72 Shark performance questions
Thread Starter
Navigator
Joined: Mar 2013
Posts: 9
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From: Marquette Mi
72 Shark performance questions
My 72 has an ATK crate motor with about 2k miles on it. I chose to use the stock Qjet 750 so put on a rebuilt one from Ecklers on top of an Eldebrok Performer intake. The air cleaner housing has the dual horns and a K&N filter in it. The exhaust manifods are the stock ram horn style. The exhaust pipes are 2.25" back to a set of Magnaflows. Factory 4 speed with a 3:36 rear end. Electronic ignition.
However, the old gal just doesn't have the git-up-n-go I expect. It seems like its not getting ehough air or gas or both. Would I benefit frrom swapping to a Holley Spread bore 750? A different air intake?
I've had no luck finding a high flow air cleaner assembly; nothing fits height wise. I'm not convinced that a set of headers would make enough difference to justify the expense, not to mention the extra heat they would dump into the cockpit.
thanks
.
However, the old gal just doesn't have the git-up-n-go I expect. It seems like its not getting ehough air or gas or both. Would I benefit frrom swapping to a Holley Spread bore 750? A different air intake?
I've had no luck finding a high flow air cleaner assembly; nothing fits height wise. I'm not convinced that a set of headers would make enough difference to justify the expense, not to mention the extra heat they would dump into the cockpit.
thanks
.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Holley doesn't make a 750 cfm spreadbore. Only 650 and 800, and the 800 is only available used. Doesn't matter, though. Unless something is really wrong with the Quadrajet -like the secondary isn't opening- you have as good a carburetor as you're going to get for that engine. You're chasing a problem in the fuel system (intake). You won't recover any power there -again, assuming the carb is functioning according to design.
Given that, make sure the carb you have is working right, then I'd go to the ignition to see if you can find some power there. But, the engine and all the systems may be working up to their potential and the engine just isn't built to meet your expectations. Hard to say since "git-up-n-go" is not as precise a measurement as a drag time slip or a chassis dyno.
Given that, make sure the carb you have is working right, then I'd go to the ignition to see if you can find some power there. But, the engine and all the systems may be working up to their potential and the engine just isn't built to meet your expectations. Hard to say since "git-up-n-go" is not as precise a measurement as a drag time slip or a chassis dyno.
Burning Brakes
Joined: Nov 2012
Posts: 788
Likes: 100
From: Indianapolis IN
My 72 has an ATK crate motor with about 2k miles on it. I chose to use the stock Qjet 750 so put on a rebuilt one from Ecklers on top of an Eldebrok Performer intake. The air cleaner housing has the dual horns and a K&N filter in it. The exhaust manifods are the stock ram horn style. The exhaust pipes are 2.25" back to a set of Magnaflows. Factory 4 speed with a 3:36 rear end. Electronic ignition.
However, the old gal just doesn't have the git-up-n-go I expect. It seems like its not getting ehough air or gas or both. Would I benefit frrom swapping to a Holley Spread bore 750? A different air intake?
I've had no luck finding a high flow air cleaner assembly; nothing fits height wise. I'm not convinced that a set of headers would make enough difference to justify the expense, not to mention the extra heat they would dump into the cockpit.
thanks
.
However, the old gal just doesn't have the git-up-n-go I expect. It seems like its not getting ehough air or gas or both. Would I benefit frrom swapping to a Holley Spread bore 750? A different air intake?
I've had no luck finding a high flow air cleaner assembly; nothing fits height wise. I'm not convinced that a set of headers would make enough difference to justify the expense, not to mention the extra heat they would dump into the cockpit.
thanks
.
And I second the comment about a Qjet being plenty of carb as long as it works properly.
Your existing air cleaner setup should suffice for your current engine just fine also, but longtube headers always seem to be worth the admission price and will increase power across the whole range of rpm.
Thread Starter
Navigator
Joined: Mar 2013
Posts: 9
Likes: 0
From: Marquette Mi
perormance
Hi:
Thanks for your response!
The orignal motor was the stock 200hp with 135k miles when I pulled it. It ran OK, just no guts, lotsa smoke and low compression on a couple cylinders.
ATK says the crate motor I bought is rated @ 290hp. Guess I expected too much.
I would consider headers but am worried that the extra heat coming into the cockpit would be a real "burner"... :
-cheers
Thanks for your response!
The orignal motor was the stock 200hp with 135k miles when I pulled it. It ran OK, just no guts, lotsa smoke and low compression on a couple cylinders.
ATK says the crate motor I bought is rated @ 290hp. Guess I expected too much.
I would consider headers but am worried that the extra heat coming into the cockpit would be a real "burner"... :
-cheers
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
The stock engine was rated at 200 NET horsepower. The replacement engine rated at 290 GROSS horsepower is only slightly more powerful than the stock engine. The same engine installed in '71 was rated at 270 horsepower using the gross rating. Your worn engine was likely down on power so it's really hard to say. The engine may be just fine and everything is working good, just doesn't make the kind of power you were hoping for. If you're looking for more off the line power, you might consider a rear gear change.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Probably the carb calibration is just a bit off. Get an air/fuel ratio gauge to see what the carb is feeding the engine, and adjust accordingly. I had a well known west coast carb shop do a "stage ll" rebuild on my Quadrajet. I wasn't happy with how it ran after that. When I checked it out, I found that the idle was astonishingly rich, the part throttle was only a touch too rich (not bad, really), and the WOT was again, way too rich.
The Qjet can give you a nice smooth idle, reasonable cruise economy, and wonderful WOT power, if it's set up correctly.
Talk to Lars Grimsrud or Cliff Ruggles.
The Qjet can give you a nice smooth idle, reasonable cruise economy, and wonderful WOT power, if it's set up correctly.
Talk to Lars Grimsrud or Cliff Ruggles.
Thread Starter
Navigator
Joined: Mar 2013
Posts: 9
Likes: 0
From: Marquette Mi
Thanks for all the responses!
My first thing will be a set of headers - if the finance company (aka the wife) will fund the purchase.
I have heard that ceramic coated headers put less heat into the cockpit - is this worth the extra $$$?
My first thing will be a set of headers - if the finance company (aka the wife) will fund the purchase.
I have heard that ceramic coated headers put less heat into the cockpit - is this worth the extra $$$?
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
Long tube headers and low restriction mufflers would make a significant improvement. The ceramic coating is worth the extra cost just to keep the headers from rusting. Additional heat into the cockpit is negligable.
Also, make sure your ignition timing is correct. Your total timing, with the vacuum advanced temporarily disconnected and plugged, should be about 36 deg. You should change springs on the advance weights in your distributor to allow the full advance to come in early, like 2200 rpms or so. Assuming your carb secondaries are opening, it should run better with these changes.
Also, make sure your ignition timing is correct. Your total timing, with the vacuum advanced temporarily disconnected and plugged, should be about 36 deg. You should change springs on the advance weights in your distributor to allow the full advance to come in early, like 2200 rpms or so. Assuming your carb secondaries are opening, it should run better with these changes.
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