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XRV8 Gremlin

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g-man View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote g-man Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2019 at 9:37am
You know I truly enjoy reading your posts.
I love the work you have been doing on the Rambler V8.
Just out of curiosity, I forgot what you said earlier...Why did you go with a dual-point distributor, and not an electronic unit?
Was it just for the cool factor? Or was there there another specific reason?

Also...have you ever looked at the possibility of using a rocker arm from another make of V8, that might interchange with the Rambler V8 rocker arm?
Or perhaps another rocker arm that will work with a minimal amount of modification?
I'm just thinking of down the road when NOS rocker arms are not available anywhere anymore.
Also maybe the possibility of using an aluminum or billet steel, full roller rocker arm?

What are your thoughts on this?

g-man
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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2019 at 7:15am
The good thing about shaft rockers is that the rocker arm can be bushed with a thin bushing if necessary, and the shaft itself wears more than the rocker. Wouldn't be terribly difficult to change the shaft diameter, provided a suitable diameter and hardness material can be found. Then hone rockers to fit. But that's way down the road...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Buzzman72 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2019 at 8:55am
Needle bearings at the shaft and a roller tip would make a high-tech set of RV8 rocker arms...
Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote amcenthusiast Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2019 at 7:43pm
Harland Sharpe specializes in making custom roller/roller tip rocker arms for anyone else who's interested.

Jesel currently has a good reputation for sturdy custom race rocker arms.

Crower makes 'special order' rocker arms for race engines.

-------------------------------

The stock Rambler V8 shafts showing wear can be built back up with brazing, and hard chromed. (hard chrome process is typical for rebuilding 'big 18 wheeler crankshafts -to restore worn crank journals)

I have a link on my website to a company who specializes in rebuilding shaft mount rocker systems, -who installs bronze bushings for the rocker arms if needed etc.

(whereupon further investigation, stainless steel seems like it would be a good choice for custom made replacement rocker shafts, but it is not, because stainless steel does not dampen micro-vibration as well as standard alloy steels = poorer 'harmonics')


Edited by amcenthusiast - May/02/2019 at 7:19pm
443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcenthusiast Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2019 at 7:55pm
[QUOTE=Buzzman72]Have you ever considered trying to adapt a D-Jetronic efi to the RV8? Or a later derivative?[/QUOTE
Part of the whole idea of this car is to show it's not stupid to build a Rambler V8 powered hot rod.
 
I'm certain I've gotten more bang for the buck using carburetion, and this setup is very dependable.


Edited by amcenthusiast - May/01/2019 at 6:36pm
443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcenthusiast Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2019 at 8:33pm
G-man, I went with dual point setup because they make a 'fatter spark' in the lower rpm ranges where the engine spends more time running (truth be told)

I saw the original article: Car Craft did a shoot out between a stock single point Delco distributor and a multi-spark discharge unit and the stock Delco won the battle under 3000 rpm.

Car Craft edited the article and now it only shows the contest from 3000 rpm up, where the multi-spark discharge system begins to show a performance benefit.

Also notice the article did not compare the 'new school' ignition to the 'old school' dual point type.

*Just for entertainment purposes, if it were not for multi-spark discharge, a fully transistorized ignition system would need very large capacitors to make the same amount of power; it would need at least one capacitor about the size of one gallon can of paint! ...so instead of making an 'electronic ignition' with huge capacitors, they use rapid/multiple discharges instead ...to mimic the stronger spark signal of a points type ignition (!)

Notice all the advertisements in Summit catalog telling about the electronic ignition systems making their multi-spark discharge signals under 3000; now you know why.

Moreover, once combustion is initiated, the flame front will complete it's burn, regardless of additional discharges by the ignition system; it's a molecular chain reaction that happens in nano-seconds.

The big powerful spark of point type ignition converts/makes more molecules ready for combustion until actual ignition. The multi-discharge unit only attempts to do the same under 3000 rpm.

