408 stroker kit - info needed

[69Tool 16]

Hello,

 

I am looking at rebuilding my stock 1969 351W. I am trying to go straight stock or put in a 408 stroker kit. I do not know much about a stroker kit, so please bear with me.

 

I love bottem end torque and take off, but I am not worried about racing this car, I simply am after a fun driver with lots of bottem end power.

 

If I choose to go with a stroker kit, will I need to replace cam, heads or anything else? Currently I have a mild cam in the car that is brand new.

 

I have a fresh rebuild on my FMX transmission, will it handle the stroker kit if I choose to go that route?

 

Is a stroker kit overkill for a weekend driver with a desire to go fast off the line?

 

Thanks for the help...

[d.reese 13]

1st off if you want to race build a race car. I say this because the weekend daily driver if modified with more horses will require more work from you and it will sit more than driven. Build one or the other, the FMX is not a horse power trans - you would want to change to a c-6. Does it have a 9" under it, if not get one. See if you beaf up in one area you will force a weak link on down the line. Thus causing you additional work , when all you sound like you really want is a good sounding daily driver that will leave the red light hard. The engine is like repairing the car, if you must go with a stroker kit- then get cam, heads ,carb, fuel pump, headers, and exhaust system. All to help it breath. If you do seat covers and not the hanging down head liner will you look at the car as unfinished? Same with the motor,oh yea forgot the distributor upgrade you'll want that one also. So the question is race or daily driver?

[coz 108]

Well stroker means bore and stroke changes so yes you are looking at new pistons, rods, cam, crank, lifters, etc... to do a true stroker.

 

There are plenty of stroker kits out there ranging from around 1k to several thousand. And like most things, you get what you pay for. If you stroke an engine most likely you will also need head work for better flow and carburation changes to allow for the increase in HP and torque.

 

Going to a 408 from a 351 I would recommend a good machine shop who can thoroughly check the block and be able to do a good bore.

 

There is a lot to doing a stroker right and it can be costly. Also, like D pointed out you should also look at the rest of the drivetrain. An FMX is not the best tranny to transfer power. 3.25 rear gears are ok but I would look at 3.55~4.10 gears to get the "full effect" of a stroker. IMO - if you aren't going to build to get 450+ HP a stroker is a waste. And if you are going to spend the money on a stroker kit and all the other goodies - think about going hydraulic roller. Again - it can get very expensive. My stroker started as a $3000 build and ended up north of $9000. But I spared no expense.

 

If I were to do it again, I would look at a Ford racing 392 stroker for the same price and with a 2yr/24k warranty. I would be giving up around 100hp with the 392 but peace of mind is nice.

 

Regardless of what you do - the old adage of planning for twice the cost and twice the time to complete is really quite true.

[69Tool 16]

Thanks, I appreciate the advice. I think I will be best suited to go for the stock rebuild with perhaps a few minor modifications for a bit of added horsepower. Cheers...

[ForceFed70 14]

The FMX will be just fine behind the 408. The FMX is plenty strong, it's downsides are lack of aftermarket performance parts availability and it's heavy. As far as strength goes, the FMX is right up there with the C6.

 

Stroking an engine has little effect on the "streetability". Compression and cam choice have much more effect on street mannors.

 

For a 408 you'll need new pistons, rods, and crank. You may also need some minor machine work done.

[Pakrat 1,043]

I know you are used to a 390 Jason but I would definitely give this engine a try without stroking for now. Much like the 302 you would be suprised how much you can wake it up with just a nice intake, carb and headers to compliment that CAM. You can always go forward later. If and when mine actually needs to get bored out finally and totally rebuilt I may consider going the extra mile and stroking to 347 while I'm at it by why bother if it can be a seat of the pants cruiser without it.

[burritoboi5 10]

I'm just going to echo the double your price budget.... My motor went from a 1000 dollar stockish slightly modified rebuild to what is now looking like about 4000-5000 reworked all roller 302 that should put out north of 325 hp (that's really conservative) Then If I decide to supercharge it'll add another 2500.....these things aren't cheap and being sure you know what you want is key. A lot easier to do things once than twice.

[69Tool 16]

I know you are used to a 390 Jason but I would definitely give this engine a try without stroking for now. Much like the 302 you would be suprised how much you can wake it up with just a nice intake, carb and headers to compliment that CAM. You can always go forward later. If and when mine actually needs to get bored out finally and totally rebuilt I may consider going the extra mile and stroking to 347 while I'm at it by why bother if it can be a seat of the pants cruiser without it.

