1988 Chevy K5 Blazer build - An unorthodox approach

[BabyDiesel]

I am finally posting up this love of mine the ball is finally starting to roll with regards to getting it back out on the road. Here is a picture -



It is the only one I have at the moment. I miss this beast... been down with a blown motor for over 2 years

Here are some stats on the K5:

350 TBI engine, stock but blown
700r4 transmission, stock & needs rebuild
3.73 gears
1/2 ton open axles
5200 lb. weight
~0.6 Cd


By the title, you know that I am planning something slightly unorthodox. But what is it

I want to build a Miller/Atkinson cycle SBC
Why? for better fuel mileage of course!

If you have ever heard of the Crower Mileage Maker system, then you done and know what I am attempting to recreate. For those that do not, the Crower Mileage Maker system came about in the late 70's to early 80's. The system utilized high compression (some say as high as 17:1!) and late intake valve closing, thereby bleeding off cylinder pressure. You are left with with less of a dynamic compression ratio, but the expansion ratio and efficiency are greatly improved. This is similar to what is going on with the Prius and SkyActive Mazda engines.

I have plans for either a 355 or a 400-406 small block. Flat top pistons are to be used because personal research has shown that flat tops promote better flame travel than domed pistons. Which is critical for good combustion. I plan to use either one of these heads -

193 TBI heads; 64cc

350 Vortec heads; 64cc

305 Vortec heads; 53-58cc

Some aluminum Corvette heads on CL; 58cc

All the above heads have 160-180cc intake ports to keep air velocity up for more atominization of fuel particles and low-end torque. The combustion chamber of all these heads will keep the compression up and promotes better burn. If needed, the heads will receive a mild port and polish.

From using CSG's compression calculator, a 355 (0.030 overbore) with a compressed head gasket thickness of 0.035 with 0 dish and 0 deck clearance have the following compression ratios:

53cc - 13.06
58cc - 12.14
64cc - 11.2

A 406 (0.030 overbore) will have:

53cc - 15.43
58cc - 14.35
64cc - 13.24

All of which seem to be able to work... except the 53cc's on the 406 lol.

I have not worked out the specs for the camshaft. I know that the dynamic compression ratio will have to be greatly reduced in order to run 87 octane. If anybody has the slightest idea, I would love you to pieces to share your wisdom! I will have Crower or Elgin do me a custom cam.

This is all I have as of now. Trying to type this up before class has got me slightly scatterbrained and I know it seems like I jumping all over the place. I get excited thinking about the possibilities

If anyone has any questions, objections, praises for wanting to try this out, or reason for not doing this, feel free to post away. I'm thick skinned and can take any heat y'all provide

Let the discussion and build begin

[JRMichler]

I like it. Is there any way to get some baseline mileage data?

I've had idle thoughts of doing something similar to my truck. I could easily tolerate 30% less power (and torque), and still get all the towing/acceleration/hill climbing performance that I need.

[Big Dave]

First order of business would be to contact Crower. I’d bet there is some old head in the Engineering Department that knows a thing or two about the Mileage Maker. He will save you a lot of expense and head-scratching. The degree to which the valves are left open will greatly affect the needed nominal combustion ratio.

In essence you are making a Chevy Prius engine. We all know they work. Atkinson engines are efficient but they lack torque. No big deal on a hybrid – the electric motor makes up the difference. You can get it back with displacement or live with less torque.

Since your 350 is blown maybe you should think of raiding a junk yard for a LS-series engine out of a later-model Chevy pickup. I have a 96 Impala (second gen 350) and even for it parts are becoming a bit of a challenge but LS-series parts are easy to come by. Get a 4.8 liter (LR4, LY2, or L20) and try to find a later model 6E80L tranny. More speeds generally equals better MPG. This lets you ditch the hunk of junk 700R4. Get the unified control brain and it becomes plug and play.

Off-roading with a torqueless Atkinson engine will be miserable. You are out of heavy snow country so I’d think about declaring the vehicle a 4x2. Gut the front diff, remove the transfer case (hundreds of pounds and a maintenance problem, plus worth a few bucks recovered for other stuff), put a 4x2 tailshaft on the transmission.

As you mention “class” I assume you are a student and don’t have much money, but something your vehicle affords you (for later on) is an aero option. Your top can be easily removed (and sold). Lay up a “fastback” top (see all the threads on aerolids for pickups. Learn to work ABS and make some fender skirts fore (a la basjoos and aerohead) and aft. Maybe a grille block. An 0.6 Cd is a tough number to fight. I’d bet a 12 degree aerolid, a grille block, and skirt of all four might knock you down to Cd = 0.50.

