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We have just finished bolting together the 521 for my 67 Mustang. The Mustang still has stock schock towers so headers are a bit of an issue. We decided to compare my FPA swap headers to a set of proper 2" tube fox body swap headers we had lying around

Small FPA headers (1-7/8 tubes into 2-1/2" collectors) made only 23 HP less than the fox body swap headers. I was amazed and also very happy. If it was 50 or 75 HP difference I would have had to buy new headers and chop the schock towers.

Engine made 708 HP with the small headers and 731 with the big ones. We didn't go past 6500 RPM as this is a simple bracket racing engine.
 

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Discussion Starter #4
specs

Scat rotating assembly, Kasse pump, flat top pistons (13 to 1). Comp Cam solid roller from Kasse (0.740 lift , 304 duration, 109 LSA). P-51's, 4150 Victor and Pro Systems 950 DP, MSD dizzy. Everything out of the box, no porting, gasket matching. Just bolt together.

Carb is probably way too small but my goal is mid to low tens (no NHRA license).

Wallace calculator says this combo will do it even with the crappy headers and small carb.
 

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Should easily do it...my 67 fastback ran 10.0s 501 edelbrock head out of the box..11.9:1 ..flat tappet..3.89 gear..c6..I used the cries headers 2 inch primary...worked great for 11 years
 

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Should easily do it...my 67 fastback ran 10.0s 501 edelbrock head out of the box..11.9:1 ..flat tappet..3.89 gear..c6..I used the cries headers 2 inch primary...worked great for 11 years
Thanks. Looking forward to getting back to the track after a two year break. Although I have aftermarket axles, I'm a bit concerned that I may have to upgrade the 9". It has a Detroit tru track and I'm worried it may not hold up.


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Scat rotating assembly, Kasse pump, flat top pistons (13 to 1). Comp Cam solid roller from Kasse (0.740 lift , 304 duration, 109 LSA). P-51's, 4150 Victor and Pro Systems 950 DP, MSD dizzy. Everything out of the box, no porting, gasket matching. Just bolt together.

Carb is probably way too small but my goal is mid to low tens (no NHRA license).

Wallace calculator says this combo will do it even with the crappy headers and small carb.
Is your Scat forged or cast, and did you go internal or external ballance. YOur build sounds darn close to what I am doing, except compression for me will be around the 10.8 area.
 

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hey 460 fastback nice build! did your cast crank take a lot of slugs to balance it! should run 9.90,s all day long if the car is setup right!
 

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We have just finished bolting together the 521 for my 67 Mustang. The Mustang still has stock schock towers so headers are a bit of an issue. We decided to compare my FPA swap headers to a set of proper 2" tube fox body swap headers we had lying around

Small FPA headers (1-7/8 tubes into 2-1/2" collectors) made only 23 HP less than the fox body swap headers. I was amazed and also very happy. If it was 50 or 75 HP difference I would have had to buy new headers and chop the schock towers.

Engine made 708 HP with the small headers and 731 with the big ones. We didn't go past 6500 RPM as this is a simple bracket racing engine.

Nice to know. Nice build and great numbers.

At the 600 HP level the headers actually make more torque and lose about 4 HP.

FPA headers have 1 3/4" primary tubes. Mine do and I am not aware of Stan offering them in larger diameters...

Thank you for sharing.




S
 

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Scat rotating assembly, Kasse pump, flat top pistons (13 to 1). Comp Cam solid roller from Kasse (0.740 lift , 304 duration, 109 LSA). P-51's, 4150 Victor and Pro Systems 950 DP, MSD dizzy. Everything out of the box, no porting, gasket matching. Just bolt together.

Carb is probably way too small but my goal is mid to low tens (no NHRA license).

Wallace calculator says this combo will do it even with the crappy headers and small carb.
I have the same rotating assembly with SCJs sitting in my garage waiting to go in my Fairlane. Now I can't wait to get it together!

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Discussion Starter #13
Scott, I'm sure you are correct. 1-3/4" sounds right. I just found it interesting that some of the recommendations called for 2-1/8" stepped headers into 4" collectors. While I'm sure that would make more power, it doesn't mean you can't get there with smaller headers if there isn't a way to fit the bigger ones in.

I guess what I found really interesting is some components (heads, cam etc) had way more effect than others. ( carb, headers )

Just a newbie trying to figure out how to run low tens without chopping schock towers or using NOS.


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Scott, I'm sure you are correct. 1-3/4" sounds right. I just found it interesting that some of the recommendations called for 2-1/8" stepped headers into 4" collectors. While I'm sure that would make more power, it doesn't mean you can't get there with smaller headers if there isn't a way to fit the bigger ones in.

I guess what I found really interesting is some components (heads, cam etc) had way more effect than others. ( carb, headers )

Just a newbie trying to figure out how to run low tens without chopping schock towers or using NOS.


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While a larger (than 2") primary likely would have made better peak HP it may have cost you some average. Those HP numbers at a 6400 rpm peak are great. You should see your et goals...

I think this is a really great example of just how good those "tiny" FPA headers really are. Thank you again for sharing your test data. What I like here is the comparison between actual headers for a vehicle vs dyno headers which are typically optimal for HP.

Stan is only a few miles away from me. I think I will start bending his ear about offering them in 1 7/8" primarys.



S



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Robert Snowballs 69 mustang fast back has a 521 with A429 heads has been 5.80's in the 1/8th with all stock shock towers and front end parts and it has 9x30x15 slicks so you can do it too!
 

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This is GREAT stuff.
This build is very similar to what I have laid out with some maybe signifcant difference.

Im building the 521, using Vic Sr intake with dominator carb.
P51s, Kaase is designing the cam now, Comp cam in with a solid roller in the 742/715 - 255/246 110 LSA. Im probably just going with all Kaase on the top as they know what works and what dont.

Its a forged Lunati crank and kit Im getting from LEM.

Headers are 2 " MPG long tubes into 3.5 collectors.

Running a DR4 with 2:79 1st, narrowed 9 in 4:56 spool, QTP 29X11s.

Car is a shaved tower 67 coup, 8 pt roll bar, not much of a diet so the weight maybe a bit high, and CALTRACS springs and bars with Ranchos. Front suspension is stock except for Moroso trick springs and Comp Eng adj shocks set to 90/10.

On the engine, though I am running pump gas freindly 10:5:1s, vice the 13:s on the slugs.

About how much will this cost me in HP on the compression?
 
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