ive got a 91 Z28 with the horrid 350 TPI thats screaming "yank me out" and im trying to decide on what to do for an engine. money is not too much of a problem but i dont want to spend an insane amount. im liking the good ol 427 for a size. i plan to go with a twin turbo set up too. now the only thing i really want to know (please no biased opinions) is which Gen engine would i be better off with for a reliable and powerfull street/track car.

Option 1 is building a 427 C5R for boost. the dilema is that this engine will be goin in a 3rd gen camaro which is a pretty simple conversion but my mind is set on twin turbos and there is no one that makes a nice set of manifolds that will fit my car.

Option 2 is buying a Dart Race block 400 main and make it a 427. now i know of 3 companies that make very nice twin turbo kits for Gen I motors so thats an ease of mind. i would also be running fuel injection controlled by FAST SEFI for the great tuning capabilities. everything would be easier and slightly cheaper than if i went with the C5R BUT, that motor is all aluminum and i am nuts when it comes to getting rid of unnecessary weight. Mowtown does make a 400 main Aluminum block "M Lite" that i can stroke to a 427 but i have not heard anything about these blocks when it comes to strength/reliability in high boost conditions. does anyone know if this block is up to par with the Dart or C5R?

also the other thing is ive noticed that LSx style heads tend to flow better when ported than ported standard 23* SBC heads. would this really make a difference if im boosting the engine? are there any companies out there that do massive port jobs for forced induction motors besides the common AFR?

 

Motown lite blocks are plenty tough and a shade chaper than the C5R blocks.

If it were me i would just take the extra 100 lbs on the nose of the car and enjoy the extra 3000+ bucks you're gonna save by going with the regular motown iron block.

Plus you could take the 3000 bucks and slap on an insane set of heads like dart's little chief 11 degree heads. Talk about some wicked power with a TT.

Also components are going to be cheaper going with the Gen I style motor. My vote goes to the motown steel block with the 427 components.

Nate

 

In my best most unbiased opinion (ok, my attempt at humor) I'd say stick with the Gen 1 motor.

Here's my top 4 reasons:
1.) The aftermarket support for a Gen 1 is unreal. Full tilt race parts are available all over the place and seem to be less expensive than the LSx stuff.
2.) Finding a good engine builder who is local to you and who knows the LSx is a little tough, but finding a good Gen1 builder who could assemble a top running Gen 1 while blindfolded is usually pretty easy.
3.) It'll be an easier fit into the chassis. As you stated, there are more turbo systems & such available for the Gen 1 than the LSx.
4.) The production LSx only has 4 head bolts per cylinder, the Gen1 has 5. Some boosted LSx's struggle with lifting the heads. I'm not sure if the C5R block has additional head bolts or not (something good to find out). If it doesn't have additional bolts, I think that can become a factor in how much boost you can run.

As to head flow, it is very important. A better flowing head will allow more air into the cylinder for the same amount of boost, and therefore make more power. You can compensate for poor head flow by adding more boost, but you're also adding additional heat (which makes the air less dense). Boost doesn't make horsepower, its the amount (quantity) of oxygen in the cylinder (with the correct amount of fuel) that makes power. So, make sure you do your homework when it comes to head selection.

Lastly, I'd check with Dart & World Products about how stong there alum blocks are. They should be able to tell you what it'll stand up to, and they may give you (if you push for it) some references of guys who are running their blocks in similar situations. If they'll give names & numbers, I'd certainly be calling and asking.

'Dreamin'

 

hmm.. my opinion in a nutshell:

if you're building a boosted motor, why go for a 427? your limited by the amount of power the engine/trans/rear/chassis can hold...

the ONLY thing the additional cubic inches add, is cost.




what are you building anyway?

a street car: get the LS1, and run mild boost on it.. (600rwhp-ish)

a full bore race car: the SBC with some SBC2.2 heads or 18 or 15 degree heads... a sheetmetal intake, and the large single turbo thats more efficent but apparently "less cool" then saying twin turbo.




in either case, going off just your post above (and i could be wrong) i highly doubt you have a full grasp of the total cost of either motor you're talking about building...

 

Yeah, I bet you're looking at somewhere north of $25k for the LSx motor (maybe significantly north of there). After all, the C5R block by itself is like $6k, and that doesn't include finish machine work, crank, rods, pistons, etc. I'd be that a serious set on kill shortblock (which you'd need / want for serious power) put together right by a competent machine shop is probably $10k plus.But that's just my guess. What exactly is your idea of insane costs?

I usually start my recommendations with "figure out what your requirements are" (how fast, etc, etc.) and go from there to "what's your budget support". Probably should have started there.

'Dreamin'

 

no im aware i can get deep into $35k for the motor....im all set up for the power..9", 35 spline axles, built T56, SFC and full suspension just need to get my cage installed and im done. oh and the most important thing...the engine. ya im gonna contact Mowtown about their aluminum block see what they say about them. thanks for the help.

 

okay maybe im the only one who thinks its weird to drop 35k on the motor for a 91z.... i mean yea if you have money in it keep it but having 50k+ on a shell thats worth 5k seems pretty ****** weird, unless youre a mad 3rd gen fan, for that much money you could just get a z06 and drop the remaining 20 in it, or but a sweet first gen get all c5 suspension etc, and you would have something that not only looks like a fast car but actually worth close to what you put in it once youre done......

but to each his own