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  #61 (permalink)  
Old 04-28-2013, 11:14 AM
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Quote:
Originally Posted by Fang16 View Post
Well, here we go. Been working on changing the stuff you advised. Please look at the attachments when you get the time. It still bogs of-course (when I rug it) but we're getting there. Drive ability is pretty good considering.
I never said a 2X4 tunnel ram won't work.I said you would be better off with smaller carbs.F-Bird absolutely knows more than me but I would like to hear his answer to this question.You jumped from 2 450s to 2 750s.Even though he made it work would it have been easier and better with 2 650s instead.Just like when he told you you were jumping up too many jet sizes at one time.

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  #62 (permalink)  
Old 04-28-2013, 11:44 AM
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Originally Posted by speedydeedy View Post
I never said a 2X4 tunnel ram won't work.I said you would be better off with smaller carbs.F-Bird absolutely knows more than me but I would like to hear his answer to this question.You jumped from 2 450s to 2 750s.Even though he made it work would it have been easier and better with 2 650s instead.Just like when he told you you were jumping up too many jet sizes at one time.
Yep, that was my mistake. Been away from tuning for over 30 years and got ahead of myself. That being said, Murphy's law has reared it's ugly head in this project a number of times also. I have 2 650's but would rather save them for the blown 350 I'm building. I also have 2 Edel 750's on my blown 350 29 Ford that I sat up long time ago that work great, but it is blown. Makes a difference.
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  #63 (permalink)  
Old 04-28-2013, 01:17 PM
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Heres an option - put your 650s on the tunnel ram and put the 750s on the blower project. The 750s will work good on the blower project.
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  #64 (permalink)  
Old 04-28-2013, 01:45 PM
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I agree totaly.1500 CFM is too much for a 355 even with all the goodies.
I think the standard for cfm is measured differently for 2bbl / 4bb / 2x4bbl induction. 1.5 inches is the calibration standard 1x4bbl. Using the same flow across two carbs , two 750s would pull about 850cfm total on that tunnel ram induction. The number of cfm the engine sees is dependent on the pressure drop between the carburetors.

850cfm is definitely okay for the application.

2x 600 would pull 700cfm on a tunnel 2x4.

My numbers are probably a little off, but do you get the concept.

Last edited by spinn; 04-28-2013 at 01:56 PM.
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  #65 (permalink)  
Old 04-28-2013, 05:54 PM
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Originally Posted by 33Willys77 View Post
Heres an option - put your 650s on the tunnel ram and put the 750s on the blower project. The 750s will work good on the blower project.
I'm contemplating that move. Have tuning kits for both.
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  #66 (permalink)  
Old 04-28-2013, 05:56 PM
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Originally Posted by spinn View Post
I think the standard for cfm is measured differently for 2bbl / 4bb / 2x4bbl induction. 1.5 inches is the calibration standard 1x4bbl. Using the same flow across two carbs , two 750s would pull about 850cfm total on that tunnel ram induction. The number of cfm the engine sees is dependent on the pressure drop between the carburetors.

850cfm is definitely okay for the application.

2x 600 would pull 700cfm on a tunnel 2x4.

My numbers are probably a little off, but do you get the concept.
Yep, understand where your coming from. Thanks for the help.
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  #67 (permalink)  
Old 05-01-2013, 05:35 PM
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what is the file name and addy of the most recent file you want me to look at.?
The one with the 600 carbs on the motor.

what is the defect on the 750 carb? If it is a real manufacturers defect like a casting flaw/Edelbrock may replace it for you.
But you have to ask.

Open up the AFR text file and edit it by writting in showing aprox throttle position/engine load/driving mode/rpm
In each area so I know what the engine is doing.
resave and
post the AFR file txt here.
That is the easy way for me to evaluate it.
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  #68 (permalink)  
Old 05-01-2013, 05:39 PM
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any carb can work but the 750's will work the best.
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  #69 (permalink)  
Old 05-01-2013, 05:53 PM
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Originally Posted by F-BIRD'88 View Post
what is the file name and addy of the most recent file you want me to look at.?
The one with the 600 carbs on the motor.

what is the defect on the 750 carb? If it is a real manufacturers defect like a casting flaw/Edelbrock may replace it for you.
But you have to ask.

