which tq converter for my 408 stroker?

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tomcat27

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1970 351W FMX trans. My engine will be a 408 stroker built on a Dart block. forged Mahle pistons, around 10.0:1 compression, AFR 195's; the engine builder is about to order a custom cam and is asking me what speed stall I'm gonna run. ??!!?? uh... I was hoping to stay stock? he says "no", you should run at least a 2500.

the stock unit seems to stall at 1500 but that is just me doing a brake check on it - and I believe there are two different "stall" ratings. This will be a street only car.

do I really want/need to replace the converter? it doesn't sound too difficult, but besides reading and watching videos I really have no idea which converter or stall speed to select. they seem readily available for 2000, 2500, 3000, 3500,

I see Hughes, and ACC/Boss Hog. others? which one to choose?
 
You and he need to get together before he orders the cam. The stall speed of the converter will vary with the torque output.

Decide what rpm range you want to make power, pick the cam, then pick the converter.

Don't select a converter then buy a cam to match.
 
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You have left out the most important consideration; what is your rear axle ratio? As well, I do not see your camshaft specs (duration, CL, lift etc.) anywhere either (custom being ordered... still you should have some basic idea here).
Thirdly... what is the weight of your vehicle (70 Cougar...? 3500#?)?

I can help you pick a converter but need these 3 things.

Your engine builder is asking you what stall to help pick the camshaft. If you have a stock or low RPM torque camshaft you will not need anything more than stock stall speeds. If you have a rough idle / high RPM torque camshaft then you will. It is a careful combination.

Your stroker will obviously eat up a lot of camshaft duration and provide good street torque. I am inclined to say stock stall for a street car or 1800-2000 at the very most (add a cooler). But I need the weight of your car really and gear ratio to be sure.

I like TCI (for street / stock), Hughes, ATI (personal favorite for high performance) and B&M but let's get more information first.

Two more things... power brakes... air conditioning?
 
I've built up V8's back in the day. Driving a car in city traffic with a high stall convertor and a rough cam is no fun unless your first priority is the sound of the engine. You can make that 408 a smooth, low to mid end torque meister which will put a huge grin on your face every time you drive it. I'd go with a 2000 RPM convertor and a mild cam. Anything beyond that makes driving it less fun in city traffic as the stall speed goes up.
 
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Power brakes = YES
A/C = YES although it is not working and I dont know if I will ever get it working. maybe.

the rear end (it took some crawling to get to the tag and alot of cleaner) is a 9" 3.00 ratio.

I don't need the lumpy idle.
according to the sales literature from 1970, the car weighs 3431 pounds. (minus some cast iron heads, intake)
I will likely run JBA short/mid headers and a quick fuel carb. no idea what CFM - I presume 650 - 750 but we have not talked about that yet.
 
sorry I don't know anything about the cam profile - I keep insisting that we keep it conservative. I can find out more tomorrow. the designer was more interested in how high of a stall I would go. once again, if I could stay with the stock stall, I would. this car is completely about street driving. we do alot of evening drives but I would also like to drive it interstate a few hundred miles at a shot.
 
3.00 is a tall gear. If you are going to keep that, i would not put in a huge duration cam. Maybe an rv style cam.
 
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Originally Posted By: tomcat27

the rear end (it took some crawling to get to the tag and alot of cleaner) is a 9" 3.00 ratio.



Ok, good, simple. That is a highway ratio not a stop light to stop light ratio and that is fine. Choose a low RPM torque smooth camshaft. If you are going hydraulic flat tappet and with a 408 stroker look for less than 224 intake duration @ .050". A mechanical flat tappet you could get away with 230. If you are looking at a retro roller (expensive) then let me know as the above numbers do not apply.

I wouldn't go beyond stock. 1800 at the most. If this was a GM the L88 converter would be perfect for you and cheap.

FMX choices are limited. Hughes only has a 2500 stall. I do not know anything about Boss Hogs. If it were my car I would be using a regular stock converter and a Lunati VooDoo as below:

•Advertised Duration (Int/Exh): 262/268
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .499/.522
•LSA/ICL: 112/108
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 1400-5800

The AFR 195 is a higher RPM port head. It is not too bad but a bit of a mis-match with the 3:1 axle however certainly not a show stopper. Your stroker 408 will eat some of that port volume and keep the port velocity reasonably high.
 
FWIW, a hydraulic roller bumpstick for a Windsor should not be expensive and the retro lifters aren't overly pricey either. I did a link-bar retrofit on a buddy's '85 Mustang a few years back.

I think the AFR's will be fine given the displacement as marc1 noted. And as long as you aren't running a Victor Junior or some other toilet-style single plane intake, you should have good low speed drivability provided the cam is reasonably sized for the application.
 
