Just wondering what the difference is between a L98 and an LT1 motor? Is the block different? Are the heads different? Weighing the options to either build an LT4 motor with the LT4 kit from pace to get 425 hp or keep (and redo) my 383 stroker. Thanks Dom

Main difference is the reverse cooling system GM implemented.
Cylinder head coolant passages changed, but ..essentially a 350
block at heart.

So yes, to anwser your question.. L98's vs. LT1/4's are different.
Both are incompatible without extreme modification.

Im sure someone will elaborate in detail

http://www.automotiverebuilder.com/ar/ar99928.htm this may help to find differences

best regards

Yep, for the most part it's the reverse cooling which makes them NOT interchangeable. Then you have the optispark instead of a traditional distributor.

Practically speaking, the LT1 has MUCH better heads, and an intake with more upper end breathing but produces less torque down low.

And dont forget about the crappy omni-spark business the LT1 has instead of the distributor in the back.

Theres nothing wrong with the opti

Its actually superior by being more accurate and less prone to wear
No gear slop, no gear to wear out, more rear clearance for a more compact engine

tell that to the many LT1 guys that have opti's that go out on them.... everyone i know hates opti

in theory they seem good, but dont really perform that well and are expensive

i think price and labor involved is y opti is bad but, i do agree with the above statement that it was a step in the right direction though.

at the same time i'd never trade my hei for it though due to what i just mentioned. + i clean my engine a lot and opti and water don't mix been there done that.

Water and your HEI dist module dont mix either

Lt1 differences

Opti spark ignition. (more accurate)
Reverse cooling.
Stronger rods.
Better pistons.
Cam driven water pump.(if your belt breaks your not SOL)
D port Heads flow much better.(plus f bodys are aluminum stock so they are less prone to detonation and disperse heat better)
intake flows much better.
larger cam profiles stock.(make good tbi 305 cams too!)
Better oil pumps. (the pickup tube is oversize stock)

Basically its a 350 inside surrounded by GMs last attempt to upgrade/modernize it before the ls1 came out.

Anyone who bashes the opti is most likely just repeating what they have read somewhere and have no real experience with it. If you maintain an opti they are fine. Just like a dizzy coil and cap, if you let it go without maintenance, eventually it will run like crap.

lt1 are great motors for reliable mid level hp.