combo for my 408....whattya think?

[POS Dakota]

ok...so now I am building two motors! My 426 is going to wait a while because I am undecided on a lot of things, and it is now going into an a-body. Not my dakota. More on that late summer.

408...

Chambers will be 62cc's and static comp will be 10.2:1. Dynamic comp will be about 9:1. (ivc of 41.)

Cam spec I am looking at is a comp "off the shelf". Indications are that it would be a nice cam for me...hold on before you judge and see my logic

The cam is a comp hyd roller 20-812-9. (because I dont want to deal with a solid, that's why. lol) Specs are 230/[email protected], lift is 541/537....BUT I am using the hughes magnum shaft rollers with a 1.65 ratio so the final lift would be I think about .595/.591 if memory serves correct...correct me if I'm wrong!

Take into consideration this engine will be in a dakota over 4000 lbs. for street, cruises, and some recreational tracktime.

I have three gearsets sitting here for my 9.25...one is 3.92, another 4.10, the others 4.88.
I drove the 4.88s for a while and they were even a ***** with overdrive. lol
I think i will use the 4.10.

Questions:

1. What do you think of the cam using the 1.65 rocker ratio?

2. What do you think about stall speed? I think torque is gonna be very strong down low, so I might not need so much. 2800?...feel free to correct me.

3. Who can tell me about piston to valve clearance with a .595 lift and as close to zero deck as I can get? Of course I'll have to check, but whattya think?

4. Will this amount of lift trash beehive springs with a max shift point of maybe 6200-6400 if that?

5. Oh! are the LA retro hyd roller lifters and the mag lifters the same height?
I need to know the pushrods will work.

I have a good idea what some of these answers are, but I like to bounce the questions off others who know just for reality check sake. If you have suggestions other than what i have outlined, shoot!


Any help would be appreciated.
I am trying to get my final "grocery list" together by friday so I can place my orders and get rolling ASAP!

 

[rumblefish360]

The cam and compresion are good to work togther. The lift math is correct.

1. What do you think of the cam using the 1.65 rocker ratio?

I have a 2 thoughts on this.

1; Is the new quicker high rate of lift going to overwhelm the Hyd. lifters capablities? I remember reading from MoPar Muscle that in a dyno test of one of there engines, they used an aggressive Hyd. cam and then moved to a 1.6 rocker and lost power and RPM.

2; Are your heads able to flow well @ .600? I personally do not see the point of lifting the valve past the point of the heads flow capablities on a street ride. Though some people do and state there point of veiw as the head will see peak flow twice and move more air (twice again, once as the valve goes up and again as it comes down) into the cylinder.

Well, if the port goes turbulant past the max lift point, it slows down and moving the valve back to a good flow point may pick the flow back up, but it has to pick it up from a point of it slowing down and now has to move more air and fuel (heavier than what was allready moving) back up to speed.

This may work well in a race ride. Your cam is clearly street bound.
Perhaps a mechanical cam of same/similar specs should be entertained.

2. What do you think about stall speed? I think torque is gonna be very strong down low, so I might not need so much. 2800?...feel free to correct me.

I'm not to sure where to go about this, so, IMO, this is the time to consult the been there done that crowd or a good, well known company like Dynamic for a converter.
My lame auto tranny thinking head say's , it dont sound bad, wheres my 4spd stick?

3. Who can tell me about piston to valve clearance with a .595 lift and as close to zero deck as I can get? Of course I'll have to check, but whattya think?

Good question. Start with the piston manufacturer and ask them what there piston is good for where they designed it to be. Then you can adjust that measurement with your engine particulars.
The best bet, it to measure it yourself with some clay on top of the piston and a micrometer on top of the valve. This isn't so easy because of the Hyd. lifter and the exact placement of the pushrod depressing the lifter.

If you use a solid roller lifter and a pushrod connecting the cams lift to the rocker with zero lash, your going to get a good idea of an ideal working Hyd. set up and max. lift possiblity with the Hyd. cam. This requires a pair of custom length pushrods used only one for this operation.

4. Will this amount of lift trash beehive springs with a max shift point of maybe 6200-6400 if that?

All valve springs have a set of specs that the manufacturer will have on hand. Compare notes with the manufacturers specs (Via phone call if possible) and ask them if they have been there and done that.

5. Oh! are the LA retro hyd roller lifters and the mag lifters the same height?
I need to know if the pushrods will work.

Another manufactuer question, unless a been there done that shows up.

A custom pushrod may be needed for this application. It wouldn't surprise me at all really. A pushrod length checker as avaialable from hugesengines, comp, etc.....

