Another cam thread... But maybe not the usual.

[Dustycolby]

I'm no stranger to building playtoy engines and putting together a performance package pretty well.
But this time around I'm goin the other direction for as much torque down low as possible with good fuel economy.

The project in question this go round is a 1980 c10 with the dreaded integral 250 (all smog equipment removed and plugged) th350 with 2:73 gears and 31" tires. I wanted an efficient cruiser and ended up with a very weak 12mpg pig.
I'm thinking with the idea of throwing together a few things I have sitting around and see if I can come up with something better.

Starting on 350 with D-dish pistons, 305 H.O. heads with 58cc chambers, 165cc ports, 1.84 Int. 1.50exh. valves. An Edelbrock performer intake and Holley 600 vac. secondary or quadrajet.
Theory is that most torque down low would have better vacuum and be in the secondaries less providing better fuel mileage.
How would the gm929, summit 1101 or an equivalent comp cam perform in this combo.

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[QBuff02]

I'd probably think about a comp cams XE256H or an XE262H for that application. either will have good idle qualities, make plenty of vacuum and provide good seat of the pants torque. But no matter what you do, you're still going to be somewhat limited by "feel" with those tall gears.

 

[ali_c20]

For fuel economy the qjet will be the better choice.

 

[Savageftr]

The only thing that stands out to me is the 305 heads. I'm not a head expert but I've heard they just don't flow well. That being said I don't have a flow bench to confirm that. Any gain from compression ratio will be negated by the poor flow.

I would do flat top pistons and a good set of aftermarket iron 64cc heads, dual plane aluminum intake, q-jet carb, and any "RV" cam should do it.

There are many ways to do it but personal preference on the how....

 

[hirschdalechevy]

If it was me and I was thinking about the best economy I would stay with your d-dish pistons and for sure go with vortec heads. Vortec's are a more efficient chamber design which will give you a more complete burn in the combustion chamber which also allows you to run more compression as well.

Then long tube header's which would fatten the bottom end torque curve. Go with a good flowing dual exhaust which would benefit the entire operating range.

For a cam I would stick with something in the 195 to 205 degree's duration at .050 and .410 to .450 lift on a 110 to 112 lsa.
Like this comp cam, cl12-231-2 or comp 12-105-3.

Vortec heads don't flow as well on the exhaust side so they do like to use split duration cams.

Q-jet and a eddie intake and go for a strong 9 to 9.5 to 1 and call it a day.

 

[Dustycolby]

Any reason why the 610 and 416 heads I already have are a problem running under 4000 rpm. I was under the impression they would be good for the compression but they got the reputation for bad numbers above .420 lift and die off around 4700.

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[shiftpro]

You don't need crappy heads to produce torque.

Since you're looking at a 350 why not stroke it to 383? There's an instant advantage to producing torque right there.

 

[hirschdalechevy]

Any reason why the 610 and 416 heads I already have are a problem running under 4000 rpm. I was under the impression they would be good for the compression but they got the reputation for bad numbers above .420 lift and die off around 4700.

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You could use them for sure, I was just thinking you were after the best you could do mileage and torque wise.

 

[Dustycolby]

Just ran into a deal on some iron eagle 49cc heads. Should bring compression to 10.75:1. With 180cc runners. What is the thought on where these will run.

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[peats]

You don't need big heads for a low rpm torque motor. Find a 400sbc and rebuild it with an rv cam, long tube hedders and a performance intake. Top it off with a qjet and you will have a reliable torque monster without having to step up to a big block. I have this setup in my '72 k5 and it is very enjoyable to drive.

 

[Dustycolby]

Also just picked up some 034 bowtie phase 2 heads as well as the tbi swirl ports.

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[yevgenievich]

305 heads worked fine for me on a 350 with the basic sum-1103 cam. Never went above 5k rpm, and never needed too. Had good off the line response. Was not in a budget for new heads for that motor. But was still around 12mpg range highway with th350 80mph. Changed to 700r4 as 3k+rpm was really tiring, but then sold the truck

 

[hirschdalechevy]

Also just picked up some 034 bowtie phase 2 heads as well as the tbi swirl ports.

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The 034 heads are really good heads, I had them on a 383 I put together moons back for my 72 camaro. If memory serve's those are 64cc with 202 valve's

 

[Raider L]

@Dustycolby,

305 heads do have that good small chamber but don't like having port work done much, thin walls, see, they're early EPA heads. Keep the 350 heads and mill them .020" and take the block deck down .010" to flatten it out. Port match intake and exhaust. Machine those heads out to 2.02" in./1.60"ex. and do get the flat top pistons with the single valve relief. The cams mentioned are good. Keep the Holley by all means, and the 600 is the one I've got on my hi-po 350 and I can get any kind of performance or gas mileage I want by just changing out jets, accellorater pump cams, and metering bodies. Holley's are the most versatile and easiest to tune carb.'s and I've run Q-jet's and even the old Thermalquads of the '60's, AFB Carters with drilled out caps on the idle jets and changed out jets. You'd be surprised how much you can do with what you've got. You've already got a lot to play around with. Keep it simple and keep it cheap, well within reason. It doesn't take long to get caught up in it all and then you look back and you've got $5,000 in the motor and you've got a pissed off wife and no beer.

 

[Raider L]

@Dustycolby,

Oh yeah, do get the headers and a good intake. Eldelbrock Performer, that's it, no RPM, no open plenum, no air gap, just a dual plane with no more than 1/2" carb. spacer. That's what makes for good low end torque not extending the floor to high. All we've talked about will give you fair gas mileage and eye opening torque. If you don't get carried away with the cam you ought to get 13-14 mpg. in town and about 16-18 on the hwy. I know you're getting that now but that's what you're going to get, it's a pickup. Now you go with carbon fiber body parts and loose about a couple hundred pounds, aluminum suspension parts where applicable like the vette suspensions, lower the truck down on the ground to cut down on wind resistance and now you've got a race car!! Oh I forgot, you wanted a truck.