knightec

Ok I’m not an expert on the LS series of engines so I thought I’d post my idea here – I’m looking at creating a 6.0 Litre version of the LS7 engine, using the standard LS7 crank throw of 101.6mm……..therefore I will need to remove the standard press-in liners and reduce the bore size from 104.8 standard to 96.9mm therefore giving 6.0 litres in long stroke format……do the LS7 liners come out easily?…..

please dont reply to this post with other ideas about short stroke cranks, nitrous, turbos, blowers etc.....I’m not interested in any of that as this will be a normally aspirated race motor running air restrictors.

The only problems I can foresee are the LS cylinder heads and principally the valves fitting inside the bore size I require of 96.9mm – I have worked out I need 51mm inlet valves, with 43mm exhaust valves - or there abouts – so that will all be snug fit in a 96.9mm bore – I know I might need to come down on those valve sizes slightly, but that’s the ball park I’m heading in.

What I’m interested to know from you guys is based on your knowledge of all the variants of LS type cylinder heads, aftermarket too – do you think its possible to accommodate a 96.9mm bore with those sorts of valve sizes – or is it totally out of the question????......

Also – I was looking that the LS’s intake ports and I must say – they looked horrific as standard – by this I mean too big – has anyone yet made attempts to make the ports smaller for faster gas velocity? ......this can be done by reducing the port size with devcon or JB weld - which are both types aluminium putty stuff that goes rock hard when dried ......or plain old aluminium welsing can work, but it often distorts the head........as my experience of ports is that bigger is not better......smaller ports create faster gas velocity, which is whats required in a highly strung race motor.

does anyone cast aftermarket cylinder heads that have sensible looking ports and the valve sizes that I require?

Thanks in advance

Knightec

Stang's Bane

iTrader: (22)

I am not sure what the mm's you quote come out to in inches, but here it goes.
There are several factory LS blocks with smaller bores, why not use one of them?

As far as the cylinder heads go, you need to match your cylinder heads to your application. The ls7 heads were designed to be used on a 7.0 liter engine and larger. Search in the LS1 internal section and that will give you a better idea of what is available. AFR offers a 205 cc runner head, Edelbrock has a 200 cc, TFS and ETP offer 215's and on , and on. Good luck!!

My90Iroc

iTrader: (26)

The stroke you're looking for is a typical 4" crank which isn't a problem. The bore on the other hand will take some work. Truthfully unless you already have an LS7 block there's no good reason to spend the money on that. Just buy a standard LS1 block because no matter what you'll need to have it resleeved to get the bore you're looking for. You're looking for a 3.81" bore which is significantly smaller than the lsx blocks out there. I have a feeling the cylinder heads will take some work also. I'm not sure what the 4.8 truck heads are like and if they'll work for you but that may be an option.

Just out of curiosity, why are you looking for this specific setup?

JL ws-6

iTrader: (50)

I'm sure this must be for some racing that has specific displacment rules.... but why try to redo a whole ls7 to the size? I think you'd have an easier time doing another lsx platform and mixing/matching parts to get to the displacment you want.

What is the engine for... I'm curious what has these specific bore/stroke rules

reddevil00

iTrader: (-1)

need to get info on ls1 with my mods going to forced induction please reply back.

reddevil00

iTrader: (-1)

typical heads n cam 490 to the rear wondering if my stock under drive will be safe at the right amont of boost an compression.

Stang's Bane

iTrader: (22)

?????? What are you talking about???

knightec

its a feasability study for a 6.0 race motor for endurance racing in open top sports prototype (leMans) running air restrictors......its been proven before that these restrictors limit engine rpm to about 7500-ish, so I need max power to be delivered well before the restrictors take effect, I'm aiming for a bore to stroke ratio of 0.95......as an example - 2Litre 4cylinder F3 motors follow a similar trend, with bores of about 92mm, stroke of about 93mm, which is a bore to stroke ratio of about 0.88, max power is delivered very low down at about 5,500rpm......and not to mention a shed load of torque.......hence this is the route I'm considering taking.

