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Twiggy - Long Rod Aluminum Block Engine Build-up
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Author:  Doctor Dodge [ Sun Aug 19, 2007 7:04 pm ]
Post subject: 
Quote:
I just looked at Doc's cam card and he made a typo above - 266 int and 254 exh (not 244)...
Good observation but there is a reason I call that exhaust lobe the "244"

I have run into this before, a lot of cam grinders have a 254 degree lobe that is based on a smaller lifter. (GM .847 diameter?) The lash ramp on this profile is shorter and steeper, it tends to like .012 to .016 of lash.

On the other hand, Mopar engineered a profile that is almost identical but it has a more gentle lash ramp and faster flank... they based it on the Mopar .904 lifter, this is the exhaust lobe that was used on the Direct Connection "purple shaft" .244 degree SL6 cam. I have a couple of those cams, one I will never use in an engine because I use that cam to "cross pollinate" it's profiles into different cam grinders, the latest was Erson. (they are cam grinder #4 to get this profile)

Note: the original DC 244 degree SL6 cam was (is) a dual pattern cam, the intake profile is slightly longer and has a different lash ramp to support the tighter .010 factory intake valve setting.

OK... my point is that I had to "convince" Erson to copy the exhaust lobe off the DC 244 cam I sent them and told them to make a master of it. The funny thing is when you profile this cam's exhaust lobe, it also comes out at 254. Erson said " we already have a 254 profile" but I told them " not this one", I sent them the lobe plots that show the difference... they agreed and made the master.

Here is the rub, I am not sure how Erson has IDed the DC 244 exhaust lobe profile / master. They continue to call it a 254... the one Dutra sent us. I hope that Erson can distinguish it from the other 254 they have, especially as the years pass.
You will know when it's installed and lashed... but that is kinda late to find-out.
DD
EDIT - I called Erson and confirmed that they have a number assigned to the DC 244 exhaust lobe profile. That master is # F212/295
To order the above grind (266I - 244Ex) you would ask for a RV15M - F212/295
Author:  Doctor Dodge [ Sun Aug 19, 2007 10:27 pm ]
Post subject:  Timing Gear Mods...
Here is a look at the back-side of the alum. / nylon timing gear.
Note that the locating pin hole has been drilled-out to 3/8 so off-set bushing can be used to adjust the cam advance / retard.
A small oil drain hole was also added to the opposit side, to make sure oil pressure coming off the front cam bearing does not build-up behind the gear and push the gear / cam assembly forward. Be sure that this drain hole cuts into the gear's side wall so the oil has a path from the cam bearing's edge and out thru the hole. Once this oil escapes to the front face of the gear, it gets flung around and helps oil the chain.
DD

Image
Author:  dakight [ Mon Aug 20, 2007 5:40 am ]
Post subject: 
OK, so there's nothing wrong per se with the nylon gear, and I understand the weight reduction. Perhaps even more important the reduction in rotating mass. But, with that you must use a conventional "silent chain." Wouldn't a roller chain and sprocket set reduce friction? Does it even matter in a race motor?
I don't mean to belabor the point and I'm sure you know what you're doing, but I'm still scratching my head.
Author:  argentina-slantsixer [ Mon Aug 20, 2007 7:51 am ]
Post subject: 
I'm sure that all the oiling gimmicks that doug created will greatly reduce the stress on the timing chain and cam/crank sprockets... he'll have the sprayer in front, for the timing assy, the oil pump gear oiler, the groove on the rear journal so valvetrain will see more lubrication,
Author:  Dart270 [ Mon Aug 20, 2007 8:34 am ]
Post subject: 
You can run a conventional chain on a big cammed (high spring pressure) motor. I did for about 40-50k miles. Saw more wear on the chain/gears than usual, but it was fine.

Lou
Author:  Bren67Cuda904 [ Mon Aug 20, 2007 8:47 am ]
Post subject: 
I would think with all this extra oiling, one would need a higher volume pump to keep up with it all. I don't remember but I thought you where planning to use the AL oil pump. I also thought that these only came in the 5/8 impeler.
BTW I plan to ship back the pump you made for me. Maybe you'll be using it on this motor?
Author:  AnotherSix [ Mon Aug 20, 2007 9:28 am ]
Post subject: 
The stock nylon timing gears have been working well for decades. They have more hours of success than any other type of timing chain setup.

I prefer a premium roller set for engines that will see high rpm or that I want to run untouched for a very long time or are expensive anyway. On stock or street engines that will not rev that high I mostly use a stock type set with the steel top gear. The nylon type is not available aftermarket or I might use them too. I have never even heard of them being a problem. The stock type of chain and sprocket is more accurate than a cheap roller that does not have a true roller chain. Those get slack within about 20,00 miles, and many have play when new and still tight. If you run the steel top gear it will stay accurate longer than a cheap, non roller "roller" will. My experience is that the stock nylon type set should be replaced at about 100,000 miles, before it fails. I've seen them go much farther, but you never know at that point. Even if it does not have much slack, the teeth just fall off one day. If you run the steel top gear it will last much longer than that.