 

[moper]

Chambers will be 62cc's and static comp will be 10.2:1. Dynamic comp will be about 9:1. (ivc of 41.)

The cam is a comp hyd roller 20-812-9. (because I dont want to deal with a solid, that's why. lol) Specs are 230/[email protected], lift is 541/537....BUT I am using the hughes magnum shaft rollers with a 1.65 ratio so the final lift would be I think about .595/.591 if memory serves correct...correct me if I'm wrong!
Bear in mind the lift and RPM ceiling will be subject to two things: lifter collapse which occurs earlier with heavy spings and the pushrod angularity which will be much worse with hydraulic rollers. So the true lift at the retainer with the 1.65s will be closer to .570 and the required spring is technically a dual assembly with 350psi over the nose. The beehive is much lighter over the nose at about 260. So I think the rpm ceiling will be lower with the beehives. Like closer to 5500-5800 if the lifter bores are not overly worn. Also, a trick I learned is the stock rollers seem to be better than the aftermarket. So if you can use the stock Magnum tappets (LA block produced after '87) do so.
1. What do you think of the cam using the 1.65 rocker ratio?
I think the duration could be larger even with the 1.65s. I'd like to see something closer to 245-250 w/1.5s
2. What do you think about stall speed? I think torque is gonna be very strong down low, so I might not need so much. 2800?...feel free to correct me.
On a street vehicle I don't like to use stalls higher than cruise rpm. A 4Klbs one makes this even more important. If you're running 4.10s and a 27" tire, I dont think anything more slippery than 2500 is required. I routinely stall 22-2500 when there's 450 pound feet available by then.
3. Who can tell me about piston to valve clearance with a .595 lift and as close to zero deck as I can get? Of course I'll have to check, but whattya think?
Depends on the piston too. I have one on the stand that with zero deck and .558 lift it didnt even touch the clay... You should have at least .200" but you need to check.
4. Will this amount of lift trash beehive springs with a max shift point of maybe 6200-6400 if that?
You don't have to worry.. With hydraulic tappets I don't think it will rev that high. IMO, the springs seem a little weak. Kinds weird the std spring is almost 100pouns heavier over the nose...
5. Oh! are the LA retro hyd roller lifters and the mag lifters the same height?
I don't think so. Close. But not quite.
I need to know the pushrods will work.
They won't. Plan to measure and order a new set of what you need. And plan to get GOOD 5/16 because of the pushrod angle and clearance issues with 3/8 where they pass thru the heads.

 

[pettybludart]

Chambers will be 62cc's and static comp will be 10.2:1. Dynamic comp will be about 9:1. (ivc of 41.)

The cam is a comp hyd roller 20-812-9. (because I dont want to deal with a solid, that's why. lol) Specs are 230/[email protected], lift is 541/537....BUT I am using the hughes magnum shaft rollers with a 1.65 ratio so the final lift would be I think about .595/.591 if memory serves correct...correct me if I'm wrong!
Bear in mind the lift and RPM ceiling will be subject to two things: lifter collapse which occurs earlier with heavy spings and the pushrod angularity which will be much worse with hydraulic rollers. So the true lift at the retainer with the 1.65s will be closer to .570 and the required spring is technically a dual assembly with 350psi over the nose. The beehive is much lighter over the nose at about 260. So I think the rpm ceiling will be lower with the beehives. Like closer to 5500-5800 if the lifter bores are not overly worn. Also, a trick I learned is the stock rollers seem to be better than the aftermarket. So if you can use the stock Magnum tappets (LA block produced after '87) do so.
1. What do you think of the cam using the 1.65 rocker ratio?
I think the duration could be larger even with the 1.65s. I'd like to see something closer to 245-250 w/1.5s
2. What do you think about stall speed? I think torque is gonna be very strong down low, so I might not need so much. 2800?...feel free to correct me.
On a street vehicle I don't like to use stalls higher than cruise rpm. A 4Klbs one makes this even more important. If you're running 4.10s and a 27" tire, I dont think anything more slippery than 2500 is required. I routinely stall 22-2500 when there's 450 pound feet available by then.
3. Who can tell me about piston to valve clearance with a .595 lift and as close to zero deck as I can get? Of course I'll have to check, but whattya think?
Depends on the piston too. I have one on the stand that with zero deck and .558 lift it didnt even touch the clay... You should have at least .200" but you need to check.
4. Will this amount of lift trash beehive springs with a max shift point of maybe 6200-6400 if that?
You don't have to worry.. With hydraulic tappets I don't think it will rev that high. IMO, the springs seem a little weak. Kinds weird the std spring is almost 100pouns heavier over the nose...
5. Oh! are the LA retro hyd roller lifters and the mag lifters the same height?
I don't think so. Close. But not quite.
I need to know the pushrods will work.
They won't. Plan to measure and order a new set of what you need. And plan to get GOOD 5/16 because of the pushrod angle and clearance issues with 3/8 where they pass thru the heads.

