MPG went down the crapper
Laughing Gas
Joined: Dec 2012
Posts: 801
Likes: 7
From: Toledo, Ohio
. Actually, the old cam should have power to 5000+, the new cam to 5500+...
. Both cams should have some lope at idle, but not as noticeable in a lower compression ratio 2 bbl. engine... as in a 11.0:1 engine... or if idle RPMs set higher...
. Both cams should have some lope at idle, but not as noticeable in a lower compression ratio 2 bbl. engine... as in a 11.0:1 engine... or if idle RPMs set higher...
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Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
This cam is said to have a 1200-4500 range, but the IDENTICAL edelbrock cam says idle-5500.
The old cam was 1200-5200. But it was a single profile with less duration.
The old cam was 1200-5200. But it was a single profile with less duration.
Laughing Gas
Joined: Dec 2012
Posts: 801
Likes: 7
From: Toledo, Ohio
. Cam companies usually conservative on RPM range because they don't know what kind of slug engine someone might put it in... most early to mid 1970's engines only had an actual compression ratio in the 7's... usually listed as a nominal '8.0:1' or '8.5:1' by the vehicle manufacturer... those vehicles with V8's got about 9 - 13 MPG... even 1990's Jeep Cherokees gov't rated 9 MPG city, 11 MPG hiway with 360" V8...
Senior User
Joined: Jan 2013
Posts: 317
Likes: 0
From: NW Ohio
282/292 on 112 lsa is 63 degrees overlap
260/260 on 110 lsa is 40 degrees overlap
23 degree overlap difference. Which is 23 degrees of air and fuel escaping the cylinder. Fuel being lost, as well as air being lost and losing compression.
260/260 on 110 lsa is 40 degrees overlap
23 degree overlap difference. Which is 23 degrees of air and fuel escaping the cylinder. Fuel being lost, as well as air being lost and losing compression.
Laughing Gas
Joined: Dec 2012
Posts: 801
Likes: 7
From: Toledo, Ohio
. If floats adjusted incorrectly and hit carb. body before shutting off fuel flow, that could mimic that problem...
. Never shake a carb. "to see if float rattles", turn upside down gently and slowly... can bend float adjustments... as can UPS/Postal/FedEx employees throwing the carb./box the length of an 18-wheeler trailer... we were required to do that when I worked midnights for UPS while in college... TV's too...
. A compression test might give some insight...
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Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
I've got the floats set how edelbrock recommends.
Stock fuel pump pushing about 7psi iirc
I'm out on a 70mile trip right now. So when I get home I'll see what kinda milage I got.
Stock fuel pump pushing about 7psi iirc
I'm out on a 70mile trip right now. So when I get home I'll see what kinda milage I got.
Laughing Gas
Joined: Dec 2012
Posts: 801
Likes: 7
From: Toledo, Ohio
. A compression test may show how much your dynamic compression ratio has dropped between cams... can you still take a reading off the old engine?
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Lead Driver
Joined: Jul 2011
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From: On the Edge of the Desert
I could try to take a comp test on the old motor, not sure I could spin it fast enough though.
I've been trying my damnedest to keep speed low and go easy on the pedal. But I just got back from a 70 mile trip and netted 12.2mpg. That just ain't gonna cut it.
I've been trying my damnedest to keep speed low and go easy on the pedal. But I just got back from a 70 mile trip and netted 12.2mpg. That just ain't gonna cut it.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
If you have access to a fuel pressure regulator and keeping the eddy, a FPR would be the hot setup.
Laughing Gas
Joined: Dec 2012
Posts: 801
Likes: 7
From: Toledo, Ohio
. And a fuel pressure gauge to see what's happening... I picked one up for $5 at a fleamarket swap... think I'll also get a MPG meter and a fuel/air mixture monitor... got lot's of vehicles/engines to play with...
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Lead Driver
Joined: Jul 2011
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From: On the Edge of the Desert
What about going to a smaller carb? I've got the 600 now, but I know I'll never even use the full of that. A 500 would be more appropriate. That would help mpg too right?
Laughing Gas
Joined: Dec 2012
Posts: 801
Likes: 7
From: Toledo, Ohio
. When you get into carb.'s smaller than 650, you also tend to get into idle circuits too small for 351" engines...
. The primaries in a 600 4bbl. are smaller and more efficient than some 2 bbl. carb.'s... you're prolly using about all a 600 has on that 351C with 204/214 cam when you get on it a bit...
. The primaries in a 600 4bbl. are smaller and more efficient than some 2 bbl. carb.'s... you're prolly using about all a 600 has on that 351C with 204/214 cam when you get on it a bit...