Straight sixes and fuel economy

[jonrpick]

The one in my wife's trailblazer does just fine. They are rated for 270-290 hp depending on year, but it's at 6000 rpm. Mine never goes above 4500-5000 even in a 30-70 traffic merge. The only problem with them is that no one makes a tuner for the ecu. I'd imagine that it would be a pain to get the thing to run with the anti theft and emissions and whatnot. The makers of LS1/LT1 edit claim ( I sent them an email asking if they could support the 4200's ECU) that in 08 or 09 their software will be able to tune the computer, which would then make it a viable option.

They are very lightweight, and have a superior engine design. Just stay away from the early production engines (99 models). They had a problem with machining and the #5 cylinder liner would become dislodged and destroy the engine.

I wasn't sure if you were going for the aluminium head or not. But I definately see the build that you proposed working just fine.

The 4200's are going for great prices on eBay right now. Seen many under a grand, complete. I did some searching and did find examples of transplants into older cars, one of which was a '51 Chevy Fleetline (I think). Another was being swapped into an Austin Healey. So maybe somebody has figured out the ECM

I had to snicker when I saw the Healey. My Dad put a stroked SBC into his Healey back in the early 60's. He said it was the only car he'd ever driven that scared him.

 

[jonrpick]

I have built a number of inline six bangers. I have done performance builds on Chevy 250s and Ford 300. I could never get one to get much better gas mileage than a good running chevy 350
The last six i built was in my 85 ford Bronco The more performance stuff I added the MPG went down. It went from 17MPG stock to 15 MPG after 390 CFM 4 barrel carb, mild cam,4 bbl intake manifold, headers,mild porting on the heads, ignition, ECt. It ran great with plenty of power. But not too good in the MPG department.
Even the new 4.2 L I6s in the TrailBlazers dont do better than 18 MPG highway. Average MPG for them is around 14 MPG. The 5.3 V8 models get around 16 MPG very slightly less MPG than the 4.2 6
IMHO good gas milage and inline sixes dont mix. If you are looking for better gas milage build a V6 or better yet build a 350 with fuel economy in mind.
I get 18 MPG highway 14- 15 average in my old 89 TBI K5 with a 350 V8

I would be curious to see how you built them, as in specs... I've known a lot of folks to add on performance goodies, only to see their gas mileage--and "performance" decrease.

And by the way, I'm not questioning you knowledge or parts selection. I'm curious because I want to learn more.

My goal is to get at least the fuel economy I had with my 305. I could get roughly 17mpg on the highway when I had it. The 292 is close enough in displacement and that's part of the reason I chose it over a 250, plus it has the advantage of the very long stroke. This engine will see a lot of engine stand time (and possibly dyno time) before it ever gets installed.

I'm actually considering building a hybrid head as seen in Leo Santucci's book, but using Mercruiser 4cyl heads instead of Chevy SBC heads as the basis for it. If I get this new job (like I hope I do) I'll be working with welders and machinists, so getting it done shouldn't be a problem

 

[vortec]

I had to snicker when I saw the Healey. My Dad put a stroked SBC into his Healey back in the early 60's. He said it was the only car he'd ever driven that scared him.

speaking of what dads did long ago, my dad replaced the dead 327 (shoved 3 connecting rods through the block on the highway) with a fuel injected 283 (the 283hp version). i'm not sure if it was actually from a 'vette, but it moved that huge impala just fine and with better mpg than the 327. the only problem with the 283 is that they are oooold. i found some really nice onces at swapmeets in the last few years, but they were mostly carbed.

 

[jonrpick]

speaking of what dads did long ago, my dad replaced the dead 327 (shoved 3 connecting rods through the block on the highway) with a fuel injected 283 (the 283hp version). i'm not sure if it was actually from a 'vette, but it moved that huge impala just fine and with better mpg than the 327. the only problem with the 283 is that they are oooold. i found some really nice onces at swapmeets in the last few years, but they were mostly carbed.

I'm pretty sure the SBC my Dad used also started out as a 283--he thought so. I'm not sure what they used as the basis for the stroker kit, but he said he broke 2 axle shafts with it!