FAQ: Smaller SC pulley? What Size?

You can't tune the PCM with just a scanner. You're going to need a DHP Powertuner or a HPtuner. Try clubgp.com in the for sale section they are selling on there a lot. You will also need a laptop to run the program but you can get a cheapy if your only going to use it to tune/scan.

I'd start with a 3.5" Pulley to begin with. Try intense-racing.com or zzperformance.com for a MPS.

Make sure to go to Autolite 104's and a 180* T-stat. Fairly simple supporting mods for the 3.5", the gutted box is a good start though.

I have the 3.5" SC pulley with no tune, and the 3" downpipe from Hogan seemed to really bring the power of that smaller pulley to light.

Best thing to do is try (and I use that term loosely) and figure out how far you wanna go with your Riv.

You need to scan for KR before going too far with a pulley swap. My mods: 180 thermostat, one range cooler plugs, gutted airbox with drop-in K&N filter. After those changes, I started out with a 3.6 mps system from Pulley Boys. Suddenly I'm seeing up to 5-6 deg of KR when I had none to speak of before. I have an LS1M scanner to check for KR.

So I have a problem with just a 3.6 pulley swap. I do have a newly ported front exhaust manifold, and a 3" Hogan downpipe both waiting to be installed. I'm hopeful those changes will take care of the KR problem so I can go to a 3.5 or maybe 3.4 later. I'd like to go with a PCM from Holland MS or Intense, maybe ZZP. Just don't see myself having the time to learn to use and USE a tuner, but would go with HP Tuners if I did.

Agreed, no smaller than a 3.6" SC pulley on a stock car without scanning. You typically won't get that much KR with just a 3.6", but every car's different, as we've seen in Dave's case.

What size pulley should I get? This is what I am running right now;

SLP Headers
No Cat or resonator (for now)
3" exhaust going into 2.5" and Magnaflow mufflers
160* thermostat
104 plugs
FWI boxed in for cooler air
HP Tuner
Always 93 octane or better

Somewhere I saw as low as 3.25 but that sounds way to small. Maybe a 3.4? Car runs absolutley perfect and always has. Higher mileage but you could not tell.

I would start with a 3.5" Modular SC pulley system. Then you can size down as your scanner tells you it's okay.

i think with that much exhaust flow and hp tunner he could run a 3.4 or maybe even a 3.3, provided he scans and knows how to tune out any KR.
just make sure all of your maint and repair items have been checked off before you go adding boost to an older motor. ie. fuel filter, pcv, 0KR right now, top end clean, TB/MAF clean, etc.

I believe 3.25 is too small w/o rockers or a cam, IIRC.

No cam, no rockers... It's like an airflow blockade inside the engine. He can probably run a 3.4", I just suggested he start with a 3.5".

Agreed, a 3.5 mps should be a safe starting point.

what is the difference in boost between the 3.5 and the 3.4. Is stock blowing about 6-8?

I believe each 1/10 drop in size, equates to approx 1-2 lbs of boost.

Gary Holland has an excellent modding guide: http://users.adelphia.net/~gholland/newbie.htm

stock pulley is around 6/7psi boost and with my 3.4 i see around 10/11 psi max.

I topped out at 9 psi with a 3.6 pulley.

i'd say you're good for a 3.4 but if you want to be safe about it, do the 3.5

Boost depends on the rest of your set up, and ambient air temp, not just your SC pulley diameter. You could slap a 3.4" on there and see 10 psi, then add a cam and see it go down to 8 psi, then wait till winter and watch it go up to 9 psi.

This is why I have 4 different SC pulley sizes. MPS is the way to go.

AA wrote:

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This is why I have 4 different SC pulley sizes. MPS is the way to go.

Yeah, wish I had a 3.8 mps pulley to swap back on, so I could race with my new exhaust mods. I only ordered it with a 3.6.

from: https://rivperformance.editboard.com/series-ii-engine-transmission-f4/intense-vs-zzp-sc-pulleys-t971.htm

After comparing the 4 companies products and reading this thread, I've come to a couple conclusions -

a) the free market system ain't exactly driving prices down

b) there's no need for the 8 thread pulley unless you're upgrading to an 8 thread belt system, which you don't need to do unless changing to a whipple SC or the like.

I'm not building a fwd car for more than 400 hp, so I should be able to get buy with a 6 thread belt. I don't like the look of the extra threads, so I'd rather have the Smoothflow or Pulley Boys MPS.

Pulley Boys has free shipping through their ebay store, so I guess they win.

Soooo - couple questions -

Is there a pulley puller going around? Can I get it?

What thermostat do I need to get?

With a FWI, AL104 plugs, and thermostat, how small of a pulley can I run, and how much power will it make?

Most would recommend no smaller than a 3.5" pulley for that setup, but honestly you will probably see too much KR than you'd want. I'd recommend a 3.6" until you open up your exhaust.

3" DP I'd say is safe for the 3.5", and then you need some form of manifold work for the 3.4" to get rid of KR.

And you need to get at 180* thermostat, unless you want to change from the 160 to the 180 for the winter. Plus, the 160 is harder on your engine. Most don't recommend it.

As far as a pulley puller goes - I would start your own thread for that specifically.

Jack the R wrote:

Is there a pulley puller going around? Can I get it?

I have one for sale... i might be able to lend it out if you'd cover shipping both ways. PM if youre interested. I'm a little nervous , since you stole Aarons strut tower brace.

As for the pulley size , i'd say a 3.6 is fairly safe , i 3.5 is kinda safe for the most part and a 3.4 is borderline.

If ever you can't find a loaner for the puller, I'll lend you mind. I will not be able to get it out to you until early July though.

Jack the R wrote:

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What thermostat do I need to get?

With a FWI, AL104 plugs, and thermostat, how small of a pulley can I run, and how much power will it make?

Jack, I'd also recommend going with a 180 t-stat. A 160 isn't ideal for street use, while a 180 will open earlier than the OEM unit, and has had no negative impact on interior heating on a -25 ND winter morning.

Unless you can scan for KR, no one can tell you what size pulley is safe with your planned mods. Read the mods in my sig. I'm still getting up to 4deg of KR with a STOCK size pulley! Granted, my timing is advanced a few degrees with the DHP modified bin file. With stock timing, I might not see any KR or maybe just a degree or so? I need to play with my Powrtuner and figure out how to back the timing off a couple degrees. I'm also concerned my injectors may not be flowing properly, after 118k miles. If partially plugged, I'm sure KR would be the result.

OK, here is the question:
what do you all think is the best size pulley to use? I don't hot rod or race but I do like to get up 5 over the speed limit as quickly as possible! I would like to go with a 3.4" but have been starting to think after reading some posts that it may be one size too small. Or maybe this is not a mod that I need to do at all with gas @ 4.61 a gallon here in Seattle! Speaking fo gas, if I drive it the same as I do now, will the milage go up, down or stay about the same?
Thanks for the time guys!

98 Riv 90,000 miles.
mods: cat back exhaust, gutted air cleaner, 104"s, k&n air filter 17" wheels, 235/55r17 tires

A good rule of thumb is to never drop pulley sizes without scanning for Knock Retard first, and monitoring for KR after the swap. If you don't have a scan tool, I'd say you might be safe with a 3.6 pulley, but again, NO one knows that w/o scanning your car.