1988 Chevy K5 Blazer build - An unorthodox approach

[BabyDiesel]

Picked up the TPI system today





All out of an 87 Corvette. The intake, plenum, fuel rails, adjustable fuel regulator, injectors, MAP & MAF sensors, distributor, and computer sans chip for $150.

If it was someone else who bought this for the same price, I'd call highway robbery lol.

I feel like it was well worth the money and can be easily resold if the need arises.

[elhigh]

Even if you can't make it into an Atkinson-ish, the much higher standard of the engine computer will open some tuning options.

Doesn't hurt that the intake runners are the business. Popping the hood on a Blazer and finding that bundle of aluminum snakes nestled around the V is NOT what onlookers would expect.

[BabyDiesel]

wmjinman -

Dunno how hard core you want to get about MPG, but my experience is that running at LOW rpms gives better mpg even if below the "efficiency peak rpm". But instead of getting lower gears and bigger tires, you can just get SMALLER tires. Again this would be a hard-core mpg play, not a "bad-ass looking truck" play, but smaller tires would also lower it and reduce aerodynamic drag.

Speaking of aero drag, depending on how much driving you'll do at highway speed, that is what will yield your biggest results (assuming the new engine runs well). And by "running well", I mean stock re-build - nothing fancy or exotic. You mentioned a bigger air dam. YES. take it down to the same height above the ground as the lowest hanging stuff under the car. Grille block: again YES. I got 2 mpg just from that. Block off as much as you can & not overheat. You might be surprised and be able to block almost all of it! Looking at your side mirrors.... again, for hard-core mpg and "screw the looks", how about getting some really small car mirrors on there? Then finally, build some sort of lightweight Kamm-back or boattail.

I know you are all into your engine mod ideas, but my experience is that as long as the engine doesn't run like crap and waste lots of gas because of that, the bigger gains will be from aero and hypermiling techniques. Of course, do the lightweight synthetic oil and remove all unneeded parasites running off the fan belt (and the fan itself, probably - replace with an electric one). And same thing with lightweight synthetic gear lube in the differentials, too. - and keep the tires aired-up to max sidewall or above.

Simple things like that will, I'm guessing, add up to more mpg improvement than the most exotic specially engineered high-efficiency engine would.

I'm reminded of MetroMPG's story (I think) about a 1st generation Honda Insight hybrid he got. Thing is - the battery pack was shot & he didn't want to buy a new one, so just disconnected all the hybrid-related stuff and got like 100 mpg out of it as a conventional gas car!!! See, it wasn't the exotic engine (hybrid system) that made the 1st generation Insight so great (although it helped - some), but instead, it was overall shape, size, and design of the car itself. I'll bet you could transplant just about any similar sized, modern efficiency gas engine into a 1st generation Insight and still get stunning mpg with it just because of the CAR, not the engine. So I say if mpg is your main goal, don't put so much effort into the engine, but instead, somewhere it'll REALLY help - like a boattail, air dam, grille block, etc, etc...

Thanks for the reply

It has come to my knowledge that lower rpms will be more beneficial for my purposes, despite the common perception that higher rpms are more efficient for these engines and trucks. 2 reasons that is so -

1) Reduced load due to aero mods

2) Lean Burn

I am serious about improving fuel economy... but I do wrestle with wanting to make the truck look good at the same time! Oh the agony! Smaller tires are a possibility. I really want to run 17x8-9 wheels with 255/75R17 (32x10) Goodyear SR-A's. I can get this setup pretty cheap, lower cruise rpms and increase FE and looks at the same time. The 17s will have more weight than my 15x8 wheels, but it does open up the possibilty of running LRR tires down the road.

I'm planning on doing the air dam and grill block soon after it is back on the road. The mirrors... ehhh, that will take time to decide to mod. Same with adding a small kammback, even though the K5s have an excellent setup for adding this. Removable wheel well coverings would be in order as well.

I pulled nearly 17 one time (not very scientific, I know) by driving to Greensboro and back. With a tired TBI 350 with 15w-40 oil and a 700r4 with no lockup. This is before I knew the awesomeness of coasting, and the only thing I did was keep it around 55 mph the whole time. I had learned to finesse the throttle to make it run near lockup rpm levels. Knowing this, I do want to focus on drivetrain efficiency as much as possible while everything is out. Honestly, I think I can hit 20 mpg with no aero mods. But they will make life easier, so they will be added after a baseline is established

I plan on full synthetics and minimal accessories. I'll have an alternator and a water and PS pump. Electrical fans are a must have. Shoot, I may run an electric water pump too... I'm just ready to get this thing back on the road!

[BabyDiesel]

Originally Posted by elhigh

Even if you can't make it into an Atkinson-ish, the much higher standard of the engine computer will open some tuning options.

Doesn't hurt that the intake runners are the business. Popping the hood on a Blazer and finding that bundle of aluminum snakes nestled around the V is NOT what onlookers would expect.

No doubt, good sir. I am looking into tuning myself with DynamicEFI with the help of GearHead EFI.com

Those intake runners are where the torque's bees knees are at! And yep, you got that right... it will look shhwweettt.

[BabyDiesel]

By the way, I called Comp Cams and they recommended the middle Tri-power roller cam for my purposes.

Here is a link to the cams --> COMP Cams: Tri-Power Xtreme™

I can't get past the top one's "Optimized Fuel Economy"! Either or will work though, but the gentleman suggested the middle one first, due to my engine having a 10:1 static compression ratio.

Does anybody think this is the right cam path? Or would a different cam be better?

[adam728]

If you are going to build the engine to be 10:1 compression, then yes, I'd go with what Comp suggested. With iron heads and the low rpm tuning of the TPI manifold that might still be pushing things in terms of detonation at low rpm, high loads.

To run the mpg cam on that link you'd likely want to run compression at no more than 9.0:1.

[BabyDiesel]

Originally Posted by adam728

If you are going to build the engine to be 10:1 compression, then yes, I'd go with what Comp suggested. With iron heads and the low rpm tuning of the TPI manifold that might still be pushing things in terms of detonation at low rpm, high loads.

To run the mpg cam on that link you'd likely want to run compression at no more than 9.0:1.

If I do remember correctly, the Light Duty TBI motors had a stock compression of 9.4:1 and they ran that itty bitty 166/175 cam with 112 LSA. The HD motors had 8.3:1 compression. Vortec 350's had 9.4:1

Here is a link to the info -> 95 LO5, Vin K, 5.7 TBI: Compression? - PerformanceTrucks.net Forums

My motor will have a 9.72:1 static compression with the present build, & and 8.103 DCR. So in theory! All should be well.

The key is the intake valve closing point

Edit: From what I can infer from Crower Cams website, the stock cam had roughly 10* of overlap and an excellent cylinder filling intake cycle. I do not doubt that the DCR was higher stock than will be in my build.

[adam728]

The HD engines are 8.75:1. The high output engine in the <7200 GVWR trucks was 9.4:1, you are right. I really thought there was less difference than that.

[BabyDiesel]

You would think so, being how they were both slug engines with good torque. The difference in the 2are 64cc heads vs. 76cc heads. I have the 64s.

I have thought about going with the 76cc TBI heads with true flat top pistons. Is this setup better than VR flat tips/slightly dished pistons with the 64cc heads? I'm trying to keep my quench as tight as possible.

[BabyDiesel]

You would think so, being how they were both slug engines with good torque. The difference in the 2are 64cc heads vs. 76cc heads. I have the 64s.

I have thought about going with the 76cc TBI heads with true flat top pistons. Is this setup better than VR flat tips/slightly dished pistons with the 64cc heads? I'm trying to keep my quench as tight as possible.