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Discussion Starter #1
my 351w in my truck is stroked and bored to a 425ci. due to the longer stroke i focused on making it low end torque build to keep RPM down. i dont like how it turned out so i plan on redoing my entire build. still dont want too high of rpm range, 5k rpm max will be the engine will probably see. i currently have AFR185 heads with a Comp 35-514-8 cam. i have 33" tires and 4.10 gears and an OD automatic trans. i am currnetly planning on going up to AFR220 with a FTI custom grind cam, either 35-37" tires and 5.13 or 5.38 gears. converter has a stall of 2300-2500. sicne its an OD trans, it will cruise around 2k most of the time. also idle quality is kidna important. do you think AFR220 are too big? im using a Trickflow R-series intake with 75mm tb which i will probably go up to a 90mm when i can
 

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The low rpm torque requirement will be determined more by the camshaft than that head on a 425 cid engine.
 

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No harm in going with a high port. If you want to turn it up later
 

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Before I spent $2k on a set of heads I would talk to Ed. He maybe able to give you what you want with what you already have. The cam he specced for my 357w in my truck build makes yours looks tiny.
 

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I don't see why you would have issues making good torque with that engine. Perhaps concentrate on gearing.
 

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Discussion Starter #6
i have a feeling the current cam and probably the 75mm intake is probably my downfall. the truck makes monster torque just off idle. but past idle its a dog. honestly feels like it makes as much power as a stock 351w would. but i also would perfer to go to bigger heads. in my mind a 185 is good for a performance 351w, so by ratio of displacement, a 425 would need a 220 or bigger. i want to make this engine into something worth a dam. also there might be something wrong with these heads, i bought them used and had a shop go through them but, did leakdown test and was fine, but i feel like something is wrong.

i think i will probably go 5.13 gears. 5.38 is the max my front and rear axle supports and i think the pinion would be too small for how much strain they will be going through offroading with lockers and heavy tires and my very rough offroading. currently building a custom 8-lug D44 TTB front axle with which which i need to finish at some point, normally i would use a D50 diff but i scored a new e-locker for super cheap. rear axle is a 8-lug 10.25" Sterling which i will use a factory Ford BC3Z-4026-B e-locker which is significantly cheaper than the aftermarket lockers.

not changing the converter tho. that thing cost as much as the transmission did.
 

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keep in mind the afr 220 exhaust port is wacky shape and you need to use headers with a 3 inch on center bolt pattern. The 2 inch center header bolt holes are just begging to be ripped out since they cnc so close around those bolt holes.
 

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i have a feeling the current cam and probably the 75mm intake is probably my downfall. the truck makes monster torque just off idle. but past idle its a dog. honestly feels like it makes as much power as a stock 351w would. but i also would perfer to go to bigger heads. in my mind a 185 is good for a performance 351w, so by ratio of displacement, a 425 would need a 220 or bigger. i want to make this engine into something worth a dam. also there might be something wrong with these heads, i bought them used and had a shop go through them but, did leakdown test and was fine, but i feel like something is wrong.

i think i will probably go 5.13 gears. 5.38 is the max my front and rear axle supports and i think the pinion would be too small for how much strain they will be going through offroading with lockers and heavy tires and my very rough offroading. currently building a custom 8-lug D44 TTB front axle with which which i need to finish at some point, normally i would use a D50 diff but i scored a new e-locker for super cheap. rear axle is a 8-lug 10.25" Sterling which i will use a factory Ford BC3Z-4026-B e-locker which is significantly cheaper than the aftermarket lockers.

not changing the converter tho. that thing cost as much as the transmission did.
If you’ve got the coin, and don’t mind having to get some headers for them the highport would be your best bet. 220cc+, really even 240cc+ would still do fine. As stated above the cam choice will have most to do with power band.

I’d consider a box r or super Vic.
 

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Discussion Starter #9
hmm yes the exhaust port is an issue i oversaw. because i have a 4x4 truck and ground clearance is an issue for offroading, this may change some things. currently using BBK shorty headers with 1-5/8 tubes because i could not get Mustang headers to work. and long tubes i never had much luck with. guessing it would be too restrictive if i drilled and port matched my shorty headers to the 3" spacing. 1-1/4 x 1-5/8 vs 1-7/16 x 1-5/8. dont know if i trust myself building headers
 

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keep in mind the afr 220 exhaust port is wacky shape and you need to use headers with a 3 inch on center bolt pattern. The 2 inch center header bolt holes are just begging to be ripped out since they cnc so close around those bolt holes.
Do you know what exhaust gasket it uses?
 

