Torque converter Question

[dave_s1987]

Hey everyone, just thought I would ask a quick question in regards to my torque converter. I finally just picked up a freshly rebuilt 355 sbc to go with my 200-r4 transmission. When i was leaving with the motor the gentlemen that built it was giving my tips on break in and what oil to run and what not and also mentioned to me that I should be running a torque converter with a stall speed close to 3000. right now I just have thew stock converter that came with the transmission (originally came out of an 88 GN i believe) and I have no idea what the stall number would be on it. I assume its only somewhere around 1900 from what i've managed to read online

So my question is what exactly will be the downside if I decide to just go with that stock torque converter? is it very noticeable? is it something I can get away with upgrading in the next year or 2 or is it one of those things that should be done sooner rather than later? I plan on putting my engine in this weekend and I would hate to have to fork out another $300 at this point in time.. Its getting harder and harder to buy parts without my girlfriend finding out about it lol

as always any help or advise is appreciated.

 

[Injectedcutty]

There are several factors that come into play with stall size..
1. Do you know the specs on the new 355 and what the powerband for the cam, intake & heads should yield. Mainly what are the cam specs and will you be running a single or dual plane intake? Carb or efi?
2. Is it gonna be a cruiser, street/strip car, or drag car? What rearend gears are you running?
3. Remember, to make that fresh motor scream with efficiency, everything has to work together....i.e. engine specs, trans, rear, etc.

I was running a 2200-2400 stall with my 355 and th350 due to it being a daily driver at the time. However, when shifting into gear it would "slam" due to the stall being off of what the engine desired. The engine wanted more stall in the 3k range due to my powerband coming in around 3300 with the cam i ran. From a dig my cutlass would fall on its face until i hit the 3k threshold because the converter wouldnt get me there quick enough if that makes sense.

Fyi, the higher the stall speed the higher your rpm's will be while cruising...having overdrive will help you though. Get us guys some specs so we can help you further if needed.
Scott

 

[dave_s1987]

thanks a lot for the info Scott. As you can tell I don't have a lot of knowledge and am pretty new to all this stuff so your help is definitely appreciated. The engine builder gave me a blueprint binder with all the info and specs so rather try and figure out what info you need I just took a couple of pics of the info for you guys to read over.

It has a weiand single plane intake and Im putting a 2 inch spacer along with my Holley 750DP on it. I just put a 7.5 bolt 3.73 posi on it as well.

This car will never see a track. I'm basically going to use it as a cruiser on the street during the summer months but would like to have the option to hammer out some good power when the urge to do so comes.

At this point I'm leaning towards spending the extra cash for a higher stall converter but wouldn't mind your guys input.

Also is there anyway to tell what the stall speed is on one of those? When it was rebuilt they just wrote grand national lockup on it and nothing about the stall.

Anyways, thanks again for any help/info you guys can give.

 

[Injectedcutty]

The cam specs aren't super crazy lift-wise, but the lobe separation (noted as spread) is pretty close at 109° which will give a lopey idle however the trade off is you might build a lot of vacuum for your brakes. With the single plane intake you really won't start building power until 3k rpm's, that's one of the reasons he suggested that stall size. Your build sheet looks fairly close to what my 355 was before it died. Did he give you an estimated horsepower?
In all honesty, if your car won't see the track i would ditch that intake for a good dual plane like the weiand stealth or an edelbrock rpm air gap to help with the street manners. Single plane intakes are meant more for upper rpm driving as that's where they make the most power, as of now with that setup it will be fun to drive but street cruising could piss you off. The 750 carb will work but ideally a 650 might work better. There's a possibility the jets in the 750 might need to be down-sized. I'm not 100%sure about the stall on your converter, it would work for now but upgrading to a larger unit would be preferable.
As stated before, it's about making everything work together nicely! Drop that motor in, get it running and drive it around to get the feel for it, intakes and carbs are easy to change while the motor is in the car. Just my 2 cents as i was once in your shoes over a decade ago. Keep on truckin, scott.

