BOSS 302 Rod Length Question
 

I'm building up a crate BOSS 302 block (the accepted S/SS one) for GT in my 68 Mustang coupe. I want to claim the BOSS 302 from either 69 or 70, but NHRA has issues with rod length. On the 69 blueprint, the BOSS is listed with a 5.155 rod length while the standard 302 has a 5.090. Turn to the 70 blueprint and only 5.090 is listed for 302 with no seperate BOSS up on the top. The 290HP blueprint specs are the same on both pages, so the BOSS engine is mentioned for both years but not named in 70.

"Independent Research" tells me that both the 69 and 70 BOSS 302s had 5.155 rods, so I assume NHRA made an office mistake and omitted the rod length info for the 70 BOSS from the blueprint.

Being the smart *** I am I had decided to build using the easier to find 5.090 rods and present the blueprint to NHRA if they ever called me on it, but after the $1000 fine deal in Ennis, I'm rethinking my strategy...:o

Here are my options as I see it:

A) Build as I had intended with a QF 780 carb and bracket race it this season. Rebuild with 5.155 rods over the winter and go GT/ next year. I don't have a trailer, so I will only sit out two or three Lucas Oil races.

B) Switch to flat top pistons and a Holley dash number carb, claim the 68 260HP Cougar engine and run GT/ this year. Would have to wait for the pistons.

C) Build as intended and claim the 1970 290HP 302 (with no reference to BOSS) like the blueprint says and take my chances with the NHRA tech guys.

Any thoughts on this? And yes, this is a rookie mistake...

Dale

Re: BOSS 302 Rod Length Question
 

69& 70 Bosss did use the longer 289 length rods, so to use the shorter rod with Boss configuration pistons would require custom Non legal pin height pistons to get the deck height in spec.
By the way, what "crate" motor does NHRA have accepted for S/S?

Re: BOSS 302 Rod Length Question
 

If you check the accepted rod and piston list it shows the 289 boss 302 with the same height.You are going to change the heads if you go to a 302 non boss right.

Re: BOSS 302 Rod Length Question
 

Rory: Not motor, block. The Accepted replacement block for the 302 Ford is the BOSS block M-6010 legal in S and S/S.

astikhossw: AFR 1399 58cc heads. Accepted replacement for Super Stock.

The rod/piston combo is the issue for me.

5.090+flat top= 302/230hp(Mustang) or 260hp(cougar) in GT
5.155+domes=BOSS 302/290 or 305hp in GT

My 090 rods are really nice Crowers and my domes are middle of the road Keith Black.

EDIT: With GT based off the heaviest car available for the year, that's 3001 lbs. for the 68 Mustang. With the HP ratings of the motors I can build, it works out like this:
290hp: GT/EA
305hp: GT/DA
230hp: GT/KA
260hp: GT/HA

The K and H builds are at the top of their weight breaks and E and D are mid or low. BOSS is looking more like a hard sell.

Dale

Re: BOSS 302 Rod Length Question
 

You just built a great bracket racing engine.
Even if there is a misprint in the blueprint sheet, building the engine to that spec will get you thrown out.
All Boss 302 engines have the 5.15" length rod.
They were also stick shift, no automatics were ever built.

Re: BOSS 302 Rod Length Question
 

I'm a little confused. If you are going to use the AFR heads it will never be a Boss 302. The Boss 302 heads are what make a Boss a Boss and there are no aftermarket versions of the Boss head. The NHRA classification guide does indicate with the && notation that the AFR1399 head is acceptable on the 302/290, but that makes absolutely no sense and is an error IMHO. All the aftermarket Windsor SBF heads are inline valve heads while the Boss 302 heads are canted valves. The Boss was essentially a 302 Windsor with small chamber, large valve Cleveland heads. Claiming a Boss 302 with an inline head is just wrong, heresy in fact. Finding real Boss 302 heads will set you back a bundle.

That being said, since you are talking about SS or SSGT, if this abomination is really legal the only thing you will gain over the 302/230 combination is the 780 Holley carb and some compression since you can use a domed piston. But in any case, it damn sure isn't a Boss 302!

Re: BOSS 302 Rod Length Question
 

All Boss 302 in the NHRA guide uses canted valve heads.
295 hp rating in GT.
Shipping weight for a´68 Mustang 428 hardtop is 3241 pounds.
GT/F at 3267 pounds.

