408 wont rev past 4500

[brainsboy]

My 408 has neck breaking power up to 4500 but after that it seems to rev up slower and doesnt want to pull as hard. It still will rev up to 6K but certainly doesnt have the power it should. Just curious what you guys thought about my setup, or if have any idea's where to start. I checked my fuel pressure and it drops to about 3psi under hard acceleration but that should still be enough I would think.

408 callies crank
Carrillo rods 6.25"
10.68:1 compression, Full floating
Aluminum topline heads 215cc runners 2.08/1.60 valves
int-289cfm@.500 exh- 202cfm@.500
Victor jr intake port matched
hydrolic roller 224/.568lift listed rpm 2500-6000
Edelbrock 750cfm carb
1-3/4" headers
Mallory distributor
MSD6-AL with Blaster 2 coil

Also I noticed when I take the coil wire off the coil, and turn the ignition on and off the coil jumps a spark to its negitive side. I thought the coil was bad so I bought a new accel coil and it did the same thing, so im guessing thats normal, just never noticed it from any of my MSD boxes before.

[relaxinrob]

The first thing I would do is check your valve adjustment. If they are too loose it will not have any top-end power.....maybe also check your float adjustment to make sure you have enough gas to get you there.

[Ron61]

Brainsboy,

Others will know more than I about this, but what you describe sounds as if you either have a fuel problem or weak spark at the higher RPMs under load. Is this a new car or has it ran ok before? I am guessing that it will wind up ok with no load on it.

Ron

[brainsboy]

Its all new. I have maybe around 300miles on it.

Are you sure about the valve adjustment being loose will cause the top end power loss? Let me tell what happen. I had this problem originaly so I went to a friends house that does circle track. I myself have always used solid cams so know nothing about hyd cams, infact I havent used a hydrolic cam since I was 17. He told me that it seemed as I had my valves too tight. He told me to adjust all the valves at .001", I tried to argue but he insisted that I adjust them all at .001" and from there to turn the nuts a 1/8" turn to snug them up. So thats where I am set right now. I also noted that the previous settings 5 were 3/4"turns and 3 were almost 1-1/2" turns. I agreed to this mostly because I have a High volume pump, and thought maybe the high oil volume was making the lifters pump up. By the way Im running the Crane hyd roller link bar lifters, that cost me about 500$

The question is do you guys really think running them loose will cause top end power loss? How are they supposed to be adjusted? And would 3/4 to 1-1/2 turns perhaps be too tight causing the same problem I had before?


Yes it winds up ok with no load, also I noticed it runs so much better cold then after its warm. If that makes a difference at all. Im running NGK heat range 9, I tried everything from .035 to .050 all with the same results, I tried heat range 7,8 also same thing

[RACER X #99]

BB
My 408 pulls great all the way to 7K and I am running an 800cfm Holley and an 825 is reccomended. I am also running a lot more cam than you are which may account for the top end power.
1. your carb may be too small.
2. you may be all out of cam.

Just my guess,
RD

[MetaJacko]

Is it possible there is too much pre-load?
I ask this becouse you say it runs better cold. As it warms up I would assume the expansion sort of adds more pre-load. (A bit like the lash being used up as an engine warms with solid lifters)

Also, a friend told me once that you can have problems at higher revs if the exhaust is restricting the flow. He described it as the power dieing quickly as you have described.

[brainsboy]

Im going to guess that set at .001" then 1/8 turn that they are not preloaded. They may have been preloaded in the begining when some were 1-1/2 turn but now the preload is probably only .005".

[392cobra]

my 418w has a comp cam hyd. roller as well.

.576" lift 252*int., 262* exh

Comp Cam recommends 1/2 turn after zero lash.

I talked with Tony at Keith Craft. They also set them at 1/2 turn.

[Goober]

392 is right. About 1/2 turn preloads the lifter around .032 which will work fine.
Just my 2 cnets

Mark

[brainsboy]

Personaly I dont think its going to make a difference but I willing to try anything at this point. I will set them all at 1/2 turn tonight.


Is that cold or hot? And the proper way to set them is one valve down one up right?

[392cobra]

Hydraulic Lifters Can Be Adjusted at Any Engine Temperature

Since hydraulic lifters can compensate for thermal expansion of the engine, the adjusting can be done with the engine cold; hot adjustment is not necessary.



