Is a more aggressive cam needed when switching to better heads?

[rjrobin2002]

I have a roller 351w with explorer efi and a Comp 35-349-8 cam, gt40 heads and love it's power curve.

Would I be wasting some aluminum AFR 165 or 185 heads better flow if I kept the same cam?

 

[Broncobowsher]

No. Small cam, big heads works great. You can get the airflow for good power without getting the rough idle of a big cam.
Probably the best engine I ever had was a very mild Edelbroke Performer clone cam with a set of trick flow heads. Good idle but would pull to 6000 RPM.

 

[.94 OR]

No. Small cam, big heads works great. You can get the airflow for good power without getting the rough idle of a big cam.
Probably the best engine I ever had was a very mild Edelbroke Performer clone cam with a set of trick flow heads. Good idle but would pull to 6000 RPM.

How was the low end?

 

[rjrobin2002]

How was the low end?

Check out the desk top dyno numbers EFIGUY ran for me using a smaller Comp 35-308 cam with 170cc aluminum heads.
That's almost 400ft/lbs tq in to 2000-2900rpms!!

 

[EFI Guy]

I think there was some miscommunication. That simulation was done with the 35-308-8 cam. It has a similar duration to your current cam but a lot more lift.

 

[rjrobin2002]

I think there was some miscommunication. That simulation was done with the 35-308-8 cam. It has a similar duration to your current cam but a lot more lift.

You're right, I'll clarify the cam. I was showing the great numbers using a mild cam with decent heads.

 

[.94 OR]

That's pretty impressive torque at 2K. Seems to hold reasonably well through 5K.

 

[Grey owl]

Not sure if your Bronco is an automatic or standard. My set up is very simple, stock 1969 short block with mild cam, 185 aluminum heads, & intake Brawler 650 DP carb, long tube headers. The one part that made the biggest difference was a Hughes 2200 rpm stall converter.
It just made the drivability so much nicer.

 

[Broncobowsher]

How was the low end?

Very good. No issues lugging down to 1000 RPM, cruised great at 2000 RPM, but would pull to 6000 without missing a beat.

 

[nvrstuk]

Not sure if your Bronco is an automatic or standard. My set up is very simple, stock 1969 short block with mild cam, 185 aluminum heads, & intake Brawler 650 DP carb, long tube headers. The one part that made the biggest difference was a Hughes 2200 rpm stall converter.
It just made the drivability so much nicer.

What was the stall b4 with the same engine?

 

[Grey owl]

What was the stall b4 with the same engine?

Not sure i changed it to a C4 when i restored it. A stock converter does not have much stall. The converter restores all the bottom end allegedly lost by higher flowing heads and a lumpy cam. It just allows the engine to get into its power band more efficiently. It makes the truck way nicer to drive in normal traffic. I don’t offroad my Bronco.

 

[ntsqd]

Higher stall does make a LOT more heat no matter where you drive it, it's just less of a problem on the pavement.

 

[Grey owl]

Yes a stall coverter makes more heat but 2200 stall converter does NOT make a lot more heat. Any additional heat is easily controled with a trans cooler and a deep pan on the trans. Its just not an issue at all.

 

[ntsqd]

I agree, on the street as you don't tend to dwell in that RPM band at or near full load.

If the application were for mixed use or off-road it would be something to really consider whether you want that added heat as it can be a lot of extra heat to dump when you're going 0.5 MPH while 'riding on the converter' (meaning that you're almost always running between idle and the stall speed at every throttle setting between idle & WOT) and the cooling systems are already challenged. Also depends on driving style, some wouldn't want that loose of a converter while off-road.

2200 is roughly 1000 RPM above stock.
Too bad that, AFAIK, the "Switch-Pitch" converters were only made for GM transmissions. Stock stall with the toggle switch one direction, higher stall with the toggle switch the other direction. A friend had one in his '56 Chevy's TH350 but I think that I heard that it went TU recently and there's no replacement available.

 

[Grey owl]

I don’t share your opinion, there simply not alot of extra heat not sure why you think there is. Yes stall converters add heat but its far from alot as you say. Any additional heat is mitigated by a dedicated trans cooler, an elctric fan pulls all the cooling air you need even at low RPM, add to that a deep pan that adds 2 liter oil capicity, and another liter for the cooler. Sorry but its just not and issue at all.

 

[lars]

The OEM-spec torque converter I bought when I installed my 4R70W was rated at 2000 rpm stall, which as I understand it was the nominal rating for that vehicle. Obviously YMMV. It's getting fed by a lot more power than a stock Explorer but so far it's been just fine. Routed the cooling lines like Ford did it on a bazillion vehicles. Out the hot port on the transmission, then through the heat exchanger in the radiator (I'm using a standard brass Bronco configuration radiator) then through the cooler and back to the transmission. Cooler is a gigantic Mishimoto unit ahead of the radiator. Warms quickly, never gets above about 185°. Even in this "hotter than the furnaces of Hades" weather we've been having in the Sacramento Valley the last few days, it doesn't get to 160°.

 

[ntsqd]

I don’t share your opinion, there simply not alot of extra heat not sure why you think there is. Yes stall converters add heat but its far from alot as you say. Any additional heat is mitigated by a dedicated trans cooler, an elctric fan pulls all the cooling air you need even at low RPM, add to that a deep pan that adds 2 liter oil capicity, and another liter for the cooler. Sorry but its just not and issue at all.

You've stated that you don't off-road your Bronco so when you start going off-road and running technical trails with a high stall converter in a C4, and then say that it's still not a problem I'll want pictures of how you're cooling the trans and want to know where you're measuring the temperature.
Until then I'll agree that a stall RPM in that range is not likely to be a problem on the street, but will maintain that off-road is a different experience that has only a little relationship to how it behaves on the street.

If you search here you can find older threads where a guy has all of what you propose with a STOCK C4 converter and it still won't stay cool on the trails. Not just one, but many over the years.

 

[Grey owl]

What are you talking about A High stall converter!!! . I have been off roading 1st gen broncos since 1974, you are welcome to your opinion but you are exaggerating the heat issue. All modifications change stock performance, and addressing related issues is part of the game. I increased the heat generated by 15% and increased the cooling by 50%. When you have 30 years experience with converters like the guys at Hughes then chime in. Frankly your exaggerated heat claims are wrong. My god you think a 1800 - 2200 converter is HIGH stall.

 

[Grey owl]

The OEM-spec torque converter I bought when I installed my 4R70W was rated at 2000 rpm stall, which as I understand it was the nominal rating for that vehicle. Obviously YMMV. It's getting fed by a lot more power than a stock Explorer but so far it's been just fine. Routed the cooling lines like Ford did it on a bazillion vehicles. Out the hot port on the transmission, then through the heat exchanger in the radiator (I'm using a standard brass Bronco configuration radiator) then through the cooler and back to the transmission. Cooler is a gigantic Mishimoto unit ahead of the radiator. Warms quickly, never gets above about 185°. Even in this "hotter than the furnaces of Hades" weather we've been having in the Sacramento Valley the last few days, it doesn't get to 160°.

You are 100% correct most modern vehicles run higher stall coverters than back in the day they also run higher fluid volumes and superior cooling. Thats exactly what i did more fluid volume, way more cooling. BTW an 1800 - 2000 stall converter could hardly be considered high stall,

 

[Broncobowsher]

Could go deeper into the weeds, while everyone in the aftermarket goes off stall speed, the OEMs go off k-factor. Which puts the torque multiplication into the math. You can have the same basic stall speed, but drasticly different torque multiplication. It's how the OEMs really tune the convertor for the application. I really wish the aftermarket would get with it.