need help w/ cam and cylinder swap!!

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reno340

reno340

I Am The Big Dog
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I have a stock 1972 Plymouth Duster 340. I am replacing my heads for some re-manufactured cylinder heads from Aerohead Racing w/ stainless 2.02's for the valves. The heads Aerohead racing ARO-CY-SB340. The springs are single w/ a damper spring inside of that. Seat pressure is 125 lbs. I want to use the XE274H cam. What do I need to make this work? A buddy tells me these springs will wipe the cam as it is too harsh. Help!

thanks
 
It's more spring pressure than Comp Cams requires. But why not call Comp Cams and ask them what they think about those pressures on their camshaft? It's my opinion that it won't hurt a thing.
 
I don't think so Tim. :D
We don't have the open spring pressure, but at 125 closed those springs are not going to kill anything IMO.
 
The Comp recommend springs are 995 for that cam, and the spring rate is 402 lbs per inch, which is pretty stiff. They would have an almost identical spring pressure, 135 lbs, for a closed valve at 1.650" installed height, as the 125 lbs cited above. So the closed spring pressure of the springs you are getting is very close, maybe a bit lower. I suspect the Aero spring are not as high a spring rate as the Comp 995's so the open pressure will be lower too. Seems like you friend is a mite uninformed on that point......

You WILL need to be very careful in your break-in procedure, and make sure you use the proper cam break in lube on the lobes and lifters. Read up several articles on proper cam break in, and follow that religiously. The cam is somewhat agressive on the lobe ramps.

The one thing for the Aero springs is that they say up to .509" lift. Your cam will be up to .491" lift. If the Aero springs actually bind at .509" then you have a problem; you need about .060" minimum margin between coil bind and max lift; you would have only .020" margin.

Now what I do not know is if the advertised max lift for the Aero springs of .509" accounts for some extra motion above that. In other words, do they mean the coil bind is actually .569" or more? I would by all means call them for a clarification, and THEN also check when you get them to see how far the valve can move before coil bind.
 
I would not work on any other cams until I got spring info from Aero.

Ask them:
- Is the .509" number the actual valve lift with at least .060" margin to spring bind, or the actual spring bind lift?
- Spring pressure at 1.650" installed height
- Spring rate
 
nm9stheham said:
I would not work on any other cams until I got spring info from Aero.

Ask them:
- Is the .509" number the actual valve lift with at least .060" margin to spring bind, or the actual spring bind lift?
- Spring pressure at 1.650" installed height
- Spring rate
Click to expand...
I called Aero and got the follwing info:

- The actual lift lift is .525 (The person stated that this was what I meant by spring rate)
- Open spring pressure is 320lb
- Spring pressure @1.650 125 lbs to seat

they also stated 90 thou to coil bind (if that makes any sense)


Hope this is what you need to help me w/ this. Do I need any more info?

Another question that I have is, do I need to get any lighter springs for break in? Any suggestions as to which ones if you do?

Thank you all in advance for your help !!!!!
 
reno340 said:
I called Aero and got the follwing info:

- The actual lift lift is .525 (The person stated that this was what I meant by spring rate)
- Open spring pressure is 320lb
- Spring pressure @1.650 125 lbs to seat

they also stated 90 thou to coil bind (if that makes any sense)
Click to expand...
Did you mean 'maximum lift' and not 'lift lift'? Assuming that is the case, and they meant .090" to coil bind FROM maximum lift, then you are good. That all is likely the case; .525" lift is not all that radical.

Open spring pressure is likely at the .525" If that is the case, then these are very close to the Comp recommended springs. I would not worry about it. That spring setup is fairly common.

Put it together, and as you rotate the cam for cam timing, you can check the springs for coil bind. That is easy to do; just read up on it.

As for the softer break in springs, we just broke in a cam with very similar springs and used the springs as is with slightly more lift. The decision is yours. Be careful to use proper cam lube and follow proper procedure, and use an oil with 1200 PPM of ZDDP or more.
 
