Would you bother swapping intakes

DorianL

solid fixture here in the forum
Staff member
I have this open plenum intake on a mile manual 1969 corvette.

ikntake.jpg

Swapping to an eBay standard Performer intake... is there much to be gained in low end throttle response for a manual?
 
you'll feel the difference, in off idle torque, if you swap, too a dual plane intake,
but I don,t think it would be worth the cost, for the minimal gains,
unless you install a high rise hood,
allowing a much better intake manifold design,
as the current lack of clearance makes any intake manifold that would fit currently,
under the low stock c3 corvette hood line, less than ideal.
there's zero question that a dual plane intake of the proper design will increase the lower rpm torque, but if you have to purchase that intake at the average price you may not see the valve per dollar spent.
or put differently, swapping to a decent cam, without a worn cam lobe,
would do a good deal more for that engines performance,
while the other engines being built,
and Id certainly rather select the cam if it was my corvette,
than buy and install one that may be cheap or even free,
if you don,t know the specs of the cam youll install,
and if its significantly different than the cam you have currently Id pass..

this is the 30 year old cam you have with the worn cam lobe
https://www.summitracing.com/parts/crn-10013/overview/

something similar to this would be rather similar to your current cam
but might provide a bit better lower rpm power with a restrictive stock exhaust.

ID want something no milder or lower in duration than this
http://www.pbm-erson.com/Catalog/Erson/Camshafts/Hydraulic Flat Tappet_E/ERSE110028

and no larger than this as a replacement cam used to repair the current engine

http://www.pbm-erson.com/Catalog/Erson/Camshafts/Hydraulic Flat Tappet_E/ERSE113321
 
Yes. Thanks !

As I say I am looking at saving up for something much better and do not want to invest too much in this one. It needs to be a decent daily driver is all. Fairly reliable and durable.
 
Yes. Thanks !

As I say I am looking at saving up for something much better and do not want to invest too much in this one. It needs to be a decent daily driver is all. Fairly reliable and durable.
I know where one sits that comes with a guarantee that everything is right and working very well. Just the one drawback, there won’t be much to do with it so you’re stuck just driving it!
 
What model is that single plane Edelbrock intake manifold?

A dual plane that will fit under your hood and accept a quadrajet carb is the Weiand 8000.
 
If you don't have enough compression to go with that Crane 10013 camshaft, then the engine will be soggy
at the low end, especially with a single plane intake manifold.
 
It does feel soggy at the low end, and I do believe that the compression is down on this engine. 882s have 76cc chambers.

I am putting a stock cam back in...

The intake that is on there right now is a Torker first generation designed in the 70s??? This is not a Torker II.

I am saving up for something better and whereas, for that reason, I do not want to sink too much $$$ in this engine, I do want it to be as streetable as possible. That is why I am returning to a stock camshaft.

I would imagine replacing the intake with a Performer or a Weiand 8000 will set me back about $200. If swapping the intake only leads to a small difference... that doesn't seem worth it.

I presume a stock cam will restore most of the low-end potential... yes?
 
the stock cam will provide more off idle torque, especially if matched to a dual plane intake,
and a well tuned carb and ignition curve,
but keep in mind, matching the static compression ratio to the cam selected,
and use of a low restriction exhaust is one major key in having the engine run anywhere close to its potential,
each component you select has an effect on how the others potentially perform.

as you limit cam duration with a stock cam, you effectively reduces the rpm your engine can efficiently fill the cylinders in, but it traps, compresses and burns a greater percentage of the cylinder volume on each power stroke, this larger mass of fuel/air mix burning produces more cylinder pressure for a marginally longer time to produce more torque

EXFLOWZ4.jpg



compec3.png

volumetric.gif
 
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Yes, I have full length dual headers.

The consensus is don't invest in it?

Swapping an intake is such an easy thing - maybe I should just run with I have and see if I can live with it ?
 
There is a different direction. Have you looked at throttle body fuel injection?
In my view it is a simple way to broaden the power curve over the generic run of the mill carburetor.
I’m extremely pleased with mine.
 
