it seems that this hole has to be perfectly centered to keep the the distrubutor gear from premature wear or binding. I belive that the intake just keeps the distributor at the right hight. So does the hole have to be perfectly centered? Instead could you just make a slightly larger hole? Just curious

Curtis

 

as long as the distributor is level, at the correct hieght, and is securely fastened down, if the hole is off just a little bit i dont see why it would cause a problem. the location of the hole itself isnt going to affect the mating of the distributor gear and the gear on the cam (unless its so far off that something is obviously wrong)

 

Actually, the distributor hole is generally larger (about 5/32nds) than the shaft boss. BUT its not level, its inclined about 8* to the drivers side. I disagree with John that you can simply drill it level.

 

TPI bases are the only ones that are angled. Look at any other SBC intake manifold. They are all level. They move the hole to compensate.

 

the TPI distrib hole is angled?hmm... ive never payed attention.

 

I have about a half a dozen TBI, TPI, Crossfire and Carb manifolds here and EVERYONE of them have the same 8* angle.

Drilling the LT1 on a level plane is asking for the distributor gear to bind and fail.

Here is an 1991 TBI intake from a Caprice



And a 1982 (carried over into 1983) Crossfire Intake from a Vette



The slant is pronounced and visible on any manifold that I have.

 

I would think if you had it too far off it would not fit. it has to slide in to a machined hole in the block right?? just asking.

 

i have a carb manifold i just looked at in the garage and it was as flat as a board, so there must be some that are flat.

 

sorry gotta throw up the flag on that one. no vette in 1983 i do see the slant though.

*update*

the more that i look at that carb manifold, maybe it is slanted. hmmm, all these years working on cars and i have never once stopped and noticed that. learn something new every day.

 

I am wrong, I just checked my old carbed manifolds. It sucks getting older, memory is the first to go.
But I conclude that they do not have to be angled. If I was to move the hole over towards the passenger side, the bottom of the distributer would still be in the same location and the distributor would be truely verticle.
the gear shouldn't ware because the lower end of the distributer must pass through a machined hole in the block first to maintain cam and oil pump alignment.

 

You're can't have both. If you move it over towards the passenger side, the potential exists to bind the distributor shaft in the guide passage in the block. Assuming that the passage in there has enough room to avoid that, the you still run the risk of the two being out of mesh from eachother.

But that aside, Moving it to the passenger side would work, BUT, you'd have to modify your template exactly to aproximate proper dist/cam gear lash. The way I had to do it was to bolt the intake to a large drill press with a template. I then lined up the boring bit with the existing base. I removed it and drilled the LT1 shaft hole, then bored the seat with a depth guide. This isn't an area where you wanna skimp. I'd leave this one step to a machine shop everytime no matter what my resources are.

 

Why, I am a machinist.

 

so should i machine the 8* angle on my shim??

 

I took the time and expense to do it. Nothing sucks more to lose a 2000.00+ dollar engine for an extra hour of work.

KR

 

It doesn't matter if you mount it at any angle or not as long as the distributor is shimed correctly to get the gears to mesh correctly. you could mount the thing upside down as long as the gears meshed correctly the angle doesn't matter. You could even mount the distributor on the other side of the distributor as long as you had the holes drilled correctly and a gear cut for the distributor cut at he opposite angle. But then you would have to run your plug wires to fire in the opposite rotation.You cut gears long enough and you get to know this stuff. comon sense helps out. I am a machinest too

 

This is becoming an increadibly interesting topic...

and in my opinion ALL theory's
lets see a GM write up on it or some facts.

Here's my thinking. The 8* angle at a given gear depth is going to put the top of the distributor drive gear MORE into the cam gear, if you straighten it straight up and down at the exact same given depth you'll now be wearing further down the distributor gear instead of as high up with the 8* angle. Thats my theory and my $.02. Now to get back to gm specs....

For those of you who've completed this. Would it be feaseable to weld a TIG bead in a circle around the drilled hole a time or two to build up some meat, then to put it on a mill and mill in that 8* angle, then redrill the hole to the right diameter. Seems to me that would put you PERFECTLY on target, assuming the welding was doable

How does this sound?

 

For grins I'll go out and check my 350 roller block out in the shed.....will the hole for the distributor in the block share the same eight degree lean or is it straight....stay tuned..

ok block leveled...


with dist installed....


it clearly leans to the drivers side. as GhoSSt pointed out, its possible to bind between the intake and block if the hole is out of place..the best bet would be when converting the LT1 intake is to have the spacer angle ground. however the question at hand is without it will it cause premature wear on the gears...that remains to be solved..

 

It would definately have to to be shimed correctly for the gear not to wear quicker. If the dist isn't placed high enough it would cause preasure on the gear and put it into a bind and cause excesive wear on the bottom and sides of the teath. If the dist is placed too high it will cause grinding on the peaks of the gears. If you check your distributors they will have a certin ammount (probably in the .030-.050 range) of up and drive travel to allow for production tolerances for the intakes. This would be more than enough to be safe if the distributor was shimed close to the correct ammount. If someone that has done this swap can stick the dist in the hole and rotate the engine with some marking compound on the gears it could tell you if the gears were making correct contact.

 

The question is....

How does the ANGLE play into the wear?


We know how horizontal and vertical placement does, but whats the story with the 8* angle?

 

If the angle was from front to back yes the angle would come into play on the wear of the dist-cam gear. However the angle in that direction wouldn't matter as long as long as the distributor is shimed correctly to eliminate that angle.

