HILBORN INJECTED 406 sbc peaking WAY early

[rewguy]

Have a 14.5-1 hilborn mech. injected (METHANOL) 406 c.i. sbc with excellent 23 degree heads. 2.125 intake valves, 2.77" CSA at welded/widened PR area. Flowed 346.5@ .750. (((Its a proven port that made 806 hp @ 7500 (and still climbing) on a previous 406 with gasoline (Q16) carbureted tunnel ram engine))) (Similar overall engine to this hilborn alcohol version.)
Hilborn injected engine is peaking waaaaaaaay low with hp at 6800 rpm (712hp), and peak tq at 5300 with 600 ft. lbs. Camshaft IS NOT the issue. Im pretty convinced the Hilborn stack length is killing us. Absolutely no reason whatsoever that this engine shouldn't peak 600-800 AT LEAST higher. I do realize that alcohol will peak a bit earlier than gasoline......but this is bordering on ridiculous. Valve springs and camshaft are more than up to the rpm task, as the camshaft is similar to our older camshaft at 281/296@ .050, .757/.730 on a 112.

NOW.... If you count the current stacks at 8 inches, and the base of the manifold at another 6 inches......that's 14 inches of intake manifold runner length. WAY WAY WAY longer than the older tunnel ram gasoline version at a 6 inch intake manifold runner length. PIPEMAX I believe recommended a overall runner length (head AND manifold) of 12.5 inches I believe for peak power in the 7800 rpm zone. This hilborn version would have more along the mines of 19 inches of overall intake runner length. Im sure good for mid range power and torque...….but not nearly short enough for the upstairs rpm we want. Does hilborn sell much shorter stacks? Am I on the right path/correct line of thought? Please chime in if you have any serious Hilborn/stack tuning experience. Thankyou very much!!!

[vds]

What does the head flow at .750" with the manifold attached ?

[rewguy]

I don't know what this new hilborn version flows. But it is such a straight through design I would imagine it would flow well. The old tunnel ram version at that lift went upper 330s

[houser45]

I am assuming it is a one piece Hilborn? Usually 7” stacks is about optimum. But every application varies. On a 360 ci spec engine (11x Brodix). With a 264/268 @.050 107 lsa cam usually peak is around 7200 for hp. 1” change in stack length won’t change much. Bolting a one piece 2 7/16 Hilborn on a 11x usually shows 20-25 com on the bench. That is a monster cam with a very wide lsa.

[houser45]

I am assuming it is a one piece Hilborn? Usually 7” stacks is about optimum. But every application varies. On a 360 ci spec engine (11x Brodix). With a 264/268 @.050 107 lsa cam usually peak is around 7200 for hp. 1” change in stack length won’t change much. Bolting a one piece 2 7/16 Hilborn on a 11x usually shows 20-25 cfm on the bench. That is a monster cam with a very wide lsa.

[MELWAY]

Do you have air fuel ratio data from dyno

Does it have a tuned high speed can on fuel system?

[houser45]

Do you have air fuel ratio data from dyno

Does it have a tuned high speed can on fuel system?

Good point! What are the pump size specs? Nozzles size? And fuel settings?

[englertracing]

Nozzles in the manifold or in the heads?

[ProPower engines]

The fuel system seems like it goes rich by your description.
As mentioned how is the barrel valve set. Also are you running a high speed and low speed bypass with a return as well.
If so..What are the bypass valves set at for pop off pressure and the AF ratio is at what??
Alky can be fickel to tune for a new guy but it can make a ton of power when done right and in some cases more then race gas.
And as mentioned the cam used has a really wide LSA for what would be used with Alky as well.
More info about what fuel system components you are using like early or late system as well
Throttle blade size long or short nozzles and nozzle numbers inlet fuel line size to the pump. Pump number etc ..............
You may also want to look at the plug choice and the gap. That can also cause issues as there is more liquid in the chamber then with any type of race gas.

More info regarding what you are using will will help with suggestions to get closer.

[rewguy]

I'll try to get details tomorrow

[Moparboy440]

What ignition system are you using? Magneto?

[swampbuggy]

What kind of racing, what length is the track/tracks ? Mark H.

[Kenova]

What is the diameter of the throttle blades? or did I miss that?

Ken

[Protech Racing]

112 sounds too wide .

[Walter R. Malik]

Have a 14.5-1 hilborn mech. injected (METHANOL) 406 c.i. sbc with excellent 23 degree heads. 2.125 intake valves, 2.77" CSA at welded/widened PR area. Flowed 346.5@ .750. (((Its a proven port that made 806 hp @ 7500 (and still climbing) on a previous 406 with gasoline (Q16) carbureted tunnel ram engine))) (Similar overall engine to this hilborn alcohol version.)
Hilborn injected engine is peaking waaaaaaaay low with hp at 6800 rpm (712hp), and peak tq at 5300 with 600 ft. lbs. Camshaft IS NOT the issue. Im pretty convinced the Hilborn stack length is killing us. Absolutely no reason whatsoever that this engine shouldn't peak 600-800 AT LEAST higher. I do realize that alcohol will peak a bit earlier than gasoline......but this is bordering on ridiculous. Valve springs and camshaft are more than up to the rpm task, as the camshaft is similar to our older camshaft at 281/296@ .050, .757/.730 on a 112.

NOW.... If you count the current stacks at 8 inches, and the base of the manifold at another 6 inches......that's 14 inches of intake manifold runner length. WAY WAY WAY longer than the older tunnel ram gasoline version at a 6 inch intake manifold runner length. PIPEMAX I believe recommended a overall runner length (head AND manifold) of 12.5 inches I believe for peak power in the 7800 rpm zone. This hilborn version would have more along the mines of 19 inches of overall intake runner length. Im sure good for mid range power and torque...….but not nearly short enough for the upstairs rpm we want. Does hilborn sell much shorter stacks? Am I on the right path/correct line of thought? Please chime in if you have any serious Hilborn/stack tuning experience. Thankyou very much!!!

Is this a "plenumized" injection unit or an Individual Runner design..?
I.R. stack injection like a sprint car will need at least 2 1/4" diameter intake manifold runners.