On-Center Front Cover Mods

[stevec]

The on-center motor appears to be .120 longer than the off center motors. The extra lenght is at the front of the motor because of the cross bolt mains I assume. So when mocking up the front cover the two oil pan bolts in the cover need to be re-drilled. No problem. My question is this will there be an interference problem between the harmonic balancer interuppter ring and the CPS. With the cover moved out .120 makes it closer to the ring. The crankshaft and balancer length did not change any. I dont think making a spacer for the crank would be the best way if they were a problem. I am going to mock this up soon and will let you know what I find. I was just wondering if some of you guys have been there done that.

BTW I am using a BHJ balancer, stock 3.8 front cover, and scat crankshaft. The cover will use duttwiler oiling.

Other mods to the cover include welding up the area on the bottom of the cover motor sealing side and milling flat. The on center block has no meat in this area. So you will get an nasty oil leak.

On more thing, I recall seeing a l reference to this issue in the Buick Stage II Racing Guide by Dave Emanuel. He was describing the difference between the two blocks stating that the on center required special connecting rods and intake, same crankshaft, camshaft, and cam drive as the offset bore blocks but required shortened front cover.

The part number for this cover is 2550169. The only problem is there is no place to mount an oil pump on this cover. I have thought about shortening a stock cover, there looks to be enough meat there but this would screw up the camshaft sensor and camshaft relationship.

Thanks for listening.

Steve C.

 

[TurboTR]

I think that one option is simply to space the damper out .120". This allows the pulley to line up with the accessories too. We just re-used the cover off my old S1 off-center motor. How the cam gear winds up aligning with the cam sensor gear might be a matter of the spacing of the cam stack up (if you use a roller). Someone else will have to say.

TurboTR

 

[750H.P.V6]

Steve,

The Most Right way to fix the problem is to shorten the cover by .120". This is'nt the easiest but will provide the best results. If you just put a spacer behind the balancer to space it out the necessary .120" this does nothing to correct the alignment problem between the cam sensor and the distributor drive gear on the cam.

The gears won't mesh properly although it will work. It is quite possible to experience accelerated wear on one or both gears. Keep in mind if you shorten the front cover you will have to remove .120" from accesssory bracket to make everything line up properly.

I hope this makes sense.

Neal

 

[EightSecV6]

OH Jeez...the cat is out of the bag!! Steve call me tomorrow and I'll give you my solution to your problem!!!!
Bill Anderson

 

[Mac in SD]

Stevec, I had my front cover milled .120 in order to keep the cam gear-sensor gear alignment straight. Probably more importantly, I did it because Buick and Ruggles said it needs to be done when a production cover is used on an on-center block.

Bill, I'd really appreciate it if you could post out your response. (Steve, maybe you could post it after you call Bill. )

On the other hand, I don't understand where the "oil leak" is supposed to be. This came up before (Lonnie? Chuck? I forget.) I went over my block and cover then, and I didn't see it. Where is this leak supposed to come from? Haven't fired it up yet, so it could save me some headaches. TIA.

 

[Bad as L]

I heard about the leak deal too, and I couldn't find anything that would pose a problem. It sounds like it is problem on a few blocks but not all of them.

On two of the stg II on- center blocks I put together, I didn't mill the front cover. ( I have in the past) I found it easier in the long run to space out the damper AND the cam sensor gear. I think the cam sensor gear spacer is available from PT&E. It replaces the fuel pump eccentric. Then you have to machine a recess in the gear itself so the bolt dosent hang out too far, I think the gear is available from PT&E also. Then you have to make damn sure you have a strong enough bolt and washer (the washer is the key here) to hold this hole mess together. If the washer is to thin and to soft it will yield under torque and then the big problems begin.
Dale

 

[TurboTR]

Thanks Dale; I was wondering if you'd step in here. I guess the spacer route is an option for the roller cams, but flat tappet is pretty much a must mill the cover thing to get the cam sensor to line up. One other nice thing about the spacer route is the accessories line up then too.

Or h*ck, get real off the wall, since we have waste spark we could also just run the dual trace crank sensor setup, along with a 3800 cover lower half and geroter oil pump driven off the crank (with milled flats) and can the cam sensor altogether, like we talked about in Kendall's thread I have several of those sensors laying in a box, but only one set of the dual interrupter rings. If that pump setup is better and worth real, useable hp vs the std pump, well I guess that'd be the hot setup then.



TurboTR

 

[Mac in SD]

Ahhh, yeeesssss....forgot about the flat tappet requirements. Good point, Todd.

 

[Chuck Leeper]

Leakz??

Mac, the leak comes into play w/ a stock ft cover, [unmilled] on the stage block. The cover is molded in such a way right below the crank sensor mount area, that the unmachined area in the cover does not contact the gasket and press it to the block, [x bolted ft and rear blocks anyhow]. I had to fill the cover w/ some Jb weld and mill it flat.. Wala! no more leak...
Also, put some sealer on the fuel pump block bolts. they go into the oil area. I used the pump block off for the relief return from the Dutt external pump..oil is pushed into the t. chain that way and drains down into the pan.

HTH

 

[S2V6RACER]

Front covers

I find it amazing how some people say the front cover CAN'T be milled, then after this thread see how many have done it.

Seems some don't want to give away secrets.

Ted

 

[Mac in SD]

Thanks, Chuck. I had my front cover off again (twice!) to figure out why it wouldn't prime. It looks like the milled cover is compressing the gasket okay. But I see what you're talking about.

Finally got it to prime, but only because Neal Steward took the time to help out a brain-dead, bitter old man like me. It was another case of a new front cover not being machined correctly. I didn't think it mattered when using the Duttweiller external pump setup, but all those holes have to be drilled just like a stocker. What a PITA.

Hopefully, I'll fire her up tomorrow. Light a candle for me.

 

[KendallF]

Mac, I've BTDT! Was it the hole that's supposed to intersect that cavity that feeds the gears? I thought I was going nuts last year trying to prime one of those. Good luck on the break-in! I want to hear how it does.

 

[S10xGN]

Kendall,

What's the latest on your custom "geroter" front cover?

 

[Mac in SD]

Indeed, Kendall, it was the same one...

...the one that intersects the feed cavities. AAAAGGGHHHHH!!!!!

It just goes to show you that, no matter how many threads some people read on the BB about front covers not being machined correctly, they'll still screw it up.

I guess the lesson learned is that, even with the Duttweiller setup, all the cover passages need to be drilled right.

I tried to fire her up late Sunday....ruh-ruh--ruh-----ruh-------ru.........dead battery. Put the charger on it overnight, but by Monday AM it was still dead...need a new one.

The ATR downpipe rests nicely on the frame...don't know exactly what I'm gonna do about that. It looks like going from a 4-bolt on-center turbine housing to a tangential would make the difference. That, or I've got to raise the straight-pipe somehow...