This is why I love this site!Excellent responce to much needed questions.:cheers:Cheers to Moper!

 

[rumblefish360]

Yea, I'm glad Moper step in on this some. I have a bit of info in my head, but he's in the trenchs...so to speak, everyday.

Measure twice cut once! Think/look before you leap...or in this case, start the engine.

 

[moper]

Yea, I'm glad Moper step in on this some. I have a bit of info in my head, but he's in the trenchs...so to speak, everyday.

Measure twice cut once! Think/look before you leap...or in this case, start the engine.

Thanks for the kind words guys... but in the interest of full disclosure... my "trenches" are a desk job where I help manage facilities nationwide for a world-wide insurance company. I havent worked professionally in a shop in years although I maintain my own customers and clients and build a one to a few engines a year for them. What I know is a combination of my own work experience and history, and working very closely with some very good teachers and automotive performance professionals... and a few really bad ones...lol. You don't learn well by doing everything perfectly the first time and I've had a few years of spending after "learning" . I am also by no means the utmost authority here. Give it time and I think you'll have more replies that are varied in opinon and demonstrate different experiences. I don't build a lot of Magnum stuff. Others here do.:read2:

 

[rumblefish360]

Your opin. is still valued. And this is where it shows;

although I maintain my own customers and clients and build a one to a few engines a year for them. What I know is a combination of my own work experience and history, and working very closely with some very good teachers and automotive performance professionals...

I haven't been doing much as of late ethier, have to confess, though most know it anyways. Damn wallet keeps draining out! Having helped on more builds than building my own, and as you can plainly see, street engines are my gem.
Been at it alot of years, though never in a shop...does my driveway count? Did that for years making ends meet. I had a nice lil'following, something everyday in the driveway...except my own rides. LOL
Good side money!

 

[POS Dakota]

Thank you guys!

Moper,

I am going to go with more duration as suggested. I keep forgetting I am no longer dealing with a 360 that would require more stall in the same situation and behave horribly without higher stall... I am sure now that the converter I have will be fine. Excellent. That's a plus.

It's been suggested that i use the LA head. And I agree, except for the fact that I am dealing with magnum everything. I do have a mag block machined and ready to go here with a brand new set of mopar roller lifters. I don't have the LA oiling passage for the shafts, don't want to attempt it myself, and block machining budget is blown. It was more than I thought it would be to begin with, so it is what it is. lol

I am going to use RHS magnum heads for that reason done up by IMM (awesome deal), and to make the valvetrain stable, the shaft roller setup from hughes. hughes also has the appropriate pushrod length to use in this combo (7.45 inch) now that I looked deeper.
I guess there are no issues with clearance using these i am told...

I guess what I now have to do is get a custom cam grind done with more duration in the 240ish/250ish range...I didnt think it would play nice given the rest of the combo, but I guess I was wrong. Again I forgot about all the extra cubes eating it up. There's definitely a concensus on that, so I'll go for it.

I dont expect that I would have as high an rpm ceiling as a solid cam with the hydraulics, but me and solids never got along. I don't know what it is. I've always had issues having to set lash too often, and once I completely wiped one. It's been painful and I'll leave it at that. hehe

I would rather have the trouble free aspect of the rollers and not worry so much about a little extra rpm. I'm just looking for something with strong kick for a fun cruiser.

Looks like the cam is something I need to do some more consultation on. I was given a suggestion on that and I think I should roll with it. Seems like others have got some great results.

This has been very helpful and I now feel more confident on the direction i need to go. Thanks again guys.

Once I get everything in my hands I will be sure to share progress, pics, and whatever else have we.

 

[moper]

The trick is to relax about it and research research research. And not "what does everyone run?" but figure out so you can understand it how the parts need to work together in your ride. It sounds like you're well on your way. Talk to Brian at Indio... He shoots straight and I'm sure can take things where they need to be.

 

[kielbasa]

now that I'm getting close to pulling the trigger for a stroker kit (if my block checks out) - I'm finding myself in a similar situation (as far as stroker builds, mildish cam)as POS.....
one thing I'm very paranoid about is detonation (especially with mild cam), as I'll be running strictly E10 pump premium (91~91 octane), and I'd love to run a lot of vacuum advance during light loads.....I'm begining to think 10:1 might be pushing it (with iron heads, I'm also really leaning towards RHS-X heads)...
POS, what are doing for pistons? Flat top or D-dish? I know (or at least I think I know) that .040ish" quench will be downright mandatory, etc......
at this point I'm just trying to sponge up as much info as I can - this is an awesome forum!

