81.5mm build... GSR or LS block? and a few more NA questions
 

I need some guidance / advise on what block to use and what compression ratio to end up at. I want to build a shortblock for road racing here in the az heat. Basically I already have a LS & a GSR shortblock that both need to be rebuilt and I'm trying to decide which to use, no spun bearings, just cracked ringlands on one and old rings on the other.

For either block I'd be boring it to 81.5mm with new cast high compression pistons, shot peening and resizing rods for arp hardware, balancing the entire rotating assembly, fresh rod/main/thrust bearings, new pumps and seals, oem head gasket, & arp head studs. I plan on keeping the rotating assembly to match the block. 91 octane tune by locash.

Info on the rest of the set up:
GSR head, has been milled a couple of time, unsure how much, fresh valve job, valve guides, and seals.
ITR Cams & Valve train
AEM ITR 3" CAI
Skunk2 intake manifold + 70mm trottle body and mild porting of head to match intake manifold
Mugen 4-1 race header with 2.5" collector, test pipe, and exhaust
usdm ITR spec trans.
large oil cooler and catch can set up.
I'm thinking this should net about 170-180whp, is that too optimistic? I'd rather be realistic than disappointed...

Here's my questions:
Would the LS or GSR will yield more power?
What's the max RPM before ITR cams completely drop in power?
What's the max RPM for stock LS rods with ARP hardware?
What's the max RPM for stock GSR rods with ARP hardware?
Ideal compression ratio? I'm thinking about 12:1?
Which block would you use and why?
Estimated whp?

Known advantages of GSR Block:
shorter stroke, thus more rev's available on the same piston speeds.
lower rod stroke ratio.
no lsvtec stuff required!
oil squirters - which my block is missing, and doesn't effect power so not really worried about it.
main girdle -really I don't care, it's a honda they don't have crank walk problems.

Known advantages of LS block:
Longer stroke = more tq, but less revs & higher piston speeds.

Please keep this on topic, and do not bring up a b20 block, trying to use what I have currently, it's a budget build, unless you have a b20 block you want to donate or sell for really cheap don't bring up b20's, and no I'm not going k or v6. I already have the head set up and other items needed for the swap so out of pocket costs are minimal.

I made 180 who on my Ls block with b 16 pistons n stage 2 cams itr head. If u want more info lmk im at work or id post my build

Itr head
Skunk2 valvetrain
Skunk2 stg2 cams
Ls block
B16pistons
Arp hardware
Ls crank
Ls rods
Ant header
Comptech 3" intake
Reving it out to 8700 for over a year
Locash tuned at 180whp with leaky header exhaust n stock fuel pump
Restricted exhaust too

GSR all the way !!
If it is going to be road raced I would give up the little extra displacement of the LS and go for the smaller more stout block with a better RS ratio.

I like the fact of the oil squirters with cast pistons.

The ls rods with arps can rev to 9+ with everything balanced

Same as gsrs

I think the itr cams make power till around 7900-8100 could be wrong

I made 200 whp 137 locash tuned gsr ftw. 81.5 bore

Your cams will run out before your PREPPED Ls rods will

The case for the GSR:
-GSR rods are beefier than LS
-Girdle helps more with bearing bore alignment than crank walk (reliability at high load/rpms)
-no lstvtec nonsense :) (read: more $)
-oil squirters help prevent detonation in a big way, def worth it in AZ with high, dry intake temps and high compression
-higher (stock rod) rev ceiling for cam upgrade down the road

The case for LS:
-5ft/lbs? Lol

Hit me up I have an interesting trade opportunity for you

gsr

all the reasons mentioned above

GSR block is stouter than a Ls block.

Orly? Thanks for being so specific!

Lawlz!

Both blocks are just as good. I don't see one being stronger then the other. For n/a power under 250 I don't see one being better then the other.

Its all about machine work. Your choice of parts, assembly, and tuning.

there is a BIG difference in the blocks. The webbing on the GSR is much different than the LS and the GSR has a girdle while the LS has none.
However I would have to agree that for a N/A motor both blocks would be fine as far as strength goes. but I would still take the GSR for its slightly better RS ratio.

to what webbing are you referring?

I would go gsr since you already have one, but I would also add the Ls/vtec line just to get some extra oil to the head. And block off the squirters.

i would say go full gsr head and block since you have it.
rs itr pistons will put around the 12 comp if not more depending on your head.
my itr (99 spec) started dropping power at 8k with just i/h/e and tunned on s300, with your set up not to sure.
that set up should be 185whp+ make sure to get at least 310 inj.

I have 440's so I have that covered.

I'm trying to find a b20 block to take advantage of the extra displacement... It's hard to justify an na 81.5mm build with lower power levels yet near equal costs to a b20

Ok here we go. GSR/B18C1 block has; crank griddle, piston oil squirters, thicker rods, thicker rod bolts, is balanced much better then the B18A/B, has a better R/S ratio and higher compression pistons. The Ls B18A/B has thinner rods but they do hold up well, thin weak rod bolts ARP's are a must, no crank griddle, not balanced nearly as well as its Vtec counter part and has a lower compression. Also the B18A has a weaker oil pump, using a PR3 oil pump and the B18B OBD2 only uses a P72.
I may also add that I have a Ls Vtec with B18B1 block from a 99 USDM Teg. I have ARP rod bolts and that is it rest of the bottom end is stock. It revs to 8k no problem. So the B18B motor is a good motor, Honda just went over kill on the GSR which is good.

that's almost all been mentioned and he's getting a 2.0 instead now thanks

Good way to go. TFTW.

A b20 would get the best numbers for torque, and if built correctly (balanced rotating assembly, arp rod bolts etc,) could get you a reliablly higher redline.

If you are using that transmission, to really take advantage of the short gears, you are going to want a higher rev limit. I personally would go with the gsr, because its overbuilt as everyone says, and to me seems to be the most reliable because its already intended for higher revs. AND you already own it (FREE)

im no expert tho and if you go b20.... SELL ME THAT BLOCK! :biggrin:

A b20v deff will yield better power and tq numbers. Best solution for n/a b series mildly built.

Have the b20 block, now just need to buy parts, machine work, and assemble...

trans specs have changed a bit, different lsd and going gsr 2nd gear, itr/b16 2nd is maxing out too early for most tracks here and it sucks bouncing off the rev limiter during auto-x

I need to buy a clutch, for boosted set ups I've only had good luck with ACT thus far, but it'd be nice to find something cheaper that'd also work well...

b20, ctr reps, pro2's, decent header and e85. 220 whp for a basic build

No, No, & No.

~ +3cc pistons, CTR's are a bit high; itr cams (already have, no out of pocket costs); 91 cheaper, easy to obtain, and less fuel burning. There are quite a few tracks that don't have e85 available, plus with a 5 gallon fuel cell e85 wouldn't last very long on a road course.

Hay hay hay common sense shoots down Captain AnswerForEverything