Chicago Crew UnderBoss

iTrader: (1)

Seriously cosidering purchasing a very blower friendly forged LS6 boost motor built with big turbo boost in mind, but even with my stock LS6 heads, the compression ratio will only be about 8:3 to 1. I don't plan on anything extreme and looking to make 650 to 700 reliable rwhp with my ECS D1SC set-up on this motor.

I don't plan on running crazy boost in excess of 12 to 14 lbs tops and do you think the compression is so low that my motor will feel like a dog when i am driving normal and not seeing any boost. I guess all i would have to do is plant my foot in the right gear to BLAST OFF, but I prefer that the motor made closer to 9:5 to 1 compression vs. a full point lower for my use of my car as a everyday nice weather driver and occassional road racer and even more rare drag racer. I guess the good news is this forged LS6 motor would give me lots or room to completely upgrade my fuel system and go with an 8 rib set-up and make in excess of 750rwhp, but for my needs that is overkill for what i use my Z for at least for now.

Please give me your thoughts on this low compression ratio and whether my car will feel like a dog when its not boosted and whether this motor makes sense for me or am i considerably better off buying a regular forged LS6 motor, with -8.5 cc blower pistons, which would make a nice perfect 9:5 to 1 compression with my stock LS6 heads!!

mahhddgtp

Honestly, it's hard to make a dog out of a V8. The full point drop (from 9.3->8.3) doesn't make too much difference in terms of power. It'll feel a little more solid with the higher ratio, but it shouldn't be 'too' far off...

You said nothing crazy? -- "I don't plan on running crazy boost in excess of 12 to 14 lbs tops."

With gas being 93-94 where you are, you should be able to run a higher compression with that amount of boost no problem... 9.1cr would be able to handle it.. That's just my $.02... Do not go off what I've said alone and quote it for truth. But I think others will

Josh@KY-Turbo

iTrader: (120)

I am building my car with the same intentions. My 346 will be around 8.2:1. I am however running a T70 turbo for my boost needs. In my opinion a lower compression ratio motor that is gonna be boosted is better for the simple fact that for me, enough is never enough, and room to grow is always good.

Just my .02 cents.

mahhddgtp

The low compression will keep you reliable, too.

Yes, room to grow... "Speed is addictive." I bet you there's been a ton of ex-Incon owners in here who can testify to that.

If I were to build one up, I'd keep compression in the 8.3-9.1 range, probably picking 8.5 as my number.

I figure either way you're going to have traction problems... So unless you're running slicks or you've got some rubber, and can actually put the power to the ground (use the down-low power that extra point will get you) it's not worth it. When you say reliable, I'm thinking some sort of street-like tire.

Chicago Crew UnderBoss

iTrader: (1)

With gas being 93-94 where you are, you should be able to run a higher compression with that amount of boost no problem... 9.1cr would be able to handle it.. That's just my $.02... Do not go off what I've said alone and quote it for truth. But I think others will [/QUOTE]

That's my exact issue I would buy this motor for sure if it was between 9 to 9:5 to 1 static CR and its not, and that is my sole issue with pulling the trigger!!

Chicago Crew UnderBoss

iTrader: (1)

POINT Well taken that enuff is never enuff and this would give me ALOT of room to grow if i wanted to get silly and upgrade my entire fuel system (which at the present moment) I have no desire to b/c 700 rwhp is more than enuff for me for a car driven on the street 99% of the time!!!

mahhddgtp

I say pull the trigger on it if the price is right. Honestly, that extra point won't give you that much of a gain ahead of a lower compression motor with a similar setup. The guy with the lower compression can just up the boost a little to compensate.

Let others come in and disagree with me, before anything drastic is done though

mdhmi

iTrader: (1)

Yea - and increasing the boost with a ProCharger is how you limit belt, idler, and tensioner life. What works well on a turbo car isn't necessarily proper for a street driven 6 rib supercharger setup.

