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  #46 (permalink)  
Old 08-13-2014, 05:49 PM
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This is not strip only. It is the setup this street motor requires to run correctly.
(with auto trans)


You wanted a motor with a racey rough idle and you got it.

AND THIS IS HOW YOU RUN IT. SIMPLE..

Now gi buy a 10" 3500 stall converter and sone 4.10 to 4.56 gears and have a fun street car that runs great, drives great and goes like hell when ya rug it.

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Last edited by F-BIRD'88; 08-13-2014 at 06:00 PM.
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  #47 (permalink)  
Old 08-13-2014, 06:48 PM
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Ok f bird. I'm going to try it. I'll report back.
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Old 08-13-2014, 08:32 PM
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This stand alone MSD 8682 box adds manual driver seat control of the spark retard.
This ( thru creative wiring of the control knobs wireing with a inline switched resistor on a toggle
can be wired to function as both a knob adjustable ignition retard and a switch controled cranking retard.
it is not a CD ignition but it also has a good built in inductive discharge type ignition amplifieer
similar to the MSD 5 box.

MSD #8682 you can download and read the PDF.

But even with this you will find the simple ignition power interupt switch very easy, effective and simple
to allow hot engine cranking-restart with locked out timing.

temember if-when using vacuum advance that you must limit its max amount to 10-12deg and also set the rate in out based on engine load (throttle).
Many vac adv allow way to much max vac advance unless modified to limit travel.

You do not want all the vac advance all added in at idle. You want the vacuum advance to modulate-regulate in-- out at part throttle cruising speeds (manifold vacuum is much higher than at idle), based on engine load,,,BUT NOT MORE THAN 10-12deg max at high vacuum (decel)
use ported vac on the carb.

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Old 08-13-2014, 09:12 PM
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OP you ask me to clarify, all I can say is getting a timing curve dialed in can be time consuming there is no one size fits all answer.

I can recommend setting up a distributor on the bench with an electrical drill and optical tach to dial in the centrifugal if your not going to lock it, its safer than sticking your head under the hood at higher rpm with a timing light trying to see timing tape marks. Remember the distributor runs at half engine rpm...1800 distrib rpm equals 3600 engine rpm.

Lots of good articles on the web on how to do it and recommendations as well, some people prefer ported to manifold vacuum and vise versa for the vacuum advance...manifold vacuum advance can add advance at idle to lower coolant temps and pull back as load is added which can be handy for heavy or tall geared cars with tight converters.

Gofastforless website has some recommendations that work well for street cars, electronic modules for retard and complete control of the timing curve are popular as well.

Distributor advance

In all cases I suggest disregarding what anyone might say and understand what the purpose of these timing methodologies are for yourself...they exist entirely to light the mixture at the correct time so peak cylinder pressure occurs just after TDC and that pressure point changes with rpm and load...this is a known fact.

Thats all its for, and I suggest that a locked timing curve does not accomplish this at all rpm and loads a street engine encounters...hence my views on the subject.
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Old 08-13-2014, 09:31 PM
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4 jaw ignore the fact of what 5the engine really needs and ignors the fact tha thte engine with this camshaft has a lot lot lot of exhaust gas reversion dilution at idl and low engine rpm..
This EGR exhayst gas dilution at idle and low rpm is independent of cylinder pressure.
This realy effects the speed of ocmbustion at idle and low speed.
The engine just needs a LOT more timing at idle and low speed than a typical curve allows.
Locked mech timing + modest vac advance for when cruising results in the BEST OVERALL CURVE.

Its just that simple.... for this car with this cam in it.
Set the locked timing at 34-36deg BTDC and enjoy.
ya its just that simple.
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Old 08-13-2014, 09:35 PM
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And 4 jaw: for reference your Ford 351W example with the "290ADV" 110LSA cam was only about 216@.050"
Max 224 @.050". Different cam different car. Likely excessive compression ratio for fuel used.
Likely other critical factors and build errors you ignored or..... A bad comparison.

I have been doing this for over 40 years.

These "thumpr,, Big muthr thumpr cams are "streetable" and actually run very well
rough idle and all, when set up correctly.
They need this very agressive timing at idle,, just like a race cam does.
They are essentually very similar to dirt oval track cams- auto trans drag race cams.
They have the same nasty idle nature and low idle vacuum and need the same ignition set up.

They work best with loose 3000+++ stall converters (auto) and agressive high ratio gears.

Last edited by F-BIRD'88; 08-13-2014 at 09:42 PM.
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  #52 (permalink)  
Old 08-14-2014, 11:45 AM
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I once had the comp cam big mutha thumpr hydraulic roller cam and let me say that thing was a pain to try to tune around for it to be streetable and I had at the time a quick fuel q series carb double pumper carb which is the same as the holley HP brand but stupid me I sold it but that's another story.

I had a issue with not being able to keep it running in gear and I have a automatic turbo 350 with a 3000 to 3500 rpm rated range stall and 3.73 rear gears in a 86 s10. I spent countless hours and days trying to tune this thing and got to the point that I was ripping my hair out. I got it because I liked the sound and I fell for there marketing scheme in my opinion.

So after doing my homework and learning the hard way its better to build for it to run good more then that rumpty rump sound. I swapped to a smaller Lunati Voodoo Hydraulic roller 282/290/231/239 @ 50 535/550 lift and couldn't be happier. It still has a nice rump at idle but twice the vacuum and also makes my engine run a heck of a lot better and stronger and still fully streetable and was easier to tune everything.

