Inliners International Forums General Discussion Engines 250 Build ?'s

Hey guys,

This is my first post I just joined. I have been looking for info on Chevy 250's and found this place which looks awesome for tech. I am planning on building a 250 I-6 for a project that is probably not the norm around here.

I am going to start building a tube chassis rock crawler next summer hopefully. I am a guy who likes to be different so I want to use a I-6 so I can have some fun with the V8 guys and turn a few heads. I know I can get an I-6 to preform as well as most of the V8 guys. The rockcrawler will weigh 3000-3500lbs, 40"+ tires, big axles, low low gears. I need to build a motor with great lowend torque but I also need it to have a little topend. How high can you rev an I-6 safely?

I am not totally familiar with all the hotrod parts for 6's but this is a little list I have started. Tell me how this sounds and what you might change/do. I want this to run on low octane pump gas so would 8.5-9.0:1 be a good ratio?

I would start with a good rebuilt motor & add:

Offy 4brl intake adapted for TBI
TBI injection (any good info?)
Roller Rockers (necessary?)
Header (what do you recommend?)
Comp 260H cam

What else would you recommend? I am not a huge motor junkie & know less about I-6's then I do V-8's so all help is greatly appreciated.

Harley

Now this sounds like a fun project.

Like Walt said most will suggest the 250 or the 292. The Jeep thing would be cool and probably has good roots in the off road world. The Jeep FI would be easier if you buy that running 4.0 FI and use the parts.

OK, I like to be different too. How many rock crawlers do you see with a Chevy I6? Humm?

The 292 would be my choice for torque, although my 235 when it had granny low, would spin the tires on concrete when pulling a tree stump while idling. This suggests any Chevy I6 with low gears.

As far as hi revs, I have seen a 292 dragster do 9.7 in the quarter mile at Sacramento Raceway on a bad run, it had to be turning some revs.

I would use TBI because it is way simpler than MPI and will be just fine unless you are looking for max power.

The Clifford 4BBL manifold may flow better the the Offy, Ive used both.
TBI, Holley.
Roller rockers, not nessesary.
I would use light weight tube headers, probably make them myself.
I would get at least a 272 grind, it's not a street vehicle.
I would add MSD ignition for low end torque.

Just my 10 cents

Luis

I am pretty sure I am going to use the 250 I-6 in my build. I have liked this motor for awhile. A good buddy has one in his 66' Chevy C10 and it does great and takes a beating with no problems. I may use a 292 if I found the motor cheap & somewhat built, or the Ford 300 depending on where I steal my transmission from & price.

I am not up on all the motor stuff but I am mechanically inclined. I just don't keep up with the hotrod parts & racing scene. I have done motor swaps, MSD ignition, & I did install Tuned Port Injection in my 85 GMC offroad truck inplace of the old carb, so I do have experience with MPFI but I want to KISS (keep it simple) this rig with with TBI.

MSD & HEI will be going on this rig. I forgot to mention that. I had good luck with it in the past & it helped my carb alot.

The 272 looks like a good grind. It sounds like it will offer good lowend and some decent midrange also.

The Chevy I6 will definilty be different that is why I want to use it. People use Jeep I6's in the rocks already but I havn't seen any Chevy's and definilty not in a full custom rockbuggy. I am a Chevy guy and fourwheel with Chevy guys so I want to stick to my knowledge and roots too.

Harley

The offy intake will give you more low end torque, better throttle response hands down I had them both also.

Yes the Clifford does & will flow more, but it will kill your torque!!!

MBHD

MBHD,

I have to agree better throttle response. It just hit me, my Clifford is in my 235 and runs good but it has always been a bit soft on off idle. I could use a smaller runner intake. This may be a good upgrade in my case. Offy doesn't make a 235 4BBL intake. Scary to think if the Clifford is killing my torque, what it would be like with an Offy.

Does anybody other than Clifford make a 4BBL manifold for the 235?

The 300 Ford is a heck of an engine, but I am a Chevy guy also.

When you get this off the ground, post some pics.

Luis

You may wanna gaze over at the ford 300, and speculate. Readily available with OE efi, plenty of low end grunt. If it can tow a heavy load via a full size truck, it would have no problems motivating your buggy. Find the right low mile efi engine, you'd save some cash, not spending cash on aftermarket parts to pep up that 250.

Just a thought.

Back to your 250, a little more compression probably wouldnt hurt anything, for what your after.

Keep us posted as you go, sounds like an interesting project.