Made some custom brackets, pulleys, and tensioner for a 355 LT1 with a vortech t-trim blower. The pulleys are 10 rib 2.75 blower and 6.60 crank. 18 pounds of boost is the goal.









What do you think for a first try? I used the calculators on the vortech site to come up with the pulley sizes for 18 pounds but I do not know where it will really end up at.

Tom

 

Looks real nice. Good job I was just worried about putting the 2.75 on my T trim. Let me know how it goes.

 

Why are you worried about 2.75? Belt wrap concerns? What is your pulley combo and boost level?

Tom

 

RMCR told me that they reconmend not to go below a 2.85 pulley. I went with a 2.95 but am probally going to a 2.85 I have zero belt slip with the RMCR setup and I have 3 postions left to make the belt wrap more if needed. Have 11psi right now with the numbers in my sig.

 

I don't think the T trim will be able to give you 18 pounds , you'll need a YSi for that. Be careful you don't overspin the blower or you'll fry the bearings on it. Don't ask me how I know that.

That setup should get you 15 lbs.

Great job on the custom fabbing on the brackets!! You must have a nice shop you work in.

 

Thanks, actaully a local machine shop spun up the pulleys and the tensioner. I just told them what to do.

Thanks,

Tom

 

Boost is technically just a measure of "restriction" of airflow in a motor. Boost is not really something that can be acurately calculated since every motor is different. You are missing alot of variables: such as what heads you are running, cam, engine redline.

I dont think you will see 18psi with that small of a crank pulley unless you are really reving the engine.

Looks like a real nice setup though
Jason

 

Looks very nice. A T-Trim is listed as being able to hit 825hp on Vortech's site, but I think folks have done better than that.

 

I made a typo on the crank pulley size. It is actually 6.6. This is how I came up with that number considering a max engine rpm of 6500:

3.33 Blower + 6.00 Crank = 6-8psi @40405rpm
3.12 Blower + 6.00 Crank = 8-10psi @43125rpm
2.95 Blower + 6.00 Crank = 10-12psi @45610rpm
2.75 Blower + 6.00 Crank = 12-14psi @48927rpm
2.75 Blower + 6.20 Crank = 14-16psi @50558rpm
2.75 Blower + 6.40 Crank = 16-18psi @52189rpm
2.75 Blower + 6.60 Crank = 18-20psi @53820rpm
2.75 Blower + 6.80 Crank = 20-22psi @55451rpm
2.75 Blower + 7.00 Crank = 22-24psi @57082rpm

I understand that

"Boost is technically just a measure of "restriction" of airflow in a motor. Boost is not really something that can be acurately calculated since every motor is different. You are missing alot of variables: such as what heads you are running, cam, engine redline."

Sooo, I made some assumptions and came up with a baseline and will adjust the pulley combo as necessary but I had to start somewhere. From what I can see the 7in crank pulley will be all she wrote in terms of blower rpm so it is what it is.

Thanks!

Tom

 

It will make power either way

For what its worth, a buddy of mine made 18psi with a T-trim on a 383 w/out of the box Trickflow LT1 heads (didnt flow that great) and a 224/236 cam......with a custom 8" ASP crank pulley and 2.95" blower pulley....HUGE crank pulley Granted the 355 will probably "show" more boost at the same blower cfm than the 383, but my point is illustrating that the "boost" chart above is really irrelevant. I struggle to understand why they even publish a reference chart when everyone's combo is so different. A 383 with poor flowing heads could "show" more boost than a 355 with great heads/headers.

By publishing a "boost" chart like that just makes everyone think that that is the standard for choosing pulley size.

On the contrary, my motor "should" (according to that chart) make 8psi but actually shows 11psi on the guage....and its far from stock (forged shortblock, cam, longtubes, mild heads, etc..).

I totally understand that you see this chart only as an initial reference for boost, so I am not trying to be difficult I just have a real problem with supercharger manufacturers "quoting" boost levels for people based on pulley sizes as the only variable....only to cause people to be let down with either "less" boost (since some people get there hopes set on a certian number), or the other extreme where people have actually seen more boost than what was "supposed to be" according to the chart, in which they damage their motor from too much boost (not expected). It seems like every post I see about people buying blowers now is "how much boost is this going to make on my motor?", or selling pulleys as "15psi pulleys" when they make anywhere from 10-20psi on a given motor.

Really, the only way to accurately quote a boost number is on a bone stock motor with a standard entry level blower kit. RPM, cam, heads, cubes, belt slip, tensioner, filter, inlet tubing/size, throttle body, and many other variables in each motor cannot be summarized into a chart.

Jason

 

Actually I made that chart based on a few assumptions so I had an idea where to start. Vortech was absolutely no help at all. Take it for what it is worth but it was the only way I could try to figure out where it would be best to start given a few known constraints. I do understand your point though.

Thanks!

Tom

 

I understand where you a coming from Tom You are right.....the supercharger manufacturer's "tech" help is not helping people much!

In any case, that is a very nice setup you have! Keep us posted
Jason

 

Looks very nice.

 

yup boost is a measure of restriction, I would concentrate more on what hp levels you are looking to achieve. Should run good.

 

I had a T-trim using the 6.66/2.75 combo and only got 13 psi on my 383 / AFR210's / 224/236 cam. The setup looks really nice, but expect less than 15 psi.

AND, BOOST IS NOT SIMPLY A MEASURE OF RESTRICTION. I keep seeing this posted and it is not true. Sure, crappy cylinder heads and a small cam will register slightly more boost than good heads and cam. BUT, you still want positive pressure in the cylinder and manifold. If your heads and cam had ZERO restriction, you still want boost because the charge in the cylinder will be pressurized and more dense!

 

Too bad we don't have an Exhaust flow meter, or an exhaust pressure sensor. That would tell the tale of increased engine throughput, which is our real FI goal, right?

FSTR-THANU - looks very nice. Is that a 10-rib belt? Also, where did you get that casting that is attached to the motor?

Thanks,

Jim

 

Looks real nice! Awesome skills, bro.....

Eric

 

Yes it is a 10 rib belt. The castings are the stock pieces the kit comes with.

Thanks,

Tom

 

Many month's later and the car finally hit the dyno. It is a turd! Barely 400hp to the tire (Mustang Dyno) and it was only able to muster 10lbs of boost. The motor is a bit of a qustion mark though. I know it is a forged 355 with about 8.5:1, stock ported heads and intake, no idea about the camshaft. I thought the thing would make atleast 15psi but obviously not. I am not sure if it is even worth trying to spin the blower any harder.

Tom

 

Im just wondering if I sent you my blower pulley setup if you could make a cog setup for me Dayum I forgot about this post!