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z31maniac
z31maniac MegaDork
7/29/20 9:23 p.m.

In reply to Curtis73 (Forum Supporter) :

Basically 91 only here in OK. A few places have 93 but it's super expensive in comparison.

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) Dork
7/30/20 7:45 a.m.

Seems odd but I would think octane requirements wouldn't change a whole lot until you are 2000' up or so. Even at sea level there is a decent performance bump from 91 to 93 on higher compression setups. Could be the availability of E85 that pushes that price up? 

NickD
NickD UltimaDork
7/30/20 8:51 a.m.
yupididit said:
NickD said:
Curtis73 (Forum Supporter) said:

Factory intakes are pretty good.  LS1 intakes are kinda unspecial.  LS6 intakes will pretty easily support 500 hp.  Truck intakes are actually quite good, but they are tall and ugly

Trailblazer SS intake is also amazing but hard to find. And the LS2 intake manifold is garbage.

Why is the LS2 intake manifold garb?

Just a compromised design. I remember seeing a test where it just failed to really perform well at all on a pretty mild LS engine. It was down on power and torque compared to every other OEM cathedral-port intake manifold. Their recommendation was that if you had an LS2 engine, go buy an LS1 or LS6 intake and sell the LS2 manifold before the article was widely read and people realized they were trash.

yupididit
yupididit UberDork
7/30/20 12:36 p.m.

In reply to NickD :

Oh I was thinking it wasn't well made like it has flaws in structural design, not actual flows badly. Damn

NickD
NickD UltimaDork
7/30/20 12:44 p.m.

In reply to yupididit :

Yeah, its as robust as any GM composite intake (meaning, pretty stout) but it just leaves a lot to be desired as far as performance. I believe the best performing OEM cathedral-port intake is the Trailblazer SS manifold, but they are rare as hen's teeth and also pretty tall and ugly.

RacetruckRon
RacetruckRon Dork
7/30/20 1:44 p.m.

In reply to NickD :

The NNBS catherdal port truck intake is the same as the TBSS intake, they are not that rare.  Also, the OEM LS2 intake may have been garbage but the LS2 Dorman replacement manifold is the best flowing cathedral port car manifold until you step up to a FAST 92mm but there's a $600 price delta between the two.

yupididit
yupididit UberDork
7/30/20 3:05 p.m.

In reply to RacetruckRon :

Dorman version? Like one you can buy from RockAuto?

RacetruckRon
RacetruckRon Dork
7/30/20 3:54 p.m.

In reply to yupididit :

Correct, Dorman 615-901. That's the hot ticket according to a lot of flow data I've seen spread around on LS1Tech and a couple Hot Rod articles. There's a supply chain issue them right now so prices have gone up 200% on them but from what I've read those are pretty close to a FAST 92mm when you port them and unported they are right around the flow of an LS6 or TBSS manifold.

yupididit
yupididit UberDork
7/30/20 4:03 p.m.

In reply to RacetruckRon :

Oh the prices are from $600 to $1000 new.  Must they supply issue really berkeleying it up lol

84FSP
84FSP UltraDork
7/30/20 4:06 p.m.
Curtis73 (Forum Supporter) said:

The main difference between 317 and 243 (LS6) heads is the combustion chamber.  317 is a great way to get LS6 flow with a lower compression.  I chose to do the 243 heads with an LQ9 block to raise compression so I'll be at 11.3:1.  Do-able on 93 octane, better on E85 with a turbo devil

By the way... the main difference between the LQ4 and LQ9 is that the 4 has dished pistons and the 9 has flat tops.  I think they had a slightly different cam as well.

You can frankenstein the crap out of LS motors as long as you stay in the same generation.  You can mix and match some things, but it's really hard to mix between the reluctor differences.

The reductor wheel is ~$20 to change.  Not fun if you are keeping the shortblock together but if it is coming apart it's not an issue - just make sure you know you are 24k or 48k.

Patrick (Forum Supporter)
Patrick (Forum Supporter) MegaDork
7/30/20 4:07 p.m.
84FSP
84FSP UltraDork
7/30/20 4:08 p.m.
RacetruckRon said:

In reply to yupididit :

Correct, Dorman 615-901. That's the hot ticket according to a lot of flow data I've seen spread around on LS1Tech and a couple Hot Rod articles. There's a supply chain issue them right now so prices have gone up 200% on them but from what I've read those are pretty close to a FAST 92mm when you port them and unported they are right around the flow of an LS6 or TBSS manifold.

I just sold a ported one for 475.  It was choking me out around 5600.  It did a really good job - I just got a bit wild for it with my high compression ls2 build.  I was dissapointed at fit quality on it but otherwise great sleepy mod.  

GIRTHQUAKE
GIRTHQUAKE Dork
7/30/20 11:00 p.m.
RacetruckRon said:

In reply to yupididit :

Correct, Dorman 615-901. That's the hot ticket according to a lot of flow data I've seen spread around on LS1Tech and a couple Hot Rod articles. There's a supply chain issue them right now so prices have gone up 200% on them but from what I've read those are pretty close to a FAST 92mm when you port them and unported they are right around the flow of an LS6 or TBSS manifold.

Holy damn, thank you. I'll have to keep an eye out for when it returns if I've got no luck on stock stuff.

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