old motorhead

I've done the reading on this site and others. Each similar build has different pieces to the puzzle and different goals for the finished product.
Here's what I'm working with...

406 with forged pistons and rods / 10.25:1 comp ratio
TrickFlow 195 (as cast) cylinder heads
Summit Stage 3 high rise airgap intake manifold
Summit 750cfm vac secondary carb
1 5/8" long tube headers with dual 2.5" exhaust
Summit hyd/flat tappet cam 225/225 .496/.496 114lsa
1.6 roller rockers
Rhoads lifters
Turbo 350 stalled at 2600 with mid 3? rear ratio
93 octane available

You guys told me that wasn't enough cam when I put this thing together. I didn't want any big cam issues.....and I don't have any. With the Rhoads lifters, the thing sounds and drives almost stock like. It will light the tires at half throttle, but doesn't pull any harder at the rpm rises. It would make an excellent tow mule engine.

I still don't want any big cam issues out of the new cam. Having lived with this one for a while, I'm confident I can go bigger while maintaining drivability. I'd like to see a minimum of 13" of vacuum at 750 rpm idle.

Of all the cams I've looked at, the Crane H230/318-12 looks like it might be a pretty good match. Specs @ .050 are 230/230 .480/.480 112lsa. With the 1.6 ratio rr's, duration would go up a bit and lift would be .512. Should I use the higher ratio rockers or leave them on the shelf?

I considered the Comp XE274, but I'm wondering if the extra exhaust duration will do anything other than increase overlap. With the big exhaust lobe and 110lsa, overlap checks in at 13 degress vs the Crane cam's 6 degrees. I'm thinking the Crane should make similar power and have better manners. I plan on using Rhoads or Crane High Intensity lifters with the chosen cam. I like the way those things work.

I'm aware of all the benefits of going to a hyd roller. That's not in the cards though. Your thoughts appreciated

ajrothm

If you are staying hyd flat tappet, I would try to get something around the 232/240 ish, around .530/550" lift and on a 110 lsa.... Something like that should pick you up some power all across the power band and definitely in the mid range on up..... Oh and get rid of those Rhodes lifters....lol...

You shouldnt have any "big cam" issues.... It would be nicer if you had a little more converter but....It should still idle pretty well and pull decent up top.

I would have rather seen atleast a 215cc head and a smaller hyd roller.... We used some home ported Trick Flow 215s (extremely ported), Custom Bullet "224" hyd roller and a ported RPM air gap on a 10.7-1 383... It dynoed 490hp, idles like a new chevy truck.. We had it in an old chevy Luv PU with a 200R4, 2600 stall(lock up) and 3.42 gears... Truck ran 11.30s@122.... After about 30k miles, we put the engine in a well set up 67' Camaro and it ran 10.77@124 with a 3500 converter and 3.73s.. That car was only 3100lbs race weight though...

Now we just stuck that same ole 383 in a 62 Chevy II with a 200R4 and 3.73s..... we are fully expecting it to go 10s and my buddy drives it everywhere....

Big heads+mild hyd roller = good power and EXCELLENT driveability.

old motorhead

No hurry here. It's actually pretty damn fun to drive like it is

Same identical cams.....one with a 108 lsa, the other with a 112lsa. I know the wider lsa would be smoother at idle and may pull a little better on the top end. What other differences would there be?

ajrothm

Maybe something like this....

http://www.lunatipower.com/Product.aspx?id=2326&gid=297

DRIVESHAFT

The 108 LSA cam will pull harder in the midrange, so it will recover better after shifts.

old motorhead

That's a 233/241 110lsa Lunati Voodoo cam (for those that don't want to follow the link). With aftermarket heads and a good exhaust, is the big exhaust split necessary? I wonder what the differences would be between that one and a 233/233 cam 110lsa. 4 degrees less overlap would probably help with drivability and effeciency.....but at what cost?

gkull

One seemingly overlooked fact is that as LSA goes down in numbers so does gas mileage. Actually over lap is what is detremental and the advancing of the intake opening.

My 79 vette was a regular for over 21 mpg on trips even with powerful roller motors

old motorhead

I guess a small part of the intake charge goes out the exhaust on high overlap cams? At high rpm, it's probably not a problem.

billla

That's a relatively mild cam...but I have a hard time seeing that as being way out of range such that it won't pull. What kind of ignition/carb tuning have you done?

I also wonder if the converter is a little loose for that engine and steep gears...

I'd put another vote in for getting rid of the Rhoads lifters.

Just tossing out a few thoughts

old motorhead

It does pull. It just doesn't pull harder as the rpm rises. It's torquey as hell. Just seems like it ought to pull harder from +-3500 rpm on up.

