408 Stroker

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70dart340

70dart340

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All right, gentlemen, after years of lurking, learning, and saving money, it's time to build my stroker. You serious guys like YR, Rumble, Crackedback and others, be gentle. Car is a numbers matching 1970 Swinger 340 with the build sheet and other factory documentation. I rebuilt the stock motor, but shrink wrapped it and put it in the corner, because I want to run this old girl. I have a 1998 5.9 in the machine shop now. It sonic checked great. I'm planning on a forged (Molnar) crank, H beam rods, and forged pistons in the 10.0 range. I'll be buying the the TrickFlow 190's to top it. I have a set of TTI's, stepped, I plan on using. I'm torn on induction between an Airgap RPM, with a 750 Quickfuel 750 mechanical, or stepping up to the Holley Sniper. My 727 was built by Pat Blaise(RIP) with a 2800 converter. I have an extra 8 3/4 rear I plan on putting a 3.55 Auburn suregrip unit in it. If I could figure out how to put rear discs on it with the SBP wheels, I will. Car will be 90% street driven, on 91 pump gas. I have many othe rparts, like a NIB E-curve distributor, my Quickfuel 4 corner mechanical secondary annular booster carb, an RPM Airgap, and a set of Schumacher anti-blow(?) motor mounts, and 10 years worth of parts I bought when I was working 60-80 hours a week. I'm thinking I need to have the block align honed and decked to 9.600. Any constructive advice is appreciated. I have a few medical conditions, so I'm making this my last and best build. All questions will be answered politely and as quickly as I can. I know I need help picking the right cam, which is the holy grail, but I'm being open minded to all sane advice. Paul.
 
I should include that even though it's primarily a street car, I'm leaning towards a sollid roller cam.
 
The converter seems a bit low. It will stall higher with the stroker. I run a PTC 9.5” stalls about 3500. I is fine driving around on the street. With the advances in converter technology higher stall no longer means a PITA on the street.
 
Sounds like you are street driving it but want 1/4 mile performance.
There will be some trade offs.
 
Good morning Paul;

The idea of showing up the kids and there Subaru's sounds like a fun idea. Before we start, what kind of power do they have and are there cars supercharged/turbocharged?

The old saying of “There is no replacement for displacement” is 98% true. That last 2% is really two things. 1, Power vs weight. The other, adding boost artificially adds displacement. You can have a really big engine making 900 HP, but, if it is moving a loaded dump truck, we’ll, that isn’t going to be to good. Adding a turbo on there 4 bangers to the tune of double the atmosphere pressure doubles there engine size.

Ask the kids;

The actual size of there engine and if it is pressurized.
(Turbocharged/supercharged)

The vehicles weight
How many speed transmission and gear ratio.

Know thy enemy and know thyself.

Which leads to the same questions for you.
“Your!” 1970 Dart swinger weighs how much?


furrystump said:
The converter seems a bit low. It will stall higher with the stroker. I run a PTC 9.5” stalls about 3500. I is fine driving around on the street. With the advances in converter technology higher stall no longer means a PITA on the street.
Click to expand...
I so totally agree with this.
 
What gears are you panning on using?
What RPM are you looking to turn with this stroker?
 
Keep the cam duration street friendly...
The stroker will have plenty of street power... Don't get caught up on chasing numbers...
 
Cudafever said:
What gears are you panning on using?
What RPM are you looking to turn with this stroker?
Click to expand...
IMO, this is yet to be determined. But this is on the right track. IMO, the stroker will not need more than a easy 6500.
j par said:
Keep the cam duration street friendly...
The stroker will have plenty of street power... Don't get caught up on chasing numbers...
Click to expand...
This is so “Ooooh” true it’s silly. IMO, the cam is still yet to be determined. And some of that is a question of what exactly are we up against.

With a cam in the 224 @050 range, a 408 can make a easy 450 HP below 5500. As far as I’m concerned, that’s 200 hp shy of what a turbocharged Suburb can make.
 
When it comes to selecting a cam, before the science & calculators comes into play, choosing a cam starts with the duration @050 for the rpm band it will perform in. This is also a variable due to engine configuration.

Then comes valve lift. I myself like to try and take advantage of the heads flow potential. In this case of the trick flow heads, more lift the merry.

I like a low numbered LSA. A 110 is a typical street machine. It’s fine on a bunch of fronts but a lot of it is also build& target goal dependent.

The camshafts lobe is also another case to look at.
How aggressive can we get without issues? There can be many if you decide wrongly. Namely, installing a race cam in a otherwise stock engine results in crap performance. Also unhappy drivers.
 
With permission of member @richmystery116
His excellent street driving, RPM, 1.5 roller rocker, trick flow 190 headed engine.
(And now you know why myself and @AJ/FormS like a cam in this range for a driver.)
His 408 cam and dyno sheet;
upload_2021-3-2_10-1-45.jpeg


upload_2021-3-2_10-2-18.jpeg
 
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I agree with most everything said above with these exceptions.

