quick easy-ish 350 upgrades

[spenser21]

Yup, that pretty much sums it up.

The Edelbrock has its detractors, but it's fine if you tune it. Most people don't, then bitch about it. You can get a good wideband A/FR meter to do it, or I can give you some tuning numbers to try -- jets and rods and springs and such. I'll tell you right now, on a truck 350, the Eddy is running richer than a cob. You should be getting 10 mpg in town and 12 on the highway (60-ish) in a mid-70s K. If not, its the Eddy tune.

For headers, the Hooker 2453 fits the K trucks nicely. 2.25 duals is all you need for a 350. A 2" H pipe behind the transfer case helps.

A dual-plane intake manifold like the Edelbrock 2701 would work well.

Once you get into the cam, we need to talk!

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hey rich... I know we said we would talk when it came time for a cam but how about that intake... any recommendations on which one?

 

[rich weyand]

See above in your post: Edelbrock 2701.

Unless you want to go with the standard thermac air cleaner like I did. Then you can go with the 2601 air-gap manifold. But you don't want to do that in Omaha without the thermac air cleaner. It will run like crap all winter without carb heat.

 

[spenser21]

See above in your post: Edelbrock 2701.

Unless you want to go with the standard thermac air cleaner like I did. Then you can go with the 2601 air-gap manifold. But you don't want to do that in Omaha without the thermac air cleaner. It will run like crap all winter without carb heat.

Ha wow, I totally went right by that... well thank you, truck is getting the exhaust on today(I don't have a welder(yet))... then I will be jumping into this a little further!

 

[spenser21]

so its now time for this intake manifold...other then gaskets and bolts, is there anything else you guys recommend getting at this time?

 

[MikeB]

if I can work with the edelbrock then id be happy. just saves me another 300-400 bucks for the other stuff. id be interested in what tuning numbers you have for it as well!!! keep in mind this is the first motor im actually getting "inside". question about the exhaust though... mine was hacked off right under the cab so im not sure what was there, but is there a purpose to the H pipe, or does a guy just run duals all the way back?

I can say from experience that adding full duals will wake up just about any engine. Back in the day, it was the first mod I did to a 307 2bbl in a 69 C10. And that was using only 2" pipes, along with turbo style mufflers. Felt like I had removed a potato from the tailpipe!

I have found the 1406 carb jetting to be pretty close out of the box, at least at elevations of 1000 ft or less. I'm not sure about the 1405, which has different boosters and its own specific calibration charts. Be sure to read the owners manual to get an understanding of what the various metering circuits do. Those carbs are pretty straightforward and easy to tune on engines with cams less than 220 degrees duration @ .050".

http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

Don't forget to check your spark advance to make sure mechanical and vacuum advance mechanisms are working properly and allowing enough advance. That would be the first thing I'd do.

 

[MikeB]

Your carb tuning changes are here:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=32168.msg272122#msg272122

Primaries: jets .092 (#1425), rods .062 x .052 (#1441); secondaries: stock; step-up springs: 8# (comes with #1464). You will also need to replace the airhorn gasket (qty 5 is #1499) when you change the primary jets. Adjust the float bowls while you are in there, as they will be wrong.

Rich, have you run a 1405 with the above changes? .092 main jets seem kind of small at WOT, considering .100 is what the carb comes with. Or are you thinking about a 1406 that comes with .098 jets and different boosters (and maybe air bleeds)?

Nice looking engine compartment BTW.

 

[MikeB]

so its now time for this intake manifold...other then gaskets and bolts, is there anything else you guys recommend getting at this time?

I strongly recommend the FelPro 1256 gasket. But toss the front and rear cork gaskets and use a bead of automotive silicon sealant instead. Set the manifold on dry to determine the sealant thickness you need. Ideally the sealant will squeeze out a little after you tighten the manifold bolts.

Before you set the gaskets in place and lay down the sealant, be sure to clean the block, head, and manifold surfaces with something like lacquer thinner. Also, run beads around the coolant ports front and rear, and run those beads down over the head/block junction.

 

[Rusty Nail]

Clean and make it pretty.
If it don't go, chrome it.

 

[rich weyand]

Rich, have you run a 1405 with the above changes? .092 main jets seem kind of small at WOT, considering .100 is what the carb comes with. Or are you thinking about a 1406 that comes with .098 jets and different boosters (and maybe air bleeds)?

Nice looking engine compartment BTW.

Haven't run this setup on a 1405. Edelbrock says they have different venturis, boosters and idle circuit. So my tune may not work on the OPs carb. The factory setup will still be too rich, so he has to lean it out.

Bear in mind that I went smaller on both primary jets and rods, so it's not as much leaner as you think. Couldn't just go with bigger rods, because I was at the biggest rods already. So to lean it out, had to go to smaller jets, then also went smaller on the rods. The gap between is what matters. And at WOT, the secondaries dominate the mixture curve.

 

[1987 GMC Jimmy]

I strongly recommend the FelPro 1256 gasket. But toss the front and rear cork gaskets and use a bead of automotive silicon sealant instead. Set the manifold on dry to determine the sealant thickness you need. Ideally the sealant will squeeze out a little after you tighten the manifold bolts.

Before you set the gaskets in place and lay down the sealant, be sure to clean the block, head, and manifold surfaces with something like lacquer thinner. Also, run beads around the coolant ports front and rear, and run those beads down over the head/block junction.

Very important to do every word of this.

 

[MikeB]

Bear in mind that I went smaller on both primary jets and rods, so it's not as much leaner as you think. Couldn't just go with bigger rods, because I was at the biggest rods already. So to lean it out, had to go to smaller jets, then also went smaller on the rods. The gap between is what matters. And at WOT, the secondaries dominate the mixture curve.

When I said WOT, I was referring to primary mixture before demand-driven secondaries start to open, like when you stand on the throttle at low RPM.

Correct. Jet area minus rod area determines effective jet size. Here's what you get with stock jetting and one of your suggestions for the 1406:

jet/rod--area---effective jet area
.098--.0075
.070--.0038--.0037
.047--.0017--.0058


.092--.0066
.062--.0030--.0036
.052--.0021--.0045

If my math is correct, that turns out to be barely leaner at cruise, but significantly leaner under load (low vacuum). Interesting.

 

[rich weyand]

Yup. All determined with a quality wide-band A/FR meter.

 

[74 Shortbed]

What brand wide-band are you using if you don't mind me asking?.

 

[rich weyand]

NGK AFX Powerdex

 

[74 Shortbed]

NGK AFX Powerdex

Thanks..