Open up the AFR text file and edit it by writting in showing aprox throttle position/engine load/driving mode/rpm
In each area so I know what the engine is doing.
resave and
post the AFR file txt here.
That is the easy way for me to evaluate it.
The main one was the T slot on the left had a casting flash (bump) that blocked the
the T slot when the throttle was at idle, would'nt even let it close all the way. Closed on the left and .060 T slot on the right. Also found a hairline crack on that side where the IMS is.
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  #70 (permalink)  
Old 05-02-2013, 01:00 AM
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Originally Posted by Fang16 View Post
The main one was the T slot on the left had a casting flash (bump) that blocked the
the T slot when the throttle was at idle, would'nt even let it close all the way. Closed on the left and .060 T slot on the right. Also found a hairline crack on that side where the IMS is.
Yup that will mess things up
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  #71 (permalink)  
Old 05-02-2013, 01:36 AM
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The idle AFR is set too lean. or the exhayst system is leaking, throwiing off the O2 sensor reading at idle.
reset the idle mix srews for best idle quality and best idle manifold vacuum.
The resulting AFR should end up being 12.5 to 13.8:1 @ idle. 15:1 is too lean at idle (or the exhaust is leaking)
The priority at idle is idle quality and manfold vacuum at idle not a perfect afr at idle.

any small ex leak will throw offf the idle AFR. false lean.

AFR at part throttle cruise When you are cruising slow, you are still on the idle circuit.

If you want to try leaning down the primary part throttle crusie AFR use a primary rod with a larger cruise diameter but the same power tip diamter.
This leans the cruise.
To get an idea of when the primary jets start working, look down the carb while opening the throttle from idle
note the rpm and throttle angle where you start to see fuel flow from the primary main nozzles..

do no use over drive at low speeds. keep the rpms up. its got a big cam and wants to rev.

Last edited by F-BIRD'88; 05-02-2013 at 01:52 AM.
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  #72 (permalink)  
Old 05-02-2013, 01:46 AM
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Your existing carb jetting 98 primary jet .070x .037 pri rod 95sec jets.

to lean down the primary crusie swap the primary and secondary jets around
ya you read that right.

New jetting 95 primary jet .070x.037 rod 4" power spring 98 sec jets.

try that.... reset the idle... how is the throttle responce from idle ,, from low cruise,, from hiway cruise.

Do not expect much from this big cam at 3000 or less rpm It wants to rev.
Keep the rpms up when it is cold .. Do not idle slow when cold. warm it up with plently of rpm.
Is the distributor advance locked out? 36deg BTDC full time.?

fix the exhaust leak ( header gasket??) Get a vacuum gauge so you can watch the manifold vacuum while driving it.

re: cruising in over drive.. try not to cruise at less than 3000 rpm... The motor with this cam likes to run.
Keep it where it is happy. The lowest rpm is not the best rpm..

Tell me how that works.
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  #73 (permalink)  
Old 05-02-2013, 01:52 PM
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Sure seems reasonable that DCR's and vacuum plays a major role in tunnel rams.Proper cam selection limiting revision should be critical.While a tunnel ram wants to run in the upper RPM ranges possible the cam doesn't or the reverse could be true.That has to be a good match for it to work.
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  #74 (permalink)  
Old 05-02-2013, 03:40 PM
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The WOT afrs look ok. For this one test.
It shows you are in the ball park @ WOT. But drag testing (MPH) will show you what WOT jetting
works best. (The afr gauge is just a guide) It is just one of your tuning tools. There is no perfect WOT AFR to target. Some engines like a bit more or a bit less WOT jetting. Thats what drag strips are for.

Try the new jetting I recomended for the 600's and tell me how it does.

Whats the chances of picking up a new or good used 750 carb body to get the 750 carbs back in service.
Might be worth a call to Edelbrock. (defective replacement) You use a lot of their stuff.
Might get some product support.

The key with a tunnel ram on the street is YOU GOT TO TAKE IT OUT AND DRIVE IT.
It needs to get warmed up.... It gets a lot more street friendly once some heat gets in the manifold.

Why is the idle AFR so lean?

Last edited by F-BIRD'88; 05-02-2013 at 03:47 PM.
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  #75 (permalink)  
Old 05-02-2013, 03:45 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
The WOT afrs look ok. For this one test.
It shows you are in the ball park @ WOT. But drag testing (MPH) will show you what WOT jetting
works best. (The afr gauge is just a guide) It is just one of your tuning tools. There is no perfect WOT AFR to target. Some engines like a bit more or a bit less WOT jetting. Thats what drag strips are for.

Try the new jetting I recomended for the 600's and tell me how it does.
Will get back on it tomorrow and change the jets as u suggested. Not sure when I'll be able to try them though. Gonna be a cool rainy week.
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