I’d lose that air gap so fast your head would spin. The TR heads will reward in spades IF you treat them like what they are, which is a performance cylinder head. They beg for lift. Give it to them. And the AG will choke them.

Use a solid roller. You can use hydraulic roller lobes but put solid rollers on them.

You really, really need a header with 1 7/8 inch primaries. TTI has them but I’m not a big fan of their collectors. There is another place back on the east coast making some nice headers that size but I can’t think of their name right now.

Don’t buy a “big” cam or a “small” cam, buy the RIGHT cam. The RIGHT cam will have short seat timing, get to .050 and .200 quicker than everything else in that duration rage and put all the lift to it you can. Realistically you should be able to NET .630 or more lift in an easy on the valve train set of lobes. You will be rewarded with a broader, flatter torque curve, smooth, clean drivability and better performance.

Before I ever bought a set of rockers I’d call Mike at B3 racing engines and ask him for his opinions on what rocker to use and then buy them from him with his correction kit. This step right here will save you time, money, grief and parts.
 
I agree 100% with the single plane vs dual plane on a 408 with very good heads. My 408 in my street use Dart with a 4 speed runs 3.23 gears and a single plane manifold. There is no shortage of low end torque on these engines. I believe fuel distribution will be much better with the single plane. I street drive my 408 with a [email protected], .580 lift cam with absolutely no driveability issues.
 
yellow rose said:
I agree with most everything said above with these exceptions.

I’d lose that air gap so fast your head would spin. The TR heads will reward in spades IF you treat them like what they are, which is a performance cylinder head. They beg for lift. Give it to them. And the AG will choke them.

Use a solid roller. You can use hydraulic roller lobes but put solid rollers on them.

You really, really need a header with 1 7/8 inch primaries. TTI has them but I’m not a big fan of their collectors. There is another place back on the east coast making some nice headers that size but I can’t think of their name right now.

Don’t buy a “big” cam or a “small” cam, buy the RIGHT cam. The RIGHT cam will have short seat timing, get to .050 and .200 quicker than everything else in that duration rage and put all the lift to it you can. Realistically you should be able to NET .630 or more lift in an easy on the valve train set of lobes. You will be rewarded with a broader, flatter torque curve, smooth, clean drivability and better performance.

Before I ever bought a set of rockers I’d call Mike at B3 racing engines and ask him for his opinions on what rocker to use and then buy them from him with his correction kit. This step right here will save you time, money, grief and parts.
Click to expand...
Thanks @yellow rose
The single plane vs dual plane in this case of which is yet to unravel would be drivers choice & as well as the usage of the car (intended purpose, already somewhat defined) & the cars weight. I myself would use a single plane and a larger carb than a 750.
There is a place in Connecticut IIRC that makes some really nice headers. To bad Stahl passed away taking his secrets.
I’m having an oiling problem with the supplied B3 rockers at the moment. I have not got to investigate the issue yet. Other engine problems popped up. It will be a while before I’m back on my feet to do anything.
Others run the Harland Sharps without issue and 2 local engine builders like them better than the B3 rockers.
I do not know the reasons why.
512Stroker said:
Rob if I am reading that dyno sheet correctly that combination is a low end torque monster.
Flat tappet or roller cam?
Click to expand...
Hyd roller and yes you are correct.
cpearce said:
I agree 100% with the single plane vs dual plane on a 408 with very good heads. My 408 in my street use Dart with a 4 speed runs 3.23 gears and a single plane manifold. There is no shortage of low end torque on these engines. I believe fuel distribution will be much better with the single plane. I street drive my 408 with a [email protected], .580 lift cam with absolutely no driveability issues.
Click to expand...
You lost a lot of bottom end torque. But like you said, the amount the 4.00 arm hands out in torque, I think most people aren’t worried. Though I’m still looking for the weight of the car. There are a lot of pounds in the engine bay and cabin that can be lost for a better weight distribution for the cars balance.
 
yellow rose said:
I agree with most everything said above with these exceptions.

I’d lose that air gap so fast your head would spin. The TR heads will reward in spades IF you treat them like what they are, which is a performance cylinder head. They beg for lift. Give it to them. And the AG will choke them.

Use a solid roller. You can use hydraulic roller lobes but put solid rollers on them.

You really, really need a header with 1 7/8 inch primaries. TTI has them but I’m not a big fan of their collectors. There is another place back on the east coast making some nice headers that size but I can’t think of their name right now.

Don’t buy a “big” cam or a “small” cam, buy the RIGHT cam. The RIGHT cam will have short seat timing, get to .050 and .200 quicker than everything else in that duration rage and put all the lift to it you can. Realistically you should be able to NET .630 or more lift in an easy on the valve train set of lobes. You will be rewarded with a broader, flatter torque curve, smooth, clean drivability and better performance.

