Thread: Maybe an LS7

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Hi All

New to this forum I have a question straight away. :-) I'm about to have a look at an claimed 454 LS7 crate engine from -71 that has been used in a speedboat. It has been used very little and not been sitting in water so the cooling channels should be ok. I have some questions that I hope you guys could help me out with.
Does someone know which casting numbers that was used (heads and engine) those years?
What numbers were stamped onto these engine blocks?
Could someone verify that there only were one version of these engines sold as crates and not a special 454 LS7 that only were ment for boat racing. I would be great if someone could verify this since I hope to fit and run this engine into my El Camino.

Thanks in advance
JR

I'm not a chebbie guy, but I thought the LS-7's were aluminum block and heads and the LS-6 was the big horse 454???? Hopefully the chebbie guru's will be along to give you the straight scoop.

Hi Dave thanks for your respons

But as far as I can understand the 454 LS7 was supposed to go into the -71 corvette with aluminum heads but that never happend. Maybe that was an all aluminum engine I do not know
The 454 LS7 crate engines on the other hand was a short block and could be bought with either cast or aluminum heads ofcourse dependent on how much the buyer was ready to spend. :-) But I have not realy found out which casting number that was used and what stamped numbers to expect on this kind of engine.

/JR

ZL-1 was the all aluminum 427. LS6 and LS7 both had iron blocks. I know the aluminum heads were the L88 option, but I don't remember which heads were on the LS6 and LS7.

But who needs a numbers matching LS7? If it runs like an LS7, it's good enough for me.

I'm pretty sure the LS7 was an all-iron motor. Compression ratio will be incompatible with today's fuels, so will the soft valve seats. The motor was never installed in any GM production vehicle, but was available through the parts department as a crate motor. I have a Nickey Chevrolet parts book from 1969 showing the LS6 Novas with 450 hp. I don't remember the rating on the LS7, but I'm bettin' it was 500 or better.

Even if it is a boat engine it will fit your Camino as well as any other big block.

i think this is the way it went the ls 6 used a closed chamber head it was iron with the 265 dome piston. the Ls7 boat type had the open chamber heads with the big open chamber pistons 580 dome 12.5 i have built some of them but i used the trw ls6 and the ls7 pistons with two bolt main blocks and the thumd rod and used the open chamber rect port heads and o port heads with big roller cam in them i have see all the ls7 stuff but with the small dome pistons in them .this was mercury marine 375 hp any way you look at it this would be a hell of a start. the open heads had heat induction seats on the ex in them you can run no lead in them BUT i have see lot of them crack from the themo shock of cool lake water. for as much as you would drive it. the ex seats are not a big deal there is a lot of them out there and there not plying up at my front door from no lead

Cracked from thermal shock? Were they not running a thermostat?

there was supposed to be a limited number of ls-7's in chevelles like maybe 5-10 if that.... p.s. i do know that a few ls-6's made it into 70 ss monte carlo's like 5 or 6 ...........scooter

the heads do crack . if you know why tell me? i have seen lot of them that are junk. and boat engine run cooler than car the themo shock is from cool lake water and the chamber heat and the fact that the heads is heat induction on the ex side to make it harder all this makes them crack . rigth at the seats .but have used them same heads on the street and not had that happpen.just know to look out for this i did work on boats and seen this

Originally posted by techinspector1
I'm pretty sure the LS7 was an all-iron motor. Compression ratio will be incompatible with today's fuels, so will the soft valve seats.

even 114 leaded tech?

Originally posted by gassersrule_196
even 114 leaded tech?

I shoulda said "with today's readily available pump gas"

Thanks every one for the info. So if I got things right this there should be no big differences between a crate engine that was delivered for a race boat and one that was delivered for a race car, right?

I should watchout for cracked heads on the exaust port.

But does anyone know what the casting numbers should be if the engine is from 71.

Thanks,
Racerelc

umm, this may be a stupid question but i thought marine engines ran backwards, or had wiered cams that wouldnt work on the street?

not all but is stuff needs to be check this was somthing i looked for when i use to work on them at the boat yard