Where is the torque?
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Where is the torque?
I have a 400ci engine from a 1981 F350 truck
600cfm carb edelbrock
Edelbrock aluminum intake
Some sort of wild comp cam with Rhoads lifter in them
It is getting bad gas mileage (i know that they have bad gas milage to begin with but it is in the single digits with light driving)
Is it that wild cam that is throwing everything off?
The Ignition advance was also hooked up to the vacuum port on the carb
I switch it to the ported vacuum.
What else can I check for?
I don't have much of a budget for the truck, all the performance mods were done by the previous owner
I am using the truck for towing so the more the low end power I have, the better
I was about to do an engine swap but reading a couple of articles on how these engines can make decent torque I am willing to try to see what I can do with the motor.
with a square engine 4" bore 4" stroke, it should be a torque monster
600cfm carb edelbrock
Edelbrock aluminum intake
Some sort of wild comp cam with Rhoads lifter in them
It is getting bad gas mileage (i know that they have bad gas milage to begin with but it is in the single digits with light driving)
Is it that wild cam that is throwing everything off?
The Ignition advance was also hooked up to the vacuum port on the carb
I switch it to the ported vacuum.
What else can I check for?
I don't have much of a budget for the truck, all the performance mods were done by the previous owner
I am using the truck for towing so the more the low end power I have, the better
I was about to do an engine swap but reading a couple of articles on how these engines can make decent torque I am willing to try to see what I can do with the motor.
with a square engine 4" bore 4" stroke, it should be a torque monster
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An '81 400 was somewhere near 150 hp and 300 ft.lb. Low compression an retarded ignition were part of the problem.
Now add a "wild comp cam". Longer duration with low compression means even less cylinder pressure, leading to low torque and power. If the cam was added to the otherwise stock engine, it's no wonder it's a pooch.
If it was rebuilt with higher compression, again, a cam made for top end power may be pretty soft on the low end. Such an upgrade would require better valve springs, so if you don't see any evidence of that, you get the worst of both worlds--soft low end, and the inability to rev.
Also, what kind of intake? Single plane or dual plane? Model number?
Now add a "wild comp cam". Longer duration with low compression means even less cylinder pressure, leading to low torque and power. If the cam was added to the otherwise stock engine, it's no wonder it's a pooch.
If it was rebuilt with higher compression, again, a cam made for top end power may be pretty soft on the low end. Such an upgrade would require better valve springs, so if you don't see any evidence of that, you get the worst of both worlds--soft low end, and the inability to rev.
Also, what kind of intake? Single plane or dual plane? Model number?
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Freshman User
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An '81 400 was somewhere near 150 hp and 300 ft.lb. Low compression an retarded ignition were part of the problem.
Now add a "wild comp cam". Longer duration with low compression means even less cylinder pressure, leading to low torque and power. If the cam was added to the otherwise stock engine, it's no wonder it's a pooch.
If it was rebuilt with higher compression, again, a cam made for top end power may be pretty soft on the low end. Such an upgrade would require better valve springs, so if you don't see any evidence of that, you get the worst of both worlds--soft low end, and the inability to rev.
Also, what kind of intake? Single plane or dual plane? Model number?
Now add a "wild comp cam". Longer duration with low compression means even less cylinder pressure, leading to low torque and power. If the cam was added to the otherwise stock engine, it's no wonder it's a pooch.
If it was rebuilt with higher compression, again, a cam made for top end power may be pretty soft on the low end. Such an upgrade would require better valve springs, so if you don't see any evidence of that, you get the worst of both worlds--soft low end, and the inability to rev.
Also, what kind of intake? Single plane or dual plane? Model number?
It is a dual plane, I will have to take a look at the numbers of the manifold
The carb is a 1406
I don't know if I have higher compression pistions. If I did a compression test, what numbers should I look for to tell me if there is evidence of higher compresion pistons?
I should take one valve cover off and see what it has for valve springs.
Well, am I back to doing an engine swap?
What can i do about my spark advance? Or lack there of? Is there anything I can buy for that.
How much would it cost to get this engine truck worthy?
How much would high compression pistons cost? and would they be worth it?
Would I be able to run 87 octane yet?
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An upgrade in the timing chain would make a noticeably improvement, as new timing chains allow you to get rid of the retarted timing that came stock. If you have already upgraded to a 4bbl carb and intake, timing chain is about the most you can do without rebuilding the engine with higher comp pistons.
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timing chain has been upgraded I have been told. Went in with the new cam,
So what are opinions suggestions?
Where should I go from here?
So far it looks like I just need a new cam for the engine.
So what are opinions suggestions?
Where should I go from here?
So far it looks like I just need a new cam for the engine.
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Joined: Nov 2008
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From: wyoming
compression test?
do a compression test and should be 140 to 160 if some compression work was done. that carb is to small for a modified 400" motor. need around 700 cfm to 750 cfm. the rhodes lifter will affect you vacume also because of the anti pump up design. hadn't heard of these in a while. stock compression is around 125psi on a good 400. like mentioned lopey cam isn't good for towing.
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