Before I ever bought a set of rockers I’d call Mike at B3 racing engines and ask him for his opinions on what rocker to use and then buy them from him with his correction kit. This step right here will save you time, money, grief and parts.
Click to expand...
Pro-Fab?
 
With strokers there is allot of debate about what constitutes a street cam and to be completely honest the example shown above is more like a truck cam with a buttery smooth idle to me. I'm not saying it doesn't make power, clearly it does but if you are truly using trickflows I would recommend something solid in the high 230s at .050 and around .550 lift at minimum to really take advantage of the heads and stroke.

For me if I'm going to spend the money you are I want see 500hp to be worth the investment, otherwise I will throw on some edelbrocks/speedmasters and be happy with my 430-450hp and fatter wallet.
 
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lead69 said:
With strokers there is allot of debate about what constitutes a street cam and to be completely honest the example shown above is more like a truck cam with a buttery smooth idle to me. I'm not saying it doesn't make power, clearly it does but if you are truly using trickflows I would recommend something solid in the high 230s at .050 and around .550 lift at minimum to really take advantage of the heads and stroke.

For me if I'm going to spend the money you are I want see 500hp to be worth the investment, otherwise I will throw on some edelbrocks/speedmasters and be happy with my 430-450hp and fatter wallet.
Click to expand...

Not that I’m knocking your choice of approximate cam duration, but as you said, it is really all relative. Your cam is a 6 degree increase, which is small. Often considered one step up in size. I’d also say the same on lift only against the heads best flowing lift. While you don’t have to lift the valve that high to actually make power, if you can the valve lift up there to take advantage of the higher flow ability of the head, there’s some more power there. The difference between a mid .400 lift or a .550 lift is good. If you can push it a tad with a rocker ratio, even better, and better yet, a little more duration at the higher lift starts to really move some air and make some more power.
F1BB9AFF-392A-4562-B437-8B724397FC47.png
 
rumblefish360 said:
Not that I’m knocking your choice of approximate cam duration, but as you said, it is really all relative. Your cam is a 6 degree increase, which is small. Often considered one step up in size. I’d also say the same on lift only against the heads best flowing lift. While you don’t have to lift the valve that high to actually make power, if you can the valve lift up there to take advantage of the higher flow ability of the head, there’s some more power there. The difference between a mid .400 lift or a .550 lift is good. If you can push it a tad with a rocker ratio, even better, and better yet, a little more duration at the higher lift starts to really move some air and make some more power.
View attachment 1715700243
Click to expand...
I would agree and it's all in what a guy wants and there are many, many combos for different tastes. Looking at the specs of the above cam the intake @.050 is 224.6 and the smallest duration I would use with a 4.0 stroke and trickflows is 236ish so we are talking about an additional 12 degrees of duration. In addition the added duration (specially a solid roller) would add a bunch of lift and help with the losses through the geometry.
 
I want to thank everyone for all the great information. Car is a bone stock appearing '70 Swinger 340 with factory A/C. Book says it should weigh about 3100 lbs, add 200(Really!) for me. I'm leaning towards a set of 3.55's for my 741 8 3/4 with some type of SG. The TC is the stock one that Pat Blaise rebuilt long ago, I think it's a given I could use more stall speed. He rebuilt my 737 with upgraded parts and increased the line pressure. It sounds like the consensus is to use a single plane intake, as the stroker isn't giving up much at low RPM. I know from reading over the years that some people are passionate about carbs, while others swear by fuel injection, like the upper end Sniper. I'm open to all suggestions while deciding. I guess my hardest choice will be the camshaft. I like tinkering, so I'm willing to live with a solid roller. I want a fun, reliable weekend warrior, with an occasional strip adventure. Most of the Subies are putting 250-280 HP to the wheels, except for one baddazz WRX STI with a BIG turbo. I guess my 10.0 to 1 is about right with the TF's. I'll reach out to B3 Racing, and maybe Bryan at IMM for suggestions/advice. Thanks to all for their sound advice.
 
To answer more questions, I'm thinking 6500 RPM is a good redline for 408 CID. Has anyone tried the billet MSD E-curve distributor, or did I just waste my money?
 
Three key words in the original post: 90% street driven.
The comment that a single plane intake has better fuel distribution is incorrect, because you have 7 cyls interfering with the cyl drawing mixture, compared to 3 cyl with a dual plane.

The Edel RPM manifold really changed the goal posts with the SP v DP intake debate. I have seen dyno tests where the RPM was better everywhere in the rpm range over a SP intake. Not what was expected, but the numbers don't lie.

If it was my engine, I would use the RPM.
In a 408, the RPM will probably peak at about 6200-6300 rpm. Because a DP manifold usually idles better & has more vac than a SP, you could increase duration by about 5* for more HP without sacrificing street manners. Also agree with solid roller lifters, either with a sol cam or hyd.
 
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