85 fuel economy and IMPROVEMENT?

Disable the secondaries will be the first way to keep mileage up, if he complains you know I was right if he doesn't you don't need to fix them anyway. Target about 2k rpm interstate speed via gear/tire size, compression increase like mentioned before, ditch the stock exhaust cat included if possible. Everyone says long tube headers increase low end performance also, not sure how much 15 tq will be noticed in a 4k + lbs truck. Above an beyond everything else make sure it has a good tune up.

All three of my trucks, 81 inline 6 1/2 ton, 76 454 3/4 ton and 74 350 3/4 ton (all longbed single cab) get between 8 and 14 miles per gallon loaded or not. It's just what it is.

4WDKC said:

Disable the secondaries will be the first way to keep mileage up, if he complains you know I was right if he doesn't you don't need to fix them anyway. Target about 2k rpm interstate speed via gear/tire size, compression increase like mentioned before, ditch the stock exhaust cat included if possible. Everyone says long tube headers increase low end performance also, not sure how much 15 tq will be noticed in a 4k + lbs truck. Above an beyond everything else make sure it has a good tune up.

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That is a thought worth considering...
I have the 2k rpm thing down now. What is the easiest way to increase compression? Plan is this will stay in the family a long time...so costs will have a good bit of time to pay themselves off but I don't want to go crazy.

Lastly,
I know Q-jets have a reputation for being better at sipping gas. Does anyone have concrete evidence of this...checked foul economy improving after a carb swap?

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Kenneth W Larew said:

That is a thought worth considering...
I have the 2k rpm thing down now. What is the easiest way to increase compression? Plan is this will stay in the family a long time...so costs will have a good bit of time to pay themselves off but I don't want to go crazy.

Lastly,
I know Q-jets have a reputation for being better at sipping gas. Does anyone have concrete evidence of this...checked foul economy improving after a carb swap?

Sent from my SM-G955U using Tapatalk

Click to expand...

different heads or new pistons will be the biggest gains, a thinner gasket will help some. Not sure how long it would take to "break even" on the swap for better mileage.

HotRodPC said:

I'll also add, the reason GM put taller gears in the 80's trucks, like 2.56's and 2.73's, wasn't for fuel economy. They'd hoped that happend too, but the main reason was emissions. The gubment put fleet requirements on the manufactuers. Both mpg and emissions output on average of their entire fleet for 8599 GVWR and lower. So the ones that ran a bit dirty, had to have some that ran cleaner to bring the average amount of pollutents down. They did this by running taller gears and keeping the rpms down. This is also why the Feds started the 55mph speed limit. Notice the 8600 GVWR 3/4 ton trucks didn't have to have Cats and still had the lower 3.73 and 4.10 gears ratios. I don't think the 3/4 and 1 tons got Cats until 1987. The half tons started getting Cats in the 70's sometime.

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81 I think to be fair but I am not 100 % certain. All I know is my 1977 Jimmy had none but I have found that K5's differ from the trucks in a few minor ways when it came to emissions.

Thank you.

You can economically increase static compression by simply changing head gaskets.

Enter the Fel-Pro #1094.

No other changes to do THAT. Simply change the gaskets from the factory 0.41 compressed thickness to the 0.15? of the 1094. That engine's factory compression is DISMAL, at best. 12cc dished pistons allow a lot of room to improve.

Outside of that...

Headers are a MUST -but smaller ones. 1.5" primary with 2.5" outlet. 0.625 is overkill and wildly unnecessary for MOST street cars/trucks that use them. Two pipes connected as close to the engine as (reasonably) possible. 2" diameter exhaust pipe(s).

This IS A recipie for low speed torque. Improve the induction and the exhaust. That doesn't mean it has to be flashy or loud...or expensive.

2 bbl carbs are harder and harder to find...I would run a ONE BARREL if I didn't have any money and didn't want to think I was going fast...but that's likely a tough sale around here.

Good luck!

Rusty Nail said:

Thank you.

You can economically increase static compression by simply changing head gaskets.

Enter the Fel-Pro #1094.

No other changes to do THAT. Simply change the gaskets from the factory 0.39 compressed thickness to the 0.05? of the 1094. That engine's factory compression is DISMAL, at best. 12cc dished pistons allow a lot of room to improve.

Outside of that...

Headers are a MUST -but smaller ones. 1.5" primary with 2.5" outlet. 0.625 is overkill and wildly unnecessary for MOST street cars/trucks that use them. Two pipes connected as close to the engine as (reasonably) possible. 2" diameter exhaust pipe(s).

This IS A recipie for low speed torque. Improve the induction and the exhaust. That doesn't mean it has to be flashy or loud...or expensive.

2 bbl carbs are harder and harder to find...I would run a ONE BARREL if I didn't have any money and didn't want to think I was going fast...but that's likely a tough sale around here.

Good luck!

Click to expand...

Thanks...lot of good info to work with there!

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*edited to correct 0.15 and 0.41 thickness*

Rusty Nail said:

No other changes to do THAT. Simply change the gaskets from the factory 0.41 compressed thickness to the 0.15? of the 1094. Th

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I looked those gaskets up after you said that. And you were right. Good reviews saying noticed a difference. So for $48 a set is not bad. Nice info.

