Hi guys, I have been poking around here for a while reading and gathering info and ideas. I am not new to boost, I have had a wieand 177 on a sbc 350 (good fun) and have owned a factory turbo car ( Nissan r32 GTR) but picking out parts to make a good turbo combination is new territory for me.

I have a 1974 Plymouth Roadrunner with a Mopar 440. The engine came from an RV and has a low compression ratio, prob 8:1. I intend to go with twins because I plan on tying back in to my dual 2.5 inch exhaust, A large down pipe would be difficult and I would have to split it into 2 pipes and route one on each side anyway. Torsion bars are also a factor in going with twins.

The motor as it is now has about 220-230'ish flywheel hp (torquey though). (an assumption based of of internet for factory RV motors) I plan on changing the heads to 440 source heads, Holley street dominator intake, and a cam swap, something like this, Duration at 050 inch Lift: 224 int./234 exh. From looking at dyno's on the internet I am assuming this would bump up the N/A hp to 350-370 flywheel hp.

http://www.summitracing.com/int/parts/sum-k6401/overview/


The vehicle weight is going to be approx 3800lbs'ish. It has 3.73 gears, 727 transmission, and a stock torque converter ( around 1500 stall). I plan on changing the converter to whatever stall I need to but this car is a 100% street car, and will prob see daily driver duty as well. May even see an autocross course once or twice. It would be nice to keep the stall under 3000rpm.

I would like a early spooling setup and I am not concerned about loosing power up top. Thinking about aiming for 650-700 flywheel hp at 6000rpm, but likely will not spin it much above 5500rpm, though I'll see how the power band ends up. Will most defiantly run water injection ( snow performance, used there systems before with good results, no experience with other systems), Can run an inter cooler if need be (lots of room for one), and planning on an msd btm or 6al2 digital. This will be a blow thru carb setup, once I figure out what turbos to go with will give csu a call, thinking a 750 blow thru would work fine.(I have no experience with blow thru carbs yet, I do have a wideband o2)

It seems I am going around in circles now trying to pick out a couple turbos, From what I am reading here the turbine side needs to be considered almost before looking at compressor maps, and a lot of the compressor maps that look good to me may be small on the turbine side. I can run big wastegates if needed. Calculations, matchbot and some other programs give me PR's of 1.7-1.8'ish generally, and 34 to 41 lbs/min (*2, twins) I am not on a budget but do not want to spend more than I need to, was thinking about a couple s200sx's? Some guys on here with stockish bbc with similar power goals have had success with the bw 475's 480's. Matchbot matched me with an efr7064 but 2 of those would be a bit pricey, especially considering this is my first go at this. The s200-51sx seems similar, is this so? Also have looked at GT3071-GT3076, and TO4E's.

Any recommendations and comments are welcome, with regard to turbo selection size, trim, and AR? Wastegate and BOV sizes? or anything else about the combination?

Regards.

 

a pair of borg s366's for your 440cid or a pair of s360's for a more conservative set up

 

What fuel ? I would think efi would be a better choice for autocross.

 

I Will be using pump gas. Once the car is on the road I may convert to efi depending on how the carb works out with Daily driving and cold starts. I posted my questions up a couple month ago, no responses, then went ahead and bought the turbos, wastegates, bov ect. I went with 2 borg s200sx-56mm, turbos, 1.22 a/r, 2 tial mv-r 44mm wastegates, and 2 tial 50mm Bov's The fabbing is done and everything has been mocked up. The engine block is out at the machine shop right now, Should have it back in a couple of weeks, waiting on a few odds and ends, rods, dampner, flexplate ect to get the crank balanced. Bought a csu 750, its here waiting for when the motor goes back in.

This is my first go at building a turbo car, was concerned that these turbos are a little small but am hoping it will work out ok with the large wastegates, and the small cam I have. Was planning to test it out on the stock motor for a while but checked the bearings and they were wiped out, so now when the motor is done it should be able to take some rpm's as well. Went with msd 6530, and an in tank fuel pump.

May have the car on the road in 3-4 weeks and then see how it all works out.

 

Bummer that you got no response the first time around.... The s300 turbine is a very good fit for twins on this, and the s200 turbines are small, and will most likely plague you with high pre turbine pressures that will only get worse with any head or cam changes, and make for a diesel like power band. This is just my 2 cents, but if the 200's are new, i'd seriously look at selling them for a pair of 300's now while you can get the most for them, again just my opinion.

 

I have already ported the turbine inlet, may be too late to sell them, though they have not been run yet, just mocked up. Thanks for your advice.Looking at the specs for the 300sx, they would fit where the 200's are with some small changes. I am so far along on this thing now I will prob go ahead and give the 200's a try. I can keep them for something else if they don't work well, perhaps a small block would work with them I am assuming.

 

They would work well on a mild 350ish cid small block. Turbine choice is more about n/a power production than it is cid. A stout small block could easily use as much turbo as a mild big block. The 200's may work decent with the stock heads/cam combo with its limited rpm, but any increase in n/a hp (heads, cam, or more rpm) and I think you'll find the boost/backpressure ratio will get out of hand, and the hp per psi will drop dramatically, and along with that comes possible head gasket issues.