Cam specs

[richie49]

Hello everyone
To start off I have a cadillac 500 out of a 1976 eldo.I just rebuilt it to basic stock. the heads are the factory stock with stock valves,compression is stock 8.2 to 8.5 depending on which chart you look at. I bought a cam and it turned out to not be a cam I wanted. The cam I got had a 108 lobe separation ,558 lift in,ex duration 293 in,ex
duration@.050 233 in ,ex. The cam may be ok with higher compression but with my low compression it wont idle under 1000 rpm and is very rough idle. I am pulling it out and going with a different cam ,but what should I go with?
The cam has to have a decent idle .The car is a driver not a race car. Any suggestions on lift,duration lobe separation ect? The engine is not in a caddy,its in a light weight 1965 corvair full g-body frame under it,turbo 400 trans, 8.5 rearend with 3.08 posi
Richard richie49 Thanks in advance

[F-BIRD'88]

This cam will idle fine in gear once the diz is recurved and the carb is set up.
The cam needs to be correctly installed with correct cam advance to work with the low cr.
Get a high stall converter. A stock gm 12" converter from any sb car with th350 is fine for this.
You will get about 2600 stall with a 12" gm converter behind a bg cid caddy motor.
The stock caddy 13" converter is too tight.
You need the 12" th350 converter.

Recurve the caddy hei diz for a modified limited 10 deg mech advance curve. Set the max timing at what ever a caddy v8 likes 32-35 deg.
With the 10 deg mech adv curve now the idle timing will be correct 22-25 deg +/-.
Now hook the vac advance to ported vac on the carb.
Limiting the mech adv to 10 degrees max on a gm hei is easy.
All this car needs is correct set up.
What carb? What trans? Gm th400…??

Again find the 12" BOP gm converter from a BOP th350.

When correctly set up it will idle rock steady in gear at 700 rpm and GLH. Idle and drive great.
If when yiu rebuikt the caddy motor if the h!ad gasket is now thicker than OEM stock was, you kill the already low cr. If so get the oem stock gm caddy head gaskets.
Did you degree in the camshaft? I bet not.
Correct cam installed phasing is critical and easy to get wrong on thise caddy motors.
This car only need correct set up details.
Post full specs on that cam.
What carb? Gm caddy QJet? Only needs correct set up and a primary power piston spring swap.

[BillK]

The cam has to have a decent idle .The car is a driver not a race car.

I would just put a stock replacement cam in it. With that torque monster 500 in that light car it will spin the tires until they disintegrate anyway.

[Baprace]

That cam should have a Corvette type of idle a little lumpy but very streetable especially with the big cubic inches , F-bird-88 has it correct on the distributor, the only thing I might add is the carb throttle blades may be open a little too much to compensate for the bigger cam and when that happens the fuel idle screws quit working, the fix is a small hole in both primary blades, I would start around .075 hole in each blade, you can always go bigger, this hole allows more air into the engine so now you have to back down the main idle screw to get the idle speed down ,and now your fuel idle screws will begin to respond to adjustments.

Billk also has a good solution, I'm a gear head so I would leave the cam in, either way it should blow the tires off when adjusted.

[F-BIRD'88]

No carb throttle drilling is needed.
Put the drill away. The hei diz recurve fixes this.
The recurve with a limited 10 deg mech advance curve
Gives the correct 22 -25 deg idle base initial timing
For this motor with this cam.
The pcv valve provides all the extra idle bypass air needed.. These give correct throttle idle position at idle.
This car only needs correct setup. But no carb drilling.
You cannot get the correct timibg curve just by swapping the advance springs. You have to limit the mech advance travel stop to 10 degrees.. 22-24 is stock hei.
Amodified 10 degree advance curve gets it right.
Easy modification on a gm caddy HEI.

[F-BIRD'88]

If this car has a gm caddy QJet you can get all the carb tuning service parts from Edelbrock for the eddy QJet carb.

[richie49]

The cam is desighed to idle at 950.I have set timing all the way to 30* degrees and the engines just rocks hard. The carb is a quadrajet that has been set up to what Cliff Ruggles said to do. It starts easy but anything under 1000 rpm is just too rough.Yes I can get a new converter,and recurve the dist.
But its actually going to be cheaper to replace cam than to go with all the extras to live with this cam.I have spent almost 2 months trying to get a fair
idle and decent tune.Havn't even got it out on the road. Any suggestion on a cam with better manners? I have heard that going with a 112 lobe seration will tame it down but need some recommendations.

Richard richie49
P.S. the distributer is a points style convert to electronic.The hei was too tall to fit.

[JodyB]

Find vac and/or egr leak.

[F-BIRD'88]

Do what I said. It will run fine.
The diz idle timing must not drop off when in gear.
When you stop being hard headed and do it the way I lay!d out for you, then that cam will suddenly be the right cam and it will idle and drive correctly.
Post the cam specs and or brand and part number.
The carb needs a power step up spring with a liw tension to keep the primary metering rods down at idle with this cam...
Edelbrock selsvthe correct power piston step up spring.
4" vacuum rated.
Recurve the diz for a 10 deg mech adv curve.
Any other hi perf hyd cam for this will also need this carb and diz set up.
Fix the setup.
The edelbrock power step up spring kit is
# 1994. You need the gold colour 4" rated spring.

[F-BIRD'88]

If the engine "rocks hard" it means the diz cap - rotor phasing alignment is out of wack.
Fix it. The conversion magnetic pick up coil in the diz is not located. Right.

[F-BIRD'88]

Find vac and/or egr leak.

Do this too.

[F-BIRD'88]

If "Cliff Ruggles" had given you the right carb and diz set up it would run correctly.
Do it the way I posted. There is no short cut and the right set up changes are very low cost.
Post the cam specs and or part number- grind number.

[F-BIRD'88]

From your other recent posts it is clear the diz is not right. Among other things.
Eg spark plug gap .035". No more...

[Geoff2]

Everyone must have missed the '8.2 to 8.5' CR. If this is the Caddy advertised CR, it is probably even lower......
And therefore not surprising that it won't idle well under 1000 rpm.

Aim for something in the 220-224 @ 050 range.

[BillK]

I just looked in the Comp Cams catalog. They have a couple of cams close to the specs of the one you have and all of them have in the description "rough idle" or Very rough" idle. Same with Crane

I still say if you want a smooth idle you need to get back to stock or close to it.