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  #16 (permalink)  
Old 05-14-2019, 05:26 PM
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You can put the O2 sensor bungs in the header reducers after the collectors without a problem, that 6" of difference downstream won't matter one bit.

At least the size of your Holley carbs can be determined by measuring throttle plate diameter, and then measuring the diameter of the smallest point of the venturis in both primary and secondary barrels in the main body. With those dimensions you can figure out the CFM.

If the current cam isn't happy running below 2000-2500 rpm now, it will be 10 times worse when you drop the rpm with a Gear Vendors OD....so plan on figuring out what you plan to do with the cam long before you purchase an overdrive.

Sounds like maybe the guy built a naturally aspirated engine by cam spec, then got blower happy after that.

Myself, I'd always be afraid to stand on it with pump gas if I didn't either check head casting number and look at pistons with a borescope to have some idea of how big/little/zero dome was there....or pull a head off and know for sure.
By the time you hear ping at WOT in a blown engine, the damage will be done before you can get you foot off the gas.

You can get some really inexpensive borescope/fiber optic camera deals that connect to a smart phone on Amazon or Ebay or similar.

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Old 05-14-2019, 06:32 PM
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Quote:
Originally Posted by ericnova72 View Post
By the time you hear ping at WOT in a blown engine, the damage will be done before you can get you foot off the gas.

X2^2 - you'll never hear the ping if the tune is way off, but you will definitely know it lol.




You can get some really inexpensive borescope/fiber optic camera deals that connect to a smart phone on Amazon or Ebay or similar.
I bought an Amazon special boroscope that Bluetooth's to my phone for $35. It will go through a 5/16" hole (also noted as 8mm on the Chinesium site). It works about 25 times better than I expected and will work well for what Eric is referencing.
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Old 05-14-2019, 06:55 PM
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I would have put that motor up as soon as possible and started building a turbo ls.
Never been a fan of blowers. They are picky how they run at best. Produce low boost compared to turbos and you can't hide them.

You want a long living motor go NA with compression under 9.5.

You want a powerful motor go high compression NA.

You want even more power install a turbo(s) and run boost in the teens.

If you want looks and less power then the NA high compression motor install a blower.

You can run a blower on the street. But your tuning the thing to run in "general" weather conditions playing on the safe side.
You can install efi, play around with cams, and other parts ending up building the engine again by the time your done. Or you can start with a setup like a high compression NA that will not only make more power safer but be easier to run/tune.
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Old 05-15-2019, 05:43 AM
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Actually I do have one of those little inexpensive bore scopes. I didn't think I'd be able to tell much dropping one of those in there, but if so I can pull an easy plug and get it down there.

So it sounds like the next best thing to do is correct the cam. Perhaps even before ignition. This is a job that I have never tackled before. Any really good info out there that I can read to get some background on the job? I can start off with the good old Google search too if nothing stands out as a great reference. One vendor to perhaps lean towards or away from when choosing parts? Does Crane still make decent cams? I'll probably have to call them up and explain the situation to get their best advice on cam choice.

The good news is I got the dash completely out last night and onto the bench. Got the template put down and had the dremel in my hand. It felt weird, almost wrong, cutting into the dash. I sat the dremel back down and decided to sleep on it. I'll be cutting it today. I guess sometimes you just have to make sure you are that committed to the project before doing something like that

One thing that sucked was getting the dash out having the full roll cage in there along with the center console. Not alot of room to move around. The bolt under the steering column proved to be the most difficult, but got it done. Almost resorted to taking the seats out.

Anyways, I'm rambling here already. I'll update the original post with some things I've learned about the car since purchase as well.
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Old 05-15-2019, 05:53 AM
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Hrm. Well I don't seem to have the option to edit my original post.

The tires are size 33x21.50-15LT
I'll grab the measurements off of the carb next time I have the scoop off to determine more about them.
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Old 05-15-2019, 06:20 AM
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Also, found this directly from the dyers website:

Best Street Strip Blower Kits and Blower Repair 471, 671, 871

Camshaft

A mild hydraulic cam is recommended in mild boost applications (7-10 psi). Specs are .500" lift, 280 advertised duration ([email protected]) and 112 lobe center. We also recommend using the top springs and highest seat pressure that is recommended by the cam manufacturer. On high boost applications, we recommend a solid lifter or roller cam. We recommend contacting a cam manufacturer of your choice for high boost cam and spring specifications.

This Howards cam has 108 degrees of separation. So definitely different.
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Old 05-15-2019, 09:36 AM
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I should also mention, earlier I had mistyped. The carbs are *not* double pumpers. I'll attach a couple of pictures of the carbs here. To me they look just like the classic 600 or 750 carbs. Maybe someone with some more exposure to different models of these can identify them right off.
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Old 05-15-2019, 12:56 PM
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Did Holley ever make 750cfm single feeds?

Just for grins, you could go to a junkyard and get a couple mufflers from an old Cadillac, they are huge and quiet, but still flowed ok, well for a stock big Cadillac anyway. The point is they would let you hear for pinging and then throw them away. They'll choke that engines power pretty good, but you'll be able to hear.
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Old 05-15-2019, 01:18 PM
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Quote:
Originally Posted by cerial View Post
You want a long living motor go NA with compression under 9.5.

You want a powerful motor go high compression NA.

You want even more power install a turbo(s) and run boost in the teens.

If you want looks and less power then the NA high compression motor install a blower.
I have to disagree with this.....there is no way a high compression naturally aspirated motor out-powers a blown engine....the torque alone made by the blown combo flat blows away a naturally aspirated motor.

Carbs look like 600 vacuum secondary's, but without measurements where 1/16" makes a difference in the venturi and blade sizes it is impossible to tell just from the pictures. They have been modified a bit....choke horns milled off, vacuum secondary cans connected to equalize opening rates between two carbs, big 50cc accelerator pumps added so without deeper inspection there is no way to tell what all has been done to them.

If you can see the piston dome with the borescope(might need to figure out how to get a fiber-optic flashlight probe in there too) you will still need to pull a valve cover to get the head casting number so you know what the head chamber volume is....as there are open, semi-closed, and closed chamber stock BBC heads.

I believe Holley at one time did make 735-780cfm range single feed carbs. If one needed to, single feed style bowls can easily be swapped onto the common 750 vacuum secondary carb still being sold.

BBChevy's have a strong tendency to eat flat tappet cams and lifters(due to smallest lifter diameter of any Big block engine with heavy valvetrain) so looking at a hydraulic roller cam conversion would be a smart move.
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