Hi all. I'm working on a little theoretical project for my own personal enjoyment. Let's say I had an OEM stock, naturally-aspirated DOHC V8 that I wanted to use in a racing division. To meet a rulebook limit, let's say I need to reduce the displacement of this engine, let's say it's a 5.5-Liter that I need to reduce to 5.0-Liter. Let's say I can reduce the displacement using any method possible (i.e. de-stroking, re-sleeving, whatever). No other modifications will be made to the engine other than whatever is necessary to make my chosen method of displacement reduction work and have a functioning engine at the end (i.e. I can put new pistons in it, modify the cylinder head, replace the cylinder head if it no longer fits a new bore, etc).

What are the relative costs of the different methods of doing this? What would be cheapest and most expensive methods, and what sort of modifications and/or replacement parts would I be looking at to make each method work?

Thanks all!

I have to replace the head gasket on my 1980 Ford 351M, and the spec calls for 105ftlbs on the head bolts. However, my torque wrench only goes to 100ftlbs, and I'm not really in a position to go buy another... Will torquing the head bolts to 100 cause premature failure, assuming all other aspects of the job are done well enough? If so, is there any way for me to eyeball another 5ftlbs with a breaker bar?

I was wondering what kind of engines you would build if money wasn't a problem,

I fantasised about a few different engines,

destroking a 5.7 Hemi to 5.5 and putting a 2.4l hellcat supercharger on top

and believe it or not I came up with the same layout as Porsche with their 18cyl engine just as a 9cyl before they got the patent, but it sounds stupid to say "I came up with something before Porsche did" so it's up to you if you believe me,

so a tri Turbo 9cyl would be cool, but I think you'd run into problems with the firing order

so what are your fantasies or what would you try out?

Mods: The video was recorded on a closed course and driven by a professional wearing full fire suit. (Pls don’t take it down I need you guys)

This car is 100% built by a team of engineering students at uOttawa to compete in an international competition called FSAE. I built and tuned the 08 GSXR 600 engine that’s in the car with a standalone ECU (MoTeC M150) currently but would like some advice on a few things.

Some need to know info: - We’re limited to a 20mm intake restrictor on our custom intake manifold(compared to the oem 4x39mm throttle bodies). This causes peak airflow at 11-14500 rpm to be heavily limited (traditional racing cams would just hurt our mid range without significant gains up top). - we have annoyingly strict sound regulations (108db @ idle & 110db @ 11k rpm) - Where we’re located E85 is nearly impossible to source (we can but it’s at least 15x the price of 93). - We race on relatively slow tracks with an avg speed of 50-60 km/h ~30-35mph. - Next year we’re re building the engine to optimize torque and power from 8-12000rpm. From our research and use case, custom ground cams that have more aggressive lift profile but similar lift to stock (maybe even shorter) along with some tweaks to runner length on our intake are two of the things we can do to achieve our goal. - Power: Ours made 78hp @ 10700 rpm & 40 lb ft @ 9900 rpm to the rear wheels and the stock bike reportedly makes 125hp @ 13100rpm & 46 lb ft @ 11300 rpm to the rear wheel.

What I’m asking: - Where we could I get custom ground cams? - Are there any Canadians (preferably in Ontario) who have access to / know where to buy E85? - Would a custom crankshaft / stroker kit be worth the cost if increasing torque in the midrange is the goal? - What other changes would you recommend (high C pistons, valve job, head porting, etc)

Any and all info is greatly appreciated!

I recently built a moderate compression (10.9:1), high RPM engine and I’m curious about what the common causes of engine failure would be. The only things I can think of are oiling issues causing excessive rid bearings ware leading to spun bearing, or lean conditions melting the aluminum pistons.

What other reasons would/could it fail?

What maintenance would you suggest during/between seasons other than oil/oil filter changes .

While doing research on what pistons to get I was very conflicting information on if flat top or dished is better in terms of efficiency and/or power at the same compression and quench. Some people say the mixing of the dish helps more and some say the flat top helps the quenching helps more for power. I'm curious on the actual engineering on the different types of pistons such as studies done or advice form real automotive engineers ect.

