351w SN95 convertible swap - Ford Mustang Forum
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post #1 of 42 (permalink) Old 01-16-2020 Thread Starter
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351w SN95 convertible swap

Hello:

New to this site. Looking at whether to stick with the 302 or switch to a 351w. (1995 GT convert.)
Already have a roller 351 but read somewhere that the swap to a convertible is more complicated
and creates some extra issues compared to a coupe. Can anyone with experience comment on this?
Thx, Fred

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post #2 of 42 (permalink) Old 01-17-2020
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Originally Posted by Fredsn95 View Post
Hello:

New to this site. Looking at whether to stick with the 302 or switch to a 351w. (1995 GT convert.)
Already have a roller 351 but read somewhere that the swap to a convertible is more complicated
and creates some extra issues compared to a coupe. Can anyone with experience comment on this?
Thx, Fred
Freddy,
Can you elaborate why they say it’s more complicated? I have a ‘95 coupe and my dad had a ‘97 convertible, and the engine bay looked to be the same from the naked eye.
Are you trying to “go fast?” Stock for stock the 302 might be faster than the heavier 351. I think the biggest pro for the 351 is that the block can handle more power and that you have the ability to bore it out to more cubes than the 302. With a good top end the 351 might win, but if a guy with a 302 with gt40 heads raced a guy with a 351 with gt40 heads it’d probably be a close race.
I’d price the difference between parts required to use a 351 like headers, etc, and the cost of rebuilding the 351 vs rebuilding a 302. I’m using mostly stock ‘95 mustang parts and 8 psi and it makes 332 at the wheels. Decent bang for buck.

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post #3 of 42 (permalink) Old 01-17-2020
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Not 100% familiar with the SN95 platform as I have only had 1. It was a 1996 convertible actually. I was unaware the convertible was any different under the hood than the coupe on any of the years though. I mean I wouldn't be totally surprised as I know the convertibles are heavier due to extra support built in, but I guess I just figured it was all built in behind the engine bay. Can you provide some of your findings for us so we can better help you?

Thanks and welcome to the site!

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post #4 of 42 (permalink) Old 01-17-2020 Thread Starter
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fredsn95

Thanks for the responses.
Have only had the car for about 8 months. It was dynoed a few years back at 365 rwhp. My goal is to up that
to about 425-450 at the wheels and make best use of what I already have while keeping the budget under control.
From what I understand the 302 block is limited to about 450 to 500 hp. Options are to go to either a 351 block or go
aftermarket block. Seems that the aftermarket option is considerably more expensive. Already have the 351.
Still haven't decided though.

Unfortunately the only things I recall reading about re the differences between coupe and convert 351 swap was that
the person said they wouldn't do it again on a convertible but would have no problem doing it on a coupe. One issue
was something to do with the steering shaft.
Sorry to be so vague. Was hoping someone had done the swap into a convert and could let me know what issues
(if any) they had run into. Hopefully I am way off base here and its the same as a coupe swap.

90lxwhite I hear what you are saying. The smartest and cheapest thing would be to just stick with what I have.
The T5 is reaching its power limits but I don't race it or power shift it so hoping for the best.
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post #5 of 42 (permalink) Old 01-17-2020
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What all do you have done to your car currently? That is a big RWHP number it can't be stock. As mentioned in a post above that is more than somebody with 8psi has. ha

Hopefully somebody with physical hard data can chime in on the swap. I am sure somebody on here has done it as we have people who have gone from v6 to v8 and people that have swapped 5.0's into older cars.

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post #6 of 42 (permalink) Old 01-17-2020
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The 302 that is in the car now is up and running and made 365 and the target goal is 450? What sort of method are you thinking about going with to obtain that goal? A more radical top end? Forced induction? I don’t have an answers for ya just questions, sorry. I guess the easiest way to make big power with the 351 would be to use your 302’s top end and a turbo.
The 302 might even live long and prosper with 450 hp if the rpm’s weren’t sky high. Add some boost to what you have now and keep it at like 6k rpm or so.
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post #7 of 42 (permalink) Old 01-17-2020
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Quote:
Originally Posted by MustangLife View Post
What all do you have done to your car currently? That is a big RWHP number it can't be stock. As mentioned in a post above that is more than somebody with 8psi has. ha

Hopefully somebody with physical hard data can chime in on the swap. I am sure somebody on here has done it as we have people who have gone from v6 to v8 and people that have swapped 5.0's into older cars.
The 8 psi guy has jinky heads.
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post #8 of 42 (permalink) Old 01-17-2020 Thread Starter
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Re Mustang life
Thanks for the response. Presently has a 2.2L KB S/Charger. Don't have a boost gage hooked up right now but
based on the pulley ratio should be at about 10 psi.(2 3/8 and 4 3/4").
I have the dyno sheet from several years ago and I don't think the numbers are out of line.
Has ported gt40x heads(which I plan to reuse), headers etc but a stock shortblock with leaky crank seals.
Motor needs to come out anyhow so deciding what my best option would be to up the power a bit
If I can figure a way to use the KB on a fairly mild 351w that might be the way to go.
Otherwise maybe a stroker 351 or an aftermarket block 302 with KB?

