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Author Topic: Problem switching to 750HP main body  (Read 3142 times)
Jeff351w
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Location: Imperial, MO
393 build & new trans in progress


« on: July 13, 2017, 10:07:36 pm »

In trying to upgrade my 650 dp to a 750HP I am finding I can not get the throttle plate screws to thread in straight to the new main body.  If I remove the throttle plate and thread the screws into the main body alone they will go in straight just fine.  If I put the throttle plate back on the 650 main body they will screw in straight just fine.  It looks to the naked eye that the 750 main body isn't sitting correctly on the throttle plate pins to align it properly.  Looking down the holes they seem slightly misaligned.  I have made sure over and over the main body is seated fully on the plate when attempting this multiple times.

Should I remove the alignment pins and just use the screws to align them properly?   If so, what is the best way to remove the pins?  I haven't had any luck with vice-grips though I have been pretty gentle so far.

Am I going about this the wrong way?  Any other ideas or better suggestions?

Thanks guys.
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Quote from: mighty mouse

I often have tires with just too much tread or a fuel tank that is just too full. Accept no substitutes!
juiced coupe
Six figures worth of don't give a f*ck
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Location: Pascagoula, MS
The land mass between New Orleans and Mobile


« Reply #1 on: July 13, 2017, 10:43:23 pm »

Have you called Holley? Maybe a bad batch.

For future reference. Once you convert, remember that the 650 uses a two corner idle circuit, while most 750s use a four corner circuit. The 650 components will require a different air bleed arrangement than those on a 750.
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Doing more with less, or something like that.
http://sbftech.com/index.php/topic,20009.0.html

Quote from: Monte Smith
Bottom line, if it was the hot ticket, the fast guys would do it.............they don't

You might need some Titanium rods and a flow bench!  LMAO on floor

I honestly don't get it.

I'm sweating, my heart is racing, my clutch foot is twichin', and my right arm punched the computer screen doing an involentary 2-3 shift while reading all that. 
Jeff351w
Big Block
*****
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Posts: 1224


Location: Imperial, MO
393 build & new trans in progress


« Reply #2 on: July 13, 2017, 11:45:43 pm »

No, I haven't called Holley yet.  I bought the upgrade several years ago in preparation of the 393 swap.  I figure there's no chance of warranty at this point, but I do still have the box with any factory numbers on it so who knows.  It would be nice to know if it's from a known problem batch.

Thanks for the tip about the swap.  Would a 750 secondary metering plate change it to 4 corner idle meaning the 750 air bleeds remain unchanged?  Anything else needed to upgrade it to a true 750?  On the flip side, my cam is mild so I may not need four corner idle until later upgrades occur.  Does a single plane intake prefer 4 corner idle?  What do you think?  

I hope to be tuning this myself eventually with a vacuum gauge and Innovate AF meter.  It would be nice if I wasn't starting cockeyed.
Logged

Quote from: mighty mouse

I often have tires with just too much tread or a fuel tank that is just too full. Accept no substitutes!
juiced coupe
Six figures worth of don't give a f*ck
Global Moderator
Big Block
*****
Offline Offline

Posts: 8394


Location: Pascagoula, MS
The land mass between New Orleans and Mobile


« Reply #3 on: July 14, 2017, 12:03:44 pm »

In addition to the metering blocks, the throttle plate is also different.

Tuning with the two corner isn't a problem, you just need to be aware of the difference. Primarily, it will change your baseline settings.
Logged

Doing more with less, or something like that.
http://sbftech.com/index.php/topic,20009.0.html

Quote from: Monte Smith
Bottom line, if it was the hot ticket, the fast guys would do it.............they don't

You might need some Titanium rods and a flow bench!  LMAO on floor

I honestly don't get it.

I'm sweating, my heart is racing, my clutch foot is twichin', and my right arm punched the computer screen doing an involentary 2-3 shift while reading all that. 
Jeff351w
Big Block
*****
Offline Offline

Posts: 1224


Location: Imperial, MO
393 build & new trans in progress


« Reply #4 on: July 14, 2017, 10:30:42 pm »

In addition to the metering blocks, the throttle plate is also different.

Tuning with the two corner isn't a problem, you just need to be aware of the difference. Primarily, it will change your baseline settings.

An air bleed kit would be cheaper for now than a new metering block and throttle plate.  I'll look into the full upgrade when it becomes necessary.  I'm more familiar with tuning a 2 corner idle anyway.  I've never touched a 4 corner setup.

Thanks for the info.   Thumb up  Now to call Holley to see if that turns up anything.
Logged

Quote from: mighty mouse

I often have tires with just too much tread or a fuel tank that is just too full. Accept no substitutes!
juiced coupe
Six figures worth of don't give a f*ck
Global Moderator
Big Block
*****
Offline Offline

Posts: 8394


Location: Pascagoula, MS
The land mass between New Orleans and Mobile


« Reply #5 on: July 15, 2017, 01:12:36 pm »

Ran across this from a while back. I knew that I had posted it somewhere.

After doing some reading, apparently Proform main bodies come with a extra set of secondary idle bleeds for carbs with two circuit idle.

I have read that some come with 31s and others come with 36s. I have also read that 28s seem to be very close when used on 650 conversions. Oddly enough, original 2 circuit 750 DPs also used a 28 secondary IAB.
Logged

Doing more with less, or something like that.
http://sbftech.com/index.php/topic,20009.0.html

Quote from: Monte Smith
Bottom line, if it was the hot ticket, the fast guys would do it.............they don't

You might need some Titanium rods and a flow bench!  LMAO on floor

I honestly don't get it.

I'm sweating, my heart is racing, my clutch foot is twichin', and my right arm punched the computer screen doing an involentary 2-3 shift while reading all that. 
Jeff351w
Big Block
*****
Offline Offline

Posts: 1224


Location: Imperial, MO
393 build & new trans in progress


« Reply #6 on: July 23, 2017, 11:59:48 pm »

Ran across this from a while back. I knew that I had posted it somewhere.

After doing some reading, apparently Proform main bodies come with a extra set of secondary idle bleeds for carbs with two circuit idle.

I have read that some come with 31s and others come with 36s. I have also read that 28s seem to be very close when used on 650 conversions. Oddly enough, original 2 circuit 750 DPs also used a 28 secondary IAB.

Thanks for posting the tips.   Thumb up

I called Holley tech.  They generously offered to test it and replace it if necessary as long as I can find my original proof of purchase.  After a week of searching, no luck, and I always save receipts.  I'm going to call Summit to see if they could possibly forward me a copy from their records.
Logged

Quote from: mighty mouse

I often have tires with just too much tread or a fuel tank that is just too full. Accept no substitutes!
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