underdrive + reroute [Archive] - GrandAmGT.com Forum

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GrandAmC9
08-04-2008, 12:27 AM
i have a few questions here
first i found a set of underdrive pulleys for the 3.4 v6 for a '93-'95 f-body
http://store.wpsracing.com/auspunstpuse14.html
will these fit on the grand am or did the bolt size/location change over the years? and if thats the case does anyone know where i can get a set (crank, alt., and water pump) like the ones above

seccond i've allready eliminated the a/c compressor via bypass pulley could i just drop the pulley all together and reroute a shorter belt? and would this combined with underdrive pulleys improve performance or does this not even make sense. i thaught that underdrive pulleys shorten the belt anyways so why not shorten it even more....

good idea or not

thanks for any help

GrandAmC9
08-04-2008, 12:08 PM
bump. any input

gectek
08-04-2008, 04:07 PM
no they wont fit...first off there isnt just a crank pulley and then a harmonic balancer like the older engines. its all one assembly now. also on the back of our balanvcer/pulley there is a timing ring that the comp need to inject fuel and get spark timing right. dont get the 3.4l iron headed engines(f bodies) confused with the 3400 engines. there was not an alum headed V6 engine that was SFI used in a RWD vehicle. thats what the 3400 is. its a newer gen engine, that is superior in almost every way. your car doesnt need to be underdrive anyway...if you want power go with intake exhaust, then ported manifolds and headers, and tuning. the pulleys are not going to hold you back that much unless you repeatedly pull over 5-6k for long periods of time, or run a supercharger. plus you dont have to worry about undercharging and/or insufficient cooling due to running a cat back...just my .02

GrandAmC9
08-04-2008, 08:58 PM
allright thanks... would it be a good idea to remove the a/c compressor bypass pulley and maybe one or both of the little pulleys on the timing cover just to shorten the belt maybe free something up or dont even bother

nickofcourse
08-04-2008, 09:43 PM
id believe minimal gains at best.

GrandAmC9
08-04-2008, 10:57 PM
well any gains would be great
edit: i also found these
http://mrzperformance.vstore.ca/product_info.php/products_id/96
http://mrzperformance.vstore.ca/product_info.php/cPath/23_25_39/products_id/97
a little pricey but still something to think about

Nick-G
08-05-2008, 12:44 PM
allright thanks... would it be a good idea to remove the a/c compressor bypass pulley and maybe one or both of the little pulleys on the timing cover just to shorten the belt maybe free something up or dont even bother

Someone correct me if im wrong but im pretty sure if you remove the ac bypass pulley your belt wont go around the water pump pulley or at least not much of the belt would be touching the pulley

GrandAmC9
08-05-2008, 07:26 PM
Someone correct me if im wrong but im pretty sure if you remove the ac bypass pulley your belt wont go around the water pump pulley or at least not much of the belt would be touching the pulley

i would just route the grooved side over the waterpump pulley on the outside, the whole thing would just be one big kinda circuar route ill post a pic soon on what i mean

plastic_indian
08-05-2008, 07:41 PM
Reducing belt-to-water pump pulley contact area by more than half is probably a very bad plan.

GrandAmC9
08-05-2008, 07:54 PM
old route
http://www.cardomain.com/member_pages/show_image.pl?image=http://memimage.cardomain.com/member_images/6/web/2982000-2982999/2982116_95_full.jpg

new route
http://www.cardomain.com/member_pages/show_image.pl?image=http://memimage.cardomain.com/member_images/6/web/2982000-2982999/2982116_96_full.jpg

GrandAmC9
08-05-2008, 08:05 PM
Reducing belt-to-water pump pulley contact area by more than half is probably a very bad plan.

im not actually going to reduce the contact area on much of anything

GrandAmGT-2008
08-05-2008, 08:07 PM
wouldn't you then be reversing the direction of the water pump therefore not pumping anything? or pumping it backwards... just doesn't seem like it would work.

plastic_indian
08-05-2008, 08:15 PM
^and an even better point! I suppose it won't much matter that you're driving a pulley with only the peaks of the belt's ribs if you're running a wp backward!

AaronGTR
08-05-2008, 09:57 PM
Why even bypass the ac compressor? There's no significant power to gain there because you aren't turning the compressor when the air is off. :rolleyes:

Anyway, no I wouldn't remove the ac delete pulley you put in. Again, not much turning resistance so you aren't gaining anything, and you risk screwing up your belt contact on other pulleys. I definitely wouldn't run it how you put it in that second diagram. First off, you eliminated the idler pulley over the crank. That would reduce the amount of belt contact on the crank pulley (bad idea!) and also change the angle and force applied by the tensioner (also bad idea!). And also you'd be running the water pump backwards the way you show the belt routed. It wouldn't work.

tejohnson
08-06-2008, 07:49 AM
This is way too easy. Have Nick-G take a picture of his new engine with an example belt routing. It is already set up to eliminate the A/C and has a FFP underdrive. You simply replace the lower idler pulley with a ribbed one. Then, get Gatorback belt 6PK1525. Done. See picture before idler pulley replacement, and look at the after picture of the ribbed lower idler that I took prior to shipping to Nick. You have to visualize the P/S pump. This would be a bad idea for anyone with a S/C setup, as there is less contact with the underdrive pulley. If you do not have an underdrive pulley, you will need a slightly longer belt.