I was planning on roller lifters; the shop was pushing that also - they were being selfish, too many of their customers wipe the cams with solid lifters and improper break-in. I could also move down to the AFR 185's - that might help me on the low to mid end; or even go Edelbrock RPM's. I'm not racing this, and don't want a bunch of mis-matched parts. (unless I have already done that by putting a stroker kit in)

thanks for all of the input.
 
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Naw, you'll be fine. You have tons of cubes. The AFR's are a big head on a 302, but you have 106 more cubes, you'll be golden. What is your intake choice?

We had the TFS TW's on the 302 my buddy had and with a Victor Jr she was REALLY high strung, like 3,500-7K, dead below that. A lot of that was intake, it had much better low range with a Weiand Stealth.

EDIT:

Actually, for another reference point, we put that same engine in an '87 and ran it with a TFS-R (that's a big dry flow fuelie intake) and it had really decent low speed manners. It was really the Vic Jr. that killed that, but it was an absolute bear with that intake and pulled harder than any of the others once you got it wound up. This was in a pretty stripped out '85 GT though with a manual trans and lots of gear, so winding it to the moon wasn't a problem.
 
for an intake I am thinking either Edelbrock RPM or a Weiand Stealth. the builder suggested Edelbrock RPM air gap - but that puts the air filter above the hood by 3/4" from what I can tell with a standard 3" filter. I suppose I could use a dropped filter, but it's not easy to measure all of that with the engine out of the car - and I'm not cutting a hole in my hood. did that once on a camaro.. goofy friend put a 396 in.... (and he had only done oil changes previous to his engine swap) fortunately we made it look nice by using the scoop from a trans am.
 
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I'd get a new one since you're having the engine rebuilt. Like the other people here I'd go with a pretty low stall speed for around town responsiveness and fuel economy since you want it as a daily driver. It sounds like the engine builder/designer has different ideas about this engine than you do so make sure you're on he same page.
 
Originally Posted By: tomcat27
I believe that Hughes does have a 2000 stall converter for the FMX - their street rod #38-20


You are right, my mistake. However I would still go stock
wink.gif
 
Originally Posted By: tomcat27
I was planning on roller lifters; the shop was pushing that also - they were being selfish, too many of their customers wipe the cams with solid lifters and improper break-in. I could also move down to the AFR 185's - that might help me on the low to mid end; or even go Edelbrock RPM's. I'm not racing this, and don't want a bunch of mis-matched parts. (unless I have already done that by putting a stroker kit in)

thanks for all of the input.

Even if you never had a problem with a flat lifter cam, you could still benefit from a roller cam. Roller cams have higher valve opening acceleration rate which means you can get more power than a flat lifter cam even if duration and lift are about the same.

That is another reason why so many auto makers decided to equip many cars with roller cams at the factory.
 
thanks. I'm doing some calculations and, if I am correct, my engine will turn at 2400rpm @ 60mph:

FMX 3rd gear ratio = 1:1
Rear end 3:1
tires are 25"

79" tire circumference divided from 5280' = 800 tire rotations per mile. considering the 3rd gear ratio and the rear end ratio, I believe that's 2400rpm @ 60 mph. obviously I dont remember, and I cant validate since the car is not running.

That being said, and per everyone's advice, I certainly DO NOT want to take the engine builder's advice of "at least 2500 stall".

we have not chosen a cam profile - that's how this conversation with the builder came up. we will talk Monday. thanks all! worst case, I stick with my stock converter and switch it out later if I'm not happy. I will push him to spec a cam along the lines of what was discussed here.

actually, since its my car, my engine, and my money, I can tell him to use the Lunati VooDoo.

why type of distributor gear with that? steel?
 
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Originally Posted By: marc1
Originally Posted By: tomcat27

the rear end (it took some crawling to get to the tag and alot of cleaner) is a 9" 3.00 ratio.



Ok, good, simple. That is a highway ratio not a stop light to stop light ratio and that is fine. Choose a low RPM torque smooth camshaft. If you are going hydraulic flat tappet and with a 408 stroker look for less than 224 intake duration @ .050". A mechanical flat tappet you could get away with 230. If you are looking at a retro roller (expensive) then let me know as the above numbers do not apply.

I wouldn't go beyond stock. 1800 at the most. If this was a GM the L88 converter would be perfect for you and cheap.

FMX choices are limited. Hughes only has a 2500 stall. I do not know anything about Boss Hogs. If it were my car I would be using a regular stock converter and a Lunati VooDoo as below:

•Advertised Duration (Int/Exh): 262/268
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .499/.522
•LSA/ICL: 112/108
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 1400-5800


what spec would change for a hydraulic roller cam?
 
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