High MPG SBC Build

[thirdstreettito]

Well, my 88 TBI 350 with 146K miles gets 12mpg city. Pretty sucky eh? It needs at least one head gasket. I was planning on swapping the heads/intake over to Vortec stuff when I do the head gaskets. But I think I may just rebuild the engine. I want MPG's. When I do the engine I plan on installing my TB spacer, injector spacer, adj fuel reg, and a TBI rebuild kit.

From what I've read so far, high torque engines get better MPG's than high hp engines. I hope to achieve 15mpg city at least. I'm planning on doing .010 over, but I'll find out when I get the engine out if that's enough, as I cant see cylinder wall damage/wear until the I get the engine apart.

So my question is, how would you build this engine? It MUST be in total under $1000.

I was thinking, Sealed Power .020 over engine kit with hypereutectic pistons and an ISKY 262 supercam. I dont know about pistons tops though, dome? flat top?

I also dont know about rod bear undersize, I am new at the specifics.

I was thinking one of these kits - http://www.summitracing.com/search/b...Asc&rsview=SKU

[blackedoutharley]

Given that you're trying to work within a limited budget I would suggest a .030" kit being that this is the most popular oversize and as such the parts are mass produced keeping cost down.
For pistons I would go with a flat top with the valve reliefs also in interest of cost.
For bearings, assuming your crank is good you would probably be able to go .010" under on rods and mains with no issues and parts are again readily available.
For the cam I would stick with something that is fairly mild and the Isky cam you mentioned would probably do well... I think that you will find most of the money is tied up in the heads and machine shop labor.

Northern auto parts does offer a nice rebuild kit with nearly all the parts you would need at a good cost. There is no need for expensive forged pistons for what you're trying to accomplish.

[fastwillie 696969]

i would go with a master kit here's a good place for kits ,https://shop.enginekits.com/osb/itemdetails.cfm?ID=522

[Marv D]

Be cautious here,, 88 TBI, I am 99% sure has the 'swirlport' heads and a -22cc dished piston. You change things around to a flat top and you will make the stock 8.6:1 become 10.6:1 in a heartbeat and your computer will go NUTZ!!! I likewise don't think the computer is going to like a cam with more than 195- 205° duration at 0.050" (closer to stock) .
Your going to have to have a custom chip burned for the OBDI computer and even blanks are getting hard to find from what my computer guy keeps telling me (but could be a stall because this guy is frickin Sloooowwww,, 18 months and 3 chips to get this TBI 383 of mine fine tuned)

Myself,, if you are strictly MPG oriented, you better stick to the stock setup and keep with the thought of putting new surfaces where needs to be new surfaces and not change the configuration / calibration.

From what I've read so far, high torque engines get better MPG's than high hp engines

That statement is somewhat of a oxymoron. Horsepower is nothing but an equation of torque and time. (time being derived from the RPM's)
Formula is: (torque*rpm)/5252 = HP
i.e.
300 pounds of torque at 1000rpm is 57 horsepower.
300 pounds of torque at 5000rpm is 285 horsepower.

TORQUE is the power that twists on the driveshaft and make the hulks move and accelerate. Making torque in your USABLE rpm range is all you need to be interested in. With the swirlport heads your foolish to even think about any rpm over 3800-4000. So you want to build and cam your motor concentrating on idle to 3800. This is going to be a SHORT duration cam (like stock). Sometimes it's hard to improve on the R&D done in Detroit

Fust a FYI, I believe the 88-94 350 made 190 HP,, it was all about torque from idle to the mid 3000rpm range.

[thirdstreettito]

Originally Posted by blackedoutharley

Given that you're trying to work within a limited budget I would suggest a .030" kit being that this is the most popular oversize and as such the parts are mass produced keeping cost down.
For pistons I would go with a flat top with the valve reliefs also in interest of cost.
For bearings, assuming your crank is good you would probably be able to go .010" under on rods and mains with no issues and parts are again readily available.
For the cam I would stick with something that is fairly mild and the Isky cam you mentioned would probably do well... I think that you will find most of the money is tied up in the heads and machine shop labor.