EDIT: Here is the pulley replacement pulley you need: http://www.partsamerica.com/ProductDetail.aspx?MfrCode=FAA&MfrPartNumber=45971

Before:
http://groomlakelabs.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=2303&g2_serialNumber=5

After:
http://groomlakelabs.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=3485&g2_serialNumber=2

GrandAmC9
08-06-2008, 01:34 PM
ya i didnt even notice the fact that the waterpump would be driven backwards, thanks for pointing that out

so the new routing would look like this

tejohnson
08-06-2008, 02:28 PM
ya i didnt even notice the fact that the waterpump would be driven backwards, thanks for pointing that out

so the new routing would look like this

Yep.

GrandAmC9
08-06-2008, 05:29 PM
thanks a lot glad to see thats its been done and thaught out before i tried it the first way i thaught and skrewed it up

AaronGTR
08-06-2008, 06:52 PM
ya i didnt even notice the fact that the waterpump would be driven backwards, thanks for pointing that out

so the new routing would look like this



That way would make the water pump turn the right direction yes... but I still wouldn't do it.

Supercharger or not, you are greatly reducing the amount of belt contact on the crank pulley and water pump pulley and the force applied by the tensioner. You are likely to still get belt slippage. There is really nothing to gain by doing this if you've already replaced the compressor with an idler pulley, so why even bother? It's a waste of time.

GrandAmC9
08-06-2008, 07:32 PM
i guess just to reduce belt length and free up space in the engine compartment although minimal its still something id like to do while the motor is still out of my car, i guess i think theres no need to have it if i dont need it, i understand your position on it but to all his own, i know heres no need for it but why not try it and see how it works, could help someone out in the future to do some other sort of modification whatever it may be...

Nick-G
08-08-2008, 03:18 PM
To make things simple if you want to do it then do it. AaronGTR has some very good points but either way you probably wont notice a difference

Cliff8928
08-09-2008, 12:13 AM
ya i didnt even notice the fact that the waterpump would be driven backwards, thanks for pointing that out

so the new routing would look like this

I would at a minimum see if you can relocate your old smooth idler over to the other side where the W-Body belt tensioner would be to maximize the contact with the crank pulley.

GrandAmC9
08-09-2008, 08:09 PM
I would at a minimum see if you can relocate your old smooth idler over to the other side where the W-Body belt tensioner would be to maximize the contact with the crank pulley.

do you have any pics of this i have no idea where the w-bodys tensioner is

AaronGTR
08-10-2008, 04:12 PM
If you go back to page 1 and look at the pics Tejohnson posted you can see a round flat area with two holes in it, kind up and left from the crank pulley and under the front engine mount. I think that's where he's talking about, where the tensioner is on w-bodies that have the 3400 in them?

I think the hole on the left is too close to the tensioner to work, but the hole on the right might leave enough room to put the smooth pulley in. Not sure if it's the right size for the bolt, but you could easily re-drill and tap it if needed. This still isn't an ideal position IMO compared to the stock location, but it would give you a little more crank pulley contact and a little more belt tension than the other way you were thinking of, so it's really a very good idea Cliff came up with. :) Of course, thats gonna change the belt length needed to something different than what Todd said you'd need, but you should be able to figure out the new length easy enough by running a piece of string around the routing path. Have someone compress the tensioner for you while you mark the string and then measure it and order.

Cliff8928
08-10-2008, 10:47 PM
W-body routing...

http://us.tnpv.net/2003/GMC200307/GMC2003071650848_PV.jpg

And just for reference.... The N-Body routing

http://us.tnpv.net/2003/GMC200307/GMC2003071650873_PV.jpg

GrandAmC9
08-10-2008, 11:14 PM
better???
just looking for the best way to do this, i really appreciate the help guys, i'll go out to the garage at some point tonight to check if the pully will fit

Cliff8928
08-10-2008, 11:27 PM
Better... The tensioner will be significantly more effective that way and you have much more belt-to-crank pulley contact.

GrandAmC9
08-10-2008, 11:35 PM
good news the bolt is the same size as the right hole, needs a longer bolt and some washers to push the pulley out far enough to line up with the belt
off topic but has anyone ever put the w-body strut engine mounts on the GA

AleroB888
08-10-2008, 11:44 PM
Btw, if you want to use a smaller SC pulley, many 3.5 inch idlers can be found in salvage yards that will replace the lower 3 inch idler, take up some slack... If you need a 3.25 inch idler, look for a mid-90's Taurus', it should bolt right on.

gectek
08-11-2008, 08:29 AM
W-body routing...

http://us.tnpv.net/2003/GMC200307/GMC2003071650848_PV.jpg

And just for reference.... The N-Body routing

http://us.tnpv.net/2003/GMC200307/GMC2003071650873_PV.jpg

but the w body doesnt have the side mount like the n body does for the engine support...they use those upper dogbones...wouldnt you have to switch to that if you use the w body mounting for the tensioner?

GrandAmC9
08-11-2008, 06:12 PM
but the w body doesnt have the side mount like the n body does for the engine support...they use those upper dogbones...wouldnt you have to switch to that if you use the w body mounting for the tensioner?

no, the smooth pully fits right in there even with the front mount, ya those upper dogbone mounts are what i was talking about, just a thaught but wuddnt bolting that up to our 3400's increase stability of the motor or something?

Cliff8928
08-12-2008, 12:03 AM
but the w body doesnt have the side mount like the n body does for the engine support...they use those upper dogbones...wouldnt you have to switch to that if you use the w body mounting for the tensioner?

Not using the W-Body tensioner. Installing a smooth idler in the hole where the W-Body tensioner would go, but still using the N-Body tensioner.

gectek
08-12-2008, 08:33 AM
ah hah, thats what tripped me out...ko got it now