Chevy 327 LM7 engine, Any good?????

Goughie · Post by **Goughie** » Thu Sep 03, 2009 10:14 am

Hi,
I have been offered a 2007 LM7 327/5.3ltr complete engine and box including all ancils and ECU etc, has been ran, but only as a test engine so in good running order, the guy wants £2000
What do you think? a reliable 275hp with matched box, nothing else to spend, just plug and play.
Or do i go for the good old 350 and rebuild it?
I know alot of this comes down to personal taste, but your views and comments would be very welcome.
Cheers

kiwicar · Post by **kiwicar** » Thu Sep 03, 2009 12:56 pm

As you have described the engine and it comes with a box, it seems a bit of a no brainer, 275 bhp for 2 grand with gearbox, sounds good value to me

The only issue anyone would have with a 327 is it's 2 bolt mains, actually until you get beyond 450 BHP this isn't an issue (so in goes the the 175 bhp of nos then)
If you are wanting more then 4 bolt main caps are about $100 new, alot less 2nd hand drilled and line bored will not brake the bank.
Best regards
Mike

Goughie · Post by **Goughie** » Sun Sep 06, 2009 8:39 pm

Bugger,
Was hoping someone would say no, do not go for it, looks like i will be raiding the piggy bank!
There is a possibility of a second set up exactly the same if anyone is interested?
This also means i will have a RV8 4.6 with performance cam, running a dizzy with brand new Edelbrock/Weber 500 SD1 front cover and sump for sale
Cheers,
Paul

crayefish · Post by **crayefish** » Mon Sep 07, 2009 4:44 pm

LM7 is an ally block right? or is that the LS6 only?

If it is that will be equivalent to an extra 50 horses or so over a huge cast lump of a 350....

Magnetteman · Post by **Magnetteman** » Tue Sep 08, 2009 12:13 am

The LM7 is a cast block, it's a smaller version of the good old 350ci iron block, the alloy version of it is the LM4.

Be very careful that it's not the smaller and more undesirable 289ci version. It can be checked by looking at a small raised pad at the back of the block, it'll have 5.3 or 4.8 stamped on it. If it's been ground away, walk away from it.

Apparently the LM7 is a very easily tunable engine that responds well to head and cam work making a respectable 450bhp fairly easily. I'm not sure if it's a 2 bolt mains or a 4 though, I'll have a google and will report back.

*returns from expedition into google land...*
Still nothing regarding the bottom end but here's an interesting 6 page write up about the beasty and improving it...
http://www.carcraft.com/techarticles/cc ... index.html

I hope that's been of some use to you..

crayefish · Post by **crayefish** » Tue Sep 08, 2009 7:32 am

Magnetteman wrote: Apparently the LM7 is a very easily tunable engine that responds well to head and cam work making a respectable 450bhp fairly easily.

Whoaa there! 450hp very easily out of a 327???? the general rule is that one hp per cubic inch is fairly easily obtainable with the usual stage 1 heads, cam, headers, carb, manifold etc...

after 1 hp per cubic inch it become significantly more difficult to get more power and you end up using wilder cams etc to get more peak power...

450hp might be 'easy' in terms of buying the kit, but it would certainly not be cheap!!!!!!! and it would probably be undriveable on the road.

When I was researching my 383ci stroker build, I found that around 430hp for that was the most i could go and that was including poor idle etc

Magnetteman · Post by **Magnetteman** » Tue Sep 08, 2009 8:00 am

Have a read of the link that I posted.

I will admit it's from an American site and although they do post the dyno figures I think they measure and rate them slightly differently to ours.

You should be able to get more than that out of a 383 without a difficult idle???

crayefish · Post by **crayefish** » Tue Sep 08, 2009 8:24 am

Magnetteman wrote:Have a read of the link that I posted.

I will admit it's from an American site and although they do post the dyno figures I think they measure and rate them slightly differently to ours.

You should be able to get more than that out of a 383 without a difficult idle???

From actual dyno results, I found that the very max I could rob get on about a £6000 budget was maybe 450 hp. The think with the chevys is they aint that great for hp, however I would have been getting close to 500ft.lb of torque which is the good figure.

The 383 is really more of a torquey motor than top end power, but with single plane intake etc they have been pushed to 500hp, but then it becomes unusable below 2500rpm which is no good for the street. The trouble is that then you have to spend big money on getting that power as it comes at say 7000 or more rpm which means very light pistons, balancing, lightened valve train and all the rest

would prob cost 10 grand to get 500 hp out of a 383 as opposed to 6 grand to get 450. the cost becomes exponential after 1hp/ci

the cheapest power, as the saying goes.... 'theres no substitute for cubic inches!'

