your thoughts on my planned build?

[jts98z28]

hey, ive been doin a little research lately and this is what i have come up with:
5.3L LM4
single plane vistor jr intake
ported 243's
MS3 cam
holley 750
3500-3800 stall (not sure yet)
TH-350
3.73 gear 8.8 rear
also a plate kit around 150-200 shot after i get everything together and make sure it all works well

so my question is does anything stand out as being completely retarded? or will this setup work well together?
thanks for any input

[The_Bishop]

First question: What is it going to be used for?

My thoughts: Intake is going to be a high RPM item. So is the cam, I think it's too big for a 346 let alone a 325. The 243's will bolster this high RPM potential, while lowering compression below stock for the LM4. If I remember right you'll be around 9.0-9.3:compression, which won't work well with that cam, the intake, or anything else. New pistons are in order to get the compression up to the very high tens/low elevens to make the cam happier. You will need a looser converter, and this thing is going to be a complete pig under 4000 RPM. Tons of overlap with smallish cubes means lousy idle quality, dirty as hell.

It'll be a high-rpm screamer. That means low life expectancy from the valve springs, total crap street manners.

In other words, this combo smacks of "the internets said it'll be gud!" I'd revise the plan.

[NJ Torque]

Redo.

6.0, stock crank, good rods/pistons, some ls3 heads would gain you much better.

[jts98z28]

i was planing on the lm4 due to how light it is and i know someone with one for sale so ill probably get a good deal on it, my car is extremely gutted so i wont need to make crazy power to run low 10's or possibly creep into the high 9's
as far as what it will be used for is mainly a drag car that ill take out for a short drive on nice weekends or something, only have a 8 gallon fuel cell so im not gonna be driving it on the street very much so the street manners arent my main concern
i did forget to add that i am planing on different pistons and milling the heads so i can be somewhere near 11-11.5:1 CR
i am curious on the converter part, i thought that n2o liked tight converters?
also im not familiar with the term bolster, does it mean that the 243 will limit the high rpm potential?
the main issues are gonna be poor street manners and going through valve spring often?
thanks again

[NJ Torque]

Main issue will be power. You'll only make say 380-400 on motor. What a MS3 would make on a stock LS1.

Your nitrous to power ratio will be down if you mill the heads too much you'll affect the flow rates of them.

[jts98z28]

i saw a build similar to my plan just with a little bit smaller cam and ported stock heads instead of 243's and it made 450hp, andwas still making power when they shut it down, i shouldbe able to hit 400 to the tires N/A, which is what im lookin for, thanks for the warning about over milling the heads though

[The_Bishop]

Definition of bolster.

Cheap is irrelevant if you don't get results. Milling the heads disrupts flow, compromises piston-to-valve clearances, creates intake manifold alignment issues, and weakens the deck surface so gasket retention becomes an issue.

What the car likes on n2o is going to be far, far different than what it likes NA. You have an instant hit of torque on n20, which will get the car moving, and why a tighter converter works with n2o. However, the combination of parts you have chosen will result in an engine that extremely lazy below 3500-4000 RPM, so that tight converter that works well in n2o will suck when you're NA, which will be roughly 99% of the time the car is running.

If you're spending money to replace pistons and rings, and re-hone the block, then why not just get a shortblock more suited to the task? Cheap is relative. What is cheap up front can cost as much if not more in the long run than a more expensive but better suited part.

Your car, do what you will with it. I predict you'll hate the car with the combo you have proposed. Also, is this going into your '98? If so, why ditch the FI? There's a very, very good reason that carburetors have been eliminated in nearly every modern engine.

[V]

in regards to the ms3... i made 425rwhp with that cam, lt headers, ory pipe, ls6 intake, real ls6 heads(stock), electric water pump, and ported/polished stock throttle body.

The tuner was sure that with a fast intake and 90mm Tb, id have hit 450.