408

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aaronk785 said:
Put my short block together last night. I'm having very good luck on this build. Never touched the decks but did check them for flat. Pistons ended up about .001 to .002 below deck. This scares me when things go this well. This is a budget build so I took a chance and it actually worked out this time. Having a lot of fun with this build. Enjoying building something again.
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What Main Bearing Set are you using?
 
Part number?....and is it a Forged Crank?......

thanks
 
Ok. Short block is done. On to the heads. How much is a 2.055 intake valve worth on my ported SM heads. Or is a 2.08 even better?
 
aaronk785 said:
Ok. Short block is done. On to the heads. How much is a 2.055 intake valve worth on my ported SM heads. Or is a 2.08 even better?
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A 2.05 is perfect in many ways. If I remember the throat was sized on the big end. And if you don’t have a flowbench to maximize the 2.08 you are going to end up with a turbulent head.
 
Those are +.100 chevy valve right. I know I have to move my rockers up and away from the valve to get the geometry close. So why couldn't I put in stock length chevy valves with a + .100 retainer to fix the geometry. I'd be moving the valve down and away instead. Am I thinking right.
 
aaronk785 said:
Those are +.100 chevy valve right. I know I have to move my rockers up and away from the valve to get the geometry close. So why couldn't I put in stock length chevy valves with a + .100 retainer to fix the geometry. I'd be moving the valve down and away instead. Am I thinking right.
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That would not effect the stem height.
Just the spring installed height .
 
It should shorten the stem height and keep the spring height the same. Putting in a shorter valve. Hope I worded it right.
 
aaronk785 said:
It should shorten the stem height and keep the spring height the same. Putting in a shorter valve. Hope I worded it right.
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The stem tip height is only effected by the valve face placement on the seat ( Proud or sunken).
Your rocker geometry will not change by using a +.100 retainer or keepers.

Maybe I am not understanding what you are getting at ?
 
But I'm using a .100 shorter valve. So shouldnt the stem height be .100 shorter. The SM heads use a +.100 chevy valve. I'm putting in a standard length chevy valve. And the keeper groove is also .100 shorter. So thats why the +.100 retainer. Hope I'm making sense.
 
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It’ll make the correction kit a lot less aggressive on the stand. Less height, less off set.
 
aaronk785 said:
Ok. Short block is done. On to the heads. How much is a 2.055 intake valve worth on my ported SM heads. Or is a 2.08 even better?
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I was told by one of my builders that production style head small block mopar has pretty lousy intake valve placement in the combustion chamber and unless the bore was substantial, meaning typically more than what most production blocks can be bored to that a 2.08 valve would be too close to the cylinder wall and be counterproductive.
 
'68cuda416 said:
I was told by one of my builders that production style head small block mopar has pretty lousy intake valve placement in the combustion chamber and unless the bore was substantial, meaning typically more than what most production blocks can be bored to that a 2.08 valve would be too close to the cylinder wall and be counterproductive.
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That’s not correct. The SBM opens the valves on the center of the bore so you can get a bigger valve before shrouding.
 
Put this engine in the dart last week and I am very pleased with the performance. I have some fine tuning to do yet but this thing screams. I'm surprised at how this engine rpms it will scream to 7000 very quickly I figure with my home ported sm heads would choke the 408 but it likes rpm. I have to watch the tach closely because I want to shift at 6500. Saturday will tell as I will be at test and tune and bracket racing.
 
aaronk785 said:
Put this engine in the dart last week and I am very pleased with the performance. I have some fine tuning to do yet but this thing screams. I'm surprised at how this engine rpms it will scream to 7000 very quickly I figure with my home ported sm heads would choke the 408 but it likes rpm. I have to watch the tach closely because I want to shift at 6500. Saturday will tell as I will be at test and tune and bracket racing.
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Thanks for the update. Can't wait to see how it performs at the track.
 
Made it to the track Saturday and my car ran 7.45 at 90 in the 1/8 mile and 11.85 at 110 in the 1/4 mile. 60 ft was 1.59 to 1.6. This engine comes out of the whole hard. I am very impressed with the bone stock suspension and snubbed. Mph is down but that might be the full 2.5 exhaust and small headers. Not the best times but good for off the trailer and absolutely no tuning. It's a torquer for sure.
 
^^^^ Great start!! You'll get that car faster soon for sure as you tune and tweak it. These 408's just beg you to unleash them!!
 
Not sure who you're asking but I used Mahle Motorsports SBM460030I16 forged pistons. -16cc volume and cut the heads to get a measured 10.5 CR.
 
Thank you @aaronk785 and @Demonx2 .

I'm building a 408 with Molnar rotating assembly and Icon flat top pistons. I was going back and forth on which piston to run with Trick Flow heads since I am shooting for 11.5:1 CR with a plan to machine the top of the pistons to get me where I want to be. Just curious what route others took.

Bill
 
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