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Author Topic: 6-71 engine #'s  (Read 1149 times)
will4104
Will 4104
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« on: October 13, 2011, 04:24:48 PM »

Can't seem to locate the serial numbers on my block, the only numbers I can locate are right above the dipstick which are as follows. 5111434, below that are the letters CFD and to the right of these are the numbers 126 which is directly above the number 69. I figure these numbers mean nothing, but posted just in case. I am trying to determine whether or not I have a four valve high block or a two valve low one. I was told a two valve low block was not worth putting any money into. Is there another way to answer this other than the numbers? And if anyone knows if this information is accurate or " just some guy talkin " I would appreciate opposing opinions. Thank you all in advance...

Will4104
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William Fenske
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Altamonte Springs, Fl.
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« Reply #1 on: October 13, 2011, 06:13:05 PM »

Pull the rocker cover and count the valves?...Cable
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Sofar Sogood
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Just Dallas
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« Reply #2 on: October 13, 2011, 06:48:44 PM »

Umm, you can have a two valve high block too.

Low blocks can be changed to high block.

Do you have an engine manual?

Have you read it?

As rusty says, pull the rocker cover!

Do you have external fuel rails?

What type of governor?


Don't be so quick to dismiss a 2 valve engine.. they actually breath better than the 4 valve at the NA aspiration specs.
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I'm just an old chunk of coal... but I'm gonna be a diamond someday.
will4104
Will 4104
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« Reply #3 on: October 14, 2011, 03:48:48 PM »

Please, oh please forgive this newbie and his unworthy question for all. I forget in this day and age of man helping his fellow man he must stay within his realm of experience...
I do have a manual and a parts book, but after twenty minutes or so searching I thought it might be quicker to ask for help online. I thought wrong. Again, please forgive me.
I will study my book and manual until, I too can ask questions that point out a persons lack of knowledge so I can feel better about myself, rather than sharing my experience and love for the hobby.  Cool
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William Fenske
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« Reply #4 on: October 14, 2011, 05:06:40 PM »

Wow, no need to be so touchy. You asked a question, you got an answer.

If you didn't like the answer, you shouldn't have asked in the first place.
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I'm just an old chunk of coal... but I'm gonna be a diamond someday.
JohnVickrey
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« Reply #5 on: October 14, 2011, 06:29:22 PM »

Dallas,  Please elaborate on the 2 valve head breathing better.  Please talk me out of changing to a 4 valve head.  I have a perfectly good motor with 2 valve head and jakes.  Could I expect better performance with a 4 valve head.  

It has N75 injectors which creates a lot of smoke if you don't keep you foot out of it.  I get 7MPG or better pulling a PT Cruiser.  I'm about to change to N65's.  What can I expect with the N65's will I still get better than 7MPG?

Expiring minds need to know this stuff Grin
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John Vickrey   -   Dearing, GA
About 2 hours East of ATL on I-20 and 4 miles south of I-20.
Got Electricity and Water for 4-5 coaches.  Less that a mile to a
dumpstation.  Stop by and sit a spell.
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« Reply #6 on: October 14, 2011, 07:15:51 PM »

John, generically speaking, with standard timing and N-60 injectors a two valve head will move as much air as it's possible to move - for the application. Adding larger injectors only adds more fuel, It doesn't add more power necessarily. If you recall the old Ford 390 V-8 engines and the sister 352, you could expect more low end power and better fuel mileage from the 352. The 390 was way over valved and the manifolds couldn't transfer enough air to be efficient. Same with the manifolds on a 2 valve 6-71. Essentially, they added more valves, although smaller, so they could use larger injectors. Too bad they didn't enlarge the exhaust ports and the manifolds.

Here's a for instance:

(And I know this is apples to parsnips),

My bus is a PD4103, 6-71, N60's, (except for one HV7), standard timing, top end about 65 mph @ 2050 rpm. It consistently delivers 9 1/2 mpg, uphill or down and although not fast, will pass a lot of charter busses with the big engines going up Jellico or Monteagle. Downhill, they pass us again, but when we all met at Cincinnati, I was there about 45 minutes before them. They were upset, and so was their boss at Klug Charters.

I use to have an oldy IH CO4070 truck and trailer, 6-71, 13 speed Road Ranger, (RTO 9513), geared for 68 mph @ 2100 rpm. It had twin straight stacks, N75's, 4 valve head, advanced timing and hauled nothing but alfalfa from Central Washington to Seattle. West bound I got almost 4 mpg, east bound empty, I could achieve nearly 6 mpg.... if I kept it at about 1800- 1900 rpm. I bobtailed it once to Eastern Washington and got nearly 7 mpg!

So, to summarize, With the same basic final ratio, the two valve head out performed the four valve in all ways, although that RTO9513 was a lot more fun!

Oh, and with straight stacks, I could blow flame out of them when I cracked open the propane bottle to get up Snowqualmie pass like the big boys.... It caused me to set a load of hay on fire one fine evening, and there was a fine tme to be had for all involved as we tossed burning bales off on the side of the road at North Bend!
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Lonnie time to go
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« Reply #7 on: October 14, 2011, 07:18:29 PM »


Bad day dallas  LOL

Lonnie
« Last Edit: October 15, 2011, 06:54:46 PM by Lonnie time to go » Logged

1976 4905
JohnVickrey
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« Reply #8 on: October 14, 2011, 08:32:30 PM »

Dallas,  Thanks.  Yep! the RTO9513 was a lot more fun.  What if you had one in a 4103 or 4104??    I think the HV7's are dribblers not injectors Grin.  I've done Jellico and Fancy Gap, 2nd gear 22MPH, watch the scenery go by.  Now, take it easy on the newbie's. 

Will, Don't stop asking questions.  I lived in St. Cloud for about 17 years, in Georgia about 4 years now.
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John Vickrey   -   Dearing, GA
About 2 hours East of ATL on I-20 and 4 miles south of I-20.
Got Electricity and Water for 4-5 coaches.  Less that a mile to a
dumpstation.  Stop by and sit a spell.
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« Reply #9 on: October 15, 2011, 07:15:52 AM »

Your serial number should be upper front corner on the blower side or right behind the water pump on that engine, 2 valve heads don't have the same cooling passages as the 4 valve heads that was the major change,4 valve heads are better heads IMO on a 12V71 and 8v71 you could maybe get a 1000 hrs from those heads, as far the N series injectors not a big fan of those sticking and leaking things lol

 N75 are a little large for for a NA engine that was standard for the turbo truck T engines fwiw


good luck
« Last Edit: October 15, 2011, 07:38:42 AM by luvrbus » Logged

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Busgeek
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« Reply #10 on: October 22, 2011, 03:52:34 PM »

Re 4 valve head.  I also have a 4103 and put on a 4 valve head with a split manifold for dual exhaust with 70's injectors and I'm happy with the power improvement with about the same mpg.  I also changed to dry air filters which I like, using the oil bath shells.  Bus geek
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