Ford Racing Boss 302 Engine

[John J Phillips]

I am looking to purchase the Boss 302 engine and install along with the T5z transmission in my MkIV. This will strictly be a street car, no track. Any comments on installation issues I should be on the alert for, i.e. oil pan size, etc? Any thoughts on intake manifold - carburetor, etc? Thanks for the feedback, the forum is an incredible resource.

[bil1024]

I have heard of no issues, maybe contact Fortes or Gordon to get their take

[edwardb]

Maybe would help to post the exact part number of the engine you're looking at. Just a quick Google search and there are several versions of the Boss 302 from Ford Racing. From bare block to pretty fully dressed. At the very least, looks like you will need a different oil pan. Max depth of 7-1/2 inches to keep from going below the frame rails. IMO, for street use you're not going to see much difference in performance between the Boss 302 and the regular stock block X306 Ford Racing crate that a lot of guys use. At about half the price. But I'm not one to talk since I chose DART for my last build.

[David Hodgkins]

Hi John, welcome to the forum. I'm doing a BOSS 302 MKIV build right now. Here's my build thread:15th-Anniversary-MKIV-build-thread (http://thefactoryfiveforum.com/showthread.php?13397-15th-Anniversary-MKIV-build-thread)

This is my 2nd BOSS 302 build. Both are primarily street cars. Both are multi-port fuel injected, and the exhaust is quieter than most by using catalytic converters and Gas'n pipes. I use the cats for their sound and the clean exhaust and lack of gas fumes is just an unfortunate side effect. ;)

The current build motor was dyno'd at 374HP at the flywheel. Here's the dyno:

https://www.youtube.com/watch?v=6i-XYmgjmx8

And here's a shot of how it sits in the bay. I still need to order some spark plug retainers and an air cleaner. Pardon the dirt, she got rained-on last weekend:
http://thefactoryfiveforum.com/attachment.php?attachmentid=41453&d=1430237457

Are you set on using a carb?

Anyway, take a look at my thread and you will see all of the components of my build. If you have any questions, feel free to ask them in my thread or here.

:)

[mike forte]

Hi John,
If you're interested in a Ford Racing BOSS 302 I sell them complete as a turnkey engine & transmission kit. Jesse fully assembles every engine to run on our in-house Land & Sea engine dyno. David Hodgkins has the You Tube video of his Ford Racing Boss 302 running. The Holley EFI we installed boosted the HP by about 30. Jesse has a preference toward the Holley as it is most adaptable for any engine options.

[John J Phillips]

Thanks David. We met at the SEMA show and you encouraged me to use the Forum. Great advice. Thanks for the 302 suggestions.

[SVOCOBRA]

I'm running what Ford suggests, an Edelbrock RPM air gap & Holley 80570 as follows: 58 primary jets, 66 secondary, purple spring, 6.5 power valve, 1/2" 4 hole spacer, K&N stub stack, oval Ford air cleaner w/ Branda tall gauze filter. I had to crack the secondaries open 1/2 turn to keep the primaries closed enough during idle.

[Avalanche325]

Holley 80570

That is a vacuum secondary carb. That might be a good idea for a Mustang, but not for a 2150lbs Cobra. You may want to consider a manual secondary carb. It is pretty much a "well known" fact around here to stay away from vacuum secondary's. They don't tend to work well with a light weight car.

Here is what I do when I call a big vendors tech line. Call two or three times and see if you get the same answer. Or even better, ask the "big guys" here, Like Mike and Gordon.

[Garry Bopp]

Avalanche325,

I had a Holley 770 Street Avenger, vacuum secondary carb on my Daytona Coupe. Worked great right out of the box. Sold the coupe with nearly 18,000 miles on it and running strong.

Garry

[68GT500MAN]

I currently have the same carb as Garry on my roadster, it runs great and runs strong.
Doug

[SVOCOBRA]

What problem are people having w/ a vac sec carb? I've built & tuned many for myself & others and they ALL ran great when I was done w/ them.

[SVOCOBRA]

I agree, my motor is actually the 308cu in, 345hp rated from 2006+/-.