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Do you know what exhaust gasket it uses?
AFR recommends the Fel-pro 1487 gasket, or you can use copper RTV. I nibbled the 1487 so it wouldn't impinge on the exhaust flow whereas the port is a little larger than the gasket. Probably makes little difference, but I did it anyway.
 

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Discussion Starter #12 (Edited)
Ed from FTI recommended the AFR205. think it would be a worthy of upgrading or should i stay with the 185? i will sell my old 185 to a friend but that still wont pay for half of new heads. they use the standard exhaust port and minimal change in height so the header issue wont be. they do seem to outflow the 185 a good bit.

i plan on ordering a new Trickflow upper to go to 90mm. is there a big differenrce between the Box R and the regular R 90mm as for flow? the regular R upper looks smoother and cleaner and cost abit less. but im sure the box R will outflow it pretty good. also worried the box R will hit hit the firewall but i cant really compare it to tell
 

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My first thought was AFR 205s, but when you said 5000 RPM max I figured you didn't need 'em. Will solve the headers issue tho. For reference, the setup in my sig makes peak torque around 5000 RPM. If it was me I'd go with the regular R (90mm) upper.
 

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I would invest money in a on3 turbo kit i think that would give you alot more bang for your $$$.also you are gonna want a long runner intake for an engine with a max of 5K rpms
 

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If Ed is going to spec your cam, I would let him pick the rest of the combo for what you need. Don't self impose the 5k rpms, as you may as well keep the 185 heads and choke the stroker to stop flowing at 5K rpms. At the end you may be a lot happier with an engine that peaks slightly higher and makes a ton more torque and hp if you do it right from the beginning.
 

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Discussion Starter #16
ya i think i will end up getting the 205s, jsut might take me awhile to save up for them when i have soo much other stuff to buy. thats why i wanted to order the custom grind cam first. lock myself into a decision instead of overthinking it for the next couple months changing my decisions every other day
 

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ya i think i will end up getting the 205s, jsut might take me awhile to save up for them when i have soo much other stuff to buy. thats why i wanted to order the custom grind cam first. lock myself into a decision instead of overthinking it for the next couple months changing my decisions every other day
Is this engine in a 2 wheel drive street truck, or a 4x4 off road truck???
 

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Discussion Starter #18
Is this engine in a 2 wheel drive street truck, or a 4x4 off road truck???
its in a 4x4 truck. mostly a fun weekend driver with the occasional offroad trips where its ran hard through trails, sand, mud. not much of a slow speed crawler, more of a budget prerunner build. i switch between this truck and another for daily driving but usually drive my work truck home during the week. like i said its going to be on 35-37" tires, depending what i do with my 3rd truck, but will be geared 5.13 with front and rear e-lockers. it has an E4OD so basically a wide ratio auto trans with OD. i have a tuner to control shift points. while the converters 2300-2500 stall isnt much, it should be able to make it have enough rpm to make power

my downfall was when i built this engine, i wanted a pure low rpm torque build. basicly have big block torque, decent fuel mileage, able to tow. then i got my F250 and i no longer needed this to tow and decided i want it to be more fun. my 3rd truck is pure offroad only but has to be trailered everywhere and only for big events. this is now more for able to drive unplanned to offroad awhile and drive back, being reliable enough to make it home
 

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ya i think i will end up getting the 205s, jsut might take me awhile to save up for them when i have soo much other stuff to buy. thats why i wanted to order the custom grind cam first. lock myself into a decision instead of overthinking it for the next couple months changing my decisions every other day
I know it gets super expensive very quick. I no longer want to add up how much money I have sinked into my stang. My suggestion is to talk to Ed, come up with a game plan and stick with it. I know a custom cam is key for a well performing engine, but I've changed my mind before even after having a custom cam grounded for my specific needs. So I know all about changing my mind all the time. Just like my build was supposed to be a rebuilt stock short block with good induction and peripherals... Once again, come up with a plan and stick to it. At the end you'll be happier. Good luck!
 

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i plan on ordering a new Trickflow upper to go to 90mm. is there a big differenrce between the Box R and the regular R 90mm as for flow? the regular R upper looks smoother and cleaner and cost abit less. but im sure the box R will outflow it pretty good. also worried the box R will hit hit the firewall but i cant really compare it to tell
Stock, the Box flowed 13 cfm more than the 90mm R on our bench. Either should work well at the rpm you will be using.
 
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