Even when new, I’d be astonished to hear this vehicle got better than 13 MPG. Lots of scope for improvement and at the end of the day you wind up with a roomy and sturdy vehicle.

[BabyDiesel]

I have just sent an e-mail to Crower asking for information on the camshaft specs. Here is the message -

"Good afternoon Crowder Cams! I am looking for information on the camshaft that came with the Crower Mileage System back in the late 70's - early 80's. If by chance the person reading this does not know what I am talking about, could they please ask around and see if someone might know? If the information can be collected, I will be buying a custom ground camshaft from Crower in the near future. Thank you and have a blessed day!"

Hopefully the declaration of giving them my cash will produce desirable results

JRMichler - The EPA estimates for a 1988 K5 Blazer are 11 city/16 highway with a combined average of 13. I do remember that my tanks averaged 14.25 - 14.75 with country driving. This is without knowing anything about eco-driving and having an occasional pedal-metal moment Best tank ever was 16.7 mpg (55-60 straight trip from Greensboro, NC to Four Oaks, NC. Minimal stops). I am with you with needing less power. The math says I will have 4.3 V6 power, with slightly more torque. I can deal with that with better FE!

Big Dave - You know exactly what I am going for The LSx swap is a verryyy tantalizing option that I have considered and even had suggested. It just is not viable at this point. I am a student and money is tight, so I am stuck working with what I have which isn't exactly too bad. I would love more gears (ahem, new 8-speed auto) though one place the 700r4 shines is its ability to coast long distances.

Case in point, my mama's Trailblazer (4.2, 4L60E, 4x4) will coast farther in gear than my ZX2 will in neutral! Coasting ability is what has net me the biggest gains so far. I know the TBR is "slippier" than the K5, but it is still a barn with curved corners

I had not thought about the 4x2 option, nor the ability to put an AeroCap on the Blazer! I will try to see what I can do in stock form and go from there in the future. Off-roading would suck with a torqueless motor... if it wasn't for 4-lo! That should compensate the loss of off-idle torque considerable. Almost 2:1 more torque multiplication.

And I will be glad to hear of your astonishment after you read what kind of FE I orginally got

[BabyDiesel]

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More pictures of my K5 from back in the day!

[BabyDiesel]

Me and my daddy had a discussion about the rebuild. He is adamant about dropping the 400 SBC idea completely I see his point in the matter. It will be cheaper in the short and long run to build up my 350. So a 355 Chevy Prius engine it will be!

I am wondering about which heads to use on this motor. I have narrowed it down between the 193 TBI heads and the 305 Vortec heads. The 193's beat the Vortrecs out in 2500 rpm & below torque production. The Vortecs have a better and smaller combustion chamber, and flow better. Both are cast iron. I have the 193's, but I can get the Vortecs @ $150-250. And sell the 193's as john boat achors lol

What say you???

I have read here --> http://ecomodder.com/forum/showthrea...4-a-22944.html & it appears that my cruising rpm might be on the low side. I will turn from 1350-1550 in usual 45-55 mph fashion. Will this be too low of a rpm for the motor to function correctly? If so, then should I regear or switch out transmisions with a TH350c?

I do know that I will be utilizing lean burn on the K5. There appears to be a deactivated setting within the computers that will allow the A/F ratio to go to 17.5:1 during light cruise. I will have to speak with a tuner and 1983ChevyVanG20 over on the Chevy forums to find out more about this.

I will be adding EGR back... yes, I believed the lie that EGR cost you power and mpg back in high school. I have since wised up and learned the truth. In fact, I would like to increase my EGR flow if possible! How could this be accomplished? A 454 EGR valve in place of the 350 one? Any pointers?

I feel certain that 20 mpg will be regularly attainable when it is all said and done.

[hondaguy72]

I'd use standard 5.7 vortec heads milled for compression and the 700r trans.

[dirtydave]

I love this truck! The full size blazers are dope AF! I cant wait to see what you can do!

[vskid3]

Awesome project, I've been wondering what the real world gains would come from atkinson-izing a regular engine in an existing car.

For the valve timing, I seem to remember that there was some discussion about figuring how the valve timing affected the compression ratio in the thread about swapping a Prius engine into a Toyota MR2. http://ecomodder.com/forum/showthrea...fxe-27266.html Probably worth at least a skim through.

[dirtydave]

Wouldn't a V6 swap get what you are looking for* without all the hard work?

*still a K5 V8 20mpg is bad ass.