On an engine like this the stock gear will work just fine. The cam will be tired before the top gear will be anyway. I'd keep it light, since that is a primary goal.

I've never seen oil pressure being an issue in an engine that had the clearances set right. Most of the time the big pumps are not needed, the idea is that they are "cheap insurance"and will cover any weaknesses. It is better to have a straight crank and actually set the clearances correctly, run a smaller pump and lighter oil. No amount of oil pump will increase the oils film strength when the clearance is too large. For that you need a thick oil, pretty soon you are losing 10 or more horsepower just pumping it and your oil does not drain back well, windage and oil system durability are more of a problem etc..... Nothing like seeing 90 plus psi on a cold morning and hoping nothing breaks.

I don't think Doug is guessing about his oil system, and I know he does not need a larger than stock pump to support it.
Author:  Matt Cramer [ Mon Aug 20, 2007 9:38 am ]
Post subject: 
Interesting cam you have there - would it work in a turbo application too, or would a more conventional cam be a better choice?
Author:  LUCKY13 [ Mon Aug 20, 2007 10:35 am ]
Post subject: 
Thats pretty cool your going to give that chain a try, I just pulled the nylon chain set out of my 71 Big Block Wagon. It had 120,000 on it. But it was so bad that I had to take the oil pan off and dig out all the peices to keep my oil pickup clear. But heck that still lasting pretty good for aluminum & plastic.

So the cam is what it is, very interesting. I guess that is telling us alot about the intake side of the /6. I have some pretty good ideas as why that would work. But IMHO there is more than one reason. LOL, the truth is, when you lay the /6 all out on the table (figurativly speaking) its about a cluster mess of a engine. Its no wander it takes a odd event of a camshaft to fuel the little beast. I do hope there will be a dyno sheet on this one in the end.

Jess
Author:  Doc [ Mon Aug 20, 2007 10:49 am ]
Post subject:  The 254 - 254 (244) Grind
Here is the other DP cam Erson and I worked-out.
This one uses their 254 lobe on the intake and the DC 254 (244) lobe on the exhaust.
I would consider a wider lobe center for a turbo application. I have to think harder about how much advince to grind into the cam.
Again, be careful when ordering,.... "now which 254 goes on which lobe??"
DD
http://www.dutra.org/pictures/engine/er ... m-212-.jpg
Author:  emsvitil [ Mon Aug 20, 2007 11:09 am ]
Post subject:  Re: The 254 - 254 (244) Grind
Quote:
Here is the other DP cam Erson and I worked-out.
This one uses their 254 lobe on the intake and the DC 254 (244) lobe on the exhaust.
I would consider a wider lobe center for a turbo application. I have to think harder about how much advince to grind into the cam.
Again, be careful when ordering,.... "now which 254 goes on which lobe??"
DD
http://www.dutra.org/pictures/engine/er ... m-212-.jpg

Does this cam just replace the MP244 intake with their 254 intake?

How do those two lobes compare?

Do you think they'd make an exact copy of the MP244 cam?
Author:  Doc [ Mon Aug 20, 2007 12:33 pm ]
Post subject: 
Quote:
Do you think they'd make an exact copy of the MP244 cam?
I think Erson would / could do an exact copy of the MP 244 and I think we looked at doing that.
There was some reason we decided to use their 254 profile on the intake but I would have to get back to my notes to remember why. I think it was to get a little more lash flexability. (lash it tighter to get more duration and lift)
DD
Author:  Doctor Dodge [ Mon Aug 20, 2007 9:39 pm ]
Post subject: 
Quote:
I would think with all this extra oiling, one would need a higher volume pump to keep up with it all.
I don't remember but I thought you where planning to use the AL oil pump. I also thought that these only came in the 5/8 impeller...
Yes, all the statements above are true...
I do think this engine may need some additional low RPM oil volume because I did open-up all the oil passage ways and the cam journal surfaces have some wear that can not be easily fixed. (the Alm block's cam rides right on the aluminum block, there are no cam bearing inserts)

I will use a factory die cast aluminum oil pump housing to save weight... and yes, the only aluminum oil pumps were made to use the 5/8 (really .680) impeller thickness.

So... I made a 1 inch impeller HV die cast aluminum oil pump by adding a spacer to a factory unit. I have set the relief spring so the pump pressure does not exceed 50 psi.
See This Post for more info.
DD
Image
Author:  GTS225 [ Tue Aug 21, 2007 3:17 am ]
Post subject: 
Doug.....I trust ALL of this, with pictures, will be in the upcoming book?

Roger
Author:  Charrlie_S [ Tue Aug 21, 2007 6:05 am ]
Post subject: 
I think the major advantage of doing this is not the weight saving, but being able to use the 6 bolt pump housing. This will close off the unused pump pocket and allow the pump gear oiling mod.
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