engine builders ??

[360 4V]

I was reffering to a stock 351W with 205 heads, long tube headers, stock camsahft, some larger fuel injectors, and a good tune. How high should this engine be safely reved with little risk of the rotating assembly coming apart?

 

[KyleQ]

Ahh, that makes more sense. I build a stock 351W with TFS 185 heads and aftermarket pistons, big ass cam, stock rods and crank - I was told that they used ARP everywhere besides the rod bolts as there was no point with the cam I had in there and the power range I had. He told me 6K was ok, but I wouldn't make power after 4500RPM.

If you have a good tune (no spark knock) and good hardware, 6K won't hurt it. Your cam won't make power there either, so anything around 6K is fine.

 

[360 4V]

Is it better to make 500 hp at 4,000 rpm with a blower or at 8,000 rpm naturally aspirated? I would think rpms to be the main culprit pulling things apart.

 

[Thunder26]

If its balanced well 8000 rpms will kill an engine slower because boost kills by the heavy pounding on your rods and pistons

 

[KyleQ]

Is it better to make 500 hp at 4,000 rpm with a blower or at 8,000 rpm naturally aspirated? I would think rpms to be the main culprit pulling things apart.

That depends on application - RPM's and tuning are what kills engines.

 

[broncnaz]

What is a good guide line for not overrevving a 351W, 6,000 rpm max? I have read many threads where small blocks are coming apart up there. Some people get lucky and rev over 7,000 rpm for few bursts, others hold it at or above 6,500 rpm for too long and it comes apart. So with my limited authority I am nominating 6,000 rpm for 351Ws redline.

guide line is if you cant controll yourslef with a tach run a rev limiter. Really a basically stock 351 will stop making power at around 4500 RPM anyway. you might get it to 6000 rpm or even above but the valves will probably start to float right around there as well.

 

[buckintone]

Anything over 6000 rpms in a bronco is absurd jmo

 

[Ranchtruck]

If its balanced well 8000 rpms will kill an engine slower because boost kills by the heavy pounding on your rods and pistons

That's true to a degree, bearing loads are more evenly spread by higher rpms but you're putting a lot more stress on the rods and pistons. I also point to turbo diesels as a prime example of making huge power at low rpms and not destroying rod bearings. The cylinder pressures are immense in those, but as long as the crank is spinning just fast enough to keep a wedge of oil pulled into the bearings, they hold up just fine.

 

[360 4V]

"Anything above 6,000 rpm in a Bronco is absurd."

Is that because higher rpms are inherently faster in vehicle speed? Tractors are low revving but 200 mph cars are high revving. It must be best to match the torque curve to the speed of the application. I would rather have a stump puller V8 with very low gearing than something that only makes torque at unsafe speeds. I do not want to go rock jumping in a prerunner that only has one speed-FAST.

 

[buckintone]

Push rod motors are not conducive to high rpms, ud be better off with overhead cam motors like a coyote or dare I say ls motor for that kinda spinning. Coyote well built will spin 8,000 all day

 

[360 4V]

What about my 330 Triton? It is similar to a Coyote. It came with 16V, 24V and 32V. The coyote has a slightly larger bore but I am pretty sure the bore-spacing is the same.

Is it the pushrod-that is just too much? Many overhead cam motors have rocker arms andlifters in the cylinder heads. Then again I have ecountered designs where the camshaft lobe presses a lifter directly which acuates a valve directly. The Volvo I worked on had hydraulic flat-tappet lifters. I re-built the lifters one by one. I even lost one spring which I luckily replaced with a spring I found in my father's Harbor Freight spring assortment.

