don't want to fit a dry sump, I have no space for an external pump and the belts are vulnerable with off road racing.

Then I'm thinking have it mapped on a rolling road.

Does this all sound like a reasonable way forward?

[C Lee Farquar]

Partsworld Performance list the spec as:

Engine type: LS-Series Gen IV Small-Block V-8
Displacement (cu in): 376 cu in (6.2L)
Bore x stroke (in): 4.060 x 3.620 (103.25 x 92mm)
Block: Cast-aluminum with 6-bolt, cross-bolted main caps
Crankshaft: Nodular iron
Connecting rods: Powdered metal
Pistons: Hypereutectic aluminum
Camshaft type: Hydraulic roller
Valve lift (in): .551" intake / .522" exhaust
Camshaft Duration (@.050 in): 204° intake / 211° exhaust
Cylinder Heads: Aluminum L92-style port; as cast with 68cc chambers
Valve size (in): 2.165 intake / 1.590 exhaust
Compression ratio: 10.7:1
Rocker armsn: Investment-cast, roller trunnion
Rocker arms: Investment-cast, roller trunnion
Rocker arm ratio: 1.7:1
Recommended fuel: 92 octane
Maximum recommended rpm: 6,600
Reluctor wheel: 58X
Balanced: Internal

Note the cam spec is different to that posted above.

[C Lee Farquar]

It's £4850 plus VAT, plus £799 for the loom, accelerator and ECU.

I'm hoping the standard pistons will be Ok

[C Lee Farquar]

Thanks, I'll look at that sump. I'm struggling to find comprehensive measurements but I'll see if we're in the right ball park. As the car is spaceframed there are tubes in the area.

Thinking with replacing the cam etc. is that it's a lot easier with the engine out, access to the top end is tight once the engines in. Also I want to get as near to the LS7 performance as I can, I'm trying to race rather than just take part.

I prefer OEM reliability. From what I can see the different versions of LS3 offered by GM are achieved solely with a cam change, so it seems to make sense to fit a cam that works for my application, with the 42mm restrictor.

I assume the LS3 at 6.2 litres will rev slightly higher than 7 litre LS7 with same restrictor?

[C Lee Farquar]

There's no chance of the bat wing sump fitting.



My engine mounts are 15" apart and the sump is 20 1/2" wide, the tubes that the mounts are fixed to are 19 1/2" apart. These can't be changed as the upper wishbones attach to them.

[C Lee Farquar]

Initially I was going to fabricate one until I saw the improved racing ones.

Do you know how well the cast ali welds? Or is it easier to start from scratch.

I had rather convinced myself that a shallow sump with Accusump would be OK.

[C Lee Farquar]

As you say we don't now the g forces or how well the oiling will work so it's guess work and balancing the amount of work against a perceived risk.

I have no doubt that the biggest risk of starvation comes on deceleration. The engine is in rear so the oil will be flowing towards the sump well.

I don't know how well Accusumps work

[C Lee Farquar]

Modified LS2 sump seems like the way ahead. I've ordered the cam and other bits.

Off topic but could I ask where best to try and buy this clamp? It's from the turbo of a DAF CF65 lorry, between the 'in' and 'out' parts. DAF don't list it as a separate part and I don't know what make the turbo is

[C Lee Farquar]

Thanks

They don't ship to the UK but once I knew they were called V clamps I found the right size on ebay for £13 delivered.

[C Lee Farquar]

Sump and EFI Live ordered Trying to work out what wideband device I need.

I've been reading the engine installation instructions. It seems it needs prelubeing, don't we all. So a few more $.

I can't get to the bottom of whether my LS7 flexplate will fit the LS3. The new engine comes with a flexplate but I don't think it will work with the TH350 torque converter.

[C Lee Farquar]

I can't remember exactly what I did when I fitted the LS7, but I have a Hughes flexplate designed for the TH350 converter. I ended up buying two torque converters as the first had too high stall. It was supposed to fit the LS engine but didn't. We had to weld a bit on one (on the bit that locates the crank) and turn a bit off the other. In 2006 information was a bit thinner on the ground for Gen 1V engines and I don't think the transmission people were that knowledgeable. I'm hoping the 2006 LS7 crank rear is identical to a 2017 LS3.

My TH350 is manual shift with (some) engine braking and a few uprated bits. I've snapped the input shaft but no problems since changing to an uprated one (300m Coan one IIRC)

I did the last rebuild with a fastidious older friend of mine. We took a while and ensured all the measurements were optimal, the improvement was significant.

Edited by C Lee Farquar on Monday 18th September 20:13