 

[lilbowtie]

Can't agree with Scott more. Make sure you use a good oil w/ zinc if you haven't already been told

 

[Injectedcutty]

Oops i found a typo....when mentioning lobe separation i meant to say you WON'T build alot of vacuum to power the brakes which need around 16" of vacuum to work properly.

 

[dave_s1987]

Thanks for the tips guys. that's all great info to have. The guy told that this was supposed to be a 400hp build. I'm not sure how accurate that is but i think its probably close enough. I ended up going to a local shop and picked up a 2500-2600 stall lockup converter today that I think will work good with my setup. As far as the carb and intake go I would have actually put a 650DP on it (thats what he had on it when he fired it up for me) but I already had the 750dp so it'll have to do until next spring when I can try a new combo out. Like you said, I'm going to drop the new stuff in and then I'll spend the rest of the season seeing what I like and don't like about the setup and go from there.

Thanks for the oil tip as well.. He was giving me a lot of info and had a lot to say about what oil to run after the break in is complete. He was saying that if I buy certain oils I would have to put an additive in it, but recommended I just buy the same stuff he uses that already has all the additives in it. I cant remember what its called but I took an empty bottle so I would remember when it comes time to change it.

also thanks for the info about the brakes maybe not having enough vacuum to work properly. I would have never thought of that to be honest lol but definitely sounds like something I'll want to keep my eye on.

thanks again for all the help

Dave

 

[axisg]

hang on to the torque convertor they pull out in case you change your mind.. Stock GN TQ should stall appx 2200 rpms. I run that convertor in my car on the recommendation of the builder and I think its just about the right stall for a cruiser. Most of my cruising is back roads at 80-90 kph so I can engage the lockup and pull it down to appx 1800 rpm on OD. If I want to have more fun/ power in the city I just leave the car in 3rd to keep the revs up. With a larger stall I don't think I would use lockup at all ( burning more fuel ) unless on the highway. I run 235/60/15's and 3.73's out back. In a friends car he was running a 2700 rpm stall and had to rev the motor noticeably higher when cruising around the city. It was more fun in the torque curve but burnt more fuel.

 

[dave_s1987]

thanks for the advise axisg. I absolutely kept the old converter just in case it came in handy in the future.. I have a hard time giving up good parts even if I may never have to use them lol Its all definitely good info for me to have although Its a little hard for someone like me with little experience to fully understand how it will all play out on the road until I actually get out there and put some miles on it. Hopefully that day comes sooner than later.

 

[Injectedcutty]

Thanks for the tips guys. that's all great info to have. The guy told that this was supposed to be a 400hp build. I'm not sure how accurate that is but i think its probably close enough. I ended up going to a local shop and picked up a 2500-2600 stall lockup converter today that I think will work good with my setup. As far as the carb and intake go I would have actually put a 650DP on it (thats what he had on it when he fired it up for me) but I already had the 750dp so it'll have to do until next spring when I can try a new combo out. Like you said, I'm going to drop the new stuff in and then I'll spend the rest of the season seeing what I like and don't like about the setup and go from there.

Thanks for the oil tip as well.. He was giving me a lot of info and had a lot to say about what oil to run after the break in is complete. He was saying that if I buy certain oils I would have to put an additive in it, but recommended I just buy the same stuff he uses that already has all the additives in it. I cant remember what its called but I took an empty bottle so I would remember when it comes time to change it.

also thanks for the info about the brakes maybe not having enough vacuum to work properly. I would have never thought of that to be honest lol but definitely sounds like something I'll want to keep my eye on.

thanks again for all the help

Dave

400hp sounds pretty close. My 355 (rip) was spec'd at 425 crank hp and it ran like a scalded dog with the weiand stealth dual plane, a 1" spacer and a 650 speed demon! Like i said earlier, from idle to 3200ish it pulled ok due to the low stall, but once the cam came in it stuffed me harder into the seat. When hobby racing at the local strip i shifted at 6800 rpm and it was pulling hard all the way to that point.

You will have some fun with your setup for sure....just fine tune it once up and running. Keep us all posted Dave.
Scott