Help, won't rev beyond 2900rpm
 

O.k. here the scoop:

Mark IV Stroker kit Eagle Crank, Rods, JE srp 9.1:1 489CID
Heads Peanut Port (Factory 330)
Edelbrock Performer intake
Holley 750 vacuum secondary
Camshaft
Duration at .50 inch Lift: 218 int./228 exh
Lift .500 .500
114 Deg Lobe Separation.
Crane Gold Race Roller Rockers
Plugs NGK FR5 (slightly rich)
Timing 8 Degrees BTDC
Mirage 23
Bravo

Combination was running flawlessly prior to implementing the stroker kit, now it will not rev beyond 2900 rpms under load.

Timing Module is 24 degree version and it is advancing the timing, at 2800rpm it was showing 25 degrees total.

The boat was sitting dormant for approx 8 months with a mix of 89/93 in the fuel tank, of which only 9 gallons remained, was topped off this afternoon with 35 gallons of 93 octane premium, no difference.

Everything is new, I've swapped carbs and attempted to advance the base timing to 10 degrees. Still will not go above 2900 rpm, I'm stumped.

I will be pulling the valve covers this eve, and running the valves again to insure my RR aren't set to tight, after this I'm out of ideas. If anyone can provide some additional insight it would be appreciated.

Re: Help, won't rev beyond 2900rpm
 

Anyone??

Re: Help, won't rev beyond 2900rpm
 

Based on the information provided you de-stroked a 454 smaller to 389 C.I. and basically no cam. If the info given is correct, you will have less HP than what you started with.

Re: Help, won't rev beyond 2900rpm
 

Sorry, typo.

489 CID

Re: Help, won't rev beyond 2900rpm
 

Problems I see with the combo

1. The heads suck
2. Cam is too small--smaller than a stock 454mag cam

I really doubt you'll see more than 350-375hp with these.


Things to check to get it to just run decent.

Plug wire order
Is the throttle adjusted properly and fully putting the carb at WFO
Valves/rockers are to tight.

Re: Help, won't rev beyond 2900rpm
 

Yes, I know the heads suck, although I've been spiraling out of control ever since I embarked upon this project, a decent set of cylinder heads and exhaust are planned upgrades.

Motor was originally a 330 so this camshaft is an upgrade. (even though it's tiny by OSO standards.)


Plug wires are a go.
WFO is a go.
Adjusted the valves/rockers with the motor on the engine stand, prior to intake installation. Zero lash, + 1/2 turn.

The same cam, heads, and carb installed upon the 7.8:1 454 cid 330 would pull to 5000rpm easily. The only item that was modified since was the shortblock, bored and stroked to 489 cid, & compression bumped to 9.1:1.

I'm leaning towards an ignition problem, which I'll begin troubleshooting this week.

Re: Help, won't rev beyond 2900rpm
 

I'd probably run 34-36 degrees total timing. Rev up to 4200rpm with the light just to make sure that you have actually reached the total.

Check fuel psi and that needle and seats are working correctly.

Tune carburetor to new set up. You may be off a good amt.

Lastly, if using stock 330hp flame arrestor, it should be changed to something that actually let's air in.

==================
That said - Griff is 1 million % correct.

The Min CSA on peanut port heads and that intake are puny. They will hit the choke point at a much earlier rpm on 490cid then on 454cid.

To put these heads into perspective, just to picture runner size, most peanut ports are around 200cc's in volume. :eek:

Good news is, proper camshaft (even mild), correct intake manifold, and a decent (not even killer) cyl head will probably gain you 100-150hp over what you have now. And more importantly, bring you to a better hp rpm peak.