the big kahuna

how much bore can I go on a turbo charged LSX race iron block where im not going to have head gasket problems?? I herd everything from keeping it a 4" bore to you can go up to a 4.125 and GM clams safely to 4.200. I don't think I want to do that basically I was thinking of a 4.100 bore and 4.100 stroke 98 mm turbo at 28 psi and of course going with the 6 bolt head *** well

69LT1Bird

iTrader: (1)

So when GM spells all of this out for you, why would you ask on a forum:

LSX Bowtie Block (Standard Deck)
• 3.990" finished siamese cylinder bores
(ready to be honed to your specifications)
• 9.26" semi-finished standard deck height
(ready to be decked to your specifications)
• Max 4.250" recommended stroke
• Capable of 364 to 482+ cid
• Orange powder coat finish
• Accepts all Gen III & IV LS heads, cranks, cams, etc.
• Approximate finished weight: 225 lbs.

For the advanced LSX competition engine builder, you will
fully enjoy reading the following features of the new LSX
Bowtie Block:
• Front oil feed holes can be plugged/restricted for mechanical
flat tappet or mechanical roller lifter applications
• Can be machined safely to 9.20" deck height
• Main bearing cap bolt threads can be machined for aftermarket
premium 12mm fasteners
• Maximum 4.250" bore at .200" minimum wall thickness
(naturally aspirated applications)
• 6-bolt head bolt pattern (for boosted applications)
• Machined for 8mm inner and outer 5th and 6th head bolts
• Standard bolt holes can be machined for 1/2" studs
• Cam bores can be machined to accept 60mm roller bearings
• Can be machined for larger diameter lifters and/or 1.060"
bronze bushings
• Front oil feed lines can be plugged and external oil pump
and/or aftermarket dry sump systems can be used via oil
pump feed at rear of block—may be required with certain
large stroke/aluminum rod combinations
• Belt cam drive systems can be accommodated—some
machining will be required
• External oil pump feed at rear of block
• 7th transmission bolt hole has been added (per early SBC), stud
can be installed for sanctioning body requirements
• Front motor plate can be used for racing chassis applications
(sprint car, drag racing, truck pulling, etc.)
• Threaded water plugs can be used for external heaters or coolers

Grimes

iTrader: (3)

You would want to leave some room for rebuild and/or refresh though - wouldn't do all out max bore. I think some of the turbo guys here have done 4.125 bore, but double check this in the FI section. If you're running crazy boost I would leave a good amount of material though.

99blancoSS

iTrader: (115)

I would go with a bigger bore shorter stroke for a FI application.
Going bigger than the 4" stroke on FI or n2o isn't ideal. For big FI application we go with a 434, 4.155 bore and 4" stroke max. So anything in between that would be good taking shelf piston size into account unless your going with a custom piston. If I can help you please let know.

the big kahuna

ya and it seas Maximum 4.250" bore at .200" minimum wall thickness
(naturally aspirated applications) ok so what would be the biggest for ((turbo charged applications)) that's why im asking this question is that a problem??

the big kahuna

ok that makes sense ill keep ya in mind maybe we can talk about the set up more if you have time and all that thanks

Phil99vette

iTrader: (11)

You need a big stroke to get a big turbo spooled, short stroke will make it rev high but no *** down low to spool. I went with:
4.175 Bore x 4.000 Stroke 438"
106mm Turbo
@ 13# makes 1100hp
@ 25psi runs 191mph at 3350lbs

the big kahuna

that sounds like a nice size combo phil99 vett I have a 106 turbo too but im thinking of having it made into a 98 mm and maybe even the smaller turbine too its still cheaper then buying a new one and selling mine it make's no sense but that the deal

Jeff@TotalPerformanceEng

iTrader: (6)

You gotta lear to sift through all the internet experts..

Talk to someone whos done it like me....Or 4 or 5 other guys in this section. Personally, I going to a cleanup of 4.190 bore/4" stroke. althou its not optimum, i'm limiting boost, and running 6 bolt heads w/L19's

Personall I woul not exceed 4.125"/4.0" on a high boost motor. This give you a ton of meat not only in the cylinder walls, but keeps the material above the rings.

Jeff@TotalPerformanceEng

iTrader: (6)

I've ALWAYS been under the impression turbos tended to like more bore, less stroke. My impression has always been with a 6.125 rod, your piston speeds are much higher. Therefore, the turbos spool faster with large bore, short stroke.

BYW, I agree on your 4" idea. I just pulled my 4.125, and went 4.0"

Jeff@TotalPerformanceEng

iTrader: (6)

Dont listen to Phil, he's slow...And he drives a Ford....

Hell, he "works" for Ford..

Ban..Ban...Ban...Ban..


Phil, Shoot me a PM and the young one status..

the big kahuna

ok I can see much clearer now on this set up I want to go with the specs of the LS7 that way I should be able to get mostly off the shelf parts im ether going to have my turbo modified for a 98 inducer and a 100 AR ex housing it has a 150 EX housing right now but im also thinking of the smaller turbine because I want to just be able to spool with out fancy brakes where I haft to creep it into the beams I use to have a 550 big block in this car but I sold it it was way to big and heavy and I think the LSX will be superior thank you all for your input

Mr.MartyStone

iTrader: (12)

Because it's not a typical build or a dumbass question.

pmbmax

Put some arm it or you will have problems spooling. you just want to keep the rod to stroke ratio in check . 4 inch stroke is where i would want it and longest rod you can get with off the shelf pistons . cam timming and compression is alot of spooling. I will give some advice check your piston to valve cleance 4 degree retard to 4 advance . Check cranking compression and try moving the cam around to get the highest you can get . You can leave the arm out and run low compression and get a loose convertor and blow thru it on the back half and burn all the fluid up you can buy . I have went thru this and put a neal chance bolt together in and no burnt up fluid but hard to spool. I have a pt 98 and a 400 cubic inch motor. just my 2 cents hope it helps

99blancoSS

iTrader: (115)

Call me when you get a chance. We build boosted applications all the time.
4" stroke is the longest you want on a boosted or N2o LS engine, unless you using the LS7 block ( but then you have the sleeve issue..LOL)