Corvetteran

According to all the literature I've seen regarding the 70 BB with A/c, and PS, there is supposed to be an idler to tension the water pump to crankshaft belt. The problem is that my 70 BB did not have one, and it seemed to function OK without it. Now that the engine is rebuilt and together, I don't see how it could have had a belt between the crank and water pump, but without a means to tighten it. According to the assembly manual there is a common belt on the second groove of the main pulleys between the crank/waterpump/PS pump, and another belt between the main pulleys and the A/C. The alternator is belted to the PS pump. That leaves the third pulley groove for the crank to water pump belt.

Is there a way to get around this, other than to spend $140 for a new idler?

Old Cheapskate...........

mayberg

I ran my 454 without the primary crank/water pump belt for several years. The risk you run is having the water pump not turn if you lose 1 belt.

70vert

This is what I did, get a belt that is a tight fit without the tensioner. To install, remove the water pump pully, slip the belt on, reinstallation of the pully will tension the belt. Obviously, this will be a trial and error effort to get correct lenght of the best fitting belt.

SmokinBBC

Hello Old Cheapskate

Did you check the mounting hole? The previous owner of my '70 broke the bolt off in the hole. So he put another ilder pulley mounted on the upper block right below the passenger side head. Of course he used a special belt.

I removed the broken bolt and put in the idler pulley where it belongs. I put on a full repro belt set and everything fits perfect.

I bought the 140 replacement from ZIP. After mounting it, I found an original off of ebay......so, as it goes, I still have the one from ZIP. It has about 200 miles on it. You can have it for $70 and shipping if you want it. You will still need to buy the the adjusting stud and mount kit..$30 at ZIP.

PM me if you are interested.

Paul

73, Dark Blue 454

Here's more info:

http://forums.corvetteforum.com/show...=captured+belt

GaryS

Yeah, there is a way. Just follow some of the steps that your fellow Bubbas have offered! Seriously, why not do it the right way and scrimp somewhere else? They designed a belt tensioner into the system for a reason. I would suspect that, without it, you will be putting a lot of lateral pressure on your main crank pulley. I don't think you want to do that!

Gary

halfmoontrail

This is a great solution...my '69 427/435 with power steering uses this setup...no idler pulley, and a captive belt on the innermost pulleys.

Steve

Corvetteran

Thanks for the replies guys........ Yes, my worry is that just fitting a belt between the water pump and crank without any way to adjust it, will add too much stress and cause premature failure of the water pump bearing.

Smoking BBC....what does the adjusting nut and mount kit consist of?

.........

Tom454

I've had the belt/no-tensioner on my LS5 since 1986... do the math.

No problems whatsoever.

Tom

SmokinBBC

The mount kit is a bolt and metal sleve that goes on the bottom of the pulley to the block. The adjusting stud goes in the top. When you pivit the pulley on the mount bolt to set belt tension, tighten the nut on the adjusting stud to hold it in place.

www.zipcorvette.com

ZIP parts #'s m2313 for stud

m2453 for mount kit w/PS or m2454 wo/PS

Sayfoo

This does work. Many people use this. Not to worry about the belt tension being too much as any new belt that you can fit on will stretch.

bashcraft

Does anyone know what size belt this is?

Tom454

They used to have a listing at NAPA for an "idler eliminator" belt...

but I just called and they no longer have that listing.

Mine is a NAPA belt.... maybe I can still read the number off it.

Sayfoo

I'll check mine also. If you have a old belt, you could cut it to the correct length and then have the parts house match it.

Tom454

This is taken directly off the belt...

NAPA PREMIUM XL 25-08003 ... made in USA

The last part.... made in USA... is a tip off that the part number is no longer valid.

I think it's time for me to change my belt. It's probably 20 years old.

Tried looking up the number on NAPA's web site... no luck.

Have to call NAPA and ask them to look it up & cross it to a new number... if there is one.

I emailed them.... we'll see.

There is a trick to putting it on since it has to be on both pulleys at the same time. The water pump pulley must be removed, the belt slid over both pulleys, and one screw installed through the WP pulley into the WP hub. Then it is pulled tight, and another screw is installed. Once you get 2 screws installed, you can use screws or studs.

You can also start the install using studs instead of screws, but it can be tough to get the WP pulley over the first stud.

Tom454

NAPA says the new number is 257315.

Advance crossed the old NAPA number 25-08003 to Dayco 15315.

I just bought a Dayco because I was there, and wanted to see if it was any good.

I'm not at all impressed with the Dayco.... looks like a washing machine belt.

Better stick with the NAPA.

73, Dark Blue 454

Can you cross the Dayco number to a new NAPA number?

Tom454

257315.... per above

bashcraft

Not sure if this will help anyone since I'm not using the stock pulleys. I have the chrome steel pulleys from Summit and they are 7.60" dia for the crank pulley and 6.30" dia for the water pump pulley. Anyway, I bought a 35 1/2" belt and it fits perfectly.

Tom454, you said the NAPA number crossed over to a Dayco 15315. That is a 31 1/2" belt so obviously my pulleys are different than the stock ones.

Tom454

Advance crossed the old NAPA number 25-08003 to Dayco 15315.

My 70 has A/C, P/S, P/B. Pulleys are specific based on accessories.

Don't know if/how this affects pulley diameters.