AvyManiac

Hey Fella's,

how to be sure if an engine is directly fittable with a vehicule

Does exist a engine fitment guide?

For exemple if i put the lq9 or lq4 in the place of the lm7, turn the key and go? New ECm? tranny bolt directly?

Some advices are welcome

Thank you

53bowtie

iTrader: (6)

An lq9 will be a direct bolt in for the lm7 because it had the 4L65e transmission which is the same basic transmission as the 4L60e which would be behind your lm7.

That being said an lq4 will most likely be easier to find and cheaper (at least they are here in the states anyway) and, although it originally came with a 4L80e transmission (which requires a different flywheel and crank spacer) you can simply use the flywheel off your lm7 to bolt it to the 4L60e transmission.

You can use the lm7 ECM with either engine swap but will have to have it retuned for the larger engine. All wiring should be plug and play as all three engines use the same intake/injectors/accessories.

Where it gets tricky is when you try to put a new engine in an older truck or an older engine in a newer truck. For example, if your vehicle is 99-06 year it is better to find an lq9 or lq4 from that same year range. After 06 they went to a different tooth reluctor wheel on the camshaft and moved the knock sensors to the sides of the block instead of the valley cover. I believe they also moved the cam sensor from the back of the block to the timing cover. And there is always the possibility of getting an engine that has DOD, although I am not sure which ones do and don't.

Hope this helps point you in the right direction!

AvyManiac

Yes is more clear for me
And concerning head, I see most people upgrade head from other ls engine, how to know the right choice ? Compatibly etc...
Really interest by porting head, I ve watched more and more vids on youtube but never explication about that

53bowtie

iTrader: (6)

The 317 heads that come on the lq9 and lq4 is actually one of the better flowing cathedral port heads GM made. They are almost equivalent to the 243 heads used on the ls6 engines just with a bit larger combustion chamber to lower compression some. If it were me I would port the heads that come on the engine or if you want to raise compression a bit find some 243 heads and port them.

AvyManiac

Find this site
Junkyard LS Engine Builds: Going From Rags To Riches - LSXTV

L92 head for a great combination but is so pricey for a ported head pair

For my lm7 what kind of head or port the original is the best way? Rapport price, effort, fiability

Thanks

53bowtie

iTrader: (6)

Are you building an lm7 or swapping to an lq9 or lq4? Thought you were going to do a motor swap??

I would stay away from L92 heads in a heavy avalanche if it were me but then you will have guys say otherwise so its personal preference I suppose. You cant run L92 heads on an lm7 because the valves are too big and will contact the cylinder wall.

AvyManiac

Sorry I m not clear.
Lq9 swapping is the first option and cam swap head etc for my lm7 is my second choice to upgrade the avalanche
I look all upgrade option

53bowtie

iTrader: (6)

In a heavy avalanche there is no replacement for displacement. I would strongly suggest swapping to an lq9 if you have that option. Most of the performance mods you would do to the lm7 would help mid to high rpm performance but not low rpm performance which is important to get the heavy avalanche moving. Short of doing a roots style blower on the lm7 I would be looking for a lq9/lq4 to swap in.

AvyManiac

According with you
What do you think about this link? LSx4U.COM

If with my future lq9, with cam swap, lifter, rockers, ported head, header , exhaust line
How many hp I can hope to get ?

Make me dream lol

SnakeOiler

iTrader: (6)

My crate LQ9 with only long tubes and eFans puts down 342hp to the rear wheels - for comparison. Your stock LM7 puts down 250rwhp, at best.