also, having a much smaller bore really helps getting a high compression ratio without having a massive piston intruder/dome......I'm aiming for around the 15:1 mark........big piston intruders are bad news on race motors, they do not help combustion and the effects of squish whatsoever........I also intend to remove the head gasket and run wills rings, which are special gas filled sealing rings, this will also help make the combustion chamber that bit more smaller in volume, therefore making the piston intruder/dome smaller again.

just found some rather smart heads from Patriot:-

http://www.patriot-performance.com/w...05234&DID=1225

the valve sizes of 2.02 in &1.57ex and 2.08uin and 1.6ex are bang on what I'm looking for, in mm they work out at 51.3in & 40ex and 52.8in & 40.6ex........

it says they also offer blank LS6 castings, which is good news too, because they might be able to weld up some of the chambers prior to machining, to help fitment on a 96.9mm bore........like you all say the LS7 might not be the best starting point, to be honest, I'm only interested in the 4" stroke crank, and the fact that the LS7 press-in liners can be press-removed and replaced with smaller bore items, the LS7 heads are of no interest to me, the LS7 valves are way too big.

not to mention the person asking me to look at this has SIX new LS7 crate motors sitting on his workshop floor

I'm assuming LS6 heads will fit on an LS7 block?????.....

My90Iroc

iTrader: (26)

If he needs help figuring out what to do with the others I'll lend some ideas.

Stang's Bane

iTrader: (22)

Yes LS6 heads wil boltup to a LS7 block.
Although the bare castings from Patriot are a good deal, probably the best place to start would be either a 5.3 casting or the new Edelbrock castings. I believe WCCH has a program for the edelbrocks optimized for the smaller bore.
Even though you say the rev limit is only 7500 rpm, in the lsx world that is relatively high. The reason I say that is the factory style intake manifolds tend to keep power peak below 7k. Most well below that.
IMHO I would talk to Katech, as they have really good expereince(they build the engines for the C6r endurance cars) with endurance engines. they have a sneak attack 5.7 liter that is a monster, and although it revs a little to high for your purposes, they could make changes to accomodate your needs.

Remember that each motor is a system unto itself, and what works well on one style of engine, may not necessarily work that well on another.

Project GatTagO

iTrader: (7)

5.3L engines have a 96.1mm bore. You can get an aluminum version of that block. Why not start there?

Andrew

Steve Bryant

iTrader: (1)

For what you want to achieve, I'd buy an aluminum 5.3 L block and bore/hone it to 96.90 mm and use a standard 4.000" (101.6 mm) aftermarket stroker crank (available from a variety of suppliers) and use some cathedral heads like the Patriots you are describing.

That's the best route for your feasibility study. Is this for a school project or something of the sort?

All my best,

Steve

J-Rod

Please don't take this the wrong way, but IMHO you are headed down the wrong path truthfully.

The heads on the LS7 were designed with restrictor motors in mind. That big intake valve, and that big intake port is ideal for intake restricted platforms. Its actually what it was optimized for....

The Pontiac and Cadillac teams have proven that. For a big port, its does pretty well. If you are planning on running a "highly strung" race motor. I'd look more along the lines of looking at what the Pontiac and Cadillac teams did with the LS7.

Restrictor plate motors are a different animal, and you do things a bit different with them than you would with a non-restricted motor to make peak power, especially in cam design. A big bore short stroke Ls7 displacing 5.7L has been shown to run effectively at 8500 RPM all day with a restrictor, and totaly dominate the field. I'm not telling you what to do, but if you do a bit of research, you will find that GM spent a lot of time and effort optimizing restricted Ls7 based motors, and it was not via bore size, it was via stroke.... You might want to look into what they have already provided, as it may help you get where you want to go...

Project GatTagO

iTrader: (7)

I misread his original post. I thought his rules mandated a max bore of 96.1mm. Bore diameter makes power! Run the biggest bore you can and get a custom crank to get the stroke you need to meet your displacement rules. Oh sorry, you didn't want to hear about other combinations. oops..

Andrew

J-Rod

For information on what I'm talking about look at the Sun Trust Pontiac Daytona Prototype running in the Grand American Rolex Series. That motor has been limited down to as little as 5.0L, and 7100 RPMs. In 2005 for instance, Pontiac led 81% of the laps in the series.

