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Discussion Starter #1
I have a 72 model 302 with GT- 40 heads, stock bottom end, mystery camshaft? Air gap intake and a mighty demon 650 blow through carb, 70 mm master power turbo with no intercooler. Fuel pressure is set at 7psi and I have a boost reference aeromotive regulator, -8 feed, -6 return, -6 to carb. 28 total timing, the dizzy is still advancing but I think I have it at almost 0 at base advancing to 28. MSD 6 with a billet dizzy. And my fuel pump is a 14psi summit brand.
This car is my second turbo car, my first build and the first turbo was EFI.
It was a budget build with e-bay and craigslist parts and stuff I had laying around.
A lot is used parts.
I first started the car and it started and idle very well, I have a EUGO 2000 wide band and it idled at 14.4 first start up.
I took it for a drive and when it started building boost it went lean fast. The air/fuel was fine but as soon as you built 2 lbs it went to 16?

I came back home and put a fuel pressure gauge out the hood to see if I was loosing or not gaining pressure under boost, drove it and it went lean again and the fuel pressure was perfect.

Pulled the front bowl off and looked at the jets and the were 72’s it had a power valve, and everything looked fine to me?
I up the jets in the primaries to 80s and the car was 100% better, but I am still going lean at 5psi? (I have the wastegate at 7 lbs, baby steps) I have not taken the rear bowl off because its going lean without the secondaries coming in?
My question is should I keep jetting it up or is there something else I am missing, I have read a lot and some guy have a lot of jet and most don’t?
Am I on the right track? Just keep jetting it up?
Thanks in advance
Lane

 

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You can keep jetting it up but its gonna get screwed up elsewhere. Do you know what size air bleeds are in it?

When you took the front bowls off did you see what size power valve it is? Instead of jetting it up i would look at opening up the power valve passages to get more fuel into the motor.

What modifications were done to the carb to set it up for blowthru?

And i would suggest finding a different location for your FPR. If you ever go to a track it wont pass tech being mounted on the firewall.
 

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Whats that line T'd into the reference line to the regulator?

X2 on putting it on its own line directly to the carb hat.

Where is your blowoff referenced?
 

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Discussion Starter #6
You can keep jetting it up but its gonna get screwed up elsewhere. Do you know what size air bleeds are in it?

When you took the front bowls off did you see what size power valve it is? Instead of jetting it up i would look at opening up the power valve passages to get more fuel into the motor.

What modifications were done to the carb to set it up for blowthru?

And i would suggest finding a different location for your FPR. If you ever go to a track it wont pass tech being mounted on the firewall.
I dont know what modification were done if any, I will pull the bowl in the morning and note the PV and and air bleed and take a couple of pics, anything else to look for?
Thanks for the response.
Lane
 

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Discussion Starter #8
Your FPR is referenced at a vac log . It needs to be at the hat .
Does it need to be by-itselef and put the gauge (what is on the hat now) on the log?
Thanks
Lane
 

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Discussion Starter #9

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Discussion Starter #10
Whats that line T'd into the reference line to the regulator?

X2 on putting it on its own line directly to the carb hat.

Where is your blowoff referenced?
The line that is Td into it goes to the bottom side of the BOV I read where that is optional but I ran it anyway? The top port (refrence) is on the carb base under the blades.
The BOV works great!
Thanks
Lane
 

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Discussion Starter #11
It looks like the FPR is referenced below the carb through the log .
I will put it on the hat and move the gauge to the log in the morning as well.
Thanks
Lane
 

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that fuel pump isnt enough for sure... i always used a aeromotive a1000 or a magnafuel 500. those r my tw0 choices
 

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Discussion Starter #13
that fuel pump isnt enough for sure... i always used a aeromotive a1000 or a magnafuel 500. those r my tw0 choices
Even with 7lbs? I know its not the best but It came with the turbo I thought 14 would be enough for 7lbs, do you think that is the problem I am having?
I wanted to get a good tune on the 7 then upgrade the pump when work picked up
Thanks
 

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Discussion Starter #16
Also, that fuel pressure regulator cannot be mounted to the firewall according to NHRA rules.
I will look into moving it after I get it to run.
I think the air-gap intake is single plane.
Thanks
Lane
 

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Like has been said , boost ref. line needs to go from the hat to the reg.

I aint gonna say your fuel pump wont work. Only because I havent tried it in a low boost combo. However I dont believe it will work. Its just not enough pump when you start making boost. On top of that i have seen multiple people on this website trying to run a summit or holley 14psi pump and all they ever did was have problems.

Last is that low profile hat. They screw with the signal to the carb badly. Build some vent tube extensions with the 3/8 steel fuel line. If you dont know what these are do a search. I tuned that same carb and hat combo and it had a serious lean issue under boost. Boost was 7 psi. Put vent tube ext. on and it tuned with ease.
 

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ur at the max psi with 7 lbs base pressure then 1 to 1 boost ref. another 7lbs is 14 psi fuel pressure pump wont work you will prob hurt something
 
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