If I were to make an LS engine to fit under the 5.0L class limit how much power can I pull easily? Right now I want to build a car that doubles as a road racer and a daily driver. I'd be using a Ls1 block and a 3.185 crank. I'd want a hydraulic roller setup. I can get the rods, pistons, and crank for quite cheap but I'm wondering about the power. Is hitting a 450-500 rwhp quite unfeasible for a decently tame daily driver?

 

a .060 over 4.8 would net 303ci
some of these engines came equipped with excellent rods, pistons and 243/799 heads. so with a healthy cam and all supporting mods. i would think 400bhp would not be so hard esp with mentioned 243 heads.

 

I guess I should have filled in with my setup. This will all be in a porsche 944 and will run about 2,900 lbs. I'll get it down lower later but I don't want to mess with the fiberglass parts quite yet. I have a set of 6.350 MCT rods (basically carrillo rods) that are 538 grams. I have a callies 3.185 crank for the setup that weighs 42 lbs. I haven't gotten the pistons figured out yet. I have a set of 59cc patriot stage II heads, Jesel J2K rockers, cadillac racing lifters, ls2 intake and tpi throttle body. I'm trying to get a good block to start with but I'm going to go with a ls1 since it works with my setup I have already. Will these heads be alright? Is there anything that isn't sufficient? I haven't decided on a cam yet but I'm hoping to setup a pretty broad powerband.

 

I think running as much compression as you can will be your friend...years ago someone did build a 302" LS1 Camaro, I forget if GM built it or a magazine did, but I remember it was cool.

What PCM are you going to use? I am thinking a really well done 302ish LS based engine will want to rev very very very high (like, north of 9000 if you try), and the GM PCM won't do that. I think 8000 is the highest you'll get out of an LS1 style PCM.

I think you can probably make some wicked top end power with one...I'm very interested to see what you do and how it performs.

 

My problem with running it north of 8000 rpm is the fact that you have to use a solid roller setup. I need to make a trip from school to home about 4-5 times a year and its 400 miles one way. I think I'd eat through solid lifters and have to mess with lash more than I'd want to.

 

Yeah, you would be adjusting the crap out of a solid setup more often than you wanted most likely. Based on your cam profile chosen, you can probably make your peak power show up early and shift around 7k.

 

What rpm would you be willing to go?

I got a 4.8l in pipemax that would theoretically make 490 fwhp (best senario) at 7200 rpm peak, and just shy of 400 ft/lbs of torque. Cam picked for this wasn't overly "aggressive" on lift vs duration, since planned use will be semi-endurance.

A ls1 based bore w/ 2.00 valves should be able to get by with a little less lift than I was working with.

Compression will be your friend, along with a good intake. You'll probably need a little dome to get decent compression out of the little engine, even with the 59cc heads. I'd shoot for the 11-12 range, depending on dome size. theres a ls1 10cc piston available, see if it works with your 6.350" rods (pin size?). I think so. I'll check and let you know who makes them, And how close they are.

A better intake than the ls2 is a good idea.

Keep the valvetrain light if you want to rev it decent. LS6 valves, pac 1518 beehives, worked stock rockers, or ultralites. A cam in the 240ish range w/ 630-650 lift won't be overly harsh valvetrain wise, and will get a 5.0 up around 7200 hp peak, provided a good intake. A slightly wider lsa will help spread out the power.

 

diamond pistons 10cc dome for ls6 heads, 1.31 compression height, (.927 pin) w/ your rods (6.35) and crank (3.185) works out to 9.2525 installed height. With a stock 9.24 deck, you're looking at .0125 out of the hole, which will work great with stock mls gaskets. Compression w/ 59cc heads and .051 gaskets is ~12.00:1

Auto, or M6? I'm guessing M6....?

 

was that right on the nose with the 12:1 SCR?

 

Pretty much. final bore size will make a bit of difference, I calc'd it at 3.9. I also didn't get too crazy with gasket dia, since I have found it makes almost no noticeable difference in online calcs. However, it should be looked at carefully on buildup, so theres nowhere for end gases to hide. Just like the area above the top ring.

I quickly ran the 5.0 w/ 12:1 through pipemax, getting a low rating of 481hp (@7200 pk hp), up to a best of 521 hp.I'm still learning how to use this program, but the numbers seems reasonable.

