Aftermarket LTX blocks?

Ive been doing some digging around and Ive come to learn that the LTx aftermarket isnt that great, or I just dont know where to look... Ive heard rumor that there is a fabled LT block with 350 mains, a 4.120 unfinished bore, and is tall decked for a stroker kit... From what Ive read, Dart had this project in late 2008 and early 2009 but scrapped it due to tooling costs and lack of demand. I later found that GMPP had 13 or so of these blocks PRODUCED that float around on e-bay for $3-5K for JUST A BARE BLOCK, and thats where the trail goes cold... I ultimately want a 427 stroker LT4 of sorts, and Im not that willing to switch to an LSx platform just yet... can anyone give me a kick in the right direction?

you'll have to get an aftermarket sbc block and modify it to work. There was an article in GMHTP awhile back about a guy who did a 414 cube all aluminum LTx in an Impala, but he started with a Dart block and had it extensively modified. The LTx aftermarket isn't that great because there are relitively few of us wanting performance parts for these motors. We are helped by the fact that a lot of Gen I SBC stuff can be made to work (I'm in the process of building a low comp LT1 with basically all factory 350 parts), but also hindered by just how different our motors are from anything else GM made.

If you want a 427 stroker, you're best bet is to get an aftermarket SBC block and have all the machine work performed to make it work with LTX heads and the reverse flow cooling system. Good luck finding one of the GMPP blocks, you are right, those things are RARE, and once in a blue moon comes around more often than one of those goes up for sale.

Dart did announce an aftermarket LTX block, but there was too little demand for the piece, so they tanked it until further notice.


LTX's are basically the redheaded step children of the SBC world. No one is quite sure what to do with us lol

Hmmm so it sounds like its going to be rather cost ineffective to go up to the 427. The entire reason I wanted one was because I could say, "yeah, its "just" an LT1" and scare the bejeezus out of a few supras Ive seen tooling around. Im not too keen on allowing someone to hack into an aftermarket Gen 1 block and have all kinds of holes all over the place either. Well it looks like Ill be going to the LS3 427 stroker kit, is the wiring x over difficult?

sighs.... the lt1 block is just a 350, get what u want its not a lt1 till u add heads, timing cover, intake and such

You can take a stock LT1 block out to 414". That is the limit as far as I know. It requires a few special parts to get it to fit, and a good machine shop, but it can be done. There may be more than 13 of those fabled bowtie bocks out there. 13 is the highest serial number that I have seen though. Brady aka "roadtrip120" has one sitting at his house. Dart claims there wasn't enough interest to justify producing them. Go to dartheads.com and click on their forums and take a look at the 2 LTx block threads. Those 2 threads were BY FAR their highest ever traffic recorded on their website. It was just bad timing. Right when they were going to go ahead with the build, the economy tanked.

Just an fyi, but the Impala guy in GMHTP was using an aluminum block and it was a 434 cid. Pretty trick setup but I don't want to know what he's got invested in it.

Postin' on the go......

The aftermarket blocks would be a nice option, but to be honest...the LT1 block has gone into some high horsepower numbers. I understand that you want to be different, but you can still put a hurting on anything out there with some work to the stock style platform. I just finished putting together my 383 that you see in my sig and its basically bulletproof, can take a hefty shot of nitrous, and claim almost anything out on the street.

Something to look into is running a modified SBC head for the LT1. Plenty of folks make some good numbers on solid roller setups with this option. Just food for thought...

Last time I saw one of the blocks for sale it was on racingjunk.com I have to agree with badblackzee. If you build the bottom end and reenforce the block in key places. I don't see why a LT1 cant put out 2000 hp with quality components. Just no one has put the time and money into it. Would like to see what NelsonRacingEngines could produce with an avid LT1 Enthusiastist's money.

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Originally Posted by hoursetraitor

sighs.... the lt1 block is just a 350, get what u want its not a lt1 till u add heads, timing cover, intake and such

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No offense, if it were "just a 350" there wouldnt be such a difficult time finding parts because vortec and gen I heads and the like are plentiful. If that were case there is a HUGE misconception with LTx owners everywhere that there isnt a low aftermarket following.

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Originally Posted by Fastbird

Just an fyi, but the Impala guy in GMHTP was using an aluminum block and it was a 434 cid. Pretty trick setup but I don't want to know what he's got invested in it.
LOL the 434 is what I HAD in my SS monte for a race motor. and you are right, for a good block and bottom end the are expensive.... I was in 5 figures for JUST the block and bottom end. Not wanting to go down that road again...

Postin' on the go......

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Originally Posted by joelster

You can take a stock LT1 block out to 414". That is the limit as far as I know. It requires a few special parts to get it to fit, and a good machine shop, but it can be done. There may be more than 13 of those fabled bowtie bocks out there. 13 is the highest serial number that I have seen though. Brady aka "roadtrip120" has one sitting at his house. Dart claims there wasn't enough interest to justify producing them. Go to dartheads.com and click on their forums and take a look at the 2 LTx block threads. Those 2 threads were BY FAR their highest ever traffic recorded on their website. It was just bad timing. Right when they were going to go ahead with the build, the economy tanked.

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Isnt the 414 dangerously close to the water jackets? I think I was reading somewhere that it was REALLY bad at overheating and had problems with warping too. This is partially why I was looking so hard for that particular block, It would still have street manners that I could tool around, but have the torque to get down and dirty when the time called... Living in Miami is a LOT of stop and go traffic, hence my issue with the 414 for fear of overheating.

2000hp on a stock lt1 block...idk about all that lol