 

[rumblefish360]

Glad ya like it here, welcome aboard!

 

[POS Dakota]

now that I'm getting close to pulling the trigger for a stroker kit (if my block checks out) - I'm finding myself in a similar situation (as far as stroker builds, mildish cam)as POS.....
one thing I'm very paranoid about is detonation (especially with mild cam), as I'll be running strictly E10 pump premium (91~91 octane), and I'd love to run a lot of vacuum advance during light loads.....I'm begining to think 10:1 might be pushing it (with iron heads, I'm also really leaning towards RHS-X heads)...
POS, what are doing for pistons? Flat top or D-dish? I know (or at least I think I know) that .040ish" quench will be downright mandatory, etc......
at this point I'm just trying to sponge up as much info as I can - this is an awesome forum!

-20.5 dish pistons (pretty sure) with a 62cc chamber and as close to 10.2:1 static as possible while keeping the quench correct. I'll need to do a mockup and make sure things are corrected as needed.

rhs heads apparently dont come at 62cc as cast it has been found. They have to be made that way which brian handles, so there is extra chamber volume to play with if you used the same piston with less milling. You could make the compression ratio less that way if needed. The heads from IMM come with back cut ferrea stainless 2.02 valves, a nice valve job, beehive springs (and the work required to fit them), the seat blended into the bowl, and the chamber volume corrected. I think I got all of it....they are very nice heads for the price and can make really good power with no real porting involved. Good stuff! They arent ported w heads, but they are perfect for a strong street/strip 408 fo sho!

Oh and I think they are good for .600 lift although some have higher than that.

 

[POS Dakota]

Update...
I called up IMM yesterday and ordered my 4 inch rotating assembly, and a set of RHS magnum heads done up nicely as we've all seen in other examples.

With that finalized, i wanted to talk more about cams...

I am firm in using a hydraulic roller profile, and I am using the hughes magnum 1.65 shaft rollers...because I think they are badass and the best for a magnum that I know of. Magnums are my preference because they are more my comfort zone I guess. Not a lot of difference, but whatever...

I guess, from what I know right now, I of course need a custom grind with 242/254 @.050. I like that. It ought to help pull really nice up higher and give me more peak power on top of a good low end. Ought to have a killer idle too! I still have yet to go into the specific valve timing, and I wont be doing that. An expert will. likely Brian. I need to get i believe around a 9:1 dynamic comp from a 10.2:1 static for things to play nice. Open to suggestions though and reasoning. I am surrounded by pump 93 and 94 in michigan, so I am not octane-challeneged as much as some of you guys.

My original spec'd lift was .584/.546 based on a 1.6 shaft rocker...
My config changes this since the ratio is 1.65.

Math tells me my new lift going from a 1.6 rocker to a 1.65 changes the intake lift to a .602int/.563exh...but the head goes turbulent there...hmmm...comments on that?

Some more questions.

This is a hydraulic and even though the cam is spec'd to give me a .602 int lift for example with my 1.65 rocker, chances are I might not even see this much regardless, correct? I ask this because my heads are setup AFAIK to handle a .600 lift with the beehives and installed height. So am I pushing it?
Should I go with a lower lift? I've heard rumors of people going higher than that...

Am I getting a more rapid valve opening with the 1.65 ratio? I'm foggy right now (still asleep), but picturing the mechanics in my head it seems so. Fast openings are typically good, but is there anything I need to know?

Is too fast a valve opening bad given my situation?
I think the spring setup and everything looks really good, but I am no expert.


...just some thoughts I had flying around this morning.8)

 

[bayyum]

this is alot to read. and i still dont know what your talkin about..... can someone put it into easier-to-read terms? LOL

 

[POS Dakota]

this is alot to read. and i still dont know what your talkin about..... can someone put it into easier-to-read terms? LOL

Dimensions, and timing of my engine. Cam timing is HUGE and complicated.

Think of it this way...you pull the comp 280 cam off the shelf and put it in your stock 318...then you wonder why it idles like crap and wont take off like a pro-stocker...well that's because there are a lot of parameters that have to be taken into consideration with cam choice, and coupled with rocker ratios, and all kinds of other things, it's smart to bounce the numbers off someone more "in the know".

What I am trying to make sure of is that everything is going to work in a desireable manner and that all of my math and logic checks out. You know, so that I DO take off like a pro stocker without bogging or breaking something.

