screw blower drive questions

We're putting a psi-D on a big chief chevy outlaw promod. We have a rcd small snout with a 34t 8mm gt pulley. Planning on 92% od. We might be able to cram a 1600 belt on it with a 32 top pulley. Is the 8mm gt a durable setup? We'd rather spend money on the 11mm stuff if it will live better. If we change the top pulley and snout we could run bigger 14mm pulleys and a 1694 belt. Is the tiny top pulley the problem with screws killing belts?

We need a .625 spacer on the bottom pulley. PSI warns against it. Anybody have any thoughts. Always worked with a roots.

If we get rid of the bottom spacer we need to move the mag. Anybody run a 44 promag with an offset in the rear chevy location? We have room and it's crank triggered so if it was a little inaccurate it wouldn't be a huge deal.

Last thing, we have a home built crank support. Most hemis run without them. We were going to get rid of it but i'm warned to run the belt super tight with the psi?

Thanks ITA,
Mike

 

are you sure about a 1600 belt fitting a big chief? seems short
I wouldnt be concerned about a spacer on the bottom, as long as you use quality bolts/studs
I like the 11mm, but I think they only offer a 1590 and 1705 length

 

I have built some Big Duke/PSI engines. I use the Pioneer front mag drive and do some minor mill work on the front of the left head and valve cover rail for clearance. I use a idler bracket that I have built to clear the front cover and bolt it directly to the motor plate using the water pump mounting holes, without any spacers. I use a PSI titanium hub with no spacers. Line the blower pulley up with the lower and drill the intake. Mill the opening to match the PSI lower plate, and make a new idler stand to fit the location. Not sure what deck height you are working with but the 11mm setup would be my first choice. The 8mm purple belt works good for me also. You can also mill the top of the intake up to .250 if it helps your pulley/belt combo. Good Luck.

 

RCD now has the front mount distributor deal (not the offset) so you don't have to space it out. You can also clock it anywhere. Ken Lowe also builds one and both can be seen here.

http://www.rcdengineering.com/files/images/ads/Drag_Illustrated_47.jpg
http://www.kenlowe.com.au/KLRC_select_engine.htm
http://www.msdpromag.com/

Dunn, Sitco and RCD also offer their front offsets if you can fit the stuff in, similar to the Ken Lowe deal. Heck, Spud Miller just came out with another variant that looks like the old dual pump Enderle drive.

http://fuelinjectionent.com/webstore/product_info.php?products_id=190

As far as the 8MM belts, I was just talking to JR the other day on this and he told me the biggest issue the 8MM belt was during staging on the two-step. They would fling the 75MM wide belts off but the 84MM wide belts seem to cure that. Barry at RCD said pretty much the same thing.

Also, and somebody correct me if I'm wrong here, I have heard that only Littlefield and RCD make GT pulleys. The point is that quite a few other folks make 8MM pulleys but they are not GT but are HTD profile. If you take the better GT belt and run it on the HTD pulley, like the ones you get from PSI (or others), there is a lot of slop between the belt and the cog. With this slop, the belt is moving back and forth within the cog, not fore and aft but clock-wise and counter clock-wise. When you pedal the car or are on the two step, the engine accelerates and decelerates and whips the belt back and forth until it fails. Because of that, using the 8MM GT-PS belt AND GT pulleys with a 84MM width should be fine and also give you the range of adjustment you are looking for. Don’t forget you can change your idler pulley diameter if the belt is too tight. Will cost you some more but will give you some more range.

Like Bill said, the better belt will help you out. The PS (problem solver) series is a great belt and I’ve run it in 14MM with absolutely no issues in stretching or snapping. Of course it is also the most expensive but I went a year and a half on one belt on a roots. Looked at the 11MM and like Shawn says, not much adjustment room.


