Monza355 wrote:I'm wondering about an intake manifold for a mild 406 engine. Max rpm is 5800-6000.
The engine has Dart Sportsman II iron heads and 225/231 Hydraulic roller camshaft with 112 lsa and 570/580 lift.
And will be in front of an automatic transmission with 2500 stall breakaway converter.
It will be used mostly on the streets. town & highway with a little strip duty.
I have two intake manifolds and i'm hoping to use either one of them, One is Performer EPS and the other one is a Victor Jr.
Would i be leaving to much bottom end with the single plane and vice versa (top end) with the dual plane ?
One thing I have noted here that does not seem to have been widely picked up on is the cam you are intending to use. The LCA is so far off what a 400 inch engine with Dart sportsman II heads needs that it is almost pointless worrying about an intake until the cam situation is fixed. What you need here is a cam on about a 106 LCA and certainly no wider than 108. It would appear that street manners are important here so choose a duration that gives the same overlap as the cam you thought you might use and it will retain the same idle (or slightly better) but have very much more low speed torque.
Once you have the cam right I would suggest the Edelbrock RPM Performer and if cold weather is not an issue go for the air gap version. REmember that since this intake is mostly divided each cylinder of the engine will only see half the carb capacity. don't make the mistake of using two small a carb as this will become the limiting factor toward top end output before the intake does. With a 950 Ultra Holley I have seen 575 hp and 542 lbs-ft from a 383. That should give you a good idea of what these Edelbrock two plane intakes are capable of given enough carb.
DV
David Vizard Small Group Performance Seminars - held about every 2 months. My shop or yours. Contact for seminar deails - davidvizardseminar@gmail.com for details.
So you are suggesting a single pattern cam with 216 @.050" duration , on a 106 LSA.
(or a similar dual pattern cam close to this , on a 106)
Lets get to the nitty gritty. Longer or shorter exhaust than intake duration on this one.? (max torque)
It will be torque y at WOT thats for sure. It will have a very sharp power band. The exhaust system has to be right.
X2 on the dual plane with divided Plenum and carb size/cfm choice for power. How about 2 carbs?
After reading one of your books David building sbc's on a budget.
I should have known that larger under valved sbc engine would favor the tighter lsa ! Once I ran a very similar 400 with 256/260 @ 50 105 lsa solid roller and it was the most fun street engine i'we ever had ! Super responsive with unbelievable torque !
However the main reason I chose this wide lsa cam was that the engine must run 91 oct pump gas, and since I went a little overboard with the compression the 112 lsa should bleed off some compression and the second reason is i'we been thinking this engine out as a mild idle low rpm sleeper with up to 200 hp nitrous for no one to see
If your plan is to run nitrous that would help in your OP...Careful with nitrous over 150 unless your running a fogger type system, duel planes and big plate system can lead to melted pistons.still if no more than 200 is used based on my experiance I would not change cam specs much from what DV is suggesting
Please Note!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
Yes we'll see how it goes. And as I said above mpg and 91 octane pump gas are factors in this build.
I'm worried that smaller cam with tighter lsa (same overlap) might get less mpg and would definitely ping on 91 octane with my engines compression.
Monza355 wrote:I'm worried that smaller cam with tighter lsa (same overlap) might get less mpg
Why? If anything, I'd expect mileage to increase with later EVO, earlier IVC, and no increase in overlap.
FWIW, I have a 217/225 cam on a 108 LSA in a 9.6:1 355. It gets 19-20 mpg with no OD and a 31-3200 rpm highway cruise speed. Tight LSA isn't a mpg killer if the duration is right.
Camking has suggested that the best economy/power combo for a 350 is 204/208/112. It was like a sweet spot for that displacement. He further stated narrowing the lsa or adding duration took away either power or economy. A 400 is 14 percent larger, making for an intake duration of 230 degrees. The question I have is where is the best lsa for a 400? Is there a sweet spot for the larger engine? A decently assembled 400 will always provide plenty of torque for most street driven uses, and as long as it is not breathing through a 2 barrel and single exhaust, its going to spin the tires for blocks. Squeezing economy out of 400 inches is more challenging.
Monza355 wrote:I'm worried that smaller cam with tighter lsa (same overlap) might get less mpg
Why? If anything, I'd expect mileage to increase with later EVO, earlier IVC, and no increase in overlap.
FWIW, I have a 217/225 cam on a 108 LSA in a 9.6:1 355. It gets 19-20 mpg with no OD and a 31-3200 rpm highway cruise speed. Tight LSA isn't a mpg killer if the duration is right.
Bullseye - you nailed it here!
DV
David Vizard Small Group Performance Seminars - held about every 2 months. My shop or yours. Contact for seminar deails - davidvizardseminar@gmail.com for details.
Monza355 wrote:I'm worried that smaller cam with tighter lsa (same overlap) might get less mpg
Why? If anything, I'd expect mileage to increase with later EVO, earlier IVC, and no increase in overlap.
FWIW, I have a 217/225 cam on a 108 LSA in a 9.6:1 355. It gets 19-20 mpg with no OD and a 31-3200 rpm highway cruise speed. Tight LSA isn't a mpg killer if the duration is right.
Bullseye - you nailed it here!
DV
David Vizard Small Group Performance Seminars - held about every 2 months. My shop or yours. Contact for seminar deails - davidvizardseminar@gmail.com for details.
Monza355 wrote:I'm worried that smaller cam with tighter lsa (same overlap) might get less mpg
Why? If anything, I'd expect mileage to increase with later EVO, earlier IVC, and no increase in overlap.
FWIW, I have a 217/225 cam on a 108 LSA in a 9.6:1 355. It gets 19-20 mpg with no OD and a 31-3200 rpm highway cruise speed. Tight LSA isn't a mpg killer if the duration is right.
Monza355 post":- I'm worried that smaller cam with tighter lsa (same overlap) might get less mpg
Why? If anything, I'd expect mileage to increase with later EVO, earlier IVC, and no increase in overlap.
FWIW, I have a 217/225 cam on a 108 LSA in a 9.6:1 355. It gets 19-20 mpg with no OD and a 31-3200 rpm highway cruise speed. Tight LSA isn't a mpg killer if the duration is right.
Bullseye - you nailed it here!
DV
Dave,
A cam for a 406 instead of a 355 engine.
pdq67[
Busier than a one armed wall paper hanger right now but I will see what I can do to work up a cam spec over the weekend and do the justification for the spec given.
DV
David Vizard Small Group Performance Seminars - held about every 2 months. My shop or yours. Contact for seminar deails - davidvizardseminar@gmail.com for details.
I would have been... with the 4.30 gears.... 4400 lbs !!!! Make that 4.56 gears. Does that thing really weight that much?
That's a Street car.
This was my drive inro Portland this morning. Do you think this looks like the kind of road where you would want 4.56 gears and a lot of torque. You live in Ontario, where there is real winter weather. Tell me you have something reasonable for winter. Although I live in the banana belt of western Oregon, I learned to drive in central NY. No one drove hot rods in the winter there, they drove real street cars.
I drive a Detroit locker 4.56/700r4 nominal 4000 stall lock-up in a vehicle about a 1000lbs lighter, and a 58% front weight bias here in the PNW in weather like this all the time. Yes, when its raining like this, pucker factor is WAAAAY up there!