I know it isn't. 015 thick but still good call on those.

Rusty Nail said:

Thank you.

You can economically increase static compression by simply changing head gaskets.

Enter the Fel-Pro #1094.

No other changes to do THAT. Simply change the gaskets from the factory 0.41 compressed thickness to the 0.15? of the 1094. That engine's factory compression is DISMAL, at best. 12cc dished pistons allow a lot of room to improve.

Outside of that...

Headers are a MUST -but smaller ones. 1.5" primary with 2.5" outlet. 0.625 is overkill and wildly unnecessary for MOST street cars/trucks that use them. Two pipes connected as close to the engine as (reasonably) possible. 2" diameter exhaust pipe(s).

This IS A recipie for low speed torque. Improve the induction and the exhaust. That doesn't mean it has to be flashy or loud...or expensive.

2 bbl carbs are harder and harder to find...I would run a ONE BARREL if I didn't have any money and didn't want to think I was going fast...but that's likely a tough sale around here.

Good luck!

Click to expand...

I had a 71 Nova with a 307, 2 speed power glide, stock exhaust, and a 2 barrel. The 2 barrel was junk on it. Once I put a 4 barrel on it and a intake to match it got better midrange and as long as you kept your foot out of it somewhat better mpg's. I've never been sold on a two barrel as a fuel saving device but maybe other's find better results. Mine were opposite in regards to that car and then when i made the same change on my 68 Bronco it was running like hell and had junk for heads to begin with so there was no way to compare before and after.

Rusty Nail said:

Thank you.

You can economically increase static compression by simply changing head gaskets.

Enter the Fel-Pro #1094.

No other changes to do THAT. Simply change the gaskets from the factory 0.41 compressed thickness to the 0.15? of the 1094. That engine's factory compression is DISMAL, at best. 12cc dished pistons allow a lot of room to improve.

Outside of that...

Headers are a MUST -but smaller ones. 1.5" primary with 2.5" outlet. 0.625 is overkill and wildly unnecessary for MOST street cars/trucks that use them. Two pipes connected as close to the engine as (reasonably) possible. 2" diameter exhaust pipe(s).

This IS A recipie for low speed torque. Improve the induction and the exhaust. That doesn't mean it has to be flashy or loud...or expensive.

2 bbl carbs are harder and harder to find...I would run a ONE BARREL if I didn't have any money and didn't want to think I was going fast...but that's likely a tough sale around here.

Good luck!

Click to expand...

I like this suggestion but I don't really care to do this on a higher mileage engine unless I know 110% it's never been run hot. Those compostion gaskets at .041 are great for sealing imperfections when the head or block surface isn't 100% true. I don't think you're talking about metal gaskets, but only time I ever used those is when I had the block decked and head resurfaced.

You know what happens next when you beef up the top end (add compression and efficiency basically) of a worn bottom end...

I speak from 1st hand experience... I have made that specific gasket swap four times in my life.
Two times I used fresh rebuilt heads out of the shop. Once was a gasket change only. Once was a straight head swap from a used block
Three personal vehicles, one was my buddies. Each time I turned every bolt start to finish and have yet to encounter any "sealing" issues but you bring up a good point @hrpc. Surface prep is critical, ..that's like anything else though. We're talking cast iron to cast iron!

The 1094 is a great gasket that works.

Used to be able to get a real-live, bonafide, COPPER shim but I haven't seen one in forever! BLING-BLING!

Rusty Nail said:

I speak from 1st hand experience... I have made that specific gasket swap four times in my life.
Two times I used fresh rebuilt heads out of the shop. Once was a gasket change only. Once was a straight head swap from a used block
Three personal vehicles, one was my buddies. Each time I turned every bolt start to finish and have yet to encounter any "sealing" issues but you bring up a good point @hrpc. Surface prep is critical, ..that's like anything else though. We're talking cast iron to cast iron!

The 1094 is a great gasket that works.

Used to be able to get a real-live, bonafide, COPPER shim but I haven't seen one in forever! BLING-BLING!

Click to expand...

True, I've not seen a copper shim gasket in probably 25 years or so. I don't doubt you a bit. In my engine builds long ago for street/strip builds I didn't mind using the thicker gaskets because I had the block decked a few thousandths, and the head too so by the time I used a thicker aftermarket gasket, usually Fel Pro, it was still equal to using a shim gasket. Proper Torque and Re Torque usually ensure a good seal and no problems.

I wonder if they make that same gasket for a big block? I've got this 454 in the C20 that's still low mileage, doesns't use oil runs fine and can't have over 50,000 miles on it, but it's a damn Piss Port as in Peanut Port engine that's low compression. I don't want to put a ton of cash in it so I want to use the same heads to keep cost down. I've heard you can easily get up to 400hp and 450ft lb or torque even with PP heads and even up to 500hp/500ft lb. Maybe just a head gasket, cam and intake swap and add headers. I'd rather save the bigger bucks for an LS build and bigger hp. I'll have to do some looking around.

Ya. I thought of the actual copper shim because that would certainly offer a superior seal if needed but I don't think they're over the counter items at your local o'reilly anymore.

I wonder why?!
I ALSO wonder if they are "cost-prohibitive" now because SURELY SOMEBODY still makes em.

Screw you guys for makin me wonder why I sound old.