Opinions on LSX 427 vs. LS7

[JUSTIFIED]

Hi All -

Long story, short... I have a broken lifter. with some bore scoring. Car was modified in May 2018 and per Dyno numbers, increased RWP by ~ 150 HP and RWT by ~ 100 Lb-Ft and lifters were stock.

This is not intended to be a thread about whether the mods caused it or not, stock lifter issues, etc. as opinions are all over the place. I'll just say that I've talked w/ a few reputable shops and have formed a fairly solid opinion that the mods were not a factor.

The block is going over to a reputable machine shop and am hopeful they can repair the bore via re-sleeve. The broken lifter led to metal shavings circulating through the engine, which will require a thorough inspection.

The purpose of this thread.... if my block is toast, I am considering going with an LSX 427 block due to durability. It is ~ 100 lbs heavier and may run hotter (not sure by how much..). The weight is a significant concern, but may make some additional mods to increase power and torque (want to remain NA, however).

There is a ton of knowledge in this forum and I'd appreciate insight on pros and cons of swapping out.

Thanks in advance for your insights!

-John

[ariZona28]

You're at a very important crossroad. What are your intentions with this vehicle? If you're going to do a balls to the wall drag race set-up then that LSX is the way to go. A maximum road course or Auto X car I would stick to an aluminum replacement if needed. If you're just going for maximum street excitement I'd say stick with the original engine (hopefully it can be saved) repair and improve as necessary and call it a day. Keep in mind the low production numbers and collectable potential.

[Little Walter]

If you want a strong block but not the weight of the LSX iron block consider going with a RHS aluminum block or LSR aluminum block.

[Gbland60]

This is something you’ve probably already either told yourself or others have told you , it really boils down to how much money do you want to spend. I’m sure if it’s just the lifter bore that’s gone it most of the time can be sleeved. If your crank is marred sometimes it can be polished out if not too bad. Camshaft well that’s gonna be replaced anyway. If it were me I’d just talk with the machinists about the block and make my 1st decision there . There are different types of sleeves also but I guess your machinist would know what’s best for the LS7 as far as oiling issues. Man sorry to hear about this. I can only imagine how you must feel.
Good luck either way. PS. We all like more power but sometimes it comes with a heavy burden and cost down the road

[ronchev]

I agree with every ones statement above but will add that unless your going for all out build looking for more HP there is no good reason to add that much weight to the front of your car, if you do end up having to replace the block there are other options without going with the heavy LSX block, leave those for the boosted drag guys that never turn.

Also if your keeping your engine modified and I assume that the cam was replaced when it was modified you would be money well spent to get a good quality aftermarket lifter for it this time like Johnson Morel etc, yes pricey but I have seen to many so called GM LS7 lifter fail and cause problems just like your experiencing when running anything other than a stock cam, There are post here from a few members that have went through it and I see it all the time on FB LSX groups. Do some research here is all Im getting at. Good Luck

[2SSRS@Gen5diy]

Last year i picked up a Z/28 engine that had been modded, with comp parts cam and lifters, 2 lifters where stock in the block and some part hit a sleeve and the 58X wheel, needles to say i was told buy a new block, i did not want to, as this is a Z/28 engine out of a 15 car, its coming together nicely, only using the Johnson Morel lifters and good parts, you know need, to know where a part is made before you use it in your car, any way use the LS7 block.

[Blownfogger540]

my 2cents ls7 block is good for stock apps if you boost it good luck too you i have 4 ls7 blocks all with various pos weak ass sleeve issues from boosting

[redrum_maro]

Originally Posted by Little Walter

If you want a strong block but not the weight of the LSX iron block consider going with a RHS aluminum block or LSR aluminum block.

The RHS block is a great engine block. It is similar to the LS aluminum block with everything taken to the next leveled consider that is expensive and is nearing the limit of a street engine and could be considered a race block by some people. It can take good power, enough to make over 1000hp safely. If I remember correctly the LSX blocks are capable to make up over 2000hp. It is up to the limit and what you want out of your car.

[JUSTIFIED]

Thanks for the great input, all!. I failed to mention that this isn’t a track car. Street only.

For my needs, I’ll likely stick with LS7 block but the other options are intriguing.

Assuming it can be repaired, I’ll be installing the Johnson drop-in lifters (2110s, I believe).

Thanks again!