Re: BOSS 302 Rod Length Question
 

OOPs 3369 for the convertible. Thought it was the heaviest 302. It's the heaviest gas engine offering of that model and year.

That puts the 302/260 Cougar engine at the bottom of GT/J close enough to move to GT/KA.

I think bracket racing what I have with a Holly 600 that would be legal on the 260 hp Cougar for this season and switching the pistons to flat tops over the Winter for GT next year is the best way to go. Carb specs for the 260 Cougar are 1563 1563 1250 1313 the Holly 80540-1 is a 600cfm carb with a throttle bore of 1563 and a venturi of 1229.

EDIT: The 68 Cougar 302 is 230 HP, but does have the Holley carb.That puts it at GT/MA with the heavy body weight of the convertible. The actual car, 68 coupe 302 is 2874. That's 495 lbs lighter than it's classification factor. Is that right? This is favorable, yes?

Dale

Re: BOSS 302 Rod Length Question
 

This is not true. The inline aftermarket heads are listed as acceptable for Boss 302 engine in SS for 1970.

Re: BOSS 302 Rod Length Question
 

I think Nick Morris from Div 3 ran the 68 302 4 bbl combo a few years ago with the AFR aluminum head in GT/MA

Re: BOSS 302 Rod Length Question
 

its my understanding that Ford connecting rods are the following lengths
289---5.1550 in
302----5.090 in
Boss 302---5.150 in
you obviously must have the correct piston pin location to be legal

Re: BOSS 302 Rod Length Question
 

How did a inline valve head become legal for use over a canted valve boss 302 head with the big intake and exhaust valves and why use a inline over a Boss head in super stock.

Re: BOSS 302 Rod Length Question
 

It is an obvious typo by NHRA.
They assumed the Boss 302 engine is a Windsor engine.
It should be the same head as the Cleveland engine; Edelbrock 61607.

Re: BOSS 302 Rod Length Question
 

since the Edelbrock # 61607 is an acceptable S/SS replacement head for the '71 351 Cleveland, if it was submitted to be used as a legal replacement for the earlier Cleveland motors it might be accepted for them also......it never hurts to ask.....

D L Rambo......Stk 1300

Re: BOSS 302 Rod Length Question
 

Maybe, but they got the rod length right in the 69 blueprint and the Accepted Parts list right. They have 289/BOSS 302 with 5.155 rods and 302 (Windsor) with 5.090 rods. I have a parts interchange book that supports the rod lengths I listed.

Should have read it cover to cover before I started this thing. Live and learn.

The BOSS 302 block is an accepted replacement for S/Stock. With the true BOSS (tunnel port?) heads hard to find, my guess is that NHRA approved the AFR head for BOSS 302 builds to allow access to the mechanical cam and big carb that was on the stock BOSS 302 in 69 and 70. You could build an almost BOSS 68 Mustang and run it in S/S, not GT.

But then that's too logical...

I'm currently researching everything I can find on the 68 Cougar to make sure the Holley carb they list isn't a typo. That's a 390 carb, and I need to verify that it was available on the 302 Windsor 68 Cougar.

Now I know why t here are so many bracket cars at the track these days. Just build it and race. Box or No Box. Nothing complicated like c.c. ing heads or micing a throttle bore.

Dale

Re: BOSS 302 Rod Length Question
 

Wow, there is a lot of incorrect information out there on this particular engine.

The 69/70 Boss 302 was not a tunnel port engine. The 302 tunnel port is a completely different head than the Boss 302 and was only used for Trans-Am racing in the late 60's. It was not very successful and it's failure to perform led to the development of the Boss 302 engine for Trans-Am racing.

As I stated earlier, the Boss 302 was a Windsor 302 block with heads that were essentially the same as the high performance Cleveland heads; canted valves and huge valves and ports. They were not true Cleveland heads since the water jackets were different between the Windsor and Cleveland engines. Magnumv8 suggested that the Edelbrock 61607 head should be a replacement for the 69/70 Boss 302 and that is not correct. If you tried to put a Cleveland head on a Windsor block you would have major issues with water passages. The Cleveland feeds water to the radiator from the heads through the block while the Windsor feeds water to the radiator from the heads through the intake manifold. While the Cleveland heads will physically bolt onto a Windsor block, they won't work without modification to the water passages. Ford actually published instructions on how to modify Cleveland heads to work on Windsor block as far back as 1969 (Muscle Parts Catalog). The modification is not trivial as it involves blocking water passages on the head surface and drilling water passage holes in the intake manifold surface. It can be done, but it isn't pretty.

