Few questions .Weekend build 318,with magnum heads

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mopardart44067

mopardart44067

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Ok my 318 in my 73 duster was rebuilt not to long ago(not sure it was but runs great)only issue is that it's leaking oil everywhere,in rear,in front,intake leaks oil.paints really clean under this film of oil everywhere.plan is to pull engine out,clean it.check everything install cam.etc
Install magnum heads.now with the magnum heads I wanna run a comp cams xe268 I love this cam.i won't change direction on it.now I will be buying the stock magnum heads you see on ebay for like 400-500 set complete .question is how will the stock springs work with the xe268 cam?I was planning on buying a complete cam kit but unsure about how well this cam kit will work on magnum heads.as the kit is for la smallblocks?once this is figured out I'll buy necessary parts for the swap.rpm airgap.knockoff.and I currently have a brand new 570 street avenger,I'm loving this carb.have it on my car now.best carb I've owned.no 750 needed lol.not looking for rocket ship just a simple built 318 that I don't want more than to just buy and bolt together.ill prob have heads checked by a professional but I'm not mak8ng any visits to a machine shop unless I have to.try8ng to keep it cheap.i lost where I was going but I'll stop here 8m babbling on .I'm trying to accomplish this on a weekend.its my only transportaion.
 
Do,you have a PCV valve hooked up? If it's pushing oil out everywhere it may have some broken rings or worn out cylinders.
 
At first i wanted to get some 302 casting heads cleanem up.just lap valves.change springs and retainers etc with the xe268 cam kit.but I'm lost between the 2.after I buy the heads what if they need parts.what if they need machine work?that's where I get idea of buying the rebuilt or reman
Magnum heads on ebay for 4-500.because there's also the floating idea of better flowing 360 heads but they lack low end and compression.with magnums it's a happy medium .they have the benefits of the 302 closed chamber heads and the 360 bigger valve heads.im sure everyone is confused.but so am I haha.so what would be the best yet cheap way to go about this?should i even waste my time going to salvage yard to try to find 302s or aim at stock magnums which is more then enough for this mild 318 build.thanks.
 
yellow rose said:
Do,you have a PCV valve hooked up? If it's pushing oil out everywhere it may have some broken rings or worn out cylinders.
Click to expand...
.it has pcv.valve.has 25 psi oil idle 50-60 on acc.in front it's leaking the seal is kinda popped out.and the intake isnt sealed properly.also has exhaust leaks.thats the only noise it makes.andvdoesnt smoke
yellow rose said:
Do,you have a PCV valve hooked up? If it's pushing oil out everywhere it may have some broken rings or worn out cylinders.
Click to expand...
 
That's also why I'd like to pull it out to inspect it.and seal it up properly.when I got this car a few weeks ago everything was wrong.all vacuum lines wrong,**** wired up wrong timing was off carb that was on it was garbage.while I'm fixing these issues it slowly started leak8ng oil.its been getting hot and this car was sitting alote .now sense I have it I drive it everyday so hopefully it's just leak8ng gaskets.
 
Even thought the throtle cable is rigged up and hose clamped and the kickdown linkage is all wrong untill I get the rite parts to fix it.it runs and drives great.runs good has dual exhaust performer intake and a 570 street avenger.
 
Might want to have a set of freeze plugs on hand or readily available. Never know.
 
Stock type springs are way too weak for any performance cam.
You would need the Hughes springs and retainers for magnum heads.
Love my 570 too... Even on a 360...
 
Sorry for the long post to follow but there is a lot to cover...

We just had a thread here recently with someone with Magnum heads suffering a broken spring with the stock springs. It was with an xe268-like cam. Turns out the springs were getting veeery close to binding and one broke. Here is the thread; it has the new springs chosen listed later in the thread.
Top end popping noise

BTW, you do know that the oiling to the Magnum rockers is up through the pushrods? That is totally different than your LA rocker shaft oiling. So you need the AMC type lifters and oil-through pushrods.

If this is a daily driver, then I would not hesitate to go with the Magnum heads when putting in a cam. You seem to know that the 318's suffer from low compression out-of-the-box, and for pure driving around, good low end torque is the way to go. And, it'll work better with your stock torque converter.

I'll give you a reality check however; the 268 cam is gonna be too big for daily driving, for your compression ratio even with the Magnum heads unless you have the flat top 318 pistons, and even then, it is gonna be marginal IMHO. Do you know the pistons inside the engine? Is there any way to borrow a bore scope and look in and see if the piston tops have 4 valve reliefs? It very likely has the lower compression pistons with the 4 valve reliefs, but the CR numbers work out significantly different so it would be good to know. OR, take cranking compression readings and report those.

