Tuning a Holley 750 DP
Thread Starter
Drifting
Joined: Dec 1999
Posts: 1,462
Likes: 1
From: Reno nevada
Happy ending to this story
George (From this Forum) came over the other day. He's a Demon Carb guy. I think that if you get enough monkeys working on something and enough time you could create of fix anything.
Here's what we stumbled across.
With the motor up to temp and running he set all four corner idle screws with a vacuum gauge. My solid Crane cam is 238/248 so getting a solid 13 at idle is pretty good @900 rpm. 14 degrees initial advance and 38 total @3000 or so rpm. I have about 10.6 compression and iron heads double hump ported heads.
Everybody on here was thinking Pink squirter cam. So with the motor running he disconnected the gas petal linkage. When you open the throttle slow. NO SQuirt at first. It didn't matter how you adjusted the pump arm.
So he took off the cam follower arm that moves the squirter. We just put it in a vice and made it more straight. The car is like new. What a moron, "ME" something so simple. From years of use the arm got bent maybe even from bottoming out at the end of the stroke.
So he also bent his arm on his demon and now were both happy!
Here's what we stumbled across.
With the motor up to temp and running he set all four corner idle screws with a vacuum gauge. My solid Crane cam is 238/248 so getting a solid 13 at idle is pretty good @900 rpm. 14 degrees initial advance and 38 total @3000 or so rpm. I have about 10.6 compression and iron heads double hump ported heads.
Everybody on here was thinking Pink squirter cam. So with the motor running he disconnected the gas petal linkage. When you open the throttle slow. NO SQuirt at first. It didn't matter how you adjusted the pump arm.
So he took off the cam follower arm that moves the squirter. We just put it in a vice and made it more straight. The car is like new. What a moron, "ME" something so simple. From years of use the arm got bent maybe even from bottoming out at the end of the stroke.
So he also bent his arm on his demon and now were both happy!
Thread Starter
Drifting
Joined: Dec 1999
Posts: 1,462
Likes: 1
From: Reno nevada
My post went away???
I was going to say that George came over and we got my motor hot and he hooked up the vacuum gauge. We also verified the timing at 14 intitial 38 total @3000 rpm with the vacuum advance disconnected.
He was able to get the Vacuum to @13 inches max at 900 rpm with my 238/248 Crane solid cam 114 LC.
We got to looking at my squirters with the pink cam. He noticed that II didn't have instant squirt no matter how he adjusted the pump arm. So we pulled of the arm that follows the cam and bent it opener. So it would ride on the cam.
It's probably got bent from the pump arms bottoming out or just to many times massing the gas to the floor.
At any rate it's a new car again. It hasn't run this good in years.
He was able to get the Vacuum to @13 inches max at 900 rpm with my 238/248 Crane solid cam 114 LC.
We got to looking at my squirters with the pink cam. He noticed that II didn't have instant squirt no matter how he adjusted the pump arm. So we pulled of the arm that follows the cam and bent it opener. So it would ride on the cam.
It's probably got bent from the pump arms bottoming out or just to many times massing the gas to the floor.
At any rate it's a new car again. It hasn't run this good in years.
Melting Slicks
Joined: Nov 2003
Posts: 2,668
Likes: 119
From: St. Charles Mo
CI 5 & 8 Veteran
LT1er, Good News So, with 14 deg initial and 38 total without vac.....does that mean you are running ported vac advance, or manifold? I finally got my 72 LT-1 running pretty good but I had to swap out the FACTORY (vac secoundaries) carb and put on a spare Holley 750 DP (mech secondaries). Looks like another rebuild in my Job Jar 
This is why I went to FI on the BBs 
Wound up, for now, I am running ~8 deg intitial with additional 10-11 deg advanced using manifold vac at idle. There is ~25 deg mechanical advance that was totally in at about 2800 rpm. Lars' post advised 18 deg at idle and to use manifold vac adv, ....was the 18 measured with or without vac advance connected??? I interpreted it with? Anyway, It's on the road for now 
Bullshark
So, with 14 deg initial and 38 total without vac.....does that mean you are running ported vac advance, or manifold? I finally got my 72 LT-1 running pretty good but I had to swap out the FACTORY (vac secoundaries) carb and put on a spare Holley 750 DP (mech secondaries). Looks like another rebuild in my Job Jar This is why I went to FI on the BBs Wound up, for now, I am running ~8 deg intitial with additional 10-11 deg advanced using manifold vac at idle. There is ~25 deg mechanical advance that was totally in at about 2800 rpm. Lars' post advised 18 deg at idle and to use manifold vac adv, ....was the 18 measured with or without vac advance connected??? I interpreted it with? Anyway, It's on the road for now Bullshark
