Bad Combo?

[MadOgre]

You answered my question I was about to post. If the th350 would be okay with the intake and carb cam. Now which rear end 3.42 or 3.73 with the above combo?

Also with the HEI what would be best? I heard it needs vacuum assist

Yes it does have a vacuum advance which is just hooked to a vacuum port on the carb. No issue there.

3:42 would be an improvement at the very least. I guess it depends on tire size and your average speed you would like to travel. If you are a highway guy probably 3:42s if you are just a cruise around town guy then 3:73 or even 4:10s

What size tires do you have and how fast do you usually go?

 

[skysurfer]

The swirly heads are a 193 casting and actually a decent head considering what they were designed for. They make good power on the bottom end but don't flow well above 4500 rpm. Nobody bothers with machining 193's, they either work for the application or get swapped out for vortecs.

 

[rich weyand]

Couple extra thoughts.

Tires is a cheap gear change: tires are more expensive than a used axle, but there's less labor. And if you need tires anyway, it's free. Shorter side walls will roll under less in cornering.

Changing the governor on a TH350 is a half hour job, assuming it takes you fifteen minutes to pry the cap off. I have an extra "one-size heavier" weight for a TH350 I can let you have, since they come in pairs and I only needed one.

The Qjet is harder to tune because it has little drilled air bleeds pressed into passages and such. So the factory set it up for the engine setup it was going on. To tune one for a new setup, you have to get those out and replace them, or drill them larger in place. Sean Murphy has been tuning Qjets forever, and knows what all of those little things need to be for every setup. Buying one off the shelf without any mind to the tune would never get you where you need to be.

The Edelbrock carb, on the other hand, is all easily replaceable parts for the tune. Rods, jets, accelerator orifices, and such. So it is easier to tune, but can be a pain to get right without an A/FR meter. That's $300 and a lot of fiddling around with extra parts to find the sweet spots.

 

[MadOgre]

The swirly heads are a 193 casting and actually a decent head considering what they were designed for. They make good power on the bottom end but don't flow well above 4500 rpm. Nobody bothers with machining 193's, they either work for the application or get swapped out for vortecs.

Yes but they will work fantastic with a 12-300-4 cam and he already has them. And yes some DIY porting can help them a great deal. Just like any head. Clean up the slag and sharp edges and gasket match the intake to the head. Just don't wreck the valve seats or its $ time

 

[RangRayy]

Yes it does have a vacuum advance which is just hooked to a vacuum port on the carb. No issue there.

3:42 would be an improvement at the very least. I guess it depends on tire size and your average speed you would like to travel. If you are a highway guy probably 3:42s if you are just a cruise around town guy then 3:73 or even 4:10s

What size tires do you have and how fast do you usually go?

I have 255/70/15s or 255/75/15s I cannot remember. Bfgoodrich radial ta's
Average speed is 45-65mph max in town is 45 but hwy is 65 and sometimes I used to go 70 but with the 3spd it sucked big time.

 

[MadOgre]

WEll I wouldn't do anything with the gears until you have your motor all done and if it seems like it needs a little more torque then you could consider a 3:23 or 3;42 rear end.

 

[rich weyand]

Here's a thought. Instead of the stock 235/75R15 (29" diameter) truck tires, put a set of BFG Radial TAs in 235/60R15 (26" diameter). Lowers the truck an inch and a half. Also makes that 3.08:1 (with 29s) effectively a 3.44:1.

I did this on my Safari in the mid 90s. That thing was a pig in the corners, rolling those tall tires under. The tires would complain all the way around a 270 entrance ramp at 30 mph! I bought it with 3:75 to one (it came stock with 3.25:1 with overdrive, which was silly), and then put shorter tires on it. I had an effective 4.2:1 ratio with all-wheel drive. It was a hole-shot monster after that, and would take the entrance ramps at 60.

