408 stroker short block questions

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Confusedcuda

Confusedcuda

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Hello all. Thinking about buying one of those ATK shortblock 408's. They are internally balanced which I think means I can just use just my stock 318 flex plate and a regular small block balancer. (I think) It's just the short block, so I was going to buy some Magnum heads and throw on. Does anybody have any input on what and where to get the right push rods and rocker arms etc. (trying to keep cost down) I was going to just copy the other complete 408's that are 375hp, that's all I really want. Their cam is the .474 .474 ones. I think I can use my timing cover, valve covers and my 904. I know I got to get a 360 oil pan, what else may I need to do this conversion. Thanks. I know about Magnum swap but the more info the better.
 
Confusedcuda said:
Hello all. Thinking about buying one of those ATK shortblock 408's. They are internally balanced which I think means I can just use just my stock 318 flex plate and a regular small block balancer. (I think) It's just the short block, so I was going to buy some Magnum heads and throw on. Does anybody have any input on what and where to get the right push rods and rocker arms etc. (trying to keep cost down) I was going to just copy the other complete 408's that are 375hp, that's all I really want. Their cam is the .474 .474 ones. I think I can use my timing cover, valve covers and my 904. I know I got to get a 360 oil pan, what else may I need to do this conversion. Thanks. I know about Magnum swap but the more info the better.
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Buy a blueprint motor from @Johnny Mac instead. Blueprint builds performance engines, ATK mostly builds stock replacements. I can vouch personally for the excellent customer service BPE offers - you won't be disappointed if you go with them. The Blueprint motor is external balance, but the cost of a flexplate is $120 and money well spent IMO. You shouldn't reuse a tired OEM balancer either.

You can buy a complete blueprint engine, dyno-tested, for only a few hundred more than you can assemble an untested combo. So I'd highly recommend that. But if you're dead-set on building your own for the sake of building your own, they offer a shortblock also which will take magnum heads. Really it comes down to how many of the parts you already own. If you don't have any heads, intakes, etc then I'd buy complete. It's warrantied and will hit the advertised power numbers every time.

Pushrods need to be measured beforehand no matter what - too many variables between aftermarket rockers, machined heads, machined decks, etc to be able to nail it ahead of time.
 
Confusedcuda said:
Hello all. Thinking about buying one of those ATK shortblock 408's. They are internally balanced which I think means I can just use just my stock 318 flex plate and a regular small block balancer. (I think) It's just the short block, so I was going to buy some Magnum heads and throw on. Does anybody have any input on what and where to get the right push rods and rocker arms etc. (trying to keep cost down) I was going to just copy the other complete 408's that are 375hp, that's all I really want. Their cam is the .474 .474 ones. I think I can use my timing cover, valve covers and my 904. I know I got to get a 360 oil pan, what else may I need to do this conversion. Thanks. I know about Magnum swap but the more info the better.
Click to expand...

There are not really any good Magnum heads currently available for cheap. Pretty much just Edelbrock Magnum aluminum heads and then all the cheap Chinese cast iron replacements.
If you do get the cast iron replacement heads that are currently available, you MUST factor in machine shop cost of setting valve guide clearance, unless they come from a reputable shop that already checks this. Most venders are just selling what is available and not checking them.
 
Bobzilla said:
There are not really any good Magnum heads currently available for cheap. Pretty much just Edelbrock Magnum aluminum heads and then all the cheap Chinese cast iron replacements.
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The other way around this is to use pushrod oiling on LA heads which requires, of course, pushrod oiling able lifters (AMC) & rockers that allow pushrod oiling. (Comp Pro Magnum rockers for one for the standard LA head.) Once that hurdle is done, any LA head can be used on the Magnum block.

Then you can graduate to a set of TF’s, or step up to any W series or a Victor head.
 
read scott foxwells utube vid on how to find correct pushrod length. its the one with the yellow rocker in the pic
 
Phreakish said:
Buy a blueprint motor from @Johnny Mac instead. Blueprint builds performance engines, ATK mostly builds stock replacements. I can vouch personally for the excellent customer service BPE offers - you won't be disappointed if you go with them. The Blueprint motor is external balance, but the cost of a flexplate is $120 and money well spent IMO. You shouldn't reuse a tired OEM balancer either.

You can buy a complete blueprint engine, dyno-tested, for only a few hundred more than you can assemble an untested combo. So I'd highly recommend that. But if you're dead-set on building your own for the sake of building your own, they offer a shortblock also which will take magnum heads. Really it comes down to how many of the parts you already own. If you don't have any heads, intakes, etc then I'd buy complete. It's warrantied and will hit the advertised power numbers every time.

Pushrods need to be measured beforehand no matter what - too many variables between aftermarket rockers, machined heads, machined decks, etc to be able to nail it ahead of time.
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Thanks for that @Phreakish . For what its worth also, we buy the edelbrock castings bare, and machine/assemble the aluminum 408 heads here. It is really impossible to buy the parts, and pay for machine work, and do it better...or for less money. Thanks!
 
408 with 375 hp , why bother you can get more out of a 360 with ease , if your going 408 just buy from bpe you get a warranty and more hp
 
Nat said:
408 with 375 hp , why bother you can get more out of a 360 with ease , if your going 408 just buy from bpe you get a warranty and more hp
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I'd have to check my dyno sheet, but that may be what my 408 made at the beginning of the curve, at 2000 rpm
 
Nat said:
408 with 375 hp , why bother you can get more out of a 360 with ease , if your going 408 just buy from bpe you get a warranty and more hp
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The equally built engines other than there bore and stroke configurations, the stroker will always make more power, period.