 

[Brian Hafliger]

Dimensions, and timing of my engine. Cam timing is HUGE and complicated.

Think of it this way...you pull the comp 280 cam off the shelf and put it in your stock 318...then you wonder why it idles like crap and wont take off like a pro-stocker...well that's because there are a lot of parameters that have to be taken into consideration with cam choice, and coupled with rocker ratios, and all kinds of other things, it's smart to bounce the numbers off someone more "in the know".

What I am trying to make sure of is that everything is going to work in a desireable manner and that all of my math and logic checks out. You know, so that I DO take off like a pro stocker without bogging or breaking something.

Don't over-think cams. With the beehive springs, they like to be run as close to coil bind as you can without going too far. And because the lifter angle of the sb mopar is so bad, you lose actual lift to the valve anyway.
So if you had .620 lift after lash theoretically, then check it at the retainer, you'll likely only have .605 because of the bad lifter angle.
So don't worry about pushing the lift with the beehive's!!
Brian

 

[POS Dakota]

Don't over-think cams. With the beehive springs, they like to be run as close to coil bind as you can without going too far. And because the lifter angle of the sb mopar is so bad, you lose actual lift to the valve anyway.
So if you had .620 lift after lash theoretically, then check it at the retainer, you'll likely only have .605 because of the bad lifter angle.
So don't worry about pushing the lift with the beehive's!!
Brian

Understood.

 

[kielbasa]

My only question would be is 10.2:1 too much for pump gas with that size of a cam?
I am getting excited also (this week I'll be pressure testing, magging and sonic checking my block), and if it checks out, most likely I'll be buying the same rotating combo and heads you did POS.....can you say bang for the buck!!!!
I'll be running a hydraulic flat tappet though.

Off topic: spent all day yesterday at John Copes tranny shop learning hands on how to rebuild your 727, heck of a seminar! Weather's getting warmer, let's get the cars ready!

 

[rumblefish360]

Sounds like a good class to take. John is a good fella.

10.2 is fine for pump gas and aluminum heads. If it's an iron headed engine, a sizeable street cam is needed to bleed off pressure or a cam with abit of over lap. Looking at the cams described above, they al look fine for pump gas.

I like what Brian said and wish more people would understand that one golden sentence alot more instead of worring about every last HP possible or be worried about being subject to ridicule.

Don't over-think cams.

Even more so in the street. It's not critical to get and use every last micro measurement of lift the engine can use or what most people think it can handle and use.

Best bet in cam selection is select a duration that will suite the RPM band you are looking for to use and the most lift you can get to work with the head flow available to suite the purpose.

Think it out without busting a brain cell or worry so much you loose hair over it.

 

[Brian Hafliger]

Also going to a 4" crank really drops the rod ratio, which helps too curb detonation. Between the good chamber of these heads, proper quench (as close to .040 as you can get) and the rod ratio 10.2 is fine.
I'm at sea level so I'm very careful not to go overboard with compression and pump crap gas.

 

[POS Dakota]

Yep, I'm using iron heads.

 

[kielbasa]

POS...did you shoot for zero deck? or did you have your block decked prior to deciding on which pistons (and hope for the best)?

searching at my local machinists (i almost don't even want to call them that), I asked if I gave them a deck height, could they just hit the numbers? They just look at me funny...I ask can they deck parallel to the crank and square the block up? Again, they look at me funny - am I that out of tune with machining? I would think this is basic 8th grade machining??
I ask can they put the bores on centerline with the crank (providing I have enough meat in the cylinder walls) - now they look at me like I'm on drugs!
Again, wouldn'y these be rudimentary, fundamental maching basics?? Maybe I'm just asking for too much?

I did finally find a machinist who "gets it".... Hallelujah..........looks like that's who's getting my business.
Which pistons did you end up going with, POS?

 

[POS Dakota]

POS...did you shoot for zero deck? or did you have your block decked prior to deciding on which pistons (and hope for the best)?

searching at my local machinists (i almost don't even want to call them that), I asked if I gave them a deck height, could they just hit the numbers? They just look at me funny...I ask can they deck parallel to the crank and square the block up? Again, they look at me funny - am I that out of tune with machining? I would think this is basic 8th grade machining??
I ask can they put the bores on centerline with the crank (providing I have enough meat in the cylinder walls) - now they look at me like I'm on drugs!
Again, wouldn'y these be rudimentary, fundamental maching basics?? Maybe I'm just asking for too much?

I did finally find a machinist who "gets it".... Hallelujah..........looks like that's who's getting my business.
Which pistons did you end up going with, POS?

Keith black forged -20.5 dish. I believe they are 1.465" comp height.