Adjusting Hydraulic Lifters for Proper Preload

In order to adjust the preload, the lifter must be properly located on the base circle or "Heel" of the lobe.

At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.

1. Remove the valve covers, and pick a cylinder that you are going to set the preload on.

2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)

3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)

4. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at "Zero Lash". Turn the adjusting nut down one half to one full turn from that point. Lock the adjuster into position. The intake is now adjusted properly.

5. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.

6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.

[HighPlainsDrifter]

Hi,
Try borrowing a tach that you know is good, lots of tachs are SLOW with the needle movement and are up to 1,000 rpm slow on a fast reving engine. I use a test set/tach/dwell meter from 25 years ago and it says my autometer tach is 400 rpm slow. Another way is to hook up a shift light with different rpm pills to see when you are shifting.
Good Luck,
Perry.
PS- try autolite #25 plugs at .040, toss the ngk's

[brainsboy]

Thanks guys I will try the adjustment tonight then post my findings.

Ben

[Big-Foot]

Ben - It sounds to me like you are just running out of carb. If you were out of fuel pressure (any "pressure" at WOT is enough) you would be going lean and backfiring and or roaching the spark plugs.

Borrow an 800+ CFM carb for that engine and try it again.

[V-8]

I'm running with a 408w too
Engine spects:
Block:Standard Ford made in 1991, O-ringed
Rotating Assembly: http://www.cnc-motorsports.com/produ...300&CtgID=9059
Balance:Internally Balanced
Carb:750HP series Holley
Intake:Edelbrock Victor Jr(ported&polished)
Ignition:MSD pro billet dist, MSD 6AL, MSD High voltage coil,MSD 3 step retard box
Cam:Comp Cams Mechanic roller 608-614 lift,110 LSA, 0.050 240-246
Rockers:Crane energizer 1.6 ratio and stud girdle
Fasteners:Full ARP and main girdle
Exhausts:Hedman Headers and Flow Masters
Cly Heads:TFS Twisted Wedge heads Full ported and polished,reshaped comb. chambers.
Comp Ratio: 13.1:1
Trans Spects:
TCI Street Fighter transmission
B&M 4000 Stall 8 inc race convertor
Rear-End:
Ford 8 inc, Richmond 3.55 gear,standard axles.
Car weight:3500lbs
Red line:6700rpm
Tires:245/45/17 Kumho's and 275/50/15 BFG drag radials.
E.T.:11.5 and 120 mil.
Gas:98 octane
I think you have a problem, with ignition specially MSD 6AL box (check it) and fuel pressure droping can make some problems like that.Because i had problems like yours.
Which kind of fuel pump are using now?(I had some problems with Holley Blue and black electrical fuel pump)

[V-8]

First i was using Holley blue and black electric fuel pump but they didn't work properly .Now i'm using http://store.summitracing.com/defaul....asp&x=19&y=10 when it is cold fuel pressure about 11psi but when it gets warm the fuel pressure drop to 4-3-2 psi (no regulator) and problems get started like yours it doesn't pass high rpms.
Now i will change it with this http://store.summitracing.com/defaul...=egnsearch.asp

[brainsboy]

Can someone do a test for me that has an MSD box in there car. I noticed when working on my distributor that when the coil doesnt have a coil wire in it, and I turn on the ignition when I goto turn it off a spark jumps from inside the coil tower all the way around and grounds to the negitive side of the coil. Is this normal? I tried different coils they all do the same thing

Can someone with MSD unplug there coil wire and turn there ignition on and off and see if a spark jumps?

[KrAzEcJ]

rev limiter in the 6AL?

[Big-Foot]

Originally posted by brainsboy


Can someone do a test for me that has an MSD box in there car. I noticed when working on my distributor that when the coil doesnt have a coil wire in it, and I turn on the ignition when I goto turn it off a spark jumps from inside the coil tower all the way around and grounds to the negitive side of the coil. Is this normal? I tried different coils they all do the same thing

Can someone with MSD unplug there coil wire and turn there ignition on and off and see if a spark jumps?

Yes - it's normal... That coil wants to discharge when the field breaks down - it's finding it's way to ground...

If you suspect a problem with the rev-limiter, pull the chip out of it altogether and try it again. Chip OUT means there is no rev limiter in the circuit.

[CowtownCobra]

A suzuki samuraiw/ 351w? I think its dying of embarassment...