Northern auto parts does offer a nice rebuild kit with nearly all the parts you would need at a good cost. There is no need for expensive forged pistons for what you're trying to accomplish.

Thanks, also I said hypereutectic, not forged lol.

Originally Posted by fastwillie 696969

i would go with a master kit here's a good place for kits ,https://shop.enginekits.com/osb/itemdetails.cfm?ID=522

Thanks for the link, but I dont see any brands there, I'd rather know who/what I am buying.

Originally Posted by Marv D

Be cautious here,, 88 TBI, I am 99% sure has the 'swirlport' heads and a -22cc dished piston. You change things around to a flat top and you will make the stock 8.6:1 become 10.6:1 in a heartbeat and your computer will go NUTZ!!! I likewise don't think the computer is going to like a cam with more than 195- 205° duration at 0.050" (closer to stock) .
Your going to have to have a custom chip burned for the OBDI computer and even blanks are getting hard to find from what my computer guy keeps telling me (but could be a stall because this guy is frickin Sloooowwww,, 18 months and 3 chips to get this TBI 383 of mine fine tuned)

Myself,, if you are strictly MPG oriented, you better stick to the stock setup and keep with the thought of putting new surfaces where needs to be new surfaces and not change the configuration / calibration.


That statement is somewhat of a oxymoron. Horsepower is nothing but an equation of torque and time. (time being derived from the RPM's)
Formula is: (torque*rpm)/5252 = HP
i.e.
300 pounds of torque at 1000rpm is 57 horsepower.
300 pounds of torque at 5000rpm is 285 horsepower.

TORQUE is the power that twists on the driveshaft and make the hulks move and accelerate. Making torque in your USABLE rpm range is all you need to be interested in. With the swirlport heads your foolish to even think about any rpm over 3800-4000. So you want to build and cam your motor concentrating on idle to 3800. This is going to be a SHORT duration cam (like stock). Sometimes it's hard to improve on the R&D done in Detroit

Fust a FYI, I believe the 88-94 350 made 190 HP,, it was all about torque from idle to the mid 3000rpm range.

I am swapping the heads to 96-00 Vortec heads, I did forget to mention that the comp would need to be programmed. How much does it cost to get a it reprogrammed?

My inspiration is this:

YouTube - ‪LKN Speed's TBI 350 idle...

--

YouTube - ‪TBI 350 truck dyno...

Also, if this helps, the specs of my TBI 350 are:

L05-350-5.7L | 210hp | 8.3:1 C/R | Cam 0.50 : 194/202 - .385"/.403" : LSA 112 | 55lb/hr injectors

[thirdstreettito]

Also, what kind of timing chain set should I get? .275/.285 Tooth width? .400/.410 tooth width? What does each do?

[Marv D]

The OBD1 isn't a simple 're-program' it has to have a new prom. The problem is finding someone worth a crap to do it. I had Howell engine managment do the first,, it was CRAP, they redid it once, still not even close (was getting 8mpg with a 383 small block,, NOT close!!) Then found a guy in So.Cal., but he's a flake with problem,, but is a damn genious with these things. Has been 18 months tying to get it right (on the 3rd prom but at least now it's going into closed loop and getting 16mpg empty, 10-12 pulling a enclosed trailer,, Just a drivability issue at low rpm throttle angle)

First chip was $350 (trashed) greedy bastages with little customer support was my experience with them.

Second guy wants $500 when he get's it right. (+ cost of blank proms)


I don't think anyone said this is going to be cheap

[thirdstreettito]

So much for making it easy. I guess a 5.3 swap would be cheaper and easier. Pooey.

[Pop's C-10]

you'd be waisting vortec heads bolting T.B.I. motor..

[djracer]

Originally Posted by Pop's C-10

you'd be waisting vortec heads bolting T.B.I. motor..

