Fuel economy of 7.4L (454) powered 3/4 ton suburban

[pgfpro]

Oh Crap you just reminded me I need to add some antifreeze to my Talon.

Thanks!!!

[oil pan 4]

It looks like my big block engine has suffered a leaking head gasket due to overheating.

First do a post mortem on the heads to see if my lean burn carb tune was burning the exhaust valves. Just need to find my valve spring tool or buy another one, last time I used it was when I put together the diesel in 2009.
From what I can see I don't expect them to be burned.

So to fix this I am going to do a few efficiency up grades.
The #4 cylinder has had coolant leaking into it to for months maybe and had developed a nice cylinder taper. To remove the worn cylinder taper I will have the cylinders bored 0.03'' over (4.28 inches).
This means new pistons will be needed, going with hypereutectic alloy speedpro dome pistons to increase compression to about 11.1:1 with a 100cc head.
Then do file fitted rings since it worked so well for my diesel, with slightly reduced tension oil rings. (the diesel runs ultra low tension oil rings, cant do that on a gas motor)
Then have the block deck milled the minimum needed if its not perfectly flat.

The engine had a bit of a knock that had been going away, possibly due to cooler temperatures and thicker oil. I have never seen nor heard of a lower end knock "get better" or go away on its own.
So its going to likely need a new crank and at least a new rod or 2, if its not being caused by a piston.
I would like to reuse the connecting rods because the forged OE 80s truck rods are pretty tough, surviving in blown, nitroused or alcohol motors with out issues.
New crank will be a internal balance 4.25 inch stroked cast steel crank.

A problem with continuing to run OE style flat tappet cam shafts is the government mandating ever lower levels of anti-ware additives. To prevent grinding a lobe off the cam I will just go on ahead and upgrade it to a hydraulic roller cam, with appropriate roller lifters and put on roller rockers. Then I can run any government mandated additive depleted SM or SN rated oil on the shelf at walmart.

The edelbrock 650 carb was on the ragged edge of being able to support this motor. It would go really lean, as in off the scale, greater than an 18:1 a/f at WOT after several seconds. But its what I had and knew how to tune so that is what I used. I am going to go with a edelbrock 800 carb so I don't starve the engine for fuel.

Edit: when I took the motor apart I pulled the exhaust valves and they showed no signs of burning. So my lean burn tune is safe.

[oil pan 4]

For my next engine build I have already pulled it gutted it and stripped it.
My 7.4L engine had a bad head gasket. I could have just fixed it but that's lame and it had other underlying problems.

The problems,
The main problem was coolant in the oil from the head gasket. After the head was off I could see where the coolant was getting into the #5 cylinder.
So coolant had been leaking into the oil for months, maybe longer.
The was a slight knock from the bottom end.
The #5 cylinder had a lot of taper due to oil wash.
Some of the freeze plugs were paper thin they were falling apart when I was trying to pull them out, I don't know how they were not leaking. I am thinking some of them had been replaced at some point.

The cause of the knock appeared to be very well warn bearings on most of the rods, possibly caused by excessive main bearing clearance. Main bearings were not just warn they were eroded, likely do to oil starvation or just 31 years of running hard for 150,000 miles. The crank is slightly scored.

To fix up and reuse the old block I have pulled the engine almost completely apart. The machine shop will acid dip, bore +0.030 hone, deck, install new cam bearings in the block. Then determine new push rod length, reuse the stock rods, have the pins floated, new bolts and regrind the rod big ends. I found the old OEM truck rods with new rod bolts are actually more desirable than new cheap rods.

New stuff will be an internal balance 4.25 stroke cast steel crank, balancer and flex plate.
Piston are -17cc cast hypereutectic alloy, they are cheaper than forged and fit tighter in the bore than forged, I don't want piston rattling around in the bore when I start it up on cold mornings.
The machine shop will balance all the moving parts together. Just like I did with my diesel. I might balance the pistons, because its easy to do.

To boost efficiency I am going to bump the compression from less than 9:1 up to about 11:1, that should make things interesting.
Then my favorite, file fit moly coated rings to keep the air and fuel in the cylinder.
Aluminum oval port heads from GMPP or edelbrock at Scoggin and dickys in Lubbock. Going aluminum saves around 50lb and the higher heat transfer of aluminum will cooperate with the new much higher compression. I am going to use 110cc heads just for the fact that they are cheaper. Turns out only edelbrock makes the 100cc heads so they can charge what ever they want, everyone makes 110cc heads.
Then I am going to upgrade to a hydraulic roller cam and lifters. GM claimed going to a roller cam increased fuel economy by about 1 to 2mpg highway in addition to the oil additive issue.
Then for block heaters I am going to do exactly what I did with my diesel. Put double 600w block heaters, one on each side of the engine.
Then for the exhaust I have a pair of shorty 2nd gen Camaro headers to put on.

