Looking for 400hp from 351w

66stang351w · Aug 11, 2011

I was just wondering if you guys could help me figure out if what I have got planned will get me to the 400 hp range from a 351w and maybe somewhat decent gas milage. And if not what would get me there.

Here goes:

1974 351w block
stock crank and pistons
afr 185 heads
performer rpm intake (maybe air gap)
Holley 4 barrel 750 cfm
custom cold air intake from spectre performance
Super comp long tube swap headers
3" exhaust
toploader 4spd
and I have no idea what gears I have in the back

Oh and any recomendations for what type of cam I should use are welcome (ie. hydraulic, hydraulic roller)

All this will be going into a 66 coupe

Thanks for any info

67GTCOUPE · Aug 12, 2011

Getting 400hp out of a 351w is as easy as falling outta bed!

Edelbrock makes a cam for their intake and it made 410hp in a 351w.

Cheap and easy.

69gmachine · Aug 12, 2011

The one thing in your list that would likely prevent you from reaching your goal are the low compression stock pistons. Get a set of flat top Hypereutectic pistons and if the bores in the block still have a decent cross hatch, you won't even have to over bore it to install them. Otherwise you will need to machine the block out to .030 as is most common.

I would also recommend having the rotating assembly balanced whenever you change pistons. Make sure you have a good harmonic balancer and flywheel also. They will need them to balance the rotating assembly. If they say they don't need them, find another shop.

As far as the cam goes, get a Hyd roller. They will give you a deecnt idle on a much larger cam than you could ever get away with in a flat tappet,plus you don't have to worry about cam break in or matching lifters to their bore in future tear downs. I'd look at something in the 280/290 duration range and .570/.590 lift (i/e).

With 10:1 compression and the list of parts you've provided, you can run on 91 octane pump gas all day and will have no problem making over 400 HP.

67GTCOUPE · Aug 12, 2011

If you are going to buy new pistons...which, would be a good idea....GET FORGED, don NOT even consider hyperucraptic....for the extra $100...forged are well worth it.

One thought...you can buy a stroker kit from places like CHP or Propower or Keith Craft for under $1000 and that gets you over 500hp with the right cam and your heads.

I do not know your budget.

If you need to do it as cheap as possible.....just pick up an edelbrock cam kit (performer RPM).

If you got some $$$$$ do a stroker kit with a custom roller cam....I love mine.

If that is too rich....you could get forged pistons and fit the rods with ARP bolts...then get them resized...BUT that alone will bring you close to the price of a stroker kit with all brand new parts.

EDIT: PS: you need a retrofit cam as this is not a roller cam block....if you want a roller cam.

65coupe408w · Aug 12, 2011

If you have any specific questions about the swap feel free to PM me. See signature...

66stang351w · Aug 12, 2011

66stang351w · Aug 12, 2011

Ok so I should get forged pistons and a retrofit roller cam.
I would go with a stroker if I could get decent gas milage.
(is 18-20 hwy feasible)

If not can I get that with a non stroked 351w
I am only asking because I have to use it as a daily driver otherwise I would definatley go with the stroker seeing as i already have the pistons to do a
393w.

Hey 65coupe408w what kind of milage are you getting with that 408w

rbohm · Aug 12, 2011

if you are going to keep the stock stroke, and you want to use the .030 302 pistons i gave you, then you need to find a set of rods that are 6.15" long. that will give you a flat top piston rather than the dished 351w pistons i gave you. or you can get a set of 6" chevy rods, turn the rod journals down to 2.1" to fit the chevy rods, and offset grind the crank to increase the stroke to 3.8", which will give you 387ci engine when you are done with that. add to that a 270 comp cams magnum flat tappet cam with the rest of your combination, and even with the performer intake and 600cfm carb i gave you, you should hit the 400+ mark easily.

67GTCOUPE · Aug 12, 2011

Here are the facts as I know them:

1) Hp=gas, so more HP requires more gas.

2) 351w are notorious for poor gas milage.

3) IF you are really concerned about milage and gas usage....302 based motor would be the way to go....you can get 400 hp out of a 306 no problem...and it will get quite a bit more milage.

Honestly: you could do a very mild Stroker and most likely get better milage than a moderate 351w build.

How much $$$$ do you have in the budget? If possible: work from square one with a custom cam guy......tell them EXACTLY what you want and then they can help you put that engine together.

As much as I do not like the guy's personality...Ed Curtis is apparently pretty damn good at it. Buddy Rawls is another guy who posts on corral.net who knows his stuff.....he would be better if you are staying flat tappet cam.

PS: If you think you are going to drive a 4-500 hp stang like a granny....you are lying to yourself....I drive my car like I fricken stole it!

67GTCOUPE · Aug 12, 2011

rbohm said:
if you are going to keep the stock stroke, and you want to use the .030 302 pistons i gave you, then you need to find a set of rods that are 6.15" long. that will give you a flat top piston rather than the dished 351w pistons i gave you. or you can get a set of 6" chevy rods, turn the rod journals down to 2.1" to fit the chevy rods, and offset grind the crank to increase the stroke to 3.8", which will give you 387ci engine when you are done with that. add to that a 270 comp cams magnum flat tappet cam with the rest of your combination, and even with the performer intake and 600cfm carb i gave you, you should hit the 400+ mark easily.