The GM Caddillac in Speed GT went from back of the pack to 2nd place in literally a couple of laps. The drivers were just loafing around. They ended up with huge restrictors, and still made crazy power. The new GM racing lifters that you are seeing came directly as a result of GM making parts that would last at extedned periods of high RPM operation.

gametech

iTrader: (1)

But if he is doing a feasibility study, wouldn't that entail going in a non factory proven direction? If he just copies an already proven design, what is the point? I guess it depends on whether the goal is to build a winner on the first attempt, or to study different designs.

briannutter

You would need to notch the top of the bores for valve clearance.

As for "horrific" ports..not when you've got 427ci baby. GM did it right for the displacement and RPM target. The only thing Horrific is they're limiting you to 6 liters and a restrictor plate

The technology in our restrictor plate Cup motors was factored into the C5r/C6r efforts. Generally maintaining the the large valve venturi and bore, but the runner cross-section and and exhaust primaries becoming smaller. On the Cup engines, getting compression isn't a problem due to the rules mandating 12.5:1 anyway. We're running (4) 7/8 (22.23mm) holes on the superspeedways...funny enough, that's almost exactly the same area of the two 31.5mm holes required in ALMS. What does your class require?

One other thought is for you to run the L92 head 6 liter block. The cross-sections are smaller, the valves themselves are smaller, yet 380cfm is still a possibility when ported . The intake is closer to cylinder centerline by about 2.5mm and drops to 2.160" from 2.200. The exhaust valve diameter drops to 1.590 from 1.650..moving an additional 1mm away from cylinder centerline toward the cylinder wall.....It's a much better fit for what you're trying to do. Nice "max volume domes" have been developed for it by Wiseco. I figured the compression ratio increase between a 4" stroke/3.815 bore (proposed) and a 3.622stroke/4" bore of our 6 liter. It's about .17 point of compression w/ the dome and combustion chamber volumes being equal (cancelling each other out with the debore)....not worth the loss of breathing in my estimation. In restricted form, I'd put this up combination to a de-bored LS7 any day due to the deshrouding of the intake valve.

slick1851

This has me wondering what they would be like with no restrictors in place?

knightec

excellent replies guys - certainly some food for thought there.......since rummaging about I have found some usefull links

this one has the latest C6R engine specs, notice for the 7.0 race motor (on the right), the bore is slightly bigger, and the stroke slightly smaller than the base LS7 motor

http://www.corvetteracing.com/cars/c...ne_specs.shtml

and this link shows a rather nice CAD picture of the Katech motor - you can clearly see which direction they have taken with the intake system.

http://www.corvetteracing.com/cars/c6r/engine.shtml

I have since found out that Katech use small valve and small runner bores for the ALMS corvette racers - these heads are not available to the public (no surprise!) - aparrently there was a feature in popular Hot Rodding when they did a feature - just what I'm told - not seen it personally.......but I remain to be proven wrong

aparrently the Katech-Corvette engines use split reverse cams, whereby the exhaust is open longer and deeper than the intake........I'm assuming its got little if no overlap, as there will be a big depression in the intake system due to the air restrictors - which you dont want pulling on the exhaust with loads of overlap

briannutter - yes your quite right about the smaller bore of 96.9mm shrouding the valves - but in my experience - this can be worked on and fixed......I have noted your points, I will dig out the restrictor sizes on monday, from memory not far off the figure you quoted......not a restrictor plate with carbs.......a pair of restrictors - running fuel injection and straight runner inlet system design.........its potentially for an open top sports prototype.........only a feasability study at the moment though........I have heard of these L92 heads - thanks for the dimensions.

Katech_Jason

iTrader: (19)

One person speculates in a post and all the sudden it's true.

1. LS7.R cylinder head spefications were never and will never be released. The person speculating was looking at the 12480090 C5-R head.

2. LS7.R cam specs will never be released. If somebody posts cam specs, they are guessing, lying or spreading rumors

3. A reverse split cam means the opposite of what you said.