l92/ls3 vs. ported 5.3 on a lq4
05-09-2011, 12:38 PM
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l92/ls3 vs. ported 5.3 on a lq4 I've spent the better part of the morning searching for an answer and havent had any luck. im trying to piece together a build and am trying to figure out which direction to go.
stock milled ls3/l92 or prc 2.5 5.3's.
lq4 shortblock, rod bolted, only acc is going to be an alternator.
the appropriate vic jr (going in a g-body Malibu)
4150 tb
1 7/8 LT's
built th350, 4500-5000 stall.
3.73
3300 race weight
custom max effort n/a cam from one of our fine vendors, shifting no higher than 7k rpm.
which head would net me a better 1/4 mile time, and why? any ballparks to what that time would be? shooting for a solid 10
stock milled ls3/l92 or prc 2.5 5.3's.
lq4 shortblock, rod bolted, only acc is going to be an alternator.
the appropriate vic jr (going in a g-body Malibu)
4150 tb
1 7/8 LT's
built th350, 4500-5000 stall.
3.73
3300 race weight
custom max effort n/a cam from one of our fine vendors, shifting no higher than 7k rpm.
which head would net me a better 1/4 mile time, and why? any ballparks to what that time would be? shooting for a solid 10
05-09-2011, 05:49 PM
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What's your budget? Both can kick *** but LS3 topends can be done on a tight budget. I don't see the 5.3's getting up to te full potential w/o porting and a fast intake (more $$$). You can do what you are looking for both ways.
05-09-2011, 10:27 PM
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I don't have a set budget, whichever I end up with, it will be bought as i get the money. I'm still in the planning stages. No matter which head head I go with, it will be topped with a Vic. Jr., and a 4150tb. Everything is pretty much in concrete, except the heads... It's good to know that I'm not shooting my expectations too high. I'm not after a HP number at all. Just that it pulls the number at the track.
05-10-2011, 10:32 AM
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Yeap. That's the main reason I'm waiting to decide which head, before i look into cams. The cam will be a custom spec, just for the sole reason I don't know alot about cam theory and only want to do this build once, that and I'd like to be able to milk every drop out of this engine that I can, while keeping it at a decent RPM.
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05-10-2011, 11:30 AM
#8
if your after high compression the, the 5.3s can yield up to or over 11:1 milled with thinner gaskets.
the l92 heads even milled also used with thin gaskets will be short of 11:1.
maybe up to 10.5:1
remember that if your going for max effort on this engine, cutting vr in the pistons is almost mandatory, at least imo.
i dont install large duration cams without cutting in vr and verifying ptv clearance in any engine.
i like to run the tightest quench possible. .035-.040 range. and highest scr/dcr possible. which gives way for larger duration cams and and high rpm shift points. 7000+
the l92 heads even milled also used with thin gaskets will be short of 11:1.
maybe up to 10.5:1
remember that if your going for max effort on this engine, cutting vr in the pistons is almost mandatory, at least imo.
i dont install large duration cams without cutting in vr and verifying ptv clearance in any engine.
i like to run the tightest quench possible. .035-.040 range. and highest scr/dcr possible. which gives way for larger duration cams and and high rpm shift points. 7000+
05-10-2011, 11:51 AM
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which set of heads will run the better times though? 5.3's at 11-1 or ls3 at 10.5-1, is that 1/2 a compression point going to put the 5.3's on top? It's going to be as max effort as the combo can be, while fitting inside the specs of what I want. 93 pump gas, just streetable enough so that it wouldn't overheat in traffic and I'd prefer to not have to flycut, thats just another reason for the custom cam. if the man specing the cam says I'm going to be leaving a ton on the table by working around that, then break out the junk head, valve and sandpaper and get after it.
05-09-2013, 12:34 AM
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which set of heads will run the better times though? 5.3's at 11-1 or ls3 at 10.5-1, is that 1/2 a compression point going to put the 5.3's on top? It's going to be as max effort as the combo can be, while fitting inside the specs of what I want. 93 pump gas, just streetable enough so that it wouldn't overheat in traffic and I'd prefer to not have to flycut, thats just another reason for the custom cam. if the man specing the cam says I'm going to be leaving a ton on the table by working around that, then break out the junk head, valve and sandpaper and get after it.
05-12-2013, 02:50 PM
#11
05-13-2013, 11:06 PM
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Still no answer to this question though. Better qm time: l92 or 2.5 5.3's? I'm in the same boat. PRC's come with titanium retainers and dual valve springs for $1,300, and the Ls3/L92 heads come with oem retainers\springs etc. so that's more money you'd have to spend on those which are about $800 for the set bare.
So basically the heads are the same price. But the ls3 intake seems to be cheaper than the ls6 for the 2.5's.
Either way, I'm leaning toward the higher compression 5.3's recommended by TSP although the L92's were my original pick and are slightly cheaper. Ahhhh!!!!!
So basically the heads are the same price. But the ls3 intake seems to be cheaper than the ls6 for the 2.5's.
Either way, I'm leaning toward the higher compression 5.3's recommended by TSP although the L92's were my original pick and are slightly cheaper. Ahhhh!!!!!
05-14-2013, 08:10 AM
#13
The outcome is going to depend on how you execute each combination.
The cathedral combo will have a fairly conventional camshaft, which will have less overlap. It will be easier to install on stock pistons.
To make the LS3 heads work well on that size engine will require more overlap, which will hurt P to V dramatically. My best advise would be to run the LS3 with the Victor Jr for making power, and then consider a set of the Wiseco junkyard dog pistons. They have a small dome to raise compression and the valve reliefs that you'll desperately need.
The cathedral combo will have a fairly conventional camshaft, which will have less overlap. It will be easier to install on stock pistons.
To make the LS3 heads work well on that size engine will require more overlap, which will hurt P to V dramatically. My best advise would be to run the LS3 with the Victor Jr for making power, and then consider a set of the Wiseco junkyard dog pistons. They have a small dome to raise compression and the valve reliefs that you'll desperately need.
05-15-2013, 02:34 AM
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Yea. No results. Everything i try takes a **** in my face... So now I have a title-less car, a scrap motor and pretty much a bunch of stuff I can't use. Buying ahouse or trying too, so can't afford itthe toys for the next year or so. I swear, one day I'm going to have a LS based turbo Malibu. One day :-/