[Daox]

Sounds interesting. I'm looking forward to hearing and seeing more.

[Daox]

That is quite the bump in compression. Are you planning to still run regular vs premium fuel?

[rmay635703]

This project is really interesting, never noticed it before and I can say I had to read it end to end.

What bothers me is the auto. My 82 C-code 2wd diesel went from anemic performance and 21mpg to 28mpg (the 6 months it was left on the road) by swapping in an NV3500 5 speed, no need for an NV4500, the 3500 can easily be built to handle the 6.2 and its 100% drop in replacement for a 700r4, plus you will never again need to worry about flexplates or overheating.

Hell I could burn rubber while already moving with 2.73 gears in 1st, I could not ever do that even at a standstill when it was automatic.

Cheers
Ryan

[oil pan 4]

I am going to try and run regular gas because the price difference between RUG and premium now in NM is like 30 cents per gallon.
Then since we already know RUG and 11.1 to 11.3ish to 1 compression should go together find just driving down the road, but will never get along under high load I am going to fix the problem WWII style with water methanol injection. Hopefully a manifold vacuum switch and proximity sensor on one of the carb linkages is all the instrumentation I will need to turn the water methanol on and off.

Everything is at the machine shop. They should be able to at least get the cylinders bored this week.
I knocked out all the freeze plugs and pressure washed the bare block. They were very happy with this.
Then I will go over there or pick the block up and fit the file fitted rings. That could take all day. The machine shop doesn't want to waste time doing little things like this, they have bigger fish to fry like 50L 16 cylinder train engines and such. I am assuming they are train engines since the nearest navigable water way is at least 1,000 miles away.

[Daox]

Have you thought about using any of the ceramic combustion chamber coatings, or dry film lubricants for rotating internals?

[aerohead]

Originally Posted by oil pan 4

I am going to try and run regular gas because the price difference between RUG and premium now in NM is like 30 cents per gallon.
Then since we already know RUG and 11.1 to 11.3ish to 1 compression should go together find just driving down the road, but will never get along under high load I am going to fix the problem WWII style with water methanol injection. Hopefully a manifold vacuum switch and proximity sensor on one of the carb linkages is all the instrumentation I will need to turn the water methanol on and off.

Everything is at the machine shop. They should be able to at least get the cylinders bored this week.
I knocked out all the freeze plugs and pressure washed the bare block. They were very happy with this.
Then I will go over there or pick the block up and fit the file fitted rings. That could take all day. The machine shop doesn't want to waste time doing little things like this, they have bigger fish to fry like 50L 16 cylinder train engines and such. I am assuming they are train engines since the nearest navigable water way is at least 1,000 miles away.

We used to mix 'ADI' overseas,for the Douglas A-1E Skyraiders.It was only used at takeoff,the rest jettisoned in flight.
We used demineralized water exclusively.I don't know how critical this is but wanted to mention it.

[oil pan 4]

As far as dry film lube goes I may use some dry Teflon spray on the rod and main bearings, just like I did when I built my diesel engine.
I expect it to be long gone by first oil change.

I would try coating but this engine pull was a little unexpected and I need a fast turn around, normally I take as long as needed to accumulate parts and funds to do what I want. All the machine work, roller this and that, aluminum heads, conversion to internal balance if I had time it may not be in the budget at this time. If I pull the heads later on I may have them sent off to be coated.

I would really like to have full roller cam bearings but the time constraint does not allow it.

I am thinking I will just use -20'F windshield washer fluid which starts you out at 40% alcohol. If I need more than 40% I may boost it with yellow bottle isoheat fuel deicer. I have alcohol hydrometers so I can mix and remix it as needed. I would mainly use it for hard take offs and not jettison the leftover.

The freeze plugs look innocent enough but they were a pain to get out, a few of them were paper thin. Thought I might have to grind them out.

I just used a wood chisel, hammer and vise grips to rip them out.


They cast that into the block incase you don't know what it is.


They may look shinny in the picture but they are not. There are rust spots and cylinder bore taper.