ANYONE RUNNING A COMP CAM XE262 IN A 340?

-
CFD244

CFD244

"THE NEW OLDSMOBILES ARE IN EARLY THIS YEAR"
FABO Gold Member
Joined
Sep 7, 2017
Messages
4,715
Reaction score
6,699
Location
Northern Ontario, Canada
Hi Folks

Looking to do a mild build 340 using the XE262. My calculated static compression ratio (used lower compression height pistons than OEM), I am still getting about 9.4:1 with the slugs .0175 above the deck and an .039 head gasket with (iron heads). Using the XE262's Intake closing event occurring at 57* ATDC, that leaves my dynamic compression at around 8 to 1 +/-. So, based on the science, this cam will not work well on pump gas. Looking for any real world experience with this cam. Comp recommended it for my package, even when I thought that my CR was going to be over 10.

I could retard it 4* since it has 4* advance ground in, but I am not sure if it would make the engine a dud.

P.S. I already have the cam.

What say Ye?
 
Last edited:
CFD244 said:
Hi Folks

Looking to do a mild build 340 using the XE262. My calculated static compression ratio (used lower compression height pistons than OEM), I am still getting about 9.4:1 with the slugs .0175 above the deck and an .039 head gasket. Using the XE262's Intake closing event occurring at 57* ATDC, that leaves my dynamic compression at around 8 to 1 +/-. So, based on the science, this cam will not work well on pump gas. Looking for any real world experience with this cam. Comp recommended it for my package, even when I thought that my CR was going to be over 10.

I could retard it 4* since it has 4* advance ground in, but I am not sure if it would make the engine a dud.

P.S. I already have the cam.

What say Ye?
Click to expand...
iam running the 268h comp 218@50 lsa in 110 in 106 intake valve close 60
i have legit 9.99 to 1 comp 169 cranking psi 8.2 dcr
it rips on 93 octane
the 262 should rip
dont retard it
 
a-bodyguy said:
iam running the 268h comp 218@50 lsa in 110 in 106 intake valve close 60
i have legit 9.99 to 1 comp 169 cranking psi 8.2 dcr
it rips on 93 octane
the 262 should rip
dont retard it
Click to expand...
Is that with iron heads or aluminum?
 
CFD244 said:
Hi Folks

Looking to do a mild build 340 using the XE262. My calculated static compression ratio (used lower compression height pistons than OEM), I am still getting about 9.4:1 with the slugs .0175 above the deck and an .039 head gasket with (iron heads). Using the XE262's Intake closing event occurring at 57* ATDC, that leaves my dynamic compression at around 8 to 1 +/-. So, based on the science, this cam will not work well on pump gas. Looking for any real world experience with this cam. Comp recommended it for my package, even when I thought that my CR was going to be over 10.

I could retard it 4* since it has 4* advance ground in, but I am not sure if it would make the engine a dud.

P.S. I already have the cam.

What say Ye?
Click to expand...

All it means when the cam is ground 4 degrees ahead is so when you line up the dots it SHOULD be at the recommended Intake Center Line.

That’s all that means, nothing more. You can retard it, but I would only retard it as far as I needed to center the overlap triangle. No more.
 
Rat Bastid said:
You can retard it, but I would only retard it as far as I needed to center the overlap triangle. No more.
Click to expand...
That's above my pay grade. A local friend suggested doing this to get a later intake closing event (unfortunately, probably a later intake opening event as well) to bleed off some of the dynamic compression. I'm affraid that I am not well versed in cam science, although I do enjoy reading cam threads.
 
That's a decent grind. Absolutely don't retard it. You should by all means degree it and put it at the 106 ICL that the cam card calls for.
 
Like @a-bodyguy I I am running the XE268H. It is an awesome cam. I think the 262 might be a bit small for a 340, but you did say you wanted a mild engine.
 
harrisonm said:
Like @a-bodyguy I I am running the XE268H. It is an awesome cam. I think the 262 might be a bit small for a 340, but you did say you wanted a mild engine.
Click to expand...
218/224 @ .050 is probably a little bigger then the 340 auto cam, duration wise and especially being ground on a 110. It's a mild one yes, but a goodun.
 
As others have said, do not retard it. Try it in the factory position first, which is a 106 ICL on 110 LSA. Two things that can cause detonation are heat & load. Retarding the cam can make the engine work harder [ load ]. Every combo is different, you just haver to try it....
 
