Engine Durability: Power or RPM

[CTX-SLPR]

Howdy,

Being on the road away from the garage means back-burner projects kinda float to the top of the whole thought experiment heap... I've stockpiled a stash of parts for a 3.0L destroker (3.800 bore, 2.660 stroke) built on a stock block for Bonneville. Land Speed Racing (LSR) means sustained engine power over miles and minutes which leads to my question of which is going to be a more durable Buick Turbo6: a 275hp motor that has to run to 7000rpm to reach the speed or a 310hp motor that only has to get to 5500rpm?

Difference really is in the transmission, an OD is going to cost more power but a TH200-4R's 0.67:1 ratio brings the rpm down and lets me run a bit taller rear gear vs. a TH350C which takes less power but requires a shorter rear gear and more rpms.

Thoughts?

 

[xlr8ngn]

More hp means more fuel burn with more btu’s to reject. Wide valve seats help keep valves cooler. Loose bores and long skirts for piston stability and growth. More rpm’s normally means more opportunity for heat from friction. I honestly don’t know, but sustained runs make tons of heat, so I would say which ever one makes more power is probably harder to keep cool and not overheat parts. I’m just rambling, but this seems close to what a powerboat sees, except they have unlimited cooling water. Oil capacity, cooling capacity, and proper clearance for maximum part growth seems most important.

 

[CTX-SLPR]

All good points, LSR tends to be long enough to tax an engine but short enough you can run a total loss style cooling system with a heat sink in the trunk. You have the primary pressurized loop that goes through the engine but instead of air to air in the nose most folks mount an unpressurized tank of ice water in the trunk with a liquid to liquid exchanger inside to dump the heat into.

 

[TexasT]

Is there data you have that shows a th350 consumes less power than a 2004r? I've not had a th350 apart but the 2004r stuff is pretty little stuff.
I think you are on the right track with a short stroke for higher rpm and less stress on the rotating assembly and block.
No intake for cooling helps with drag too, so i guess that is why it is done.
Spinning it with a heavier flywheel/crank/ balancer might make for keeping it spinning but the lighter components might let it accelerate the spinning quicker but that is more acceleration/drag strip than high speed sustainability. Lots to think about. Also there are engines with tight tolerances that require a preheat before start and I would guess something like that has a big budget for replacement parts and labor.

"There are no solutions, only trade offs." Thomas Sowell

 

[dynoman]

As far as what to do about heat in the motor , I would give Swain Tech a call and look into a fully coated motor . From pistons to exhaust valves , ports headers to keep heat in the exhaust system to heat rejection coatings for intake manifolds , engine blocks , cooling systems and friction reduction coatings . A good read .

Dare to Compare, Swain Tech’s Coating Make Car 1 Second Per Lap Faster – Swain Tech Coatings | Industrial Coatings | High Performance Racing Coatings

 

[SPOOLFOOL2]

What class are you wanting to run? Kenny Duttweiler would be the best one to talk to IMO.
He is usually quite reachable. I'd love to hear more about the build and goals for this car. I'm not sure what will be the best of balance of RPM vs Boost. What works at the drag strip doesn't always work in LSR. Most TBs keep the rpm low and crank the boost up. By the time things are getting heat soaked, the quarter mile run is over. What about an Indy car engine? It'll buzz 10,000 RPMs all day long at close to 1000 HP. Classic problem I've seen, is people take drag race heads / engines that make big power, but sacrifice water flow to optimize air flow. Catastrophic detonation and pistons and rods leaving the engine usually happens at the last part of the run. Ask me how I know.

I'll be turning some wrenches on the salt this year.
As long as the car is ready.

Mike Barnard
Spoolfool Productions

 

[Chuck Leeper]

which leads to my question of which is going to be a more durable Buick Turbo6: a 275hp motor that has to run to 7000rpm to reach the speed or a 310hp motor that only has to get to 5500rpm?

Obviously, the loading of the components changes with the increase in RPM.
It's calculated by the square of the difference.
IE: 6000 vs 7200. Loads go up 144%.
My last look at an SBC LSR chebby was an eye opener! Wrist pins had nearly a 1/4" wall.
Not sure how serious you are about the endeavor, but items such as ccw crank, piston oilers, modified coolant flow, oiling mods, would be on my list.

Chuck Einstein
2024

 

[CTX-SLPR]

My apologies for the delay in a response.

Goals are to get a stock bodied 1981 Regal up to 199mph as the safety rules change at 200mph so the goal is to keep out of that safey zone till I can afford the upgrades. I'd be racing in the Classic Production Supercharged F-motor class which also means no EFI as well as a stock body. I'm planning on running Bosch k-jet mechanical injection since it's rules compliant and not a carb. From the aero calculations I did a few years ago (this project has been floating around for nearly a decade at this point) I'll need about 275hp to make it to the target speed including a 20% drivetrain loss. How I get there is mostly the point of this thread.

Engine is a 3.0L destroker, that's a 2.660in oddfire forged Molodex crank with SBC rod journals and 6.300in Arrow forged rods with SBC pins and Ford bank offsets. While I have old 3.800in bore forged TRW (i.e. BMS) flattop pistons, I don't like the longer style SBC pins and the weights came back from the machine shop all over the place relatively so considering getting custom Diamond/JE's with coated skirts to match compression distance dead nuts vs. these off the shelf "close enough" units. I do plan on running piston oil squirters made out of MIG welding tips, external drain lines from the rocker area, and since I'm likely to fab my own intake along the lines of an Indy box ram, four corner water returns. The other thing I already snagged from the yard is a Rover "intermediate" timing cover with a Gerotor oil pump and a distributor hole but it's for a 14 bolt pan.
The block is an open question. I have an 85 20-bolt block that looks like it'll work with a hone but it's not made it to the machine shop yet and there's the timing cover/oil pan miss match that would basically require a girdle to seal up. The alternative idea is to get a 4.1 block and then sleeve it down to 3.800in (Melling makes off the shelf sleeves that are perfect for a 0.030in over 4.1) that would also get me much thicker cylinder walls for bore stability but still the question of the bottom end at extended rpm.

How's that for a plans and knowledge dump

 

[FJM568]

Rover "intermediate" timing cover with a Gerotor oil pump and a distributor hole but it's for a 14 bolt pan.

Could you share the year and engine source (or part #) for this cover and whatever else it needs to be fitted to the 3.8L?

Thanks!

 

[CTX-SLPR]

Could you share the year and engine source (or part #) for this cover and whatever else it needs to be fitted to the 3.8L?

Thanks!

Rover 3.5/3.9 "Intermediate" Timing Cover

Howdy, So I have a hybrid Series II/Stage II timing cover on my Riviera that works great and gets rid of the wear prone spur gears, however it took quite a bit of work to make it fit and I had to customize quite a few things including chopping a pair of timing covers in half to make it work...

turbobuick.com

Here's the work I did years ago on what would need to be fabricated to get the belt drive to work.

 

[Chuck Leeper]

What's the min wt for the class?

 

[CTX-SLPR]

What's the min wt for the class?

No rule though with 3 or 5mi to run the number weight tends not to be a concern and to some level you need the weight to keep from being traction limited at the top end as aero mods are strictly prohibited. That being said, I've never run on the Salt so this is just a product of reading up on the issue.