If you do this, you would need to change the speedometer driven gear to get the speedo accurate, but those are cheap and there's a million of them.

http://www.tirerack.com/tires/tires...TARWL2V2&vehicleSearch=false&fromCompare1=yes

 

[rich weyand]

So, lessee. A summary so far:

HEI distributor (with built-in stock advances, or you will be fiddling with an adjustable one forever), SMI custom-tuned Qjet, on an Edelbrock manifold (make sure it's one of the ones for the spread-bore carbs), keep the TH350 but knock the shift points down 500 rpm, Comp 12-300-4 cam, Hooker 2453 headers, 2.25" dual exhaust all the way out, maybe some Flowmaster 40s (noisy) or 50s (quieter), and BFG 235/60R15s and a speedometer driven gear swap.

Yeah, I think that would do it. And not that expensive compared to what you were thinking.

What do you think, MD?

 

[RangRayy]

Thanks for all the input really it is appreciated. Most people on forums these days say we'll use the search button and research before asking "stupid repetitive" questions.

That's why I am trying to gather as much as I can to do a write up on the carb switch since I can't find one anywhere and I will use his as reference as well.

I plan on going with what MadOgre suggested with a cam and crab intake setup and then go from there.

 

[MadOgre]

Yep I think that sounds like a good plan! No sense wasting money if you don't have to!

 

[MadOgre]

So, lessee. A summary so far:

HEI distributor (with built-in stock advances, or you will be fiddling with an adjustable one forever), SMI custom-tuned Qjet, on an Edelbrock manifold (make sure it's one of the ones for the spread-bore carbs), keep the TH350 but knock the shift points down 500 rpm, Comp 12-300-4 cam, Hooker 2453 headers, 2.25" dual exhaust all the way out, maybe some Flowmaster 40s (noisy) or 50s (quieter), and BFG 235/60R15s and a speedometer driven gear swap.

Yeah, I think that would do it. And not that expensive compared to what you were thinking.

What do you think, MD?

Definitely will need a set of headers for sure. IMO its worth spending the money on Stainless if its the right header. I put a set of stainless shorties on my shopping list

 

[MadOgre]

Thanks for the input guys. Cash rules everything haha and I am not one of the lucky ones who comes across deals of a lifetime on Craigslist or eBay or swap meets simply due to my cash funds and the deals never coincide. Oh well.

Well I have thought about converting to carb because my intake is leaking and while I have it off why not switch it out. My only concern with going carb is that carbs are getting out dated and always having to adjust it. Plus it looks like a headache switching everything over. Now before everyone rants at me if it were a DD still yeah that would be a pain to have to adjust every time I needed to go somewhere. Seeing as this is my project why not do it. Also I'm already deleting the air pump so would there's a plus.

I've searched and searched on switching tbi to carb and no where is there a list of all the parts needed.

The obvious:
•intake
•carb (650cfm)
•inline fuel regulator
•vacuum advanced? Distributor?
And that's about all I know of

One thing we forgot is that you will need a fuel pressure regulator for the carb and Im not sure if there are any issues with the in tank fuel pump and a carb? Anyone ???

I would think that a fuel regulator would be all you need but I have never run a carb from the TBI tanks so im not sure.

 

[RangRayy]

I've heard mixed reviews on that but more positive notes with just an inline regulator for the intake pumps. Maybe. I vaguely remember reading that they have a max psi output but I do not recall what it is. More than 15 bc you can put an adjustable regulator on the tbi and boost it up to no more than 14psi

 

[rich weyand]

For the carb it has to be in the 6psi range. Regulator should do it.

Oh, BTW, that should be Hooker 2452 headers above. 2453 is for 4WD trucks like mine.

So, to have it all correct in one place:

HEI distributor (with built-in stock advances, or you will be fiddling with an adjustable one forever), fuel pressure regulator, SMI custom-tuned Qjet, on an Edelbrock manifold (make sure it's one of the ones for the spread-bore carbs), keep the TH350 but knock the shift points down 500 rpm, Comp 12-300-4 cam, Hooker 2452 headers, 2.25" dual exhaust all the way out, maybe some Flowmaster 40s (noisy) or 50s (quieter), and BFG 235/60R15s and a speedometer driven gear swap.

 

[RangRayy]

Any suggestions on fpr's? Or HEI distributors and or coils?

When switching intakes should I delete the egr as well or find one with the provisions?