13 replies to this topic

[Shtstr]

Well I will be building LS1 for my gmh LX8 and haven't seen anyone build one before as people just buy from wreckers and run them.

I've decided to bump up the static compression ratio from factory 10 to 1 upto 11.78 to 1 static compression ratio.
Dynamic compression ratio works out to be 9.1 to 1 or 194psi so perfect for pump 98 fuel.
I've gone with a medium size cam from comp cams. It's a 227/235 with a 113 plus 4. The rpm range is 1900rpm to 7000rpm.
Big wide power curve.
I've decided to go with the gen x 215cc heads topped with the comp cams 26926TS spring kit and Jisel shaft rockers rockers to keep it all under control.
Inlet manifold is a Holley mid rise single plane 4150 with a 2''spacer to increase the runner length.
It's going to be topped off with a 4150 4bbl throttle body.
Fuel will be delivered by 8 550cc Bosch ev14 injectors. When run at 57psi with the stock fuel pressure set-up they will flow around 620cc per minute.
Fuel will be pumped to the engine via a walbro intank 460 pump that will supply more than enough fuel.
1/2'v fuel lines will be way large enough for the supply and return lines.
The exhaust system is 4 into 1 custom made 1 7/8 headers to twin 3 inch system through a pair of 100 cel cats followed by a custom built 350 cubic inch x pipe setup to create an open header effect backed by a pair of 3''race mufflers

[Rockoz]

Ive got the bits and pieces to build one for my current project.

Not going overboard with the rebuild.

More of a freshen up.

Had the bores honed and the block cleaned.

Forget which cam I went for, but not silly wild.

New rings and bearings of course, and went for a bronze bush kit for the rockers.

Going with 8 x ITB because I really like the look of them.

 

Cheers

 

Rob

[Shtstr]

Ive got the bits and pieces to build one for my current project.
Not going overboard with the rebuild.
More of a freshen up.
Had the bores honed and the block cleaned.
Forget which cam I went for, but not silly wild.
New rings and bearings of course, and went for a bronze bush kit for the rockers.
Going with 8 x ITB because I really like the look of them.
 
Cheers
 
Rob

From all the reading and research I've done over the last few years.
They really respond well to static and dynamic compression ratio of 11.5 to 12 to 1 and dynamic of 8.8 to 9.2.
With that being said the USA guys and girls build them like that for 500 rwhp numbers and the cams they use are in the 227 to 240 duration @50 zone.
I've learned a lot in the last few years now about these engines and from what the American's have done with them over the years.
From what I've read and seen the Australian market pushing big cams for these engines are well off the mark.
If you go with good compression 11.5 and a cam no bigger than 235 intake and 243 exhaust @50 you will make good power with a decent set of head intake and exhaust system.

[gtrboyy]

Going to sound angry as hell with 1 7/8 pipes...had them on m6 sv8 for short bit then went 1 5/8 tri-y 100 cell cats on twin 3" x-force...everyone loved how angry it sounded justy all bolt on mods otr/tune etc.

 

Manuals seem fine but auto tend to drone without decent sized stally.

 

Compression helps alot so does cubes lol...ported heads seem like little gain for money compared to shaving heads.

 

One thing for sure with Ls engines not much exciting happens untill get the revs up high even on stock cams so big cams be virtually useless on street cars.

Edited by gtrboyy, 09 January 2023 - 10:20 PM.

[Shtstr]

Going to sound angry as hell with 1 7/8 pipes...had them on m6 sv8 for short bit then went 1 5/8 tri-y 100 cell cats on twin 3" x-force...everyone loved how angry it sounded justy all bolt on mods otr/tune etc.
 
Manuals seem fine but auto tend to drone without decent sized stally.
 
Compression helps alot so does cubes lol...ported heads seem like little gain for money compared to shaving heads.
 
One thing for sure with Ls engines not much exciting happens untill get the revs up high even on stock cams so big cams be virtually useless on street cars.

I've noticed that the Australian market pushes big duration cams @50 but they are losing power out the exhaust.
I've spent many years around racing and building old school engines for racing.
We always ran what people called baby cams .
But we also have Australian titles and state titles to our names too. We have beaten engines with 4 times as mumoney spent on them because of the simple fact people over cammed their engines and turned them into slugs haha.
Being a street car you need the rpm range to be as wide as possible and start as low as possible.
Something that people don't know aroller cams and is widely mis understood is the duration @50 vs compression ratio.
Roller cams are actually 15 to 25 degrees more duration @50 than listed because of the ramp rate they open at.
So a roller cam that has a duration @50 227 like the one I'm using is the equivalent of a flat tappet cam with 243 to 253 @50.
Being that this engine has 11.78 to 1 static compression a cam between 244 to 250 @50 is what you need when looking at flat tappet cams for this compression ratio.
So take 15 to 25 off the 244 to 253 and you are left with a cam around the 219 to 229 @50. So I'm right on the sweet spot for the engine compression ratio.
That is very mis understood by people and it's why the factory cams for a ls1 10 to 1 compression ratio is around the 198@50 area.
Yes they respond to bigger cams but they all have a narrower LSA to increase overlap and exhaust scavenging.
This engine will be very snappy and have excellent throttle response with this cam.
That's what you need on the stret.

[yel327]

^^ Good advice. Essentially what Crow told me for the hydraulic roller to suit the 377 SBC for my HK GTS that will also be about 11:1 or thereabouts (flat tops with 58cc chambers). I think it went something like "with the suggested cam it'll be down a few peak hp but will have that much torque it'll make for a far more streetable engine, have good brake vaccum, work well with a traditional shifting TH350 and won't get upset with air and steer pumps". They even suggested I drop back to a 2700rpm converter rather than 3000 as it'd work better with the cam and the 3.0-3.25 diff gears.