 

The pin is where I get screwed over. I got the crank and rods for $800 but the pin is a .748 which doesn't give me any options but custom. If you have any ideas where I get the cheapest custom pistons that would be awesome.

What's the highest compression I can run on 91 octane. Its the highest octane consistently offered in North Dakota. I don't think I could run 12:1 without running into problems since it will also serve as a daily driver. I think 11.2:1 is about as high as I ever should go but correct me if I'm wrong.

What do you suggest for a better intake? I'd rather not go for the fast 102mm because that starts to get pretty pricey for not a whole lot of gain. I also think I'll be running some sort of straight ram aim so I should be getting quite a bit of air.

If I could get 481hp at the crank I'd be okay with it and if I could get 521hp that would be awesome.

As far as rpm, I'm willing to go as high as a hydraulic setup will get me. I think the cadillac racing lifters are the best since they can get up to 8,000rpm. I had someone I know test them and they gave out at 8,200-8,300rpm. I think that should give me most of what I want.

I have a set of Jesel J2K rockers but I don't have the rest of the valvetrain bought yet. Is it possible to get a set of the new NASCAR titanium rods and have someone adapt them? I have a friend that I can get them from for $200 for a set, intake and exhaust. If I could get someone to machine them and get them to the right size I would be setup with some pretty light valves for pretty cheap. If I were to do this what should I look for in the valves what specs do I need in them before they're machined.

Is there a way to set this up that I don't pull a whole lot of power from 0-2,500 rpm so I can get good mpg? Then from 3,000 to 8,000 it pulls like a banshee.

These are the heads I have with the patriot stuff on it but I think I probably should upgrade from it.
https://www.patriot-performance.com/...&cat=37&page=1

 

Looks like a fast 90 should be really close to the proper tuned length to work in the higher rpms.
Scroll down a little bit, you can see what rpm pks are at. The ls2 peaked at 6400, the fast 90 did not peak within the range of dyno testing done, which was 7000.
http://www.lsx-tuning.com/forum/view...&t=188&start=0

You'd want to set your hp peak goal at the first limiting factor. Plan on running about 500-700 rpm past this point.

A small cube high rpm engine is not going to be the easiest engine to drive on the street. A small cu engine has a harder time breaking things, so things like the 10 bolt should be ok.

The lifters are going to give out at different rpms depending on how intense you cam profile is, and how heavy the valvetrain is, which requires more spring to control it.

A set of worked 243's with ls6 valves and pac beehives would be my recommendation. Flow without killing the velocity too much should be the goal with these heads, as they are plenty big for a ~300 cui engine.

 

I have a ls6 intake, I don't know why I said ls2. If I port the throttle body and intake that should bring me close to the peak I want, yes?

What makes this lack street manners? Will it be the cam profile? What can I do to make it more street friendly?

So what defines a "light" valvetrain setup. I have the patriot gold dual springs on the heads already which I think are pretty decent but I'd be willing to upgrade. I have J2K rockers which are about as light as I'm going to get. The Cadillac lifters may be a little heavy? I'd sacrifice a little cash to make this setup more durable if at all possible.

 

The ls6 seems to have plenty of top end pull. Should work. According to previous link, an "oval" throttle body (78mm?x90) made the most power of the ls6's, but could have been pull discrepancy.

A small engine going to 7500-8000 rpm is going to need a fairly well thought together combo to make good power up there, and most of that is sacrificing low speed characteristics. Big cam mostly, but larger ports and valves than would be neccesary for lower speed operations. Everybodies limit for streetability is going to be different.

I consider anything past the pivot point of the rocker where the weight matters. so valves, rocker tip, springs, retainers. Ls6 valves weigh ~78 grams intake, 65 exhuast. Ls1 valves weigh 99 grams int, 85? exhaust.

Beehive springs work to coil up the lightest part first, so any weight unspringing is as light as possible. Retainers are far smaller in dia, so are far lighter. The lower leverage from the smaller dia also helps prevent the valve from rocking around as much.

Lifters and pushrods should be up to the task, the higher the rocker ratio the stonger the pushrods have to be, and the less effect they have on float. same goes for lifter.