[edwardb]

Lots of discussions on this and the other forum about vacuum vs. mechanical secondary carbs. The key to any carb installation is the setup. Rarely are they exactly right out of the box. But many, myself included, were never able to get a vacuum secondary carb to run well in one of these. Bottom line is this: Light car, high power, normally manual transmission. All not the best for a vacuum secondary carb. I personally struggled to get a good vacuum signal to properly bring in the secondaries. That was with a Holley 570 Street Avenger in a 306 powered Roadster. Tried every spring available, multiple different settings, etc. and it just never worked very well. Went to a Quick Fuel SS-650 double pumper and the car lit up. You will hear this same story from many people. But you will also find some that make the vacuum secondary work OK.

[CraigS]

I agree on mech secondary carbs. I spent a few years working on a Demon vac secondary carb and the car ran great. Tried all the springs and had to go w/ the next to lightest. W/ the lightest spring there was a bog going to full throttle when the secondaries opened. I assumed that was because they were slamming open but there is no accelerator pump. When I went to a same size QF SS650AN carb it felt like I gained 30 hp at WOT. It would be interesting to mount a gopro camera looking at the vac linkage to see if it ever opens fully. From my experience, I doubt the secondaries are fully open.

[SVOCOBRA]

Good info guys. I did notice that w/ the plain sec spring, that since the motor gained RPM so quickly in second gear that the secondary signal "caught up" about 3200rpm & snapped open, giving a kick in the ***. I went to a lighter spring & brought them in sooner, smoothing the transition. I'll hook a paperclip to my sec linkage and/or put a camera under the hood & see how much they're opening & get back to ya by Sunday.

[edwardb]

Just to add to what I already posted -- and respond to yours -- when I was trying to tune the Holley Street Avenger, I did the paper clip thing and was able to confirm the secondaries were opening. I never felt them opening or not was the problem. It was the timing. I was never able to get the off idle and transition bog to go away. But even if I had, my experience was the same as CraigS. The new double pumper carb felt like I added significant horsepower to the engine, bog or no bog. Every aspect was better. It started easier, was driveable almost immediately, had instant throttle response, even launching with the clutch was easier. I suspect there were multiple reasons. The Street Avengers, as I understand, didn't quite have the CFM as rated (mine was a 570) so perhaps it wasn't enough carb for the engine. Also, comparing kind of an entry level carb like that version Holley to a much higher end carb like the QF SS-650 maybe isn't a fair fight. Finally, it seems that based on my experience plus many others that a mechanical secondary setup is just plain better for these cars. You may get yours to run fine, and wish you the best and hope you do. But likely you will never really know the difference unless you compare the two side by side. I did.

[SVOCOBRA]

I read the same thing about ratings lately too. I'll be keeping the 80570 through the summer anyways. When I bought the car it had a QF 650 mech sec that the previous owner put on to eliminate the stumble off idle that he had w/ the 80570. He had the same stumble w/ the QF too. He wanted the QF back, so back on went the 80570. Like I mentioned earlier, I just had to crack open the sec a hair so I could close the pri venturis & cover the transfer slots back up. Its a common thing w/ the Street Avenger line from what I've read lately.

[SVOCOBRA]

Update: After swapping back in the oem 31 shooter, (thinking it would extend the shoot longer) I had a stumble. went back to a plain sec spring & got rid of 90% of it, telling me that the sec's were coming in too fast. Will try the brown spring tomorrow to slow it even more. Back in the day, I had to run a brown spring in a Holley 600 (1850) to get rid of a bog in a Chevy 305.....

[Avalanche325]

Avalanche325,

I had a Holley 770 Street Avenger, vacuum secondary carb on my Daytona Coupe. Worked great right out of the box. Sold the coupe with nearly 18,000 miles on it and running strong.

Garry

It might have run fine. But I'll guarantee you that you were leaving some performance on the table.

From my experience, a vacuum secondary carb is more likely to feel OK out of the box than a mechanical. But it is not doing what it is capable of.

[SVOCOBRA]

I agree, if one can open the sec's w/ a shot to cover the lean spot it should equal more go-go.