tons of questions about engine build

[j69302]

I want to build a 393 or 408 based windsor, hopefully around 450-ish hp and torque. This will be a street/strip engine but mostly for street.

I do not know the limitations of 351 blocks and the rest of the drivetrain so I have a bunch of questions.

How much horsepower/torque can a 351(production) block handle. What RPM will the block/mains fail?.. At what torque/hp level would i need 4 bolt mains?

How much power/rpm can a cast crank handle versus a forged crank?

How much power/rpm will forged I beam rods last versus forged h-beam?

Whats the power limitations of a stock c4 and a typical(if there is such) 8 and a 9 inch rear end? would a 8.8 be something to look into over a 9 inch?

I know I will most likely have to upgrade the drivetrain and I plan to go with a manual overdrive or a AOD conversion. I just want to make sure that when I build this, it can handle the abuse and not going to break.

 

[fvike]

You should order the Feb. 2007 issiue of Popular Hot Rodding Magazine. It has an article about a 418ci Windsor build, and answers some of your questions. It states that the Windsor can safely handle 650 - 675 hp, and they can manage 1,000 hp, but then you don't know for how long.
The mains bearing speed is said to become a problem at "higher RPMs", but isn't a problem on the build in the article, because it is a "low RPM engine" at 7,500 RPM! Also, the Windsor mains is very stout, because they are huge 3" units with fat 1/2" bolts. On the build in the article, they built a 670 hp engine and they used 2 bolt mains. The problem with the Windsor 3" mains is that they create friction. A usual modification is to use the smaller 2.75" Cleveland mains.

A Ford 9" can handle anything you can throw at it. The Ford 8" can too, except the killer drag launches with sticky tires. However, if you are gonna spend money on it, it might as well be a 9". I don't know much about the 8.8, but it is a proven preformer.

A C4 would perhaps need strengthening, I'm not sure. I think 400-450 hp is where it gets into trouble. In fact, the FMX is stronger, but heavier. The FMX was actually used behind the 427 SOHC "Cammer" (along with the Top Loader), because the C6 wasn't invented yet.
Anyways, I'd go with a Tremec TKO 600...

 

[ratio411]

A member here didn't crack a production block until around 700 or better hp.
It was boosted though.
I was impressed.
You don't hear about too many 351w block failures.
Never really heard about 302 failures either until folks started using thin 5.0 blocks.
The weak point in any Ford is generally accepted to be the fasteners... And in particular the rod bolts.
I say that head and main bolts are always a good idea, but good rod bolts are manditory. Just my opinion though.

8" rear is weak IMO. Alot of folks tend to argue, but with that kind of HP you are considering, even they will admit you need a 9".
The 8.8" is strong, however it is heavier and there never was a bolt in version, so you need to make plenty of custom fabrication to get on in.

Cast cranks are not generally considered weak in Fords.
Racers in the 70s and 80s didn't have a choice and ran cast cranks on some pretty serious engines. 351c guys in particular really beat some cast cranks without issue.

A stock tranny will not hold up IMO.
C4 uses far less power to spin than a C6, but must be built up stout.
I know nothing about AOD, except the ones that don't use computer control are weak. Those are the ones that we generally use in the old cars, so they must be pro-built.

Good luck
Dave

 

[j69302]

Thanks for the replies. I have a much better idea of how strong to build it.

 

[rbohm]

a few recommendations for you:

1: use the ARP wave loc rod bolts when having the rods rebuilt.

2: use ARP main studs, and/or a main cap girdle, when building the bottom end.

3: since you are not going to make big power, you can use a good cast crank. i prefer the 3.85 stroke crank so you can use stock 351w rods and replacement 302 pistons for an economical, yes powerful package.

4: before you assemble the short block, infact even before you have any machine work done, deburr the block. essentially you will use a grinding wheel to eliminate any sharp edges, and smooth out the casting flash. you also want to polish the valley area to aid oil return to the pan.

5: before you do final assembly of the short block, verify that there are no clearance problems between the block, cam, and rods. do this by installing a connecting rod/piston combo, without rings, but with a bearing installed, as well as the timing chain and gears you will use and the cam(of course), and spin the crank through a few revolutions. notch the pan rail as needed for rod bolt clearance. if you have any clearance problems between the cam and the rod bolt heads, you will need to grind each rod as needed to clear the cam.

6: for the power level you plan to have, you will need either an 8.8 or 9" rear end. the 9" is likely going to be easier to install, though the 8.8 is lighter and has nearly as much stuff available for it as the 9".

7: using either the C4 or AOD, you will need to beef them up a bit. the AOD will be easier to beef up as you really only need to install a one piece input shaft, and change the valve body to a lentech unit. the advantage of the lentech valve body is you not only gain performance and durability, you also get a revised shift pattern(from 1-3-OD to 1-2-3/OD).

 

[ratio411]

the 8.8 is lighter and has nearly as much stuff available for it as the 9".

Lots of great stuff there.

I just have to disagree with this part.
It is a misconception that just won't go away.
The 9" is actually lighter than the 8.8".
Just like it is generally believed that the 9" is much heavier than the 8"... However it's not true. The 9" is only slightly heavier than an 8". It's only when you start beefing up the 9", using big brakes, and bracing the housing that it starts to get porky. Even with all the HD stuff, Lincoln housing, monster brakes, and back brace, it is only 30#s more.

Anyway, I wish I could remember the weight of an 8.8" off top my head.
It is not a great deal, but the 8.8" outweighs the 9" by more than the 9" outweighs the 8".

 

[D.Hearne]

I'll add too that the block failures with the 5.0's aren't related to strength vs the older blocks. The failures started when the engines were bored and stroked beyond what they were intended for. A late 80's & 90's 5.0 block weighs the same as the older suposedly stronger 60's block. The roller 87-up block weighs 126 lbs. The casting quality is far beyond what the older ones were. Ditto for the cranks.

 

[CraigMBA]

I saw a 600 hp sprayed 5.0 fail in 1998 at LACR.

My buddy was in the pits with another racer who made a pass. He noticed when he shut down that his oil pressure was -0-. Hmn......

It cracked the block from the cam journal all the way to the mains. Didn't hurt any of the parts because he shut it down right away.

So, I think the rule is, if you stay away from spray or a blower or prolonged endurance road racing the stock 5.0 block is probably fine to 500hp. The 351 block I wouldn't bother to start worring about.

I was around a lot of racers in the 1970's and 1980's. Everybody complained about Ford cylinder heads, nobody ever mentioned the bottom end back then. Today, nobody ever talks about heads and all they do is complain about the bottom end, even though there REALLY haven't been that many failures and whoever broke it was making monster horsepower.

 

[ratio411]

It may be so that the blocks, old vs new, weigh the same, I haven't put them on a scale... However I believe it must be distributed differently.

I agree with Craig, back in the day, you did see sprayed and blown 289/302s, but you didn't see them split in half.
Personally, I have seen all kinds of pics of split blocks, but they were all later blocks. I have never seen or heard of an early SBF splitting. Not saying it doesn't happen, but you gotta admit that it is a late block issue.
Point taken on the 347 kit comment, but early blocks get stroked too.

 

[mustangdave]

Stoc 351W's do not like high r.p.m. beacuse of the large journals.
Stock 351 rods and bolts will fail in a stock application (i know).
When the rods/rod bolts fail, it will destroy a block(again, I know).
So, keep r.p.m.'s around 6,000, use main girdle, better rods, better bolts throughout and you can make serious h.p. and torque.
C4's to handle 650 h.p cost about $1,000 and they can be built to handle much more.

 

[j69302]

Thanks again for all the infor everyone