Engine and Transmission Tech

Jim Stuart and Mike Moore both run the 300, and a handfull of others. I've not personally run the 300 but my 340 is coming along. I got spoiled running the blower on my 215 and quickly realized that torque is where it's at, regardless of your redline, and wanting both I naturally opted to increase the displacement. It may not be cheaper to build a Buick to stock, but on a price per cubic inch basis it's kinda hard to beat. My cost to build this engine is less than Nic's budget and perhaps significantly so. I haven't added it all up and I'm not going to. But I've spent much less on the heads. Nic is right, that's where the performance is. But instead of spending the money to get the heads to flow I just decided to force feed them. Not a whole lot of money spent there either, but it's not everyone who can make their own blower intake so yes, I cheated. I did put a bit into the bottom end, Scat rods and forged pistons. And I hope the wrist pins don't cave in the first time it goes over 7 grand. But if they do... well I just may have to start all over at that point with a whole different car. I've had this one a long time and abused it horribly and if you know where to look it is pretty obvious. Be kinda fun to start over, correct all of the mistakes and make a whole batch of new ones.

Jim

Robert - then there's always the 100 h.p. shot of progressive nitrous for when you OCCASIONALLY need that extra 100+; that's the route I'll be taking with my 4.6 that's arriving tomorrow!

Thanks again for all the responses.

People seem to want to know my motivations for my choices.
So, you may not agree with some or all of my reasons, but here they are. I have though them out over the past 10 years and am pretty much set on these things so argument over them would be a bit pointless IMO.

There are multiple reasons why I want to use the 4.6 block

First and most important to me is the weight.

As pointed out it is easy to compensate for the weight in straight line performance, but weight affects handling as well.

I am building my car as a streetable track car and have factored weight into everything I have done to it.

I chose to stick with 13" aftermarket wheels for weight/handling reasons.

I completely striped out the interior panels, carpet, and factory sound deading (it had all gone bad anyways), which, in case you were curious, weighed a total of 60 lbs.

I straight piped the exhaust as much for weight as sounding good (thats 2 cats, 2 mufflers, and 2 resonators)

I replaced the factory cooling fans and starter with lighter aftermarket units as much for weight as function (my originals still worked)

I relocated the battery to a more forward position in the trunk.

I replaced the heavily weighted convertible front bumper with a much lighter coupe front bumper.

Second, I bought my TR8 beacuse it is a rare, unusual British car with some performance potential.
As such, when modifiying the car I care as much about keeping the "spirit" of the car as much as possible, even at the expense of cost or all out performance. That said, when I think of the "logical successor" to the original 3.5L Rover V8 in my TR8, I think of all generations of Rover V8s that came after it, so that is what's going in my car. Personally, when I look TR8s that have been built up with a 350, T5, and Ford 9" rear I don't see very much TR8 anymore. I don't want that.

Third, I can certainly appreciate the benefits of torque, but at least for me, torque is not king (yes I know HP is torque per unit time). My current engine has a torque curve that looks like the rock of Gibraltar, which is the only reason my car is at all quick, but as a car enthusiast and and a manual transmission enthusiast I hate with a passion the effective 4500rpm redline that comes with it. A friend of mine has a 13 second Dodge Dart with a built up 360 in it, and it's the MOST BORING 13 second car I've ever experienced because he built it as "torque monster" that doesn't rev worth a damn.

The most enjoyable V8's I've ever driven were the solid lifter commando 273 in my friend's 1967 barracuda, the 4.6 DOHC in my cousin's 1996 cobra, and the 2003 Z06 I test drove. Why? cause they loved to rev!

That said one person I talked to suggested I build up a 4.0L Rover V8 instead of a 4.6L because of it's shorter stroke and longer rods, but I do recognize that displacement is the easiest way to make more power and that it would be even more difficuilt to meet my power goals with a 4.0L

Speaking of the 4.0, castlesid suggested I run 4.0L rods in the 4.6L. I've thought about this but was concerned I would not have enough compression height on the piston. According to my calculations with the 4.0L rod and the factory 4.6 crank I would only have a maximum of 31.384mm = 1.2356" of compression height with the piston all the way to the top of the bore.
In looking around it seems like most pistons have much more compression height than that.

Mr. T, while I would prefer not to use nitrous, part of the reason I want to go with forged pistons is so I can in case I change my mind or don't meet my power goals.

Well, I'm sure that's more than enough of my reasons for everyone so I'll end it here.

-Robert



Edited 4 time(s). Last edit at 11/24/2009 04:17PM by V8WEDG.

Hmmm. If I wanted a 'logical successor' to the 3.5 with its 2.8" stroke, an engine that can spin up pretty good, I wouldn't be putting in a big stroker crank.

Have you thought about offset grinding a 4.0 crank to get a 2.9875" stroke with a 2" journal, using long rods to reduce the piston acceleration? That will get you a smooth 4.2 with a reasonably short stroke.

I'm reading Hardcastle's book about tuning Rover engines. He seems to think that the 4.6 isn't as smooth as the 4.0, and recommends using the 4.0. I can only imagine that the Buick 300 crank will make is even less smooth.

But, as they say, your money, your choice.

Well put, Robert. Your issues with weight are exactly why I worked so hard to build my engine and why I chose it. I was regretting not just going with an LS over the past couple years but now that I've actually gotten the chance to weigh things I'm really glad I built this engine. At the end it's looking like it's going to come in at a mere 300 lbs. That beats the LS by 45 lbs.

My intentions are identical to yours. I have stripped my car down to it's essentials for the sake of weight savings for track days. I built a wicked straight-cut T5 dog-box to sit behind it for the significant reduction in power loss through the trans. It also helped me save 30 lbs.