There is a lot of info out there on doing the swap to a coupe but was wondering about to a
convertible? If it requires mods that might be over my head then 302 block it is.
Comes down to cost vs gain and the amount of work. Don't think the stock 302 block will be up to it though?
Peace of mind and reliability are also important.
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post #9 of 42 (permalink) Old 01-17-2020 Thread Starter
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Sorry I guess I should have included more info from the start. My bad. I had only put it in my profile.
450 might be a bit too optimistic but I expect 425 rw should be doable?
My main interest is whether or not the 351w swap to a convert is the same as or similar to
a coupe and am hoping someone on here has done this exact conversion. Anybody?
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I had read a thread today that stated the 86-95 KB SC kits had been discontinued and the thread was from several years ago & a quick glance at KB's site didnt list any kits for these model years.Do you know if this is true?? When the mod motors hit,they pretty much left the Foxbody & Early SN95 owners out in the pasture.A big issue with this would be the lack of availability of parts if an issue arises with the compressor unit.The KB was a fun rush of power though in the midrange & down low,if you can get the power to stick to the pavement.I miss mine.

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post #11 of 42 (permalink) Old 01-17-2020 Thread Starter
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Wbrockstar

I believe you are correct about the 5.0 KB. No longer available. Not sure about parts though?
Mine has about 15 to 20k miles on it over a period of about 13 years. Supposedly they are good for
a long time if maintained correctly but your point is a good one. Don't know the reason why they quit
producing them back then with so many 5.0 engines still around. Hmmm?

I agree that they are a lot of fun with the instantaneous power. Only going up to about 5300 or so rpm max.
Probably says more about my stock cam although it has the longer rockers
More power equals more fun, right?
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post #12 of 42 (permalink) Old 4 Weeks Ago
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Quote:
Originally Posted by Fredsn95 View Post
Wbrockstar

I believe you are correct about the 5.0 KB. No longer available. Not sure about parts though?
Mine has about 15 to 20k miles on it over a period of about 13 years. Supposedly they are good for
a long time if maintained correctly but your point is a good one. Don't know the reason why they quit
producing them back then with so many 5.0 engines still around. Hmmm?

I agree that they are a lot of fun with the instantaneous power. Only going up to about 5300 or so rpm max.
Probably says more about my stock cam although it has the longer rockers
More power equals more fun, right?
With ported gt40’s and 10 psi it seems like you’d be at or over 400 wheel horse already, my e7’s and 6-8 psi kit made 330.
At any rate, if you were to reuse the gt40’s and KB on the 351 it’ll probably make close to the same amount of power as your 302. If you’re not going to add more power then it probably be cheaper to just rebuild the 302 because you won’t have to buy the “351 swap parts.”
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post #13 of 42 (permalink) Old 4 Weeks Ago
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The 351 weighs right at 80 pounds more than the 302..... all in the block area....specific to the larger rotating masses (crank, flywheel)...but the 351w is still classified as a small block- FYI.....IIRR, the 400 was also classified as a small block as well.

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post #14 of 42 (permalink) Old 4 Weeks Ago Thread Starter
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With ported gt40s and 10 psi it seems like youd be at or over 400 wheel horse already, my e7s and 6-8 psi kit made 330.
At any rate, if you were to reuse the gt40s and KB on the 351 itll probably make close to the same amount of power as your 302. If youre not going to add more power then it probably be cheaper to just rebuild the 302 because you wont have to buy the 351 swap parts.
Thanks for the replies. I only have the dyno info from 2007 to determine where things are at now. As far as I can determine from all of the old parts receipts, the setup is essentially the same now as when it was when dynoed in '07. The same owner had the car since 1998. There are a couple areas where simple improvements could potentially be made. One would be increasing the throttle body from 65mm maybe up to 70mm
or 75mm. Another one would be to get a better air source outside the engine compartment and the other (big one) would be to get it professionally tuned. The PO told me it has never had a proper tune. I think he just went by the KB instructions/advice when installing everything back in the day although he is a smart guy.

Problem is that if I am able to get the power up to my goal of at least 425rwhp then I am really pushing the limits of the 302 block and don't think
that is a particularly good way to go.

@ Beechkid:
Didn't know that the weight difference was that high between the 2 shortblocks (351 vs 302). I thought it was closer to about 50 lbs?
The Dart 302 blocks are even heavier than the 351w blocks from what I read. Haven't found any definitive info on the subject yet though.
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post #15 of 42 (permalink) Old 4 Weeks Ago
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Quote:
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Quote:
Originally Posted by 90lxwhite View Post
With ported gt40’s and 10 psi it seems like you’d be at or over 400 wheel horse already, my e7’s and 6-8 psi kit made 330.
At any rate, if you were to reuse the gt40’s and KB on the 351 it’ll probably make close to the same amount of power as your 302. If you’re not going to add more power then it probably be cheaper to just rebuild the 302 because you won’t have to buy the “351 swap parts.”
Thanks for the replies. I only have the dyno info from 2007 to determine where things are at now. As far as I can determine from all of the old parts receipts, the setup is essentially the same now as when it was when dynoed in '07. The same owner had the car since 1998. There are a couple areas where simple improvements could potentially be made. One would be increasing the throttle body from 65mm maybe up to 70mm
or 75mm. Another one would be to get a better air source outside the engine compartment and the other (big one) would be to get it professionally tuned. The PO told me it has never had a proper tune. I think he just went by the KB instructions/advice when installing everything back in the day although he is a smart guy.

Problem is that if I am able to get the power up to my goal of at least 425rwhp then I am really pushing the limits of the 302 block and don't think
that is a particularly good way to go.

@ Beechkid:
Didn't know that the weight difference was that high between the 2 shortblocks (351 vs 302). I thought it was closer to about 50 lbs?
The Dart 302 blocks are even heavier than the 351w blocks from what I read. Haven't found any definitive info on the subject yet though.
When I got my ‘95 tuned after the blower there was a 90 some odd horsepower difference between the baseline and the final pull. I’m using an fmu that was provided with the kit and I guess it didn’t do well enough on it’s own to “feed it.” That was my situation anyway. Ideally I’d like to get large enough injectors to not need the FMU, but big injectors and a re-tune is kind of spendy.

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