Tom

 

drive

I have a summer bros front drive with the mag smashed into the head as Bill mentioned. I'm pretty sure if I get rid of the spacer the belt will hit the magneto shaft. The psi gave me a TON of room behind the blower so I was thinking of moving the mag out of harms way.
The engine is 10.7 deck with 23.75 between pulley CL. RCD's chart shows that we can get a 1600-8mm belt on with a 32 top pulley.11mm 1705 looks workable also.
We ran a roots with 14mm htd and noticed the belt life was better when using an air throttle with the 2 step. Seems like NHRA screw cars do better with belts and I think it might be from the lack of 2 steps. I've noticed most adrl guys are staged with the blades cracked too.

 

I doubt you can get a 1600 8MM belt on with that height. I have a 10.2" deck with an Indy intake and when you add the PSI plate, my height is 20.625". I can only get 98 teeth with a 4.4" idler. Can't even get the belt on with no idler at 101 teeth per the chart.

I'm sure you can figure the chart as well as me, looks like a 1705 11MM with low 30's or high 20's for the top as well as bottom's in the mid to upper 50's range.

Oh, on the crank support, I'd keep it. Really helps on the upper front main. A lot of Hemi's have the crank support built into the front cover now so some of them may still have it when it looks like they don't.

Tom

 

the 1600 8mm belt fits my 9.8 deck engine fine with indy intake/psi just fine.

 

Going through this same dilema now.

Any updates on this stuff ?

 

Rear Drive

Stay away from the rear mag drive for a Chevy.
The cam gear drives the oil pump and the 44.
If you are using 60 /70 wt. oil and it's not heated prior to start, the work load on the cam gear will allow you to have early margaritas without the smiling face.

If you have your blower set back as most do, and you're not using the angled pump drive, when the cam gear gives way, you then have to pull everything to start the operation.

 

That would've been good info to have before I killed 2 dist. gears in 20 runs. I'm intalling a new cam this weekend. Mike Dunn assures me that the setup works on numerous pulling tractors. I like the idea of heating the oil...has to help.
1705-11mm is the one to run on a 10.7 big chief with indy manifold. I have 100 and 125% pullies.
It's all expensive but the 11mm has lived for 27 hits. 7 wide open on 2 step, the others were air throttle.
The big chief with a screw runs really strong. Do not follow the hemi guys into 8500rpm+ or lean tuneups. The chevy will pull a lot of gear ratio and eat lots of fuel.

 

my chevy with indy intake 9.8 deck,1600 8 mm belt combo worked fine,as mentioned earlier in post,i redrilled intake and radiused entry to suit psi plate worked fine,
as for the mag drive deal i ran a rcd tri drive,44 mag,peterson dry sump pump and waterman fuel pump again no probs,

 

Front Mag Drive

Overkill69

IF........ your going to use one of the above front mag drive assemblies, and it has the drive shaft that mates with the cam bolt, throw that idea away!!!!!!!!!!!

The portion of the hex drive shaft that is inside the "cam bolt" is only 3/8's of an inch long.The mag 44 takes so much torque to turn it, that the front mag drive hex shaft will turn in the cam bolt. The belt drive has 4 bolts to secure the "adjustible" portion of the belt drive to the cam hub. The shaft in a sense, can't keep up with the rpm's of your motor, because of the tug by the mag, allowing the weak link to now be recogonized. The hex shaft inside the hex cam bolt! This "torque" will then put additional stress on the 4 adjusting bolts, allowing the timing ring to turn, changing your cam timing. Then your pistons / valves enjoy the kiss of death.
Your handle might be "Overkill69", which I'm sure that does not relate to the thickness of your wallet!
So......... no drive shaft for a front mag drive, using the cam bolt as the point of attachment for your 44 mag. Go to a gear drive!!!

 

Oil Pan Heater

Steph's Fabrication Specialties:

Oil pan heater #6769
Works great.

 

While on mag drive subject, heres another option for the olds set up. http://www.trbmachine.com/TRB_Machine/Misc_Parts.html