drive belt for Spit

J

jbecker

Well-known member
I am building a LP Spitfire and am having trouble finding a fan belt that will work without an Alternator. I believe the belt will be 9.5 by 725. I have tried all the local auto parts houses and have had no luck.. I found a gates that is 730 long but that is too loose. Any help would be appreciated.
 
At Road Atlanta, I broke one on my Spridget. I think the oversize pulley is messed up. Advance, Autozone and O'Rielly's had the 27 in and a 28 in belt but I needed a 27.5". My friend David called NAPA and they had one so we got it on Sunday morning after practice. For the Sunday morning practice session, I used a 28" lawnmower belt, its fatter so it worked.
 
Bill, I like that, I thought of similar solution like that for years but never did it. On my current MGB vintage race car I now use a single stage TDC external oil pump, so I now have similar belt adjustment with the bracketry for it. Note this is my team mate's car, not mine, I did the pump conversion on his car yet, and this was the pic I had in this computer, but my car is basically the same set up. David Headley helped us with this conversion, since he had done this previously on his vintage MGB.
 
jbecker":872br5r3 said:
I am building a LP Spitfire and am having trouble finding a fan belt that will work without an Alternator. I believe the belt will be 9.5 by 725. I have tried all the local auto parts houses and have had no luck.. I found a gates that is 730 long but that is too loose. Any help would be appreciated.
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On your LP Spit, which water pump are you using? Also which engine, as the crank pullies are different diameter (unless you have a custom pulley)?

I have found that different belt brands have slightly different V shape so one 9.5x725 may fit and another may not. Also, some are designated 9.5/10.

One trick you can do on the Spitfire if you are just running the crank and water pump pulley is to slot the three bolt holes for the water pump housing. You can get a little adjustment this way by getting the bolts almost snug, applying desired tension then fully tightening. For this it works better not using a gasket where the housing meets the head but rather a good bead of strong RTV sealer.

Bill's suggestion may be a good engineering fix, but tons of laps have been done with the above simple solution.
 
Tom;

"One trick you can do on the Spitfire if you are just running the crank and water pump pulley is to slot the three bolt holes for the water pump housing. You can get a little adjustment this way by getting the bolts almost snug, applying desired tension then fully tightening."

Did the same on a Sprite Series A motor decades ago. Slotted bolt holes and pivoted on one of the dowel pins. Used the gasket with no leaks.

Also noted that different makes of belts have different dimensions. Some fit deeper/higher in pulleys and some are just longer/shorter. Have quite a collection of these somewhere.

RJS
 
jbecker":3gf5rza0 said:
I am building a LP Spitfire and am having trouble finding a fan belt that will work without an Alternator. I believe the belt will be 9.5 by 725. I have tried all the local auto parts houses and have had no luck.. I found a gates that is 730 long but that is too loose. Any help would be appreciated.
Click to expand...

I had the same problem with my Sprite. No "off the shelf" belt would fit just right. I asked a friend of mine (who was a Napa parts guy) and he suggested going to an industrial supply house. So I went to Detroit Ball Bearing (now called Applied Industrial Technology) and they had the right widget for me. I ordered three so I wouldn't have to screw with it again.

Tom's solution is the next best option to finding a perfect fitting belt. I've seen it done a bunch and works well.

Dayle.
 
Thanks for all the help. I will try one or more and look forward to getting the Spitfire back on the track after about 20 years in a garage. Won't be ready for the Runnoffs but maybe later this year. Any of you at Laguna in October look me up and we will have a beer. I will be racing the Yellow Mini in HP.
 
With no real adjustement getting just the right belt could be tricky.

I had a similar problem many years ago, with a ford thunderbird turbocoupe, it had this silly twin belt set-up. Sure there was a adjustemnt, but it had two belts going around the same pulley's just try replaing those and getting two that will work.

Many newer cars have a spring loaded tensioner that could be adapted, or having some small adjustment like the slotted pump mount.

Might also try McMaster Carr, industrial supply, they might have belts in different length and width.

I use a alternater, gives a place to adjust the belt, with the large aluminum pulley, can't be much power lose.
 
Tom Broring":1tnz91vr said:
One trick you can do on the Spitfire if you are just running the crank and water pump pulley is to slot the three bolt holes for the water pump housing. You can get a little adjustment this way by getting the bolts almost snug, applying desired tension then fully tightening. For this it works better not using a gasket where the housing meets the head but rather a good bead of strong RTV sealer.

Bill's suggestion may be a good engineering fix, but tons of laps have been done with the above simple solution.
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Tom's correct. The simple solution described worked well for me. Until it didn't.
Killing a perfectly good cylinder head when the steam leaked out of the water pump housing/cylinder head interface was all the incentive I needed to do some engineering.
 
Used the elongated holes in the water pumps pivoting on one stud or alignment pin on our Sprite engines since 1990 with no problems. Used gaskets glued to the pumps and Hylomar non hardening sealer on the gasket to block faces. Understand Hylomar is hard to get now but Coppercoat etc. works just as well. Silicone sealers will not work as they won't "follow" the pump as you adjust the belt.

Bob
 
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