VAC carb build

[dwilfong]

Well here is my attempted to build my first carb from scratch.

Only thing left is the spray bar. Just have to spend some time on the flow box to get it right.

I also cut down the VAC drum and intake housing a .120 to bring the carb closer to the valve opening as I was advised by Andy Brown.

I also ground the front of the drum to .625 from the stock .588 size to accommodate the .605 finish boar of the carb.

The air horn is made to slide on and off to try different shapes.It is made from nylon rod that I got at the surplus store. It is easy to work with as it will sand with easy to make different shapes.

Will be testing it on my VAC 1.05 eng as I get the time and money to get some new bearings for this set up.

Going to give some full complement full ceramic bearing a try and see if thy hold up to the beating of the 1.01 piston on the VAC .91 bottom end.

I'm getting there Luis I have not forgot about you.

 

[RodneyPierce]

Looks good Big D

 

[Jose F Cid]

Very nice looking carb....any information Andy gave you is great as he knows his motors.

Good luck keep us informed.

 

[Pumpin]

what size bearings are you going to use??? i have a few vac 91`s and have had a few bearing issue`s with them also found that the crank and rod touched the bottom of the case, so i have clearenced both the crank and the rod.

thanks kevin.

 

[Tom Foley]

what size bearings are you going to use??? i have a few vac 91`s and have had a few bearing issue`s with them also found that the crank and rod touched the bottom of the case have you found a fix for this.

thanks kevin.

Never had this happen but you have to replace bearings before they get loose or blow up . Use fuel with 18 - 20 % oil . These engines are powerhouses and will rev to the moon but you really have to treat them to rear bearings regularly .

 

[Joe Warren]

Well here is my attempted to build my first carb from scratch.

Only thing left is the spray bar. Just have to spend some time on the flow box to get it right.

I also cut down the VAC drum and intake housing a .120 to bring the carb closer to the valve opening as I was advised by Andy Brown.

I also ground the front of the drum to .625 from the stock .588 size to accommodate the .605 finish boar of the carb.

The air horn is made to slide on and off to try different shapes.It is made from nylon rod that I got at the surplus store. It is easy to work with as it will sand with easy to make different shapes.

Will be testing it on my VAC 1.05 eng as I get the time and money to get some new bearings for this set up.

Going to give some full complement full ceramic bearing a try and see if thy hold up to the beating of the 1.01 piston on the VAC .91 bottom end.

I'm getting there Luis I have not forgot about you.

C3 P5 will last you longer......... hate to hear your balls are failing...... :huh: :huh:

 

[dwilfong]

Joe I went to the loacal bearing house and thy did not have a sorce for the P5 bearings.

Hase bin a pain to find the better grade bearings.

Where do you get yours?

Going to spend some time and try balancing the eng. After the steel carb barrle broke I think there might be a little vibration involved. <_<

 

[Pumpin]

Hi joe,

what`s the difference between p5 bearings i run c3 now but have had issue`s with these also, i agree with tom vac`s will rev to the moon but would last a lot longer if the cranks were longer and they had bigger bearings from the factory. We take some weight off the piston and the con rod and remove some material from the crank and the bottom of the conrod, also found that any less than .014" piston to head and they would touch.

I thought david might have found away to fit bigger bearings to the vac case, does anyone in the usa rebalance the cranks with mallory metal evan though this would make the crank heavier on the current bearings, i remember john ackerman used to rebalance cranks on ops 67 and picco 80 motors with a lot of success.

Is there anyone doing that type of balancing now???

Thanks Kevin.

PS i agree joe nothing worse than when you have balls that fail :unsure: :wacko: :blink:

 

[Don Ferrette]

Hi joe,

what`s the difference between p5 bearings i run c3 now but have had issue`s with these also, i agree with tom vac`s will rev to the moon but would last a lot longer if the cranks were longer and they had bigger bearings from the factory. We take some weight off the piston and the con rod and remove some material from the crank and the bottom of the conrod, also found that any less than .014" piston to head and they would touch.

I thought david might have found away to fit bigger bearings to the vac case, does anyone in the usa rebalance the cranks with mallory metal evan though this would make the crank heavier on the current bearings, i remember john ackerman used to rebalance cranks on ops 67 and picco 80 motors with a lot of success.

