PistonHeads.com Forum

Effect of a 38mm restrictor on an LS7

Effect of a 38mm restrictor on an LS7

Author
Discussion

PhillipM

5,183 posts

112 months

Tuesday 14th February
quotequote all
Yes, there was a sudden rash of V8 'charged conversions. And then a sudden rush on new gearbox and drivetrain bits shortly after...some of them still aren't reliable biggrin
RE: The motor just stick it back in with some thicker oil for a year! hehe

C Lee Farquar

Original Poster:

1,932 posts

139 months

Sunday 26th February
quotequote all
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

Original Poster:

1,932 posts

139 months

Monday 4th September
quotequote all
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

Original Poster:

1,932 posts

139 months

Monday 4th September
quotequote all
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.

Boosted LS1

16,504 posts

183 months

Monday 4th September
quotequote all
What's the price of that package out of interest and you did notice it uses cast pistons?
Advertisement

C Lee Farquar

Original Poster:

1,932 posts

139 months

Monday 4th September
quotequote all
It's £4850 plus VAT, plus £799 for the loom, accelerator and ECU.

I'm hoping the standard pistons will be Ok smile

stevieturbo

12,688 posts

170 months

Tuesday 5th September
quotequote all
Is the Vette sump not regarded as one of the best and lowest profile ? I thought the LS2 shallow was one of the worst ?

http://www.improvedracing.com/baffled-oil-pans/baf...

As for changing cams and springs etc....why not just try the engine as is from the factory first and then see how things go ? They will all be very much endurance tested, so you could thrash it all day long and be confident with reliability.

Although yes no doubt, a cam upgrade is bound to help performance, especially with sucking through a little restrictor as long as you can get somewhere up to the job of retuning the factory ecu ok to suit this.

Boosted LS1

16,504 posts

183 months

Tuesday 5th September
quotequote all
I think the ls6 vette sump was the best GM made Stevie. It has wings and baffle plates. After that they all became basic sumps in terms of shape, ls7 excluded. As for depth they only get as shallow as the bell housing mounts if that makes sense.

C Lee Farquar

Original Poster:

1,932 posts

139 months

Tuesday 5th September
quotequote all
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

Original Poster:

1,932 posts

139 months

Tuesday 5th September
quotequote all
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.

Boosted LS1

16,504 posts

183 months

Tuesday 5th September
quotequote all
Big wing sumps are appx 53 cms wide and 12 cms deep so pretty close to your measurements. The second version with a detachable bottom cover is slightly bigger. An ls7 dry sump will be about 12 cms deep but I've not measured it.

stevieturbo

12,688 posts

170 months

Tuesday 5th September
quotequote all
Dimensions of pretty much every sump available are here. Long thread, but lots of info.

https://ls1tech.com/forums/conversions-hybrids/817...


if ground clearance is ok....What about some sort of custom wet sump, maybe just to one side of the propshaft ? That would allow you to build in capacity and probably make it fairly well baffled etc too ?

C Lee Farquar

Original Poster:

1,932 posts

139 months

Tuesday 5th September
quotequote all
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.

stevieturbo

12,688 posts

170 months

Tuesday 5th September
quotequote all
I had a couple of cast sumps welded by a friend years ago....they warped like fk !!

But others have welded them successfully too.

There are loads of sumps available though, whether steel, cast allow, fabricated alloy etc so there are plenty of bases to work from if you were to modify an existing unit.

The shallow ones may work, but depends the sort of angles or g's the vehicle may be pulling. As said before, the shallow LS2 sumps are deemed the worst of the lot.

I use a steel Autokraft that I needed to modify slightly, but bought the steel as at the time I had no means of alloy welding myself, so it made more sense.

You could maybe start with a shallow LS2, but then add a further sump to one side of the propshaft, along with suitable oil pickup mods ? That should add more oil capacity, but also encourage all the oil into a smaller more reliable pickup area for the pipe ?

C Lee Farquar

Original Poster:

1,932 posts

139 months

Wednesday 6th September
quotequote all
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


stevieturbo

12,688 posts

170 months

Wednesday 6th September
quotequote all
C Lee Farquar said:
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

I wouldnt have too much faith in them

They only hold a small amount and then they take time to refill...and holding a small amount can only inject a small amount when required.
I'd far rather have a reliable oil system than the likes of those.

I cant see any negatives to modifying the likes of an LS2 with an additional sump box down beside the prop, unless it is at risk of physical damage down there

C Lee Farquar

Original Poster:

1,932 posts

139 months

Monday 11th September
quotequote all
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


GreenV8S

24,877 posts

207 months

Monday 11th September
quotequote all
Hard to make out the profile - these guys any use?

http://www.clampco.com/products/v-band.asp

C Lee Farquar

Original Poster:

1,932 posts

139 months

Monday 11th September
quotequote all
Thanks smile

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

Original Poster:

1,932 posts

139 months

Monday 18th September
quotequote all
Sump and EFI Live ordered smile 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.