It all depends on if you like driving an engine that bogs at low RPM's for a daily driver, and so that is why I ask. I have run some numbers on a typical 318 LA bottom end with the Magnum heads and the thinnest head gaskets (Mr Gasket 1121G) and the XE 268 cam, and the DCR (dynamic CR) works out to be in the mid 6-ish range. That is a bit lower than with the stock cam and heads, so it is a 100% mistake to think that the low RPM performance will be any better with that cam. If you are keeping the stock torque converter, then if you push hard on the gas from a dead stop, it will bog....bog...bog and then finally take off.

Please consider a smaller cam like the 256 range. Stick with the XE or Voodoo type of cams so you can get the best lift to duration ratio. I personally like the 112 degree LSA of the Voodoo 10200701 or you could go with the XE256. And with the 1.6 Magnum rocker ratio, either of these cams will have THE SAME lift than the XE268 with the 1.5 LA rocker ratio. So you are not losing lift here, just helping your low end torque in the type of driving where low RPM torque is important to have.

And I agree with the goal to save $$, but you might also want to consider milling the heads .030" or so. Anything to help DCR....I'd also suggest the Mancini MRE262 chain set (or similar) so you can advance the cam timing 4 degrees.

Using the xe256 cam, milling the heads .030", and advancing the cam 4 degrees (for a total of 8 degrees cam advance with that cam's 4 degrees of ground-in advance) to get the ICL to 102 will get you up to a DCR of 7.25; that is a lot better. Not quite a tire frying monster but it will have more kick than stock at low RPM's. The smaller cam will also help your fuel economy, and with the top end parts will work fine well past 5000 RPM.

Then work on the ignition timing and mechanical advance and I think you'll really be pleased.

BTW, your carb size is nice for this, IMHO.
 
nm9stheham said:
Sorry for the long post to follow but there is a lot to cover...

We just had a thread here recently with someone with Magnum heads suffering a broken spring with the stock springs. It was with an xe268-like cam. Turns out the springs were getting veeery close to binding and one broke. Here is the thread; it has the new springs chosen listed later in the thread.
Top end popping noise

BTW, you do know that the oiling to the Magnum rockers is up through the pushrods? That is totally different than your LA rocker shaft oiling. So you need the AMC type lifters and oil-through pushrods.

If this is a daily driver, then I would not hesitate to go with the Magnum heads when putting in a cam. You seem to know that the 318's suffer from low compression out-of-the-box, and for pure driving around, good low end torque is the way to go. And, it'll work better with your stock torque converter.

I'll give you a reality check however; the 268 cam is gonna be too big for daily driving, for your compression ratio even with the Magnum heads unless you have the flat top 318 pistons, and even then, it is gonna be marginal IMHO. Do you know the pistons inside the engine? Is there any way to borrow a bore scope and look in and see if the piston tops have 4 valve reliefs? It very likely has the lower compression pistons with the 4 valve reliefs, but the CR numbers work out significantly different so it would be good to know. OR, take cranking compression readings and report those.

It all depends on if you like driving an engine that bogs at low RPM's for a daily driver, and so that is why I ask. I have run some numbers on a typical 318 LA bottom end with the Magnum heads and the thinnest head gaskets (Mr Gasket 1121G) and the XE 268 cam, and the DCR (dynamic CR) works out to be in the mid 6-ish range. That is a bit lower than with the stock cam and heads, so it is a 100% mistake to think that the low RPM performance will be any better with that cam. If you are keeping the stock torque converter, then if you push hard on the gas from a dead stop, it will bog....bog...bog and then finally take off.

Please consider a smaller cam like the 256 range. Stick with the XE or Voodoo type of cams so you can get the best lift to duration ratio. I personally like the 112 degree LSA of the Voodoo 10200701 or you could go with the XE256. And with the 1.6 Magnum rocker ratio, either of these cams will have THE SAME lift than the XE268 with the 1.5 LA rocker ratio. So you are not losing lift here, just helping your low end torque in the type of driving where low RPM torque is important to have.

And I agree with the goal to save $$, but you might also want to consider milling the heads .030" or so. Anything to help DCR....I'd also suggest the Mancini MRE262 chain set (or similar) so you can advance the cam timing 4 degrees.

Using the xe256 cam, milling the heads .030", and advancing the cam 4 degrees (for a total of 8 degrees cam advance with that cam's 4 degrees of ground-in advance) to get the ICL to 102 will get you up to a DCR of 7.25; that is a lot better. Not quite a tire frying monster but it will have more kick than stock at low RPM's. The smaller cam will also help your fuel economy, and with the top end parts will work fine well past 5000 RPM.

Then work on the ignition timing and mechanical advance and I think you'll really be pleased.

BTW, your carb size is nice for this, IMHO.
Click to expand...

Damn good post....good information

Jeff
 
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