The combo is a '71 Demon with an automatic transmission with a TF1 installed. Differential is a 3.23 SG unit running 245 60 14 tires (no bigger than 26"). The engine is a .040 over forged crank 340 with Silvolite 1267 pistons and '68 exhaust manifolds. Stock heads, intake, and TQ. The car also has PS and PB. The car will see no track time. Looking for a punchy cruiser. The only high RPM it will see is passing another car on the highway.

Edit: Chrysler electronic ignition with Hi-Rev 7500 box, and a brass shaft MP performance distributor.
 
Last edited:
I think You will be fine on your calculated dynamic compression running that cam installed per the cam card. 92-93 premium no issues. No way would I retard it. Work on timing curve and jetting. If your that concerned run a thicker head gasket but I would use what you have.
 
CFD244 said:
:wtf::)
Click to expand...
You already have the cam.
Some of the most experienced guys out there already gave good advice.
A lot of guys want to recommend bigger cams, which just pushes the power to a higher rpm, which pushes it to a higher roadspeed.
With 3.23s and your stated useage, you neither need nor want that.
Yur gonna love that cam.
 
Dont run a bigger head gasket if anything put a thinner gasket on it
Degree it and punch it
Before i changed from 3.23s to 3.91s
Dead stop punch from idle dual plane tuned 650dp manifolds 2 1/4 exhaust
instant tire smoke tach jumps to 5500 rpm for 40 to 50 feet shift to second 15 feet and it grabs
3.91s 1st and 2nd 50 feet if i want
 
Thanks for everyone's input. I am going to install, and degree the XE262 as per the cam card. :thumbsup:
 
CFD244 said:
That's above my pay grade. A local friend suggested doing this to get a later intake closing event (unfortunately, probably a later intake opening event as well) to bleed off some of the dynamic compression. I'm affraid that I am not well versed in cam science, although I do enjoy reading cam threads.
Click to expand...

If you want to center the overlap triangle you would install that cam on a 109 Intake Center Line.

Thats not what I call retarding a cam. Thats what I call installing the cam straight up so it’s not retarded.

A 110 or later ICL would be retarding the cam.
 
If you install your rear axle incorrectly rat will call you out on your cam timing watch out!

:poke:
 
Got it in today. Degreed at 105 1/2.........Close enough. Used Rat's .250 from max lift formula. It really does make a difference. After I beat my brains for a couple of hours only to find that the wheel slipped 3.5 degrees :BangHead:
 
CFD244 said:
Hi Folks

Looking to do a mild build 340 using the XE262. My calculated static compression ratio (used lower compression height pistons than OEM), I am still getting about 9.4:1 with the slugs .0175 above the deck and an .039 head gasket with (iron heads). Using the XE262's Intake closing event occurring at 57* ATDC, that leaves my dynamic compression at around 8 to 1 +/-. So, based on the science, this cam will not work well on pump gas. Looking for any real world experience with this cam. Comp recommended it for my package, even when I thought that my CR was going to be over 10.

I could retard it 4* since it has 4* advance ground in, but I am not sure if it would make the engine a dud.

P.S. I already have the cam.

What say Ye?
Click to expand...
I would not retard the cam. Degree it to verify cam card timing. Retarding the cam tends to raise the max torque RPM point which thus moves the max HP higher. It does not change the toque value. For a punchy street machine you want that low RPM torque. Then deal with your timing needs from there.
Another point to consider is modern fuels with ethanol blends. Fuel that is 100% gasoline has a stoichiometric value of 14.7:1. E100 has a stoichiometric more like 8.5:1. E10 fuel stoichiometric is close to 14.1:1. What this indicates is the jet sizes need to be a couple of sizes larger. This will aid detonation resistance.
GT350 Garage has an excellent 2 Youtube videos where Matt discusses this in depth. Do not let the GT350 trip you going in the door, as the information presented is not specific to the hood emblem.
Matt also in this series has a video that goes over ignition timing setup.
 
CFD244 said:
Hi Folks

Looking to do a mild build 340 using the XE262. My calculated static compression ratio (used lower compression height pistons than OEM), I am still getting about 9.4:1 with the slugs .0175 above the deck and an .039 head gasket with (iron heads). Using the XE262's Intake closing event occurring at 57* ATDC, that leaves my dynamic compression at around 8 to 1 +/-. So, based on the science, this cam will not work well on pump gas. Looking for any real world experience with this cam. Comp recommended it for my package, even when I thought that my CR was going to be over 10.

I could retard it 4* since it has 4* advance ground in, but I am not sure if it would make the engine a dud.

P.S. I already have the cam.

What say Ye?
Click to expand...
Post a pic of the cam card.
 
You must log in or register to reply here.
-

Back
Top