xxxhp

I've been enjoying my MTI C5-R 427 for 3.5 years and it is still running fine like new. But oh well, I've decided to take it to the next level & join the dark side . I haven't decided yet on which form of Forced Induction (blower or turbo) Iam gonna go with.

Currently Iam in the middle of a dilemma of whether to rebuild my current 427 with different pistons to lower the compression ratio, or sell it all together & get a low CR LS2 402. My 427 would sell between 9-10k, which is roughly the price of a new 402 long block. So basically I will not be making any money by doing that. Here are my two options

1-Rebuild my current C5-R 427 engine

Pros
-Can make more power than a 402 assuming same boost
-Will not lose the $$ I invested in it when I bought it
-Better area under the curve and the cam (MTI G1) would be more streetable with the added 25 cid
-The magical 427 number, oh yeah

Cons
-Lowering the CR could be more involved than simply changing pistons.
-Expensive to repair when things break, especially since it has a C5-R block (breaking a C5-R block is my worst nightmare )


2-Get a new LS2 402 long block

Pros
-Starting with a fresh long block ready for boost.
-Cheap to repair when things break. LS2 bare block is only $1K and complete 402 shortblock can be had for $4k
-Lots of proven combos are running 402 engines

Cons
-Compared to a 427, a 402 would have to be boosted more to make the same number the 427 would. IMO, more boost=more issues to deal with
-Area under the curve is less than what it would be with a 427. Also the cam would have more lope & worse drivability
-Have to deal with LS2 block compatibility issues (cam sensor, knock sensor etc..)
-If I go with a 402, I might start thinking about upgrading to a 427 once again


Iam not sure what option should I go with, but anyway, thanks for reading and please throw in your $0.02

98turbls1

iTrader: (17)

What is your cr?? I really doubt you would break a C5R block unless there was some extreme detonation or you threw a rod through the block...I would honestly just swap out the pistons, maybe change the cam depending on how it is right now and then freshen everything else up...I mean you have a $6500 block that most of us dream of...You should at least use it you know...If you can give us more details of your current build we could probably help you with which would be better determined on what your current set up is and how easy it would or would not be to convert it to FI friendliness...

RyanJ

I wouldnt worry about breaking the block unless something is done wrong.

However, I would do the 402. You can sell your 427 for a chunk of change...which you'll need for sure with FI. W2W 402 + Lots of fuel + BS3 + turbo(s) - $ from 427 = happy.

solobaric

iTrader: (5)

Have to agree! I really doubt you could break the C5R, those things have survived some of the worst torture testing they could throw at an engine.

xxxhp

Here is what I remember

-C5-R block, 4.125 bore
-Lunati 4" stroker crank
-Lunati connecting rods, not sure which pistons
-Comp Lifters
-Stage 3 LS6 heads with 2.08 intake valves & 1.6 ex valves. Flow at .600" is between 320-330 cfm. Don't remember CC size
-S1 cam (244/244@610" -114 LSA)
-Double valve spring-hardened pushrods-titanium retainers...etc
-Jessel shaft mounted rocker arms
-High Flow oil pump
-11.2 CR

Besides changing the pistons to lower the CR, I will be going with the G1 cam at 115 LSA so that my car idles like stock.

Thanks

BUYAMERICAN

Buy blower pistons, rings, a turbo cam and the base C5 STS TT kit with a BAP, 60's, walbro and alky kit. Also account for another $2,000 to tear down and rebuild, rehone the motor with new gaskets, etc. The cool thing is that you will have a completely fresh motor.

This kit will do 800/800 at 12 PSI. on a 402/427 on a MAF tune.
This kit will go over 800/800 but it gets expensive.
Talk to Rick at Synergy.

You will need 725 torque across the board to get 9's and 142-145.

Slowhawk

iTrader: (12)

Keep the 427ci and change the pistons-possible rods too.

You can go F1 Procharger or Turbo.

EPP

iTrader: (22)

I agree. Bob

Wet 1

iTrader: (4)

I also agree with slowhawk. You already own the expensive stuff, just change the pistons and you have a better foundation.

OUTLAWZ RACING

iTrader: (9)

I went with what I thought was a 427 but when i reviewd my spec sheet it was a 422ci not a big deal sorry if i mis lead some people But 427+boost= a good time!!!! just my 0.02$

sorry for thread jacking!!

2001WS6Vert

Keep the C5R since you've already got it. 427 sounds cool and so does C5R.