okay, so i was talkin to a buddy, and he mentioned how 327s are just destroked 350s.. so it made me think.. why is it that everyone does 355s and 383s, but no one does 327s? i know there are some damn fast smaller displacement engines that spin like theres no tomorrow.. so does anyone know any 327 lt1s?? woudlnt they be cheaper to build, since you just need a crank and rods (and a valvetrain that can handle it) where as with 355s and 383s (and beyond) you need the machinework too?

 

theres no point?

what is there to gain? you lose torque.

 

extended powerband?

think of a really really big import engine.. its smaller but it spins way higher... so a 327 would be the best of both worlds

 

The factory PCM is a big factor. I have spun my 355 to the limit at 71-7200, and a 327 would like alot more rpm if built for the track.

 

I have heard of people doing it for supercharged/turbo applications, and I beleive it is fairly common in circle track racing. It will need an aftermarket engine management system though.

A forged 327 LT1 can hold a ton of boost and spin to insane rpms, but it is very costly.

 

why is it so much more costly?

are there alternatives to the stock pcm?

 

Nobody does it because it's a lose/lose situation in a street application. A 350 will spin just as high as a 327.

 

I turned a 350 into a 331 (.030 over 327) a few years back. Not one of my smarter moves. Yes, it did rev a little easier, but that was about the only benefit I could see. If power is something you're wanting, go with more cubes....plain and simple.

 

I have never personally destroked a 350, but have seen the topic come up enough disagree. You do not see any LT1s, or most 350's for that matter, spinning anywhere near as high as the destroked 327's do. It is not just from PCM limitations. The ones that do need very exotic parts, and still do not spin up as quickly. The shorter rods and tigher tolerances let it rev up quicker(therefore building boost faster) and hits higher rpms then a standard 350 - less torsional load on the rods and less stress from a shorter stroke.

Of course everything has its drawbacks, in this case the engine will not make as much low end torque. That isnt such a big deal in a supercharged or turbo race application, which is probably why the few times I have heard of it done were for insanly boosted high rpm engines.

It is good for a pure race engine, but not for a street/strip vehicle. To run enough boost to make it worthwhile, you will need low compression ratio - around 8:1. Low compression + low cubes = low torque, which is no fun at all. The car will be a dont until boost hits - and again, with a big enough turbo to be worth it the boost will hit violently. The car will only be fun to drive at WOT at a track!

 

The connecting rods on the old 327's were the same length as the 350's. The 400 cid small blocks had a shorter rod. The earlier 327's had a smaller big end of the rod. No center to center differences. All 5.7".

 

So your going to build a high revving 327 for cheaper than a 350??? Sorry to burst your bubble, but it's the valvetrain parts that are important, and will cost the same for both motors...

Tighter tolerances just because of the shorter stroke

Shorter rods??? Wrong on both counts....like was said above, factory motors used the same rod length, and with after-market parts you will have to go to a .250" long rod to use the same compression height piston.

So you disagree...then you agree later?

 

To bring an old thread back from the dead....

I was reading a book on engine building over the weekend and something I read struck my curiosity on destroking.

Rod Ratios. If you put a 3" crank in, and used a 6" rod, you will have a rod ratio of 2:1, and this would incresase dwell. In theory with the increased rod ratio and dwell, you would have a smoother running engine. Is it worth it for the increased rod ratio and dwell? - I still dont think so b/c there is no replacement for displacement!!! I guess theoretically the best case scenerio would be to have a block with a 1" higher deck and we could run 3.48" cranks with 7" rods, which would keep displacement up and increase the rod ratio and dwell.

 

The rod ratio debate is endless. To date, there has been no consistent differences found in dyno or track testing from different rod ratios. This means that the differences are small and probably combination specific. IOW, there are great running motors with rod ratios at both extremes and in the middle. FWIW, the LSx small blocks were a relatively clean sheet design, AFAIK. The stock rod ratio for the original LS1 is 6.1/3.622 = 1.68.

Rich

 

My stepdad, has a 2007 Impala SS 5.3 (LS4) His car is pretty quick for what it is. I don't know the stroke, but I think it's a 325. Impressive, for being a 4 door sedan.

 

The LS4 is a lot closer to being a "square" engine, with a 96mm (3.78") bore and a 92mm (3.62") stroke.