Where does this statement come from? I always run vortec heads on warmed over small blocks. I have had a couple that ran way good. One was a 350 the other a 377.

Marv who did you deal with at Howell? Troy Brown at Howell has done a few chips for me.

[Marv D]

I can't remember kids name Kevin, only thing receipt says is Jennifer which I'm sure is accounting. Sent the guy a complete build sheet for the motor, and the VIN and he pulled up the factory chip. First chip would run, but billowed black smoke and BEST I got empty on the HWY we figured was 8mpg. Put about 1000 miles on it trying everything from adjustable regulator in the Holley TBI unit, to a chassis dyno. Was PIG fat and would never go closed loop. Washed the rings and had to hone and re-ring. Called and they insisted chip was right. Faxed a printout of the log from a Equis scaner. Never bothered to return my call. I washed my hands of em.

Found this OBD1 geek through my machinist (had written a number of ships for them) and the were raving about how great he is. Guy is 'sidetracked' but first chip was a billion % better than the Howell. Mileage went to 13mpg, was adjusting fuel in closed loop, Has a small 'flat spot' in low RPM's and he's working through it. Keep having me send the logs from the Equis scanner and he's on chip 3 getting it 'perfected'. Right now it's running like a CHAMP . He's slow as molassas in January getting things finalized. Not complaining, he isn't asking for a penney until it's perfect!

[thirdstreettito]

Yeah, I'm lucky enough to have a world class machine shop 8 miles from me and a TBI specialty shop 160mi(yikes) from me. I will have to call them and see what their prices are.

[thirdstreettito]

Ok, so here is a breakdown of the engine rebuild kit.

Chevy 350 Vin-K Truck TBI 1987-1990
MainBrgs: .10
Pistons: .30
Rings: .30
RodBrgs: .10
HypereutecticPistons: pistons flattop # H345ACP + $52.32
CleviteBrgs: clevite brgs + $14.71
OilPumpShaft: High Volume oil pump shaft w/steel pin sleeve + $7.99
FrostPlugs: brass + $9.10
Gaskets: FelPro #260-1269 + $31.91
MolyRings: moly .200 deep oil ring groove used with aftermarket pistons + $13.86
Camshaft: Comp #12-388-4 1000-5000 RPM 252/262 adv duration .425/.440 lift. Computer Compatible for use with TBI and Crossfire F.I. + $124.05
CompLifters: Comp Lifters + $57.08
piston: flattop

Northern Auto Parts P/N: EK1088

What do you guys think?

Other things I would buy would be the vortec heads/intake, new plugs(stock A/C Delco?), $250 Howell PROM, or go to the TBI shop here in NC and see what $$ they want to do it.

Can you guys think of anything else?

Thanks, Bradley

[djracer]

Bradley
When you order the kit make sure to get them to upgrade to vortec intake gaskets. Personally until you tear the motor down I wouldn't order the over sized pistons. If the block doesn't need to be bored I wouldn't bore it. You need more clearance on hyper pistons than cast or forged anyway so chances are you can save that money. Machine work is not cheap anymore. If you do deal with Howell don't talk to anyone but Troy Brown.

[djracer]

Marv,
Do you have your map vacuum coming from the front of the tbi? The holley tbi's are different than the gm. Make sure the map sensor is mounted higher than the port and make sure you have no droop in the vacuum line going to it. It took me a year to get my 377 to run any better than my 240k stock 350. It ran pretty good when I got it all sorted out. It went 9.20's in the 1/8 and 14.50's in the 1/4. It did pretty good burnouts too. LOL

[thirdstreettito]

What do you mean hyper's need more clearance? You mean they shouldn't be a super tight fit in the cylinder?

Also, could someone give me a list of tools I will need? So I can buy what I dont already own. That would help a lot!

Thanks, Bradley

[djracer]

Talk to your machinist but yes that what I mean is the piston to wall clearance I believe is more with hyper pistons. Are you gonna assemble the motor yourself?