Is there anyone doing that type of balancing now???

Thanks Kevin.

PS i agree joe nothing worse than when you have balls that fail :unsure: :wacko: :blink:

The smaller bearings and long stroke are the Achilles heal of the VAC91's in my opinion. It's my personal belief that CMB used the 67/80 sized bearings to keep the overall case size smaller and make it a viable drop in replacement for the now defunct K90's (same bolt pattern). They are stout runners right out of the box and as previously mentioned will rev like no other 90 I've ever run. Because of the motors geometry I'm seeing the need to change bearings often, typically 12-15 heats is about all I'll get out of them before the clearances start to open up. Oil percentages didn't seem to make a difference one way or another and too much oil actually will worsen it as the balls will start to skid rather than roll accelerating the race wearing out (which is what I'm seeing worn when changing bearings). Starting out with a tighter fit like Joe mentioned may extend the bearing life and I'm going to give that a shot on my VACs.

 

[dwilfong]

I am going to try a new scenario with my next build. With putting the 1.01 P/L in the VAC case has just amplified the already short comings of the bearing.

Have talked with a few people and will try to balance the rotating Assembly with tungsten inserts.

Some have told me thy would make a full complement bearing from two bearings to keep the old OPS square head eng alive.

I will try this bearing set http://www.ebay.com/...9#ht_1197wt_679 http://www.ebay.com/...9#ht_1199wt_679 for the next build and a 30% balance on the assembly using the formula that Jack O'Donnell recommended in one of the treads before.

Will See if this combination will help solve the problem.

I look at this way if you have to change the bearings after 2 gal of fuel all the time. The cost of a good bearing will make up for all the bearing changes.

I spent some time testing the VAC 1.05 eng as it was a new setup and having the bearing fail made it a tough time testing. Could not tell what was what with all the bearing problems.

Got the boat all set up and smoking fast to have it all go to SH!$ in the first heat at the race was heart breaking.

Could only get about 6 runs till it went down hill fast.

I will tame this beast if it's the last thing I do. Ain't no toy boat eng going to whoop my A$$.

 

[stan simpson iv]

Well here is my attempted to build my first carb from scratch.

Only thing left is the spray bar. Just have to spend some time on the flow box to get it right.

I also cut down the VAC drum and intake housing a .120 to bring the carb closer to the valve opening as I was advised by Andy Brown.

I also ground the front of the drum to .625 from the stock .588 size to accommodate the .605 finish boar of the carb.

The air horn is made to slide on and off to try different shapes.It is made from nylon rod that I got at the surplus store. It is easy to work with as it will sand with easy to make different shapes.

Will be testing it on my VAC 1.05 eng as I get the time and money to get some new bearings for this set up.

Going to give some full complement full ceramic bearing a try and see if thy hold up to the beating of the 1.01 piston on the VAC .91 bottom end.

I'm getting there Luis I have not forgot about you.

How did the Carb do...did you guy's run it.

 

[dwilfong]

Well here is my attempted to build my first carb from scratch.

Only thing left is the spray bar. Just have to spend some time on the flow box to get it right.

I also cut down the VAC drum and intake housing a .120 to bring the carb closer to the valve opening as I was advised by Andy Brown.

I also ground the front of the drum to .625 from the stock .588 size to accommodate the .605 finish boar of the carb.

The air horn is made to slide on and off to try different shapes.It is made from nylon rod that I got at the surplus store. It is easy to work with as it will sand with easy to make different shapes.

Will be testing it on my VAC 1.05 eng as I get the time and money to get some new bearings for this set up.

Going to give some full complement full ceramic bearing a try and see if thy hold up to the beating of the 1.01 piston on the VAC .91 bottom end.

I'm getting there Luis I have not forgot about you.

How did the Carb do...did you guy's run it.

No Dale wimped out on Friday didn't want to mess with it before the race.

I left it with him to try when he gets some time.

 

[shoboat]

David,

I have the "Blacksmith Special" almost done.

It came out with some great numbers.

More constant pitch, it should work well.

I hope that new carb will pull it? LOL!!!

Thanks,

Mark

 

[dwilfong]

Did you use the 22oz Estwing and the hitch ball like I recommended. :huh: