Lapping plate

Hi Guys,
To make sure your blower manifold is flat many teams use a "lapping plate" which is a flatness plate with sand paper attached. What is the proper proceedure and what type of sandpaper and grit. Where can you get such large sheets?

Thanks yankeedoodle

 

I will look to see if I have the name and numbers for you..Dave

 

http://www.sassyengines.com/featuredpart.html

We made our own plates. One was from 3/4 and the other 1" thick alum plates, than we have the machine shop deck them just like if they were doing a cylinder head. We use the sandpaper from the machine shops big belt sander that they use to flatten exhaust manifolds. We cut up that belt and glue it to the alum plate which we cut the leading and trailing edges at a 45 degree angle.

 

If you dont want to spend the extra time making and finding stuff JR at RBS superchargers sold me a great one a couple years back , I belief it was close to $ 175 and I bought like 10 sand papers from them . I havent used ones of the extra jet and have lapped like 5 times after making big changes.

Get yourself a good 18" straight edge to find where your dips and humps in the manifold top are.

Sometimes when in doubt I coat a little dye and careful and steady do some figure eights until the top is completely sanded , then verified with the straight edge.

We have found this , have the engine completely assemble and ready to fire, seal all ports , lapped the top , assemble blower and start the engine , let it cool down then the manifold will keep the shape. If you lap and take the manifold off IT WONT KEEP THE SHAPE please believe me I tried like 4 times and it always went back warped...

PM me if you need more info...

Hope this helps

JP

 

Lapping plates normally have grooves and are used in conjunction with lapping compound and used ones can be purchased at reasonable prices.

You could also use a Granite inspection plate with the sandpaper attached to it to use as a lapping plate, they strong, won't flex and are usually much truer in flatness than most normally machined plates.

 

Over complicating something that is complicated enough already

O-K sorry but I can not go two posts without trying to reinvent the wheel.

It seems the purpose of flattening the manifold sealing surface is to ensure its flatness when the bolts are torqued so that the blower is not distorted, following the idea that you have to torque the manifold to the heads first to keep the manifold from distorting it would also seem that when you torque the blower bolts they also cause distortion of the manifold surface.

So if you really wanted to be anal about it, you could use pressure film to study the actual distortion and resultant clamp laod changes the bottom of the blower would see when you torque to the intake. Then by only surfacing the high spots you would ensure the surface is flat under load.

Of course because of the small and even nature of the torque of the fasteners that hold the blower, you might find that as long as the surface was flat to begin with that there was little or no distortion when you torqued the fasteners? And who knows how likely it would be to repeat when reinstalling the manifold between rounds, but in this day and age of 18K blower lease programs maybe it would be worth a try for one of the high rollers.

http://www.tekscan.com/prescale/pricing.html

 

I/ and a few of the TF teams I worked on use a torque plate (1" plate with 8-12 dial indicators) as far as manifold to blower find it hard to think that 20-25lbs are going to make a diffrence when puttin almost twice that manifold to head.

 

I have experimented with pressure film. Although its neat, I didn't see anything different than what the lapping marks already showed me.
The key is, spin the blower by hand when not bolted down tight and than again after the studs are torqued, if it changes you are not flat.

 

What type sandpaper?

Still looking for info on what type of sandpaper(aluminum oxide?) grit(120?) and where is it available in such large sheets?
Thanks yankeedoodle

 

See my post above, I don't know the grit or type.

 

I have seen very big rolls in 36"wide aluminum oxide 80 - 120 grit. I have used 80 grit to straighten intake manifolds flange on passenger cars with a heavy 2" square 20 long straight edge BUT in my personal manifolds tafc I use the ones sold by JR at RBS they have glue on the bottom...

I dont know but you can check grainger as a supplier of regular sand paper??

 

we always used alumium oxide. 80 grit works fine .I have some left if you need some.

 

Maybe a stupid question but how do you keep all the grit and junk out of a newly built engine? I was also thinking if you did this lapping after every time you put the intake on too.

 

taf 316 is go it...that is what we use and you wont need to lap it as much I think mine has around 12 dial ind. on it it is the cat meow..Dave

 

If I knew how to post pix I would post pix of it

 

We just put a lot of rags and duct tape EVERYWHERE!!!!! inside the manifold.

On our setup we can take the manifold and blower in one piece out so that helps when taking everything apart while the engine is hot. I understand that if you take off the manifold without the blower while the engine is hot I could make the manifold uneven as it will cool out of shape.

At the track if the engine needs to come apart we take both manifold and blower in one piece also when putting it back together I start to torque the manifold in steps 10-20-30 from the middle outward while turning the blower , it shouldnt change the force required to turn the blower at all...

Also I last lapped this manifold two years ago when I first put this engine together so If done property you shouldnt need to lap the surface to many times...

JP