 

so is ponchos prognosis that you can install a distrib with a 0* tilt from side to side?

 

I would argue that the intake plays less into this than appears. The block is bored at an 8* angle, and the lower half of the distributor has 2 different mating sections over a 3 inch area corrosponding with the bore in the block. I say the intake "sets" the height of the distributor only, regardless of any angle, the intake is just to thin and is the uppermost of three alignment points. I have heard of oil leak problems from several people who have done this swap. No I dont know this to be fact or not, but it lead me to think of this. Now for my ...the distributor angle is controlled by the block, with that, the bottom of the mounting flange on the distributor will be perpendicular to that angle.. if the top flange surface of the intake in question is parallel to the bottom of the intake then the mounting flange will be up on one side.. even with a gasket in place, the uneven pressure across the flange, oil will seep out the weak side..I agree, for the swap to be "correct" an angled spacer would be best.. Bob

 

Hmmmmmmmmmmmm

I think im starting to piece together all this madness

I still want to know what effect increasing or decressing this angle is going to have??


We've talked about positioning the distributor UP, and DOWN, and LEFT, and RIGHT, but what happens if you go from 0 degrees to 8 degrees to 16 degrees? What problems will or wont this cause???

 

as long as the installed height is correct I dont see whether the hole is straight or at 8* effecting the gears, just the possibility on a nasty oil leak

 

I've lived with oil leaks as long as I've owned a GM

I just want to make sure I dont eat up more metal than I already have with these last 2 damned 305's

 

I also think people are confusing are confusing the issue. the angle being referrred to is the angle to bore thru the intake , not moving the location of the hole drivers to pass side in reference to the centerline of the block..right?

 

The distributor when sitting FLUSH against the intake on a GM intake manifold is slanted, it isn't level, its at about an 8* angle

THats the angle im talking about, whats the significance of that.

If i put the hole in the exact same spot but with 0* angle, what happens.

 

Lord only knows why gm put the distributor at a 8* angle (guy in germany scratches his butt, a tree falls in the woods in tibet, and a engineer puts the distributor in a small block chevy at 8*) but changing the angle But there isn't any reason that the angle should cause any problems. Let me see if I can explain it in simple terms. Ok take your self two pincils and stick them perpendicular to each other. Set one pencil strait up in the air and one pencil in front of you facing away from you now you want to rotate the angle to 8* offset. Does the contact points of the two pencils change...No. OK now just set one of the pencils on a table (the one facing away from you) and come back up to strait now the tip of the pencil is higher than it was at the 8* that is why you would have to change the shiming higher than normal. Just imagine the pencils as your cam and dist. When you start to do this you will start to see the reason the gears will still contact in the same way. You arn't changing the angle on the gears. Just try to think of it in the simplest terms (kiss Keep it simple stupid) you can. You have to imagine things like this in a 3D image in your mind. It is like taking a blueprint and being able to see how the part will look after you are through. Some of it just takes practice.

 

I am going to put the LT1 intake on my car very soon I am currently shoping for one. I will still put the gear at a 90* (strait up) I will check how the gears contact each other before I come up with a finished diminsion. Who knows how much veriance there could be at the mounting point of the distributor? It could be as much as .050 on that rear cast section. So each intake could need a different shim for the correct geometry.

 

im thinkin that the distributor HAS to be at a 8* angle seeing how the block is machine that way. All the intake does is keep it from going too low. Since people are mounting em on a flat angle on the intake, this is causing the oil leak. I will shim my intake when i do it.

 

I agree

For the extra 5 min on a mill the piece of mind of having it at OEM specs is worth it!

 

Any stabs at this idea?

I think its the route im going to go. Tig it, then it IS part of the manifold, mill it and how much closer to stock/cast can you get? No screwed on shims, nothing to break or fall off, etc etc

Does this idea sound good?

 

Sounds like it would be easier to mill the spacer to the 8* angle then weld the spacer to the manifold.
John

 

*patents his Idea really quick*

 

Well, if its worth anything I can give you guys some real world experience with my distributer. I've had mine straight up for about two weeks now and There is less oil on my manifold than before. Not a drop has been spotted. As far as I can tell the distributor meets the gears fine as well. So, I don't know if there will be trouble later but its A-OK for now.

 

Hehe now I'm shopping for an intake...lol I think how I may go about mine is to find the center of the hole, tilt the manifold 8 * and mill a mating surface the same outside diameter as my spacer. Adjust the thickness of the spacer for the gears, and it wont have to be ground to an angle. Not sure if this will work or not, don't have a intake handy to see if the intake deck is thick enough to handle the milling of the 8* seat, if not i'll just bore it out at 8* and mill the spacer. have to see once I get one here. cheers, Bob

 

Intake deck is very thin, MAYBE a little more then 1/8"

 

Update!

The hole in the distributor does not affect dist gear mesh in anyway. The gear mesh is attained by the long machined bottom part of the dist that lined up in the engine block distributor bore.

The intake angle is for the gasket seal only to prevent leaks. Once you install the distributor in the block even with the intake not bolted down you cannot move it around, it is rock solid. My intake hole is larger then the distributor also just like factory.

I am going to put the angle on the spacer when I turn them on the lathe, won't be hard and will eliminate any chances of leaks.
See the attached picture to see the angle relative to a loose fit intake. there are no bolts in the intake and i cannot move the distributor around at all.

 

You're just the man

 

hmmm....now where did I hear that?

 

I remember you mentioned it and I just had to verify it. You are the man!

 

actually I tip my hat at you for sorting the whole thing out in the first place...