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Cam Recommendations

M

Mike snyder

Donation Time
Hi all,
Things are calming down and I am back to working on the Alpine and I need a lift and duration recommendation for a cam. This is what I have got.

Block: 1592cc bored .040 over
Pistons: Hepolite flat tops .o4o over
Con rods: These were made for Alpine Racing and bring the piston almost to the top of the block.
Crank: stock
Valves: Stock dimensions
Valve Springs: Isky Duels 625 626
Rockers: Harland Roller Rockers 1.5/1
Head: port matched with Vissard Modifications
Carbs: Two DCOE 40 Webers with a Redline intake
Exhaust: Custom header
Distributor: Pertrox electronic with Bosch high output coil

I have had sort of a Goldilocks moment with cams. I tried a stock cam first. Way too cold. An Isky race cam 430 lift 286 duration WAY to hot. I have a Cal Cams cam in it now which I have no idea what the lift and duration are but I think it is comparable to a KB grind. It is barely adequate but I am not getting the most out of this engine. I am going to get a cam cut.

So, what do you think? Your thoughts would be greatly appreciated.
Michael Snyder
 
alpine_64

alpine_64

Donation Time
Mike,

1. what compression is it running?
2. What igntion is it running and who set the advance and curve?
3. What jetting on the dcoe's?

When you say a KB grind would be barely adequate.. Im thinking there might be some fundamental issues with the jetting and timing that are holding the motor back.

Also what are you expecting from the motor? Is it lacking mid level or top end punch? Is it sluggish? Its hard to know your measure.

Have you run it on a dyno and checked its AFR mixtures?
 
R

RootesRacer

Donation Time
alpine_64 said:
Mike,

1. what compression is it running?
2. What igntion is it running and who set the advance and curve?
3. What jetting on the dcoe's?

When you say a KB grind would be barely adequate.. Im thinking there might be some fundamental issues with the jetting and timing that are holding the motor back.

Also what are you expecting from the motor? Is it lacking mid level or top end punch? Is it sluggish? Its hard to know your measure.

Have you run it on a dyno and checked its AFR mixtures?
Click to expand...

On DCOEs, the size of the chokes are everything and need to match reality.
From there, you can tune to make things work but the wrong sized chokes for what the engine can deliver is a show stopper.
 
alpine_64

alpine_64

Donation Time
RootesRacer said:
On DCOEs, the size of the chokes are everything and need to match reality.
From there, you can tune to make things work but the wrong sized chokes for what the engine can deliver is a show stopper.
Click to expand...
Good point Jarrid, i automatically assume when people have dcoes on an alpine they have 30mm chokes... But possible they could have larger or smaller....

A 1592 .040 for the street that has stock valves I'm thinking is not going to be breathing too hard...
 
R

RootesRacer

Donation Time
alpine_64 said:
Good point Jarrid, i automatically assume when people have dcoes on an alpine they have 30mm chokes... But possible they could have larger or smaller....

A 1592 .040 for the street that has stock valves I'm thinking is not going to be breathing too hard...
Click to expand...
I am thinking that even 30s are too large for most engines and drivers expectations.

A mild to moderate 1600 would be more streetable with 28s or even 27s.
 
Barry

Barry

Diamond Level Sponsor
Mike snyder said:
Hi all,
Things are calming down and I am back to working on the Alpine and I need a lift and duration recommendation for a cam. This is what I have got.

Block: 1592cc bored .040 over
Pistons: Hepolite flat tops .o4o over
Con rods: These were made for Alpine Racing and bring the piston almost to the top of the block.
Crank: stock
Valves: Stock dimensions
Valve Springs: Isky Duels 625 626
Rockers: Harland Roller Rockers 1.5/1
Head: port matched with Vissard Modifications
Carbs: Two DCOE 40 Webers with a Redline intake
Exhaust: Custom header
Distributor: Pertrox electronic with Bosch high output coil

I have had sort of a Goldilocks moment with cams. I tried a stock cam first. Way too cold. An Isky race cam 430 lift 286 duration WAY to hot. I have a Cal Cams cam in it now which I have no idea what the lift and duration are but I think it is comparable to a KB grind. It is barely adequate but I am not getting the most out of this engine. I am going to get a cam cut.

So, what do you think? Your thoughts would be greatly appreciated.
Michael Snyder
Click to expand...