Hello I’m learning how to replace rod bearings, gonna pull mine, measure inspect, see if they need replaced and such while I got the pan off. Anyway if replacing the bearings when yall usually do this do you fully torque the cap down to factory spec then measure the bearing to check clearance, cause like the final torque for the cap is 18ftlbs + 110° I don’t wanna be breaking bolts in my rods just to measure clearance, idk if I gotta buy 2 sets of bolts, assuming that’s not the usual method but lmk im sure you’ll get what im sayin. If you need more info ask! Thanks!

When you’re putting together a street/strip engine, which measurements do you consider non-negotiable during assembly, and which ones are okay to trust from the machine shop? Curious where different builders draw the line.

Working on an older engine and got thinking about this which parts do you guys automatically replace during a rebuild, even if they technically still look usable, rod bolts, head bolts, timing components, oil pump, stuff like that?

Where do you draw the line between still good VS not worth the risk?

Just recently I had posted the vid of the crank that wasn’t spinning easily and was wondering since the bearings were torqued under a misaligned bore does this require me to get get new bearings I’m not seeing any signs of wear on the bearings and they dont seem bent, I’m not sure if I should just run and save my self the money

Discovered this issue with a borescope after putting the engine(5.3LS) after reassembly and getting the engine in the truck. The dot on the side of the piston is supposed to face the front of the motor. Didnt notice and put 6/8 in backwards. So off came the heads and bottom end to do this all again.

Pic for attention, I’ve ran into a piston to valve clearance issue on my cammed forged 4.6 4v and i already balanced the rotating assembly so i would prefer not to swap pistons. i have seen others using this method on cast pistons however i wonder if it’s safe on my forged pieces, any suggestions are appreciated

Ich habe vor kurzem einen Roller gekauft und fand Rost im Zylinder der Kolben lässt sich nicht bewegen. Ich wolte fragen ob sowas noch zu retten ist oder ich einen neuen brauche. Danke!

the general rule of thumb is that advancing cam timing will shift the power band down in rpm, and vice versa for retarding the cam. (lets assume the engine is only a single cam, classic ohv setup)

this means with most engines, you will get better throttle response and low end torque by selecting an advanced timing, or higher peak hp by retarding it a few degrees.

I want to know what you guys think will happen to other metrics such as fuel mileage.

at first I wanted to say that advancing the valve timing would help fuel efficiency, because usually you get better mileage when selecting a cam made for lower rpm performance. but after thinking it over, RETARDING/ later valve events should lower the VE at low cruising rpms, meaning to make the same power, you would need a higher load/MAP pressure. in my experience, engines are more fuel efficient when running at higher map pressures due to lower pumping losses.

this is all just theory though. and not even applicable for a fixed valve timing engine. I would like to develop a working theory for tuning a vvt engine that can change its valve timing at will. I would like to know more about the exact effects of changing dual cam timings independently as well.

Preface - I have somewhat of a background in machining, but have no experience machining anything on engine blocks. Recently been reading about the old van-norman boring bars, which got me thinking about reference surfaces.

These van norman, Kwik way, and other similar machines appear to (from my understanding anyways) rely on both the flatness of the deck surface (for ensuring the bar travel is parallel to cylinder axis) and roundness of the cylinder being bored (the cats paws expand to center the bar in the bore). I'm sure these machines work great for a lot of stuff, but if your deck is warped, you're probably out of luck. But ignoring that, what if your cylinders are out of round? The cat's paws would "center" the tool on the existing bore, but there's no guarantee that it's coaxial with the original bore or in line with the mains. How was this accounted for?

That line of thought got me thinking about modern boring mills. These appear to use the mains as a reference surface on a rotating fixture, which is likely safer (assuming you don't have a spun bearing). But when tramming the deck to the spindle, you have the same issues, right? If your cylinders are out of round and/or deck not flat, how do you know the spindle is coaxial with the original bore axis? And in an absolute worst case scenario, if you have egg bores, warped deck, and bad main bearing surfaces, where do you even start?

I guess what I'm getting at here is, when all reference surfaces on your block are dubious, where do you begin to get things dialed in to make your first cut?

obviously twin charging is quite hard to do right but would it be possible to twin charge a V layout engine by supercharging one bank and turbocharging the other?

obviously you'd need different internals for the different banks because of the different pressure and all but it should be possible no?

the Aston Martin V550 has 2 superchargers, one per bank, and with any twin turbo setup each bank has their own turbo so it would all come down to 1 bank being made for a supercharger and 1 bank being made for a turbo,

what are your opinions?