I'm probably too late, but don't put a stock-style cam in it... Put a modern grind in it with appropriately matched springs. Faster ramps mean more torque on the bottom end and more HP on the top end at the cost of longevity/the requirement for better springs. Just get a good hard cam core (not Comp) if you're going with a FlatTappet (friend don't let friends run Comp XE lobes). -If you don't spin it up in the RPMs then there's even more reason to go with a faster ramp modern cam.

Voodoo lobes aren't a bad option; there's just not a lot of duration options.

Your full-length headers and a faster ramp cam will help support the bottom end despite the single plane intake.
Also if your timing chain is old and stretched out; replace it at the same time and you'll get some more bottom end.

Run a quick DCR calculator and see if that bottom end would benefit from the cam being advanced a few degrees or getting a bit of advance ground in (most cams will already come with some advance ground in; not sure about the ye olde timey dinosaur cams).

Adam
 
Thanks Adam...

(friend don't let friends run Comp XE lobes)
:D:D:D

I appreciate the input. Lots of good information there.

I got the cam about free. It seems to be roughly equivalent to the old GM workhorse, the 929 camshaft.

Not being able to tell the health of the motor I didn't want to invest too much into it. I first wanted to see how it would fare with a cam swap back to near OEM.

The oil pressure is good. Temp is good. Etc.

Sadly, while idling I thought I detected once again a vibration (that seemed to be audible) that was there prior to the cam swap. Something didn't feel right. It made driving at speeds above 60 mph and 2500-3000 rpm, the vibration was annoying. That is when I decided to reset valve lash running to make sure all cylinders were firing on par. That is when I discovered the very worn cam lobe.

I figured that a new cam would clear the vibration up. It seems not. Again, a test drive this weekend will yield more data... if I really am sensing an anomaly.

At this point I am suspecting worn mounts.

In any case, I'll be resetting the valve lash running this weekend. If there is oil on the rocker ends and the push-rods are spinning, that will be a good sign.

I am being pressured by the wife and kids (!) to get the car running. And I agree, once the engine is in a rather reliable state, I need to do a power brake conversion (I would not want the wife driving this car without it) and I need to get the lights and wipers fully functional (a must for a reliable daily driver). I hope to get the lights and wipers working properly this weekend.

I was too chicken to pull a main or bearing cap. But peaking up, I could see little wear in the bored or on the piston skirts. They looked in very good, fresh shape in fact.

I have been considering a GM H.O. crate engine... but if this lump turns out to be in good shape, I probably will go for new heads and a cam + fuel injection (possibly) and be happy for a while.

But first - I want that vibration gone. o_O
 
Flywheel or clutch and disc could be a cause of vibration. You did say it was a manual tranny?
 
Flywheel or clutch and disc could be a cause of vibration. You did say it was a manual tranny?
Agreed ! And yes it is a manual.

And considering the "bubba" fixes I have seen on this car... that is a likely suspect.

If the mounts check out, that is the next stop.
 
Check the crankshaft thrust bearing.
Since its a Muncie 4-speed and cam lobes failed.
Can check on the car.
Remove the flwheel cover.
With a large screwdriver move the flwheel forward and back.
Then install a dial indicator and measure.
Thrust bearing failure happens.
Will cause a hard to trace banging or clinking noise.
Abnormal engine vibrations.
 
Check the crankshaft thrust bearing.
Since its a Muncie 4-speed and cam lobes failed.
Can check on the car.
Remove the flwheel cover.
With a large screwdriver move the flwheel forward and back.
Then install a dial indicator and measure.
Thrust bearing failure happens.
Will cause a hard to trace banging or clinking noise.
Abnormal engine vibrations.

If you can manage to get your hands on it, grab the harmonic damper and try to move it back and forth as a quick indicator.
 
Crankshaft end thrust needs to be checked.
Hopefully OK.
I have had them fail on me, the Suburban 350 SBC that I towed with Heavy Loads.

I have seen the thrust bearings fail in LS Street Race engines.
Appears to be the weak spot in those engines.

BBC has the largest surface area of popular Chevy engines.

BOP Buick Olds Pontiac Engines have large thrust bearing surfaces too.
 
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