 

[buckintone]

The modular motors need to be shoehorned in to a bronco, I wouldn't recommend it, takes serious frame/eng compartment mods

 

[broncnaz]

Pushrod motors have there limits overhead cam engines do tend to rev higher than pushrod engines due to less valve train components but you also tend to have very long timing chains to deal with so timing can change easily.
Pushrod engines tend to be smaller more compact and lighter(ok yes most of todays OHC engines are lighter due to use of aluminum), where OHC engines tend to be larger and taller. but pushrod engines do tend to have limited intake ports due to the need to fit pushrods in there somewhere. OHC engines dont have that limitation so the ports tend to be bigger, So there are trade offs in both cases.
Last I checked NASCAR engines were still pushrod engines and they can see 8500+ RPM for up to 500 miles. A few years back pushrod engines were still winning indy car races and I believe they are rev limited by rules to 10,300 they used to have a 12,000 RPM limit. but that was about the limit for conventional valve springs.
Take a look at the formula one's DOHC v8's they hit RPM's of around 18,000 RPM. they use pneumatic valve springs which are capible of allowing 20,000 RPM.

Basically there are a lot of different valve train options out there some allow more flexibility than others. In production car valve trains you tend to see hydraulic tappets or lash adjusters because they require less maintenance and are quieter setups. Where in race type vehicles lifters or lash adjusters tend to be solid so valve lash can be set to certain specs and you dont have to deal with lifter pump up during high rpm's

As for a 330/5.4 vs the coyote engine the only thing they do share is bore spacing and journal size. The coyote engine was loosely based upon the 4.6L engine but was still totally redesigned so much so that I dont beleive any parts are swapable between the engines at all.

 

[buckintone]

All true, the only thing I would add is, the pushrod engines that rev that high are usually rebuilt after a few hours of run time. I do believe the 4r70w trannies hook up to the coyoties and 4.6s, but I'm not dead sure.

 

[broncnaz]

yeah I believe the bellhousing pattern didnt change. just most of the engine itself changed meaning that swapping any parts between the 4.6/5.4 and 5.0 is very unlikely

 

[360 4V]

The Coyote 302 engine has a special firing order. It has try-y headers. They are shorty try-ys. With try-ys pairs of non consecutive firing cylinders are paired. On a 302 small block, on the left side, cylinders 5 and 7 are paired and cylinders 6 and 8 are paired. This is due to the small blocks firing order. They Coyote's firing order is so that there does not have to be a primary tube swap on the left like on the small block.

Comparing overhead cam engines and pushrod engines opens up a vast discussion. The weights are different. Modulars weight as much as big block Chevys. When I look at my Triton, it is as wide as a big block. Later I will go compare weights of pushrod and overhead four cylinders. In the past when I have looked into it overhead cam engines tended to be heavier.

Why do pushrod engines not last as long as overhead cam engines at high rpms? Is it just the valve train that fails sooner?

 

[360 4V]

As for bellhousings, the 4.2L V6 has the same bellhousing pattern as the small block Ford. The Modulars had their own bellhousing pattern. the 4.2L V6 has been discontinued in favor of the twin turbocharged 3.5L V6. Whatever was the last year of the 4.2L V6 is the last year Ford made transmissions for our small blocks.

 

[buckintone]

Less moving parts, mass and less inertia to overcome, thats why they build revs quicker and seemingly are less likely to come apart. But I'm no expert.

 

[360 4V]

But how many overhead cam engines still have lifters and rocker arms? By eliminating the pushrod from the design, the camshaft is closer to the valve. If all that has been eliminated from the design is the pushrod then how much work has been eliminated? I know that Comp Cams makes a lot of high performance pushrods that are ligher and/or stronger. The pushrod seems to be a weak link. But if it is just the pushrod then I would get a ligheter or stronger, ect one.

 

[broncnaz]

well no OHC engies that I know of use pushrods. they use either lash adjusters which are essentially lifters, some do use rocker arms or they just use the cam lobes to work the valves. for instance your 5.4l has overhead cam with lash adjusters and rocker arms which they call followers.

stronger pushords are better suited for higher RPM's but its tough to get both stronger and lighter in the same package. Where the lighter weight really helps is in the valves themselfs and valve retainers as when you reduce the mass of the valve its less likely to bounce at higher RPM. Also part of the reason that pushrod engines reve a little slower than OHC engines is the more parts you have and the farther away those parts are the longer it takes for the valve to start to move.