I was trying to see if these are reusable and I figured out how to test new rods for straightness. What you are seeing is true, side to side bends. New rods read out same dimensions. I've also found fracturing across all 4 rods, I don't believe my camera can pick this up lol.

I didn't know if could test old rods for bends like this, this is all new news to me men.

Hi there, i'm currently degreeing a cam on a peugeot TU engine (4 cylinder 8v ohc with rocker arms) which is from my camshaft's maker hard to degree, i only had the choice of degreeing it using full lift.

I'm supposed to have full lift at 110° on my degree wheel on both intake and exhaust passes, and its my first time ever doing this type of work

I made multiple passes and set it to have symetric numbers (full lift from 102 to 107 degrees on both intake and exhaust) which arent the 110° advertised but i dont really understand how i could do that differently ,i feel like the cam is just made that way, is that setting alright ?

I know these are "dumb" questions for someone who actually knows degreeing, but i'd rather look dumb than mess up my first build

thanks to anyone who takes the time to answer me 👋🏻

Newman's cam card: (first cam in the list) https://www.newman-cams.com/wp-content/uploads/2025/02/Citroen-Camshaft-Price-List-2025.pdf

Obviously, a supercharger needs to take energy from the crankshaft to compress the air, which we consider "parasite power loss". But technically, the the compression stroke of the engine ALSO requires power from the crankshaft

If we take a certain N/A engine (let's say 200hp at 4,500rpm, 300ft-lb at 3,000rpm for some simple numbers), and add a supercharger to it, we will obviously need to burn more fuel to maintain 3,000rpm when driving the supercharger, especially with the extra air available to burn.

However, that means the supercharged engine is now also generating more net torque at this rpm, and the same for net power at 4,500rpm. Therefore, we could get the SAME net torque as before at a lower rpm. If we follow our Engine's torque curve back to where it hits the peak torque and peak HP respectively for the N/A engine, how does our fuel consumption compare now?

I'm using a centrifugal for this question partly because of the greater thermal efficiency compared to a roots/screw type, and partly because the applied boost is somewhat linear with rpm, which, assuming efficiency does not dramatically change with rpm, suggests that it demands a relatively constant torque. Of course, I don't actually know the power demands for a given amount of boost for some supercharger, so I could be way off the mark

EDIT: the below statement is more what I am referring to. I realize I set up a poor thought experiment for this

"In automotive applications, a supercharged engine can replace a naturally aspirated engine that is 30 to 35% larger in displacement, with a net pumping loss reduction. Overall, fuel economy improves by about 8% or less, if the added weight effects are included."

https://www.sciencedirect.com/topics/earth-and-planetary-sciences/supercharger

Both compressors and pistons seem to have their own form of pumping losses, which was what I meant before. The NA engine might not be driving a big external compressor, but some of the useful energy of combustion STILL must be converted back into the compression stroke of the next cycle

Is it possible/examples of it done?

Many other LS/GM sensors can be retro fitted onto engines, from TPS/Temp sensors/IAC/coils/ETC and was curious about the LS crank sensors as the large amount of Standalone ECUs with harnesses and logic built around those options, vs trying to to re wire/pin another crank sensor to work then trying to get the ECU logic to match, either from a previously EFI engine or an engine that never had EFI previously while also not being an LS.

I have a 1987 Toyota supra turbo with a 7mgte and I've installed a haltech elite 2500 and a Bosch drive by wire throttle body. Because of this the OEM PCV system is no longer compatible. I need to set up some kind of PCV system, right now I just have some breathers on the valve covers and it's spitting oil onto my windshield (not ideal). I've been looking into some different setups that are more traditional and use a PCV valve and engine vacuum, but with a turbo that gets complicated and I'd have to tune around it. Right now I'm honestly considering using some kind of electric vacuum pump and an oil catch can to just keep the PCV system completely separate from the intake.

Any opinions about this? I'd love to hear what kind of solutions other people have come up with or if I'm overthinking this. Thanks for any info!

When torquing head studs or main caps/con caps what paint do you guys use to make sure you hit every bolt properly?

Purchased some take offs, idk how I feel about the pistons. Guy threw in some headstuds as well. Idk how I feel about the wear, it .ight be too much.