Mark

Chicago Crew UnderBoss

iTrader: (1)

MARK,

Your right BRO, and its this type of feedback that is driving me !! How much more $ is that infamous 8 rib set up that you are always TOUTING?

marleyskater420

If everything else on the engine is primo, why not swap pistons? Or do you just not want to take the time to do so?

The extra boost you would have to add to accomidate for the loss of compression (however many PSI) will just add further wear-and-tear on your engine. However, there are no heads you can swap that would increase CR either?

If the motor is primo, and the price is super right, worth not building your own motor over, then go for it. So you have to live with a little less low-end grunt, and add some extra stress onto your motor. Either way, 700rwhp on a DD car is going to add wear and tear whether you like it or not. Regardless, whether you go with a different motor or not, your best hope is to get the best setup you can to protect engine life either way. If the extra boost is going to lessen engine life THAT significantly, then don't do it. But if it really isn't going to make much difference, then by all means, boost away!

fash00

iTrader: (10)

Well you know how I feel. I dont honestly feel you will lose anything down low that is noticeable enough to worry about. But I can understand your concerns. Was trying to find a price on the 8 rib upgrade for you but no luck as of yet,as I feel with any new motor you put in and turn up the boost it's going to belt slip.

mdhmi

iTrader: (1)

Around $1,000. It's much better than a six rib, especially when you're talking about a low compression motor and more boost.

Mark

EPP

iTrader: (22)

The ATI ProCharger 8 rib upgrade kit from a 6 rib for the f body is $350.00. You will also need to purchase a different harmonic balancer to bolt the 8 rib pulley to. It is made by ATI Performance Products, and goes for $450.00 to $475.00.
On the C5 you will also need a different harmonic balancer, and I'll have to check on the cost of the conversion kit, it is going to be a lot more expensive, as it includes a new accessory drive pullies, to upgrade everything to eight rib pullies. Bob

Slowhawk

iTrader: (12)

With the stock LS6 heads I would run compression at 9.5-1 (we do it alot and make 700rwhp on pump).For the 8rib I would run the ECS crank pulley which is bigger.When/if you switch to a Turbo put on 72cc heads and bring the compression down to the 8's.

Chicago Crew UnderBoss

iTrader: (1)

YEAH, my recent research also shows that for my set-up with a Procharged D1SC Street car untilizing my stock LS6 heads, that 9.5 compression is really perfect!!

How many lbs of boost do your stock LS6 headed run and are they all using an 8 rib set-up to achieve 700rwhp (which is also the minimial goal) that i want to achieve when i go to a forged motor!!

Wet 1

iTrader: (4)

You'd likely never notice the difference between 8.5:1 and 9.5:1 CR, we're literally talking about 10-15 hp here... Put a cam in it and you'd gain that right back and then some. H/C and you'd make even more. If you think you might be adding more boost in the future (or be going over to turbos), I'd suggest you go with the lower compression to begin with. If you want a little more compression, sell your LS6 heads and get a set Patriot's w/ smaller chambers (plus you'll pick up a little more power just from them). If you want lower compression later, just change the heads over to a 72cc head and you're ready to go.

white2001s10

iTrader: (4)

Here's a car that runs well with lower compression as a NA daily driver.
It only took some tuning to pick the bottom end back up.
https://ls1tech.com/forums/vehicles-sale-lsx-powered-only/498465-98-c5-corvette.html

Boostaholic

iTrader: (4)

My new CR will be right around 8.0:1

Slowhawk

iTrader: (12)

Actually on a supercharged car you will see a huge difference when compression is changed on a 346.Expecially in the midrange.
Run a 8.5-1 comp. motor at 10lbs,then change it to 11-1 comp and see the almost 200hp gain Of course that is extreme on compression change but you get the idea.

mahhddgtp

How is that? Are you assuming that you're going to be needing race gas when you do the 11:1 ratio? I'm curious, why is the change that drastic?