 

LOL, pak, you know me too well...haha, at least for not having met in person yet...Anyway, this was posted on Stangnet by Ratio411, a person who seems to have a tonne of knowledge, what are your thoughts on this approach?

 

"If you are just doing a straight rebuild for the street, the most economical way to go is the 393 crank alone.

Doing it this way only adds a trivial amount to the cost of a 351 rebuild.

The crank can be had inexpensive, you then use all the stock components except substituting 302 pistons rather than going back with 351w pistons.

Then, when you take your heads apart to rebuild them, port the exhaust while they are bare. The engine you have really has excellent heads once they have been opened up a bit! With porting they outflow or match many aftermarket heads.

The 393 crank, .030" over 302 pistons, and a little grinding on the heads will have you crusing strong."

[bnickel 10,004]

LOL, pak, you know me too well...haha, at least for not having met in person yet...Anyway, this was posted on Stangnet by Ratio411, a person who seems to have a tonne of knowledge, what are your thoughts on this approach?

 

"If you are just doing a straight rebuild for the street, the most economical way to go is the 393 crank alone.

Doing it this way only adds a trivial amount to the cost of a 351 rebuild.

The crank can be had inexpensive, you then use all the stock components except substituting 302 pistons rather than going back with 351w pistons.

Then, when you take your heads apart to rebuild them, port the exhaust while they are bare. The engine you have really has excellent heads once they have been opened up a bit! With porting they outflow or match many aftermarket heads.

The 393 crank, .030" over 302 pistons, and a little grinding on the heads will have you crusing strong."

 

 

Dave (ratio411) is pretty much right one there, execpt for one thing that always concerns me, compression ratio. you need more compression with aluminum heads and less with cast iron heads, so if you put this stroker motor together with stock heads for now and then upgrade to aluminum later on, the correct compression for either version of the engine (using the same short block) will be have to be a compromise as far as compression is concerned. the general consensus used to be that aluminum heads will allow about 1 full point more compression than a comparable iron head but in actuality the consensus now says that aluminum heads can ALLOW as much as 2 full points and actually NEEDS 1 full point more compression than comparable iron heads to make the same power.

 

 

so the only way to really do this without making that much of a compromise is to use aluminum heads that have a much smaller combustion chamber than the iron heads they are replacing, which is all well and good but if your 351 is the stock 69 engine it already has the smallest combustion chambers you can even get on most aftermarket aluminum heads (60cc) though some do offer a slightly smaller chamber (58cc) but it's not enough of a difference to make up 1 full point of compression. you'd really need to go from around a 64cc chamber to around a 58cc chamber to even get close to a full point.

 

 

in any case, i'd recommend running a flat top piston for a better quench area and better flame propagation. dish pistons pretty much suck, IMO, inless they are matched to the shape of the combustion chambers in the head, then they are actually better for that quench area and flame travel.

 

you might also want to consider a long rod version of the 351 and not go with a stroker. that's what i'm going to do. you can check out www.speedomotive.com for the long rod kit or a stroker kit too, they specialize in strokers.

 

 

i would also have to disagree with the fmx not being up to the task. the fmx is actually a very stout trans and almost indestructable in normal everyday use, in fact the trans will usually outlast the car it was originally installed in. although it does have a couple weaknesses when you start putting lot's of power to the ground and the main weakness is usually only a problem ONLY if you have installed a heavy duty shift kit then they like to snap the cast iron 2nd gear band. that's an easy fix, though, by replacing the stock cast band with a steel "flex band" then no more problems. the other weakness is the lack of aftermarket support that bottlefed mentioned, however, there are stall convertors and other hi-po parts available from Art Carr, TCI and some others but are generally limited to convertors and shift kits and maybe better friction material. but probably the main reason that there isn't a lot of support is that it's really not needed because the FMX is strong enough to easily handle 400hp in stock form other than a convertor.

[69Tool 16]

Thanks for the info b. Currently my plans are to have the original cast iron heads rebuilt and just use them for the forseeable future. If that is the case, what pistons and compression would you recommend, 9.5:1 flat top piston? Thanks for the help, that is greatly appreciated.

[bnickel 10,004]

at least 9.5:1, in reality i would be be looking for 10:1 or 10.25:1 with the aluminum heads and even 10:1 with the iron heads if you have a really healthy cam. the 9.5:1 will be fine with the iron heads but IMO is a little low for the alloy heads.