I haven't done any tuning since the original setup. 35 degrees total timing if memory serves. Probably are improvements to be made there. I was advised to get a 3000 stall speed converter. Glad I didn't. I think the 2600 is just about right. Not bothersome at all around town or at cruise.

Why the disdain for the Rhoads lifters?

billla

I understand that the Rhoads tend to give exactly the type of issue you're seeing - they make the cam milder at lower RPM, but at higher RPM they don't allow the cam to develop full lift. Vizard has noted a number of times that he's seen this on the dyno.

I have no personal experience with them, having never used them.

I would certainly invest some effort in tuning before looking at a cam swap as well to ensure the engine is delivering everything it's capable of and there are no other issues biting you.

DRIVESHAFT

I have heard that from several sources.
Rhoads claims that at high rpm there is no longer time for the lifters to bleed down, but apparently thats not entirely true.

old motorhead

I'm just about through my busy season. I'll have a little more time to tinker. Hope it's that simple. A little tuning and swap the lifters. Or can you even swap just the lifters without changing the cam? The good news is that Gen 1 cams are relatively inexpensive compared with the Gen 3 and 4 stuff.

billla

I think I'd go the tuning route before swapping the lifters.

General guidance is that new lifters on an old cam is a no-no, and I generally won't do it. That said, I (and I'm sure many others) have done it. I use an old trick I was taught and chuck them in my drill press and take a light touch with some solvent-soaked crocus cloth...but honestly I'm not sure if that's really required.

ajrothm

New lifters on an old cam = no problem
Old lifters on new cam(or any cam for that matter) = big problems...

I have ran down to Autozone and bought new Melling lifters and stuck them on used cams tons of times....never had an issue.... Make sure the lifters spin freely in the bores though before pushing the push rods in and setting lash.

Ben Lurkin

The cam you have should pull like a freight train at 3500 rpm. I would look at ignition timing, what rpm it comes in at and how much, and carburation first. I played with Rhoads high bleed rate lifters many years ago. The one thing they were good at is making your engine sound like it has a solid cam in it. I honestly didn't seen any benefit and as others have mentioned, some have documented a power loss with them.

Another issue with a tight lsa is you will notice a vacuum loss at an idle; something you mentioned you wanted to avoid.

The Money Pit

I ran the XE-274 in mine for about a month,..flattened a lobe on that one. But while it was in I felt it too tame for my liking. Idled smooth as stock, and only pulled to about 5000 or so. I then went to the XE-284, and it was much better, pulling to about 6000, and driveability wasn't that bad. At the time I had only a 2200 stall, and it had no problem with that. I did feel the throttle response was not as snappy with the XE-284 when compared to the XE-274.

Now I run an Isky Z-35 solid with 254@.050 and 108LC. I may have gone a bit too big for keeping it on the street, but I'm OK with it. Pulls to 7000 and shakes the fenders at idle. I plan on going a bit smaller next round,.....maybe,..I say just maybe I'll try a roller next. I do like my solid cam though. Pulls like there's no such thing as a red line.

Gkull is right about the mileage. My Isky gets about 11 mpg, where my XE-284 (Had 110 LC) got about 15 mpg. I did change converters to 3000 with the Isky, and rejetted the IFR's a bit richer to deal with idle problems I was having, so it's not a real apples to apple comparison.

So I guess my .02 would be to pick a cam in the 235-240@.050,with LC in the 110-112 range. These are not big cams when installed in a 406.
If you go solid,...just add about 10 degrees duration to that.

gkull

I ran the Cranes HI for about 10 years. They are just an improved Rhoads. I believe that the idea is great, but only under ideal conditions. They have a bleed of rate. So at low rpm and lower oil pressure they would give less lift and duration. But change idle oil pressure, oil weight, and oil temperature and the bleed of rate is all wrong.

You have to look at the motor and figure out where the restriction is. If it doesn't pull harder over 3500 rpm. where is the restriction. Is your VS carb opening up all 750 cfm? Is the intake restrictive to 406 CI? Your heads should be fine for power out to 6000. Ignition, A/F ratio, Then finally restrictive exhaust

old motorhead

Thanks guys I'm going to have to brush up on my carb and ignition tweaking. The last time I fooled with a Holley carb was in the late 70's. At least I don't have to fool with points and dwell.

Can anyone suggest some good reads on the subject? Hopefully not "War and Peace" long

73, Dark Blue 454

From experience, I can tell you the heads are bit small for a healthy 406. I learned the hard way on a 406 with AFR 195's (the older castings). Made a switch to 210's and the engine woke up, especially after 4000.

After years of trial and error, I can attest to one thing; big-ish heads with small-ish cam is a great combination. Conversely, smallish heads coupled with a big-ish cam is a recipe for misery.

FWIW