The explanation only gets more technical from here... how spark and combustion actually occurs on a molecular level. 


Edited by amcenthusiast - May/02/2019 at 7:21pm
443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcenthusiast Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2019 at 8:43pm
The big fat spark of a dual point with a super coil is still the hot ticket for any street engine running a cam with 'long overlap'.

Without variable valve timing systems, there is no such thing as an 'optimized cam' for any engine having a continuously changing rpm level.

On engines that have no variable valve timing system, one may expect to have an approximate 4000 rpm usable rpm range: this is basically why all full production AMC engines came with a 5000 rpm redline (because the engine is made to run from about 800 to 4800 rpm)

By tradition, what hot rodders do is install a cam that will allow the engine to breathe beyond it's stock redline & turn more rpm (and make more power) The trade off is that the same cam will very likely have a rough idle, where the engine will tend to run rich because of 'overlap'.

This is how we cope with a cam that will make power past 5000; we run a 'lumpy cam' with a super hot ignition so it will still run decent 'down low' also. -it's a way to extend the normal 4000 rpm rev range to gain a wider usable rev range.

That's basically 'it' in a nutshell.


Edited by amcenthusiast - May/02/2019 at 7:31pm
443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcenthusiast Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2019 at 1:00am
For clarity, a points type ignition is also called 'inductive discharge ignition'...

A 'capacitive system' is a system using capacitors = 'transistors', aka: what mainstream auto people are trained to call 'electronic ignition'.

Quote: "The advantage of inductive ignition systems is that inductive coils are generally more efficient than capacitive discharge coils as they provide longer spark duration that can ensure complete combustion, especially on lean burn and turbo charged engines. The longer spark duration is because inductive coils only provide enough energy to cross the spark gap; the remaining energy from the ignition coil is used to maintain the spark. Capacitive discharge coils release almost all of their energy instantaneously, considerably reducing the amount of energy available to maintain the spark.
With inductive ignition systems more energy can be delivered to the secondary winding of the coil than in a capacitive ignition system. With the same power supply current draw, up to five times more energy can be delivered to the secondary winding of an inductive coil than to a capacitive coil. Typically a capacitive discharge system will deliver a maximum of 10 millijoules of energy compared to an inductive ignition system delivering more like 50 millijoules of energy and potentially in excess of 100 millijoules. This difference in supplied energies will mean an inductive system can provide spark duration of 2000 microseconds or more in a single spark, compared to 600 microseconds for a capacitive system."

copied from: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=2ahUKEwizyZ7LivLhAhUKi6wKHbt8DhEQFjAGegQIABAC&url=https%3A%2F%2Fwww.gillsc.com%2Fassets%2FUploads%2FIgnition-Technology-Explained.pdf&usg=AOvVaw0T-DmC7aGGJc3n9MV_2l7l



443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/
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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2019 at 9:03am
The comment about the D-Jetronic conversion is because it's very similar to the old Bendix Electrojector system. The electronics are updated, but the system is virtually the same. Bosch bought patent rights to the Electrojector system back in the 50s or early 60s. Instead of tubes the D uses transistors, but it's otherwise about the same as the Electrojector. One thing Bosch did to improve cold weather starting was to add a central injector to enrichen the mixture under a set temp... in other words, to mimic a choke! Made a world of difference.. the Electrojector setup was hard to start under 40 degrees outside.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcenthusiast Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2019 at 11:46am
Good explanation Farna, thanks.

There seems to be a dead end street many times when we want to learn more about this or that automotive product. There may be some engineering description or some scientific explanation in the advertising of the product but typically only enough to sell the product.

Here is a website that contains much information about the science and engineering on a scholarly/academic level for anyone else who might be interested:

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

...I like carburetion because it's purely mechanical and does not add another (electric) motor to plausibly increase the efficiency rating of the original 'prime mover' design, where 100% efficient 'Carnot Heat Engine' is still the supreme model, in theory.


Edited by amcenthusiast - May/02/2019 at 7:45pm
443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/
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