[thirdstreettito]

Thanks Kevin, yes I plan to do it myself, I can't afford to pay someone to do it. I'll of course buy a book(any suggestions?).

[Warrens69GMC]

Why not go with a roller cam?

[thirdstreettito]

I thought that's what I was going with. You mean a solid roller cam? Dont you need solid lifter for that?

[Warrens69GMC]

12-388-4 = Hydraulic flat tappet

http://www.summitracing.com/parts/CCA-12-388-4/

[Pyrotechnic]

The cost/benefit ratio of tuning those TBI computers seems to be a pretty bad deal.

I would recommend going with a Megasquirt swap. I've seen them done where they use the connector from the stock computer to make the Megasquirt a direct plug-in to the stock harness.

For less than what having a single chip burned will cost, you can have a computer that is way ahead in technology, but most of you all, you can actually tune it yourself with a laptop for FREE. No hassle with burning chips.

[thirdstreettito]

Originally Posted by Warrens69GMC

12-388-4 = Hydraulic flat tappet

http://www.summitracing.com/parts/CCA-12-388-4/

That obvious what the link is. What are you getting at?

[Super73]

Originally Posted by thirdstreettito

Ok, so here is a breakdown of the engine rebuild kit.

Chevy 350 Vin-K Truck TBI 1987-1990
MainBrgs: .10
Pistons: .30
Rings: .30
RodBrgs: .10
HypereutecticPistons: pistons flattop # H345ACP + $52.32
CleviteBrgs: clevite brgs + $14.71
OilPumpShaft: High Volume oil pump shaft w/steel pin sleeve + $7.99
FrostPlugs: brass + $9.10
Gaskets: FelPro #260-1269 + $31.91
MolyRings: moly .200 deep oil ring groove used with aftermarket pistons + $13.86
Camshaft: Comp #12-388-4 1000-5000 RPM 252/262 adv duration .425/.440 lift. Computer Compatible for use with TBI and Crossfire F.I. + $124.05
CompLifters: Comp Lifters + $57.08
piston: flattop

Northern Auto Parts P/N: EK1088

What do you guys think?

Other things I would buy would be the vortec heads/intake, new plugs(stock A/C Delco?), $250 Howell PROM, or go to the TBI shop here in NC and see what $$ they want to do it.

Can you guys think of anything else?

Thanks, Bradley

Originally Posted by Warrens69GMC

12-388-4 = Hydraulic flat tappet

http://www.summitracing.com/parts/CCA-12-388-4/

Originally Posted by thirdstreettito

That obvious what the link is. What are you getting at?

He is telling you that the cam you plan on using is a hyd flat tappet according to Summits web page. IE the link he gave you is a link to summits web page with that part number. I highlighted it in red for you.

[C-10 simplex]

As someone who has done/is doing scientific testing regarding mpg (will provide links later maybe) i would suggest based on your plan(s):


1) concentrate on actually saving money on gas first before anything else; i.e., mobil has/had a card that offers .15 off pump price. This is fast easy cheap way to save on gas. If that is no longer available, there are a slew of credit cards that offer 1-2 maybe higher % off any purchase. Also, look into a sam's or costco membership.

These 2 things alone may account for up to $2 off every fillup. This is immediate savings requiring no investment. (i know sam's and costco require a membership fee, but i'm talking about the credit cards)

2) Based on recent observations, aerodynamics really helps. In fact, i think it's more important than weight reduction. i just apparently jumped about 1.5- 2 mpg just by adding a tonneau cover. i think aero is much cheaper and easier than engine work.

3) Don't be too quick to condemn the engine. Of course a 350 in a truck isn't not the ideal combo for high fuel mileage. While it's true that you can make big gains by switching engines altogether or modifying one, it's all about the total combination AND i think there are better (cheaper) ways to improve mpg first.

My point is do other stuff first, THEN work on the engine because the payoff is better with other things.