Or buy a 393 crank (3.85" stroke) and use the stock 5.95" 351w rods with those 302 pistons....JUST watch out the CR gets high quickly with flattops. The noduar iron 3.85" crank is under $300 and will do up to 750hp.....This is probably the cheapest way to get a great engine. Speed-O-Motive and CHP sell these cranks.

rbohm · Aug 12, 2011

67GTCOUPE said:
Or buy a 393 crank (3.85" stroke) and use the stock 5.95" 351w rods with those 302 pistons....JUST watch out the CR gets high quickly with flattops. The noduar iron 3.85" crank is under $300 and will do up to 750hp.....This is probably the cheapest way to get a great engine. Speed-O-Motive and CHP sell these cranks.

that is the other alternative i suggested to him when he picked up the stuff i sold him.

67GTCOUPE · Aug 12, 2011

rbohm said:
that is the other alternative i suggested to him when he picked up the stuff i sold him.

Certainly worth a look.....depending on the chamber size of his AFR's. Custom can guy can bleed off excessive compression as well.

66stang351w · Aug 12, 2011

I guess I was being a little optimistic with those numbers that I put out.
but for me any improvment over the 10 mpg hwy I am getting with my 302. not to mention the poor power its got (I am being beaten by tuners "aka stock jetta's" and trucks).
Mostly what I want is to have better power and to have better gas milage than what I have now (is 15-17 hwy mpg more realistic)

Yeah your right 67GTCOUPE, I wont drive it like a grandma and I will drive it like a mad man, but I would like to at least know that if I wanted to slow down I would be able to get "okay" gas milage.

67GTCOUPE · Aug 12, 2011

66stang351w said:
I guess I was being a little optimistic with those numbers that I put out.
but for me any improvment over the 10 mpg hwy I am getting with my 302. not to mention the poor power its got (I am being beaten by tuners "aka stock jetta's" and trucks).
Mostly what I want is to have better power and to have better gas milage than what I have now (is 15-17 hwy mpg more realistic)

Yeah your right 67GTCOUPE, I wont drive it like a grandma and I will drive it like a mad man, but I would like to at least know that if I wanted to slow down I would be able to get "okay" gas milage.

What I would encourage is a stroker.

Since you have 302 pistons in hand...... bore the 351 block to 0.030" over use those pistons (I assume they are forged...if not...sell them and get a complete 408w kit)...if they are forged.....buy a 393 nodular iron crank from CHP or Speed-O-Motive for instance, get ARP rod bolts installed in your 74 351w rods...need them resized as well....MAKE SURE YOUR MACHINE SHOP gives you large bearing clearances!!!!!! 351w have large bearing surface...run the clearances on the BIG side...at least one thou per inch of journal! I ruined a brand new 351w due to this fact.

Get the whole assembly balanced as well. I run the Mellings high volume RACE oil pump and a 7 quart milodon oil pan as well....I DO NOT want any oil starvation issues.

As far as a cam.....AFR website has a bunch of test engine articles on their site...I know they had a 393/403 with 185's....I would look at that to see what hp they got and what cam they ran...I think it was a comp XR series???

65ShelbyClone · Aug 12, 2011

There is something seriously wrong if your 302 is only getting 10mpg on the highway, especially if it's gutless. Carbureted smallblocks aren't fabulous on economy, but you should be getting at least 16mpg if the engine is mild....more with a very good tune on the carb and ignition.

Personally, I would get the fuel and spark on your current engine sorted out first. See how you like it, drive it for a while, and then think about more displacement. You might decide the 302 can offer what you want. I doubt mine makes more than ~330bhp and it's no slouch. Gets a lot better than 10mpg, too.

65coupe408w · Aug 12, 2011

66stang351w said:
Ok so I should get forged pistons and a retrofit roller cam.
I would go with a stroker if I could get decent gas milage.
(is 18-20 hwy feasible)

If not can I get that with a non stroked 351w
I am only asking because I have to use it as a daily driver otherwise I would definatley go with the stroker.

Im running a T5 but I see about 18mpg on the freeway....

66stang351w · Aug 12, 2011

Ok I am slowly moving towards doing the 393 stroker but I am going to need a little more convincing. Would somthing like this get me closer to my milage goals or is it worth it.

65ShelbyClone · Aug 12, 2011

For that kind of money, I would be looking into a Tremec 5-speed conversion. You could possibly even use a cheaper T5 if you went with a 302-based build and kept street tires on the car.

66stang351w · Aug 12, 2011

65shelbyclone, I have looked into the t5 and IMO it isn't right for me. The reason is that at some point I plan on building more power into the engine. Another is that I already got the toploader, shifter, flywheel, 351 block, 2 sets of pistons new, crankshaft, and oil pan all for $400 . So I figured that with the money I saved there I could do something that I wouldn't have normally been able to do. Now whether its the over drive or something else I don't know but I am going to stick with the toploader and the 351.

67GTCOUPE · Aug 12, 2011

66stang351w said:
65shelbyclone, I have looked into the t5 and IMO it isn't right for me. The reason is that at some point I plan on building more power into the engine. Another is that I already got the toploader, shifter, flywheel, 351 block, 2 sets of pistons new, crankshaft, and oil pan all for $400 . So I figured that with the money I saved there I could do something that I wouldn't have normally been able to do. Now whether its the over drive or something else I don't know but I am going to stick with the toploader and the 351.

I have a toploader and 393w in a 67....BLAST TO DRIVE!!!!!!!!!!!!!!!!!!!!!

If you have the cash to put in the overdrive....AWESOME!!!! Thant will get you waaaay better milage...and the 393 has more than enough torque to move your ass out at any rpm!

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