 

The hydraulic they suggested @0.050 with 1.5 rockers (I'll be using 1.6 so will be slightly different) is 227 inlet and 231 exhaust.

[Shtstr]

^^ Good advice. Essentially what Crow told me for the hydraulic roller to suit the 377 SBC for my HK GTS that will also be about 11:1 or thereabouts (flat tops with 58cc chambers). I think it went something like "with the suggested cam it'll be down a few peak hp but will have that much torque it'll make for a far more streetable engine, have good brake vaccum, work well with a traditional shifting TH350 and won't get upset with air and steer pumps". They even suggested I drop back to a 2700rpm converter rather than 3000 as it'd work better with the cam and the 3.0-3.25 diff gears.

The hydraulic they suggested @0.050 with 1.5 rockers (I'll be using 1.6 so will be slightly different) is 227 inlet and 231 exhaust.

What does the inlet valve close at ABDC.
That will govern your dynamic compression ratio and if it will run on pump fuel or not.
For iron heads you want no more than 8 to 1 dynamic compression ratio and a tight quench say around. 035 to .040. If you have alloy heads you can get away with upto 9.3 to 1 dynamic with same gasket thickness for quench.
Alloy allows you to run a higher dynamic compression ratio and avoid knock more than iron heads.
Dynamic compression is what you see on a compression tester when you do a compression test with all plugs removed and crank the engine over on the starter motor.

Edited by Shtstr, 11 January 2023 - 04:49 PM.

[yel327]

They are alloy heads. I can't remember exactly what the planned compression was, From memory flat top Wisecos, deck hasn't been cut yet to get the piston to deck right. Heads are 58cc GM alloys. Without choosing the head gaskets yet on paper it'll be around 11-11.5:1.

 

Cam at 50 thou:

 

7 39 226

46 6 231

 

LSA is 108 with 2 deg advance ground into the cam.

 

Lift is 0.4796 inlet, 0.4818 exhaust with 1.5 rockers.

[gtrboyy]

I'd rather engine/car be snappy as fcuk & feel like an animal on street than have dyno numbers or crazy timeslip to brag about yet feel like a slug to cruise in.

[Shtstr]

They are alloy heads. I can't remember exactly what the planned compression was, From memory flat top Wisecos, deck hasn't been cut yet to get the piston to deck right. Heads are 58cc GM alloys. Without choosing the head gaskets yet on paper it'll be around 11-11.5:1.
 
Cam at 50 thou:
 
7 39 226
46 6 231
 
LSA is 108 with 2 deg advance ground into the cam.
 
Lift is 0.4796 inlet, 0.4818 exhaust with 1.5 rockers.

Here is a link to the online calculator I use.

http://www.wallacera.../dynamic-cr.php

[yel327]

Thank you, much appreciated.

[Shtstr]

Thank you, much appreciated.

Dynamic compression is what you need to keep an eye on.
I'm aiming for between 190 to 200psi so 9.1 to 9.2 to 1 for my ls build. That way it will have good low end torque and push the torque and power curve higher.
Factory ls1 engines actually have a very good dynamic comp at just over 200psi and run fine on pump 91 fuel. So I know I will be fine at 194psi dynamic compression.

[yel327]

When I entered the data for it (4.040" bore, 3.75" stroke, 5.7" rod) it comes up as 10.46:1 dynamic with 230psi pressure. It might be too high. I haven't ordered the cam yet, was waiting until I know the deck to piston clearance and cc the heads plus select a head gasket so I know what the static compression ratio will be. If I drop it to 10:1 static it gives me 9.3:1 and 198psi. This isn't totally impossible either for me as I had been considering buying a set of those new alloy fuelie copies which are 64cc. I don't need the bolt holes in the heads as the Wheels within Wheels serpentine setup uses the water pump mounts to anchor it all. I'll also talk to Crow about maybe delaying inlet close a bit, 49 degrees makes a significant difference - gives me 9.97:1 and 217psi, and see what they think. I'm pretty sure they kept the LSA at 108 to have good brake vacuum.

 

I'll be running 98 in this, it won't be an everyday driver. The Holley Sniper and Hyperspark are fully programmable too so I can use an external switch to take some timing out of the dizzy if I get stuck and have to run 95 or E10/94.

[Shtstr]

When I entered the data for it (4.040" bore, 3.75" stroke, 5.7" rod) it comes up as 10.46:1 dynamic with 230psi pressure. It might be too high. I haven't ordered the cam yet, was waiting until I know the deck to piston clearance and cc the heads plus select a head gasket so I know what the static compression ratio will be. If I drop it to 10:1 static it gives me 9.3:1 and 198psi. This isn't totally impossible either for me as I had been considering buying a set of those new alloy fuelie copies which are 64cc. I don't need the bolt holes in the heads as the Wheels within Wheels serpentine setup uses the water pump mounts to anchor it all. I'll also talk to Crow about maybe delaying inlet close a bit, 49 degrees makes a significant difference - gives me 9.97:1 and 217psi, and see what they think. I'm pretty sure they kept the LSA at 108 to have good brake vacuum.
 
I'll be running 98 in this, it won't be an everyday driver. The Holley Sniper and Hyperspark are fully programmable too so I can use an external switch to take some timing out of the dizzy if I get stuck and have to run 95 or E10/94.

If you have zero deck height and a 035 gasket you will get away with 200psi dynamic compression.
If you run a thicker gasket you will get knock