Bottom line is that if you want to run a 69/70 Boss 302 combination, the only real head to use is the OEM C9ZE-A iron head which are very rare. If you are a purist, the NHRA specs are actually wrong on the valve size as the '69 heads had a larger intake valve than the '70 but NHRA says they are the same size at 2.235". The '70 head was actually in the 2.16" range.

There is a ton of information on the 69/70 Boss 302s on various websites. The important thing to note on this forum is that the Boss 302 was developed to compete in Trans-Am road racing, not for drag racing, and the engine has never been particularly good in drag race format. I think it has potential, but the massive ports argue for massive RPM which introduces its own problems.

When Ford brought out the "Boss 302" block, it added confusion to the whole mess. The original 69/70 Boss 302 block was unique in that it had four bolt mains and more material in the crank web than the usual 289//302 block. The re-issue of a Boss 302 block, which is really just a beefed up 8.2" deck small block casting was a nice addition to the racing world, but building a small block Ford engine using a "Boss 302" block doesn't make the engine a Boss 302.

Re: BOSS 302 Rod Length Question
 

Bill: Thanks.

The reason I bought the, um, Ford Racing Replacement 302 block was out of frustration in finding a quality 302 block that I could trust. The 4 bolt mains and extra material were the selling point for me. I knew I could take this block and build several engines, including what NHRA called a BOSS 302. I have a Chilton book that covers 68 Mustang and Cougar and the Cougar did run a 302 (not BOSS) with a Holley, but they claim it was a 4160. When I can be sure of the carb specs, my engine will be the 230 hp Cougar. It has a larger carb than the 68 Mustang 302/230hp.

Dale

Re: BOSS 302 Rod Length Question
 

I stand corrected, thanks Bill.

Re: BOSS 302 Rod Length Question
 

The 68 302 with the Holley is legitimate and is a good combination. Based on the parts you already have it would certainly be the best way to go. As someone already noted, Nick Morris ran this engine in SSGT for several years and it was a stout runner. He has since switched to the 2010 352CJ in his Mustang, but he and his dad probably know the 68 engine as well as anyone out there.

Re: BOSS 302 Rod Length Question
 

What I find even more odd about this particular situation for the 1970 Boss is that while the classification guide shows that the inline head is legal there is actually a horsepower adjustment for the engine in SS when using aftermarket heads. It went to 305 HP on Jan 1 2012. That either says that someone actually built such a thing and went fast invoking an AHFS hit (highly doubtful) or the NHRA just slapped some number on it for the hell of it.

IMHO it is just flat out wrong to have the "&&" on that engine at all.

Re: BOSS 302 Rod Length Question
 

Jim Kuntz knows the 1968 302 SS/GT combo very well. He and SE Buchannon hurt some feelings in a bad way to include current Pro Stocker Greg Stanfield

Re: BOSS 302 Rod Length Question
 

A car with 230 Hp in GT/MA (14 lbs per hp) has a minimum weight of 3390 lbs.
14 x 230 = 3220 + 170 lbs for driver.

Re: BOSS 302 Rod Length Question
 

Just a thought ,but even if you did run the inline head,wouldn't you still have to use the "stock" domed piston for the boss motor? Even if you cut reliefs for the valves in a different location,I can't imagine it would make for a very efficient combustion chamber.

Re: BOSS 302 Rod Length Question
 

Stock style domes with valve reliefs, yes. A dome designed for the true BOSS head wouldn't be very efficient in an inline aftermarket head like the AFR 1399 but a dome with reliefs designed for the AFR would. You have to watch the math and keep it to a max CR of 10.5:1, 10.1 cc dome and a .047 gasket, though.

You can build a better combo without being the BOSS.

Dale

Re: BOSS 302 Rod Length Question
 

"Class is determined without driver weight"

Someone needs to run a thread that breaks the GT classification math down into steps. It's hard to read.

Dale