Engine and Transmission Tech

Carl, that's interesting--thanks. I now wonder if anyone had done a specific comparison of these larger port late Rover heads and the 300 heads.

As an aside, I did a rough calculation on the Ford Triton pistons that Jim N. found--I *think* the dish is about 19cc, if my calculation is correct.

Dan Jones has probably done the most flow testing and documentation but we'd need him to say if he has the info needed to do a proper comparison. Should be close but I just don't know. By all rights both heads should be fitted with the same size valves for testing but the thing is, if you are going to fit larger valves you'll tend to go as big as you reasonably can rather than stop at the stock 300 sizes. So it might be relevant to ask if a late Rover head with big valves can flow as much or more than a stock 300 head. But then, big valves aren't free so it's also relevant to ask the results if the 300 heads also have the big valves. Easy enough to see why this might not have been done.

Jim

I think I skimmed the earlier thread and saw JimB's 22cc piston dish mentioned and conflated it with JimN's eBay pistons. Doing a quick cad model of the Ebay pistons, I get 14.6cc's of dish. With a 40 thou skim of the deck, the numbers start to look pretty good with 54cc 300 heads.

Chad, what with the 29cc heads?

14.6cc dish, 29cc heads gives 12.96 compression, 89 thou squish. No bueno.

Jim B, yes, you're thinking the same thing I was really wondering--has anyone maxed out those late Rover heads and the 300 heads and compared them?

And Chad's analysis begs the question, what is the maximum compression we'd ever want to see?

I found a set of forged pistons [uempistons.com] with 18.33 of dish (and with a bit of machining I think could be machined out to about 22). With 22cc dish and the 29cc heads, and 51 thou head gasket, the squish is 45 thou, but the compression is 13.11. But go to .070 head gaskets and the compression is 12.42 and squish is 64 thou--still not ideal.

Chad, your spreadsheet is making much easier to compare options :)

Below is a link to a cleaned up version of that spreadsheet that anybody can swipe, with imperial and metric units accommodated. When I was piston hunting, I had about a dozen of these going as I compared the trade offs.

Also, here's just a table I've added to as I've seen numbers posted here and elsewhere of the various heads for the RV8.

[www.dropbox.com]

I've seen those numbers and they are helpful but what we don't have are unported big valve Rover or 300 numbers. That's what I'd really like to see, then I'd have a very good idea of what just the big valves or just the porting job would do. Well, I guess we have what just the porting job does with the Rover, but not the big valves. Still hard to make a valid comparison and what's the deal with the two 300 columns? Doesn't show what's different. Is one unported and both with big valves? (mislabeled) If that's the case we still have everything BUT what we need to properly compare the heads.

Jim

The two 300 columns were just different sources, different people reporting their numbers. With the stock Rover I stacked the numbers from two sources; not sure why I did it differently with the 300s. Probably just did them at different times, and didn't remember to follow the same format.

I currently have stock/untouched and an unported 300 head cut for big valves that I plan to put onto a flowbench, so that curiosity itch may soon get scratched.



Edited 2 time(s). Last edit at 11/22/2022 11:03AM by Roverbeam.

V6 Triton pistons, $170 for (6) spend $340. for almost useable ? "350" crank= 3.8" stroke ? How heavy of a car that "needs" 3.8" stroke ? Cast crank with mains turned down to 2.5" ? How fast could the power of TA heads and a single plane,
destroy this combo ? What octane requirement with what dynamic compression ratio ?
Good luck with a 6k rpm. torque monster, in a 2,200 lb. car. Art.

The engine is "adequate" with the 3.4" stroke, even with the 2bbl intake. The 3.85" stroke makes it better. Good heads make it better. Light pistons and rods make it better. A roller cam makes it better. A blower makes it better. TBI and mappable dizzy make it better. It's mostly a question of budget and how carefully you can spend it.

I sort of understand you de-stroker guys a little bit, but it's really going too far in the other direction. A stroker 300 with light rods, pistons, wrist pins, and aluminum flywheel will rev faster than is really comfortable on the street and a 7K redline is as easily achieved as with the short stroke. So what are you gaining? Because it isn't economy.

Here's the thing. You say you want a fast revving engine but it still has to move the car. With any given load and at any given engine speed assuming gear ratios and tire sizes are the same the engine with more power will accelerate the car faster. At any given rpm and assuming equal builds the engine with more displacement will produce more power. So the bigger engine will rev faster. Until you get significantly over 7000 rpm you really aren't going to change that and the 3.850" stroke SBB is quite capable of redlining at 7 grand if it's built right. De-strokers have their place but it is usually in racing where rules restrictions artificially influence natural progression such as F1. On the street things are a bit different. And yes, we all loved the SBC 302, but that was a very special engine built specifically for racing. Again, Rules.

Jim

Back to the heads, big difference between the two 300 heads, too much really for just using a different flow bench it seems. Something there doesn't quite add up.

Jim

Art, I hear what you're saying. But as Jim says, it's a question of budget. I think, to a certain extent, those TA heads are probably not necessary (and money that I can use elsewhere--such as having EFI, which will make the car way more drivable). Without them, I still think I can get to the high 300s in horsepower, which along with the torque curve that engine should have, should make it fun, but not scary. On the other hand, we haven't been discussing gearing either. I wonder how much can be gained in having a balanced driving experience by having the right gear ratios. I am thinking that my rear axle ratio might be around 3.55, to keep me from burning up a set of tires too fast.

Went back and did some more on piston options for the 300 heads. This one looks very promising.

Eric, What piston is this? What pin size?



Edited 1 time(s). Last edit at 11/22/2022 04:42PM by mgb260.

Jim,

It's a Chevy forged racing piston: [www.summitracing.com] It has .927 pins, so a bit of honing/reaming and rebushing will be required on my rods, but from what I can tell, it should still leave plenty of material at the small end. And while they are more expensive than many of the pistons I've been looking at, at $537 they are not unreasonable.



Edited 1 time(s). Last edit at 11/22/2022 05:59PM by Airwreckc.

"At any given rpm and assuming equal builds the engine with more displacement will produce more power. So the bigger engine will rev faster."

I don't follow that logic.


" I am thinking that my rear axle ratio might be around 3.55, to keep me from burning up a set of tires too fast."

I think the engine on your drawing board is going to eat up the tires even with that 3:55 gear, Eric. May want to look into a 3:08. ;)



Edited 2 time(s). Last edit at 11/22/2022 06:19PM by MGBV8.

Good advice Carl. I was wondering about that. I actually might be in luck--I think it's possible that my rear end has a 3:08 gear. Haven't looked at it in quite awhile, I need to dig it out.

3.08 vs recapture rates. In other words, pavement velocity vs tire velocity. If you break loose 3.08's in a smoking way, that much harder to recover versus higher numerical ratios.

'Cept 3.55, 3,9, 4.11, etc are easier to smoke. ;)