The comp spring for a xe274h is the 995 double spring which is 115 at 1.700.

The extra 10# on the seat isn't likely to hurt anything.
 
crackedback said:
The comp spring for a xe274h is the 995 double spring which is 115 at 1.700.

The extra 10# on the seat isn't likely to hurt anything.
Click to expand...
Decent,hate seeing extra valve spring pressure on the nose ,and closed ,when not needed....
It's so frustrating,to learn the hard way,.....
 
Well, since the spring numbers are nominal numbers and there will be variations around that, then your 125# spring could be easily 130-135# on 1 or 2. If a lobe fails with 10 extra pounds of spring pressure, it was gonna go early anyway. I think more about the spring rate than the closed pressure.
 
nm9stheham said:
Well, since the spring numbers are nominal numbers and there will be variations around that, then your 125# spring could be easily 130-135# on 1 or 2. If a lobe fails with 10 extra pounds of spring pressure, it was gonna go early anyway. I think more about the spring rate than the closed pressure.
Click to expand...

This is pretty much exactly where I was going with it when I got a DISAGREE from Bomber. :D
But some of you guys know a lot more about it than I do, so I'll let him get away with it. LOL

BTW, the "I don't think so Tim" was a Tooltime show reference.
 
TrailBeast said:
This is pretty much exactly where I was going with it when I got a DISAGREE from Bomber. :D
But some of you guys know a lot more about it than I do, so I'll let him get away with it. LOL

BTW, the "I don't think so Tim" was a Tooltime show reference.
Click to expand...
I just don't like excessive valve pressures ,on flat tappets on break in,Greg...It's not a roller,so you have to be touchy on non roller cam ,break in Greg.... If you still have that narrow lobe center cam,from White Punk,look at the valve spring pressures,they recommend....Pull the inside spring out,on 130 on the seat,or buy those pricey "break in reduced rocker ratio " rockers....I won't gamble on flat tappet break in,with higher pressures....(Ask me,how I know...)
Not arguing with you,just stating where I seen failure,hopefully you understand...
 
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That 125 closed might be ok and all......but that spring is a single with damper. The 274xe requires a dual spring which will have different pressures all through the lift range. Best to stick with what Comp requires here. Valve springs are cheap.
 
RustyRatRod said:
That 125 closed might be ok and all......but that spring is a single with damper. The 274xe requires a dual spring which will have different pressures all through the lift range. Best to stick with what Comp requires here. Valve springs are cheap.
Click to expand...

I've had Comp recommend their beehive spring instead for the 268xe cam and the 274xe when I talked with them on the phone.
 
Abodybomber said:
I just don't like excessive valve pressures ,on flat tappets on break in,Greg...It's not a roller,so you have to be touchy on non roller cam ,break in Greg.... If you still have that narrow lobe center cam,from White Punk,look at the valve spring pressures,they recommend....Pull the inside spring out,on 130 on the seat,or buy those pricey "break in reduced rocker ratio " rockers....I won't gamble on flat tappet break in,with higher pressures....(Ask me,how I know...)
Not arguing with you,just stating where I seen failure,hopefully you understand...
Click to expand...
What do you recommend then?
 
Abodybomber said:
I just don't like excessive valve pressures ,on flat tappets on break in,Greg...It's not a roller,so you have to be touchy on non roller cam ,break in Greg.... If you still have that narrow lobe center cam,from White Punk,look at the valve spring pressures,they recommend....Pull the inside spring out,on 130 on the seat,or buy those pricey "break in reduced rocker ratio " rockers....I won't gamble on flat tappet break in,with higher pressures....(Ask me,how I know...)
Not arguing with you,just stating where I seen failure,hopefully you understand...
Click to expand...

Oh yea, I understand completely.
I just didn't think that little bit of difference would really matter that much, but apparently it freaks people out a bit.
Do you think it has something to do with newer oils or the process or has it always been like that?
 
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