If you’d doing it in another way, cost wise, as a cheap *** penny pinching grinch master miser, rebuilding the 360 is a cost savings in which the cost difference MAY, just MAY be enough to roll over into ported or porting heads. Which will make more top end HP but NOT low end to mid range torque.
 
What does everybody think of 360 Magnums. Good price, 320 hp pretty sweet
 
Confusedcuda said:
What does everybody think of 360 Magnums. Good price, 320 hp pretty sweet
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Cheaper than a stroker.
Used engines tend to be in good shape because the EFI doesn't wash as much oil out of the cylinders as a carb does, and so the cylinders tend to remain in very good shape for 100k+ miles.
Hardest part is intake manifold selection and that part ain't that hard. There's several magnum compatible intakes, and even dual-pattern intakes available for what you're looking for.
The OEM roller cam system delivers decent longevity so it makes a great engine for street use. No need for super-special oil formulations or other cam-saving voodoo to keep it alive.
Find one with clean oil and clean coolant and drive it until the heads crack. Pressure test the cooling system prior to yanking it (if possible) to ensure the heads aren't already cracked. That's probably the one drawback of the magnum that gets reported often.
Personally I'd look for a pre-magnum roller engine (TBI motors). Not uncommon for them to cost less than a magnum engine, and they have all the same benefits except that if/when the heads crack you can drop LA heads onto them and they take LA intakes too.
 
diymirage said:
I'd have to check my dyno sheet, but that may be what my 408 made at the beginning of the curve, at 2000 rpm
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ok, i was off, my 408 passed the 375 mark at 3500 RPM
(my readout starts at 2900 rpm and 243 horsies and 442 foot pounds)

rumblefish360 said:
The equally built engines other than there bore and stroke configurations, the stroker will always make more power, period.

If you’d doing it in another way, cost wise, as a cheap *** penny pinching grinch master miser, rebuilding the 360 is a cost savings in which the cost difference MAY, just MAY be enough to roll over into ported or porting heads. Which will make more top end HP but NOT low end to mid range torque.
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i think his point was, if the goal is 375 HP there is no need to spend the money on a stroker rotating assembly
a stock 360 with headers, dual plane and decent cam will get you there
 
It’s just a 4” stroke crank. That doesn’t therefor mean the engine must be built for big horsepower, needing a cam with big duration and lift, a single plane intake, mombo headers and carb etc etc. or else it’s just a waste and that you should stick with a 360. Theres lots of ways to build a complete package around the increased stoke.
 
diymirage said:
i think his point was, if the goal is 375 HP there is no need to spend the money on a stroker rotating assembly
a stock 360 with headers, dual plane and decent cam will get you there
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I do get that very much but, it seemed you were considering a brand new engine. I went from that stand point.
 
I bought a dressed 408 from Blueprint in 2008? I have abused it to no end and it has performed fine. I’m still running the block/rods/crank at this time. When I pulled it apart to change pistons to bump compression the bores were still straight and round. The crank was still straight. Two little things that I ran into. It came with a Kevko oil pan which I really like, is only about 3/4” lower than the k frame, but The drain for the oil located outside the baffled sump area. So when you change oil it holds over a quart of oil that doesn’t drain. I email Kevko about it, no response. I mean it is such an easy fix. In the end I just installed another drain plug in the sump area. Also a week after I got it the dip stick missed the hole through the baffle in the pan and got snapped off by the crank. Not a big issue, but a bit bigger hole would be nice. Maybe they would listen to Jonny Mac.
 
furrystump said:
I bought a dressed 408 from Blueprint in 2008? I have abused it to no end and it has performed fine. I’m still running the block/rods/crank at this time. When I pulled it apart to change pistons to bump compression the bores were still straight and round. The crank was still straight. Two little things that I ran into. It came with a Kevko oil pan which I really like, is only about 3/4” lower than the k frame, but The drain for the oil located outside the baffled sump area. So when you change oil it holds over a quart of oil that doesn’t drain. I email Kevko about it, no response. I mean it is such an easy fix. In the end I just installed another drain plug in the sump area. Also a week after I got it the dip stick missed the hole through the baffle in the pan and got snapped off by the crank. Not a big issue, but a bit bigger hole would be nice. Maybe they would listen to Jonny Mac.
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We actually tested the standard oil pans vs those kevkos for windage, oil pressure, horsepower and saw no gains for one vs the other, so since we know the oe pans fit everything, thats what we are using. I agree its weird the aftermarket pans hold so much oil. You should see the firds......

Awesome to see an older one still ripping it up!!
 
Confusedcuda said:
What does everybody think of 360 Magnums. Good price, 320 hp pretty sweet
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The way I understand it, other than the electronics (fuel injection, sensors), the main difference between LA engines and Magnums were the camshaft and heads. The Magnum heads are arguably the best flowing stock small block heads, and of course they came with a camshaft that would support that.

Lots of guys swap magnum heads onto LA blocks, then use a carb intake (magnum bolt pattern). I think it would be a good setup for someone looking for torque on the cheap
 
RussellSullivan said:
The way I understand it, other than the electronics (fuel injection, sensors), the main difference between LA engines and Magnums were the camshaft and heads. The Magnum heads are arguably the best flowing stock small block heads, and of course they came with a camshaft that would support that.

Lots of guys swap magnum heads onto LA blocks, then use a carb intake (magnum bolt pattern). I think it would be a good setup for someone looking for torque on the cheap
Click to expand...
Don't forget roller cam shafts in the magnum
 
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