Advice/help on 302 or 351 build up?

nmcgrawj · Aug 30, 2004

Whats up guys? I have been planning a 351w build up, but i am been getting cold feet with it lately. I am trying to decide to go with a h/c/i on my motor now, 96k miles, or to build up a freshly rebuilt 351. I already have bbk 351 conversion long tube headers and some tfs twsited wedge heads. I know a guy with a FMS oil pan that will let me have it for the 351. And i also know another guy who has a distributor and such.

Now my worry is the performance. I know i know, mustangs are not meant to be fuel economic, but as a daily driver it can not be terrible. So, how much worse will the fuel economy be on a 351 compared to a 302 with a h/c/i? I talked to one guy on here, cobra351 i think is his name, and he said with his edelbrock 351 he gets about 18mpg on the highway. So im guess granny shifting in the city it will be about 14-15? And with a heavy foot 10-12 mpg?

I want the max performance of whatever i do. I would love to not touch the engine for the next couple years and be able to focus on the body/paint so thats why im leaning towards a 351 which will basically be brand new.

Im just looking for any advice that anyone might have. One point was that with my 302 and doing the h/c/i, i will still have close to stock gas mileage, spend less money and still get a good performance boost and later on after i do the body i can go back and do the 351 if i still want that. Or should i just do it now?

Sorry for being to long.....

Nik_95Cobra · Aug 30, 2004

You said you wanted max performance, so in that case a GOOD WELL DONE 351 based motor including parts can easily run upwards of $7-8K. I've done lots of reasearch on this, as I've been debating a 393 or 347. I'm not talking some budget backyard deal, I'm talking a well done one, and with that prices can be very high. The way I look at it is, I can do a 347 now, and be entertained at least for a lil while, then do a turbo or s/c down the line after I get bored with it. Good luck whichever choice you make.

nmcgrawj · Aug 30, 2004

let me clear that up....when i said max performance i meant max performance from whatever i could do with what i have for the 302 or 351.

I did not mean spending big bucks to get every last drip of power.

But yea im thinking about doing the 302 now and adding a vortech later or something. But then i could add one to the 351 too.....this is gonna be a tough decision.

cb18201 · Aug 30, 2004

do the 351, more cubes will be better for you in the long run if you do plan one day to get a vortech.

nmcgrawj · Aug 30, 2004

anyone have any ideas on the gas mileage issue? Im 19(will be 20 when the motor is done) so i do a lot of driving so i dont want that to be another BIG cost from the swap.

GTPhreak · Aug 30, 2004

with a 351w...even with the same top end stuff...even if you make the same horsepower as a 302, you WILL be making more torque which will make the car that much funner. In my plans I have a 94 351w roller block and crank, some 92 rods, and some speedpro forged pistons for a good deal...then I will probably just get trick flow/summit racing to put together one of their top end kits

also the 351w block is stronger than the 302 block so you can throw more at it

nmcgrawj · Aug 30, 2004

yea thats true, the tfs tw heads have the fox lake stage 1 port job sothey should flow close to afr 185's so it should make plenty of power.

I just need someone to give me a reason to get the fuel economy debate out of my head. Besides just dealing with it....lol

Nik_95Cobra · Aug 30, 2004

You'll need bigger injectors for the 351. More fuel = worse economy. I agree with you, big decision. Wish it were an easier one!

mustangman33 · Aug 30, 2004

A 351w is a big gas guziler, seems like I get 100 mpg per full tank, but Im carbed, are you going carbed or fi, I think fi would make a difference but not a big one.

nmcgrawj · Aug 30, 2004

I will be FI. Hmmm thats what im scared of. Guess im leanin towards a 302 h/c/i for now.

I just want to beat LS1's and this kid with a gtp that runs "12's". Speaking of that, anyone know a lot about those pre-04 grand prix gtps and what it takes to get them running 12's?

Thanks again guys

T_5.0_N'works · Aug 30, 2004

I know how to swap a 351w in a fox, is it much different to swap it in a sn95? Will my 7q quart Canton oil pan swap over to a sn95 chassis?

nmcgrawj · Aug 30, 2004

How is it that LS1's with a 350 can make so much power and still get the good gas mileage?

Does theirs drop like the 351's do once they do a cam or something?

Its just not fair

Grn92LX · Aug 30, 2004

Just a 351 or stroekd to 393, 408, 418, 427, 436 etc? If just a 351, dont waste your time. It will get expensive to do the 351 based motor. You'll need a new hood + paint which is like $700 or so done right and a HUGE waste of money for an unnecessary item. I'd build up the 302 or rebuild it to a 347.

Grn92LX · Aug 30, 2004

nmcgrawj said:
How is it that LS1's with a 350 can make so much power and still get the good gas mileage?

Does theirs drop like the 351's do once they do a cam or something?

Its just not fair

346 you mean Its different technoligy than our 302 engines. I have heard their intake manifolds are equivelant to a victor for our cars and those ls1 heads flow great. hence, their really good top end and how they do good from rolling races. Their down fall is the weight.

T_5.0_N'works · Aug 30, 2004

nmcgrawj said:
How is it that LS1's with a 350 can make so much power and still get the good gas mileage?

Does theirs drop like the 351's do once they do a cam or something?

Its just not fair

Because they have good heads from the factory AND they have a 6 speed. This means they have a good amount of torque for a 346ci LS1 to push 2 (5th and 6th) OD gears at like 1k RPM, that's how they get HIGH MPG's.

351 Isn't a waste, lots of people get a new hood anyways.

nmcgrawj · Aug 30, 2004

T_5.0_N'works said:
351 Isn't a waste, lots of people get a new hood anyways.

Yea i already have a hood.

So if i got a 6-speed(not like i can really afford it) i will be able to get good mpg out of the 351?

Lookin like the 302 h/c/i fellas

Grn92LX · Aug 30, 2004

nmcgrawj said:
Yea i already have a hood.

So if i got a 6-speed(not like i can really afford it) i will be able to get good mpg out of the 351?

Lookin like the 302 h/c/i fellas

No, a couple hundred rpm lower cruising rpm wont do chit for you. More power = more gas, but with efi, you'll still get decent mileage. Its the carbs that drink up the gas.

nmcgrawj · Aug 30, 2004

Grn92LX said:
No, a couple hundred rpm lower cruising rpm wont do chit for you. More power = more gas, but with efi, you'll still get decent mileage. Its the carbs that drink up the gas.

So are you sayin to go for the 351? Or will it still be a big noticeable difference in gas mileage?

Grn92LX · Aug 30, 2004

No, I say keep it 302 or stroke the 302 to 347 and build a killer combo. Dont worry about gas mileage man

Black95GTS · Aug 30, 2004

Worry about the gas mileage. I just turned 21 so I'm real close to you. Let me just say two things happen when you turn 21: You go to the bar a lot and you spend a lot of money. If I got 100 miles per tank I'd probably kill myself. Just wait on it if this is your daily driver and do the H/C/I. There are guys with h/c/i 302s running mid-low 12s with 20mpg highway ratings and 300 rwhp. Not bad at all and you will beat on stock LS1s.

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