Mike,

How was the "286 duration" measured? 286 degrees advertised duration would be in the ballpark for a "street performance" cam, but 286 degrees duration at 0.050" tappet lift would be a honkin' big race cam.

According to WSM-124, the factory camshaft duration (both inlet & exhaust) is 246 degrees at 0.012" inlet rocker clearance (0.008 tappet lift with 1.5 rockers) and at 0.014 exhaust rocker clearance (0.0093" tappet lift with 1.5 rockers). That equates to something like 255 to 260 degrees advertised duration and something like 210 to 215 degrees duration at 0.050" tappet lift. By any standard, that is a pretty tame camshaft.

A modern "street performance" flat tappet camshaft would have something like 280 degrees advertised duration and something like 235 degrees duration at 0.050" tappet lift with a lobe separation angle of about 110 degrees. Valve lift would be whatever your rocker arms and valve springs can safely handle.

RootesRooter was right on about verifying your camshaft. IMO, the only way to be sure about a cam is to check it yourself with a degree wheel and a dial indicator.
 
Last edited:
husky drvr

husky drvr

Platinum Level Sponsor
Stock ratio is between 1.38 and 1.42 depending on how sloppy the machinists were on that day.

These are actual ratios I have measured on several engines worth of rockers.


RootesRacer, Apr 26, 2009

#2

This is from a discussion in 2009.
 
Last edited:
Barry

Barry

Diamond Level Sponsor
Don,

The original posted stated "Rockers: Harland Roller Rockers 1.5/1".

If you want to get extremely nit-picky, using a 1.4:1 rocker ratio instead of a 1.5:1 rocker ratio changes the intake tappet lift from 0.0080" to 0.0086" and the exhaust tappet lift from 0.0093" to 0.0010". A difference of less than 0.001" tappet lift is insignificant in any picture and the factory camshaft still equates to something like 255 to 260 degrees advertised duration and something like 210 to 215 degrees duration at 0.050" tappet lift and that is still a very tame camshaft.
 
Last edited:
M

Mike snyder

Donation Time
Hi all, I had the day off and was able to get the info everyone asked for. So here it is.

Compression: 115
Ignition: stock rebuilt distributor with an electronic ignition
DCOE Jetting:
idle jet: 55F2
Main Jet: 125
Emulsion tube: F15
Choke tube: 30

I would like to auto cross this car. I have not had it on a dyno yet. It is sluggish low and mid and improves with speed/ higher RPM. The jetting is not right (too rich) but I wanted to figure out the cam situation and then tune to match what I have. I will most likely be taking it into a shop that can tune Webers.

"How was the "286 duration" measured? 286 degrees advertised duration would be in the ballpark for a "street performance" cam, but 286 degrees duration at 0.050" tappet lift would be a honkin' big race cam." This was an unused Isky race cam that came with car and the lift and duration were stamped on the tag. Unless I had push stared the car it wasn't going to run.

Cal cams seems to be out of business. I couldn't find them. there is some info etched on the end of the cam but it seems to be part numbers and not related to lift and duration.
 
R

RootesRacer

Donation Time
55F2 is a bit rich, try 45F8 or F9s
I am not familiar with the characteristics of the F15 emulsion, normal emulsions for our bore range are F9, F11 and F16 with F2 at 1900+ CC.
The 125 main jet is in range where it should be for 30mm chokes.

Low and mid is where your idle jets live, this is going to take some tinkering to get working well.
Order some Czech 28mm choke tubes off ebay, drop down to 115 on your mains and I'll bet it really wakes up your setup. Rule of thumb for the air bleed is ~55 plus your main size.

For ignition, you will want to have your dizzy recurved for all mechanical.
15 degrees at idle and 32 degrees at 3500 RPM (set timing at 3500 RPM).
(Just tell the dizzy shop you want 17 degrees of total mech advance).
 
Last edited:
M

Mike snyder

Donation Time
Thanks guys! I am going to talk to Elgin cams in Santa Rosa on Monday and see what they can do. I will be re-jetting per Rootes Racers recommendations when the cam is back in.
 
Mike Broome

Mike Broome

Silver Level Sponsor
Hi Mike, Looking at your compression number of 115, you are way down on what an engine in good condition should, read which is - 180/200 lb/in2.
Did you have the throttles wide open and all the spark plugs removed when taking the reading?
 
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