kiwicar · Post by **kiwicar** » Tue Sep 08, 2009 10:17 am

Hello Goughie
I just want to clarify here which engine we are talking about, owing to Chevy's habit of recycling names of engines, are we talking mid '60s onward gen1 327 engine (lm7 also available as the lm327 crate engine) or '99 onward 325 lm7 gen3 thin wall casting ductile iron version of the LS* series. If it is the former with box for £2k then it is a bargin, if it is the latter then I hope you have bitten his hand off.
got a picture?
Mike

crayefish · Post by **crayefish** » Tue Sep 08, 2009 10:25 am

Though if you sold the engine and kept the gearbox, you could probably make a bit of money!

edit... as in you could prob get 2000 for the engine if it is new, and have a free gearbox... or sell the gearbox for 500 and make 500 quid!

kiwicar · Post by **kiwicar** » Tue Sep 08, 2009 1:30 pm

If this is the later gen 3 engine the ECU will be hooked into the gearbox, best to keep them as a pair.
1 bhp per cu in is what was aimed at for road use for a gen 1 sbc in the '70s, 1.25 to 1.4 / cu in is more like a target now, 1.5 to 1.6 for a weekend drive to circuit drag car.
For the Gen 3 you are looking at alot more, they also the ductile iron blocks are only about 50lb heavier than the ally ones and they are seriously strong.
Mike

crayefish · Post by **crayefish** » Tue Sep 08, 2009 3:12 pm

kiwicar wrote:If this is the later gen 3 engine the ECU will be hooked into the gearbox, best to keep them as a pair.
1 bhp per cu in is what was aimed at for road use for a gen 1 sbc in the '70s, 1.25 to 1.4 / cu in is more like a target now, 1.5 to 1.6 for a weekend drive to circuit drag car.
For the Gen 3 you are looking at alot more, they also the ductile iron blocks are only about 50lb heavier than the ally ones and they are seriously strong.
Mike

I really dont think theres that much difference between the 70's designs and the current ones... the block isnt too different, modified cooling doesnt really affect the power much and the cylinder heads are still 50's technology pushrod opperated 2 valve heads! Admitedly fuel injection helps a bit, but ultimately the chevy/ford etc V8 designs have nothing like the power/ci potential of modern european and japanese engines

still... you cant beat a V8 because it is, well.... a V8!

kiwicar · Post by **kiwicar** » Tue Sep 08, 2009 4:07 pm

Hi
The gen 1 and gen 3 engines are very different engines, the only thing they have in common is the bore spacing. The gen 1 block stops at the centre line of the crank, the gen 3 extends down like the rover. The oil system is different, the deck hight different the firing order different the heads are more like Ford windsor than gen 1 chevy, the closest related chevy engine is the SB2 nascar engine. Sorry just a totally different beast and you are missing the whole point of the engine and the progress made when these engines came out. They are as far from the '50s engine design as you can get, yes they have 2 valves/ cylinder yes they 8 cylinders yes they use pushrods to activate the valves but to say they are a gen1 chevy with different cooling is like saying a RR meteor engine and a aston martin V12 are the same thing because they have 12 cylinders and overhead cams

.
Sorry I am out of this thread
Mike

crayefish · Post by **crayefish** » Tue Sep 08, 2009 4:19 pm

I would love to see dyno results for a 327 that could put out 520 hp N/A!!! Especially ones that can be reasonably driven on the road, so that counts out the engines making peak power at over 7500rpm!

Goughie · Post by **Goughie** » Sat Sep 12, 2009 10:44 am

Hi,
Sorry for the delay in replying, have just got back from my hols

I will be veiwing the engine/box early next week, i am only going on what i have been told, as this is:
It is a 2007 build LM7 cast block with alloy vortec heads, complete with all ancils including cast stock manifolds, ecu and auto gearbox
Wikipedia states:

5300 Generation III
The Vortec 5300, or LM7/LM4/L59/L33, is a V8 truck engine. It is a stroked (by 9 mm) version of the Vortec 4800 and replaced the 5700 L31. L59 denoted a flexible fuel version, while the LM7 was the standard version of the engine.

Power output is 285-295 hp (213-220 kW) and torque is 325 lb·ft (441 N·m) to 335 lb·ft (454 N·m). Displacement is 5.3 L (5328 cc (325 cu in)) from 96.01 mm bore and 92.00 mm stroke. Vortec 5300s are built in St. Catharines, Ontario, Romulus, Michigan, and Silao, Mexico.

LM7
The LM7 Vortec 5300 was introduced in 1999, and can be considered the "garden variety" version of the Generation III 5.3 liter V8's.

LM7 applications:

2002-2005 Cadillac Escalade 2WD
2002-2006 Chevrolet Avalanche
2003-2007 Chevrolet Express/GMC Savana
1999-2007 Chevrolet Silverado 1500
1999-2007 GMC Sierra 1500
1999-2006 Chevrolet Suburban/GMC Yukon XL
1999-2006 Chevrolet Tahoe/GMC Yukon

How true it is i do not know

Will try and take some photos and post them up here, is there anything i can check to confirm what the chap is saying?

Magnetteman:
Cheers for the link, had a quick look, will read it proper when i have a bit more time

Thanks for all your help