You can make it work but the more overlap a cam has the more picky everything gets and they all have to work in hand from timing, to carb and cylinder heads and compression etc. Trust me I have made a lot of mismatch combinations over the years. My build is not perfect but close.

I have a holley 04777 650 double pumper like you have on yours and mine from stock was not rich enough on the idle circuit to keep my truck running when put into gear with out it stalling even with the right timing curve. I ended up having to open the primary blades to much exposing to much transfer slot on the front while while if I had the rears open too much I could not get the idle down while also having the front correct in relation to the transfer slot and getting a nice clean idle. It would run pig rich because of this.

I swapped out my stock metering blocks with a pair of quick fuel billet blocks and compared them to the stock blocks for sizing of everything etc and adjusted and tuned the blocks to what my engine liked as far as idle feed restrictions goes and also for jetting.

After it was all said and done with my 650 double pumper it idles at a nice and easy 1000 rpm and drops into gear at about 800 rpm and the idle is nice and clean and crisp and has great throttle response and I get 19 mpg and I jetted down to 65 front and 72 rear and it runs excellent with a nice set of tan looking plugs. I don't have a 02 censor setup yet to get the perfect tune but those cams have way more overlap then the comp xtreme energy line and comp cams says

"Applying a camshaft design originally created for sports car endurance racing, they incorporate early exhaust valve opening, long exhaust duration, and a generous amount of intake and exhaust overlap. Best of all, Thumprs will not negatively impact power output or streetability".

I disagree on that but that can be argued. Even the smallest thumpr one is not small by any means and needs a lot tuning involved.
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  #53 (permalink)  
Old 08-14-2014, 06:22 PM
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eric had all this tuning trouble only because he really did not know what to do.

Starting with simply locking out his distributor to get the required
idle timing. Then the rest is easy.

It is easy when you dothe right things to dial in these cams.

Comp severly under states the required converter stall.
And will not help you with timing mods or tuning.
But I do. I have layed it all out for you. Not hard once you know how.
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  #54 (permalink)  
Old 08-15-2014, 09:34 AM
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You know Fbird I will never be the expert tuner like you but yeah I did not do it right the first time because of lack of knowledge and ignorance on my part. On my recent build I had everything else in place with plenty of timing with recommended amounts in the 20 plus initial range and limited mechanical travel even before touching my 650 double pumper.

I am not going to argue with you in what you know as I will never know what you do but I know enough not to mess up like before and butcher things. I am also not the guy who just adjusts his idle mixture screws and idle and calls it a day.

I do my homework.Problem is and when it comes to hotrodding there is always going to be differences in certain things. Locked out timing or limited timing etc. If you did not mean anything offensive then I apologize for my comment. But I do thank you and others like your for sharing your experience and knowledge as without it I would not have gotten this far as for many others.

Last edited by eric32; 08-15-2014 at 09:57 AM.
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  #55 (permalink)  
Old 08-19-2014, 04:23 PM
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Ok fbird. I've locked out the timing and cranked out the adjustment on the vac advance to 12deg. It does run and idle, but it is tricky to get started. The gear drive starter I have does not seem to spin the motor fast enough to catch it when I hit the button for spark. I can get it but not every time.

I does seem to be running pretty well, but I haven't got to drive it yet. Definitely seems to have reduced the fumes at idle.
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Old 08-19-2014, 08:38 PM
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ok .......
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Old 08-19-2014, 09:40 PM
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Quote:
Originally Posted by gufnstuf View Post
Ok fbird. I've locked out the timing and cranked out the adjustment on the vac advance to 12deg. It does run and idle, but it is tricky to get started. The gear drive starter I have does not seem to spin the motor fast enough to catch it when I hit the button for spark. I can get it but not every time.

I does seem to be running pretty well, but I haven't got to drive it yet. Definitely seems to have reduced the fumes at idle.
Check the normal things, wiring, battery strength, grounds etc, there should be no issue rolling it over with the ignition interrupted. As for fumes and idle quality, give it a shot as is, then try manifold vacuum vs ported and see if the idle cleans up that much more. Some react differently then others.
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Old 08-19-2014, 11:03 PM
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trouble is manifold vac and thus the idle timing drops off when put in gear.


first verify pri and sec t slot position. get it balanced on both, as required.

is the pcv valve hanging wide open, when in gear, or in he correct idle flow mode.?

then check off idle transition afr at various small throttle positions.
if it goes real lean or... in any one spot may need idle airbleed tweek....or...

but now you got the idle timing where it needs to be.

a bit of practice will get your starting method better when hot/using the interupt switch.


when hot, allow thestarter to crank and purge the hot gasses from the intake, before ya hit the spark.
If it fails to fire and strains, do not force it. stop and repeat. it will fire right up.

you will learn, with practice how much cranking before ya hit the spark, what works best.

like buddy said charge tge battery and clean all connections so the starter gets full power.
you,d be surprised. especially if the car has been in storage. grounds and cable connection must be hand cleaned
twice a year. this is normal car maintainence

Last edited by F-BIRD'88; 08-19-2014 at 11:11 PM.
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Old 08-19-2014, 11:18 PM
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watch the starter motor on the block as someone starts the car. if it is wiggling on the block get/make/fab a brace bracket to support the end of the starter motor.
It must not twist and wiggle on the block.

factory Ford oem ignition has included cranking retard for years.
Gm is just too cheap. You can add a ad on cranking retard box.

i don't use one. Just the interupt switch.
But the cranking retard is a nice add on.
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Old 08-19-2014, 11:30 PM
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...or recurve the distributor and enjoy easy starting without the hassle.

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