It just so happens that just this morning I weighed my car with some simple chassis scales. I've worked very hard to balance my car as much as possible but I still ended up with a little more weight in the front than I wanted: 184 lbs heavy in the front. My weight dist is 53/47 with a total weight of 2616 lbs. with me in it and 80 lbs. of fuel. If I added another 80 lbs. to the front then my dist goes to 55/45. Not terrible but I want to do all I can... I guess technically "all I can" would have meant chopping the firewall and moving the engine back farther. I was able to move it back 2" right up to the firewall though. That had to help. Here's a pic:




I like the idea of using the 4.0 rods. You could pair that with the Ford 4.6 forged pistons. Nice pistons. and your rod ratio would be up almost 1.9! That's pretty hot. I bet you could build a pretty bitchin' 4.6 that way.
You could even add more stroke and use the Ford 4.6 stroker piston (1.19). You could do the 3.3 stroke with a small offset grind.



Edited 1 time(s). Last edit at 11/24/2009 05:00PM by NixVegaGT.

I feel ya Robert/Nic regarding the weight issue. My car is under 2200 with 50.5/49.5 (or maybe 51.5/48.5 - can't quite remember) balance and could probably shave another 50 with switching from LT-77 to T-5 and certainly more is to be had (those b lever shocks/rear leaf springs are freakin heavy), but since this a street car that's good enough. I had been contemplating possibly replacing my 3.9 with buick 300 or ford 302 (makes since from $ standpoint), but there's something about that "little aluminum engine that could", sticking with a british engine in a british car and weight wise I just didn't want to go the opposite way.

Robert, you really should give Woody a call. He can do an offset grind on your crank, set you up with a schweet cam and has worked out some lightweight (saves 1.5 lbs.) reciprocating parts that'll get you those revs your seeking.

Robert,

The 4.0 longer rods are used in combination with the 3.7" Modular ford piston with the rods bushed 100 thou. and this should put the piston approx 14 thou. down the bore at TDC, the standard pistons are no good with the 300 heads probably only 8/1 comp ratio.

If you want more than 9.75/1 you could machine the decks for zero clearance height after careful measuring, shopuld get you to over 10/1

The basic engine spec I suggested will rev to 6000 with no problem with the right head mods and camshaft selection, even the Crower 50232 I'm using will rev to 6500 if required. but dont go so wild on the cam that going to put the power band too high up the rev range.

Kevin

Robert,

The comp height of those special pistons is 1.220" and the price has gone down to $315.00

the 4.0 rod is 6.111" being longer than the 4.6 rod.

The deck height is 8.96"

So throw of crank = 1.615 + 6.111" + 1.220" = 8.946" You cant get closer than that prior to decking and a very cheap bottom end will leave you more cas to spend on the heads and induction system.

Kevin.

Thanks for putting numbers to it, Kevin. That's what I was talking about.

Inch and a quarter is plenty of compression height, talk to your piston maker about it. They will happily go quite a bit shorter than that, even to the point of having the oil rings cross the wrist pin bore. I'd guess it probably stabilizes the piston. Very common to be in the 1.220" range.

Jim

Robert-

Sounds like you building a body shell with an engine! I like the approach. Tim Lanocha built a 4.6 with custom pistons and possible rods that make 285 rwhp. He also has a 5.0 that makes over 340 rwhp. I have an older engine of his he built that is a bored 3.5 that is 320hp at the flywheel. There is nothing wrong with building a nice 4.6 at all and it is common but just so you know if you use the 4-2-1 headers and the rover heads you will not buildpower past 6200 rpms. That is the weak point on these motors. Using the Buick 300 heads will get some more rpms but not much. The headers at this point struggle and hold the engine back. The key is a 1-3/4 primary tube with a 4-1 arrangement.

Good info, Mike. I'm glad I went that route.

Kevin -thanks for the specifics on the pistons. That setup sounds VERY attractive!

Anyone got any 4.0 rods they want to sell cheap? :)

Mike -thanks for the info on the headers. I'm not aware of anyone making 4-1 long tube headers for the TR8, do you?

Nicolas -did you get my PM?

-Robert

Robert-

The 4-1 headers will be custom. Tim Lanocha has about 10-15 4.0 liters in various states and I know he might be using the internals as wheel chalks......give him a call.

Here is the 4-1 for a stock TR8 in the background and the multipiece Group 44 headers also 4-1.

Welcome to the board, Robert! I'm totally in agreement with your priorities - keeping everything absolutely as lightweight as feasible, sticking with the unique and classic aluminum V8, etc., etc. - A "streetable track car" is exactly what I want too.


So I've been following this thread with great interest... and now even more interest because my buddy just offered me a free Rover 4.2 today.

I'm in Northern Virginia visiting my mom for Thanksgiving, and the engine is here. I have until next Tuesday to do something with it before flying back to Colorado. I haven't actually seen the engine yet - it's recently been removed from a Range Rover and neither I now my buddy know whether it ran when pulled - but I'll get my hands physically on it tomorrow. I want to give it a quick inspection to decide if it's worth rebuilding and using the short block. I rebuilt some Rover 4.0 heads and put them on my Buick 215 last summer... so my 2100# MGB-GT is ready for another big bump in performance, right? If the block and crankshaft appear to be in good shape, I could carry it down to Abacus Racing (3.5 hours south of here, in Virginia Beach) for the machine work... they're the same shop that rebuilt my heads last year, and I know they've re-sleeved and built up Rover V8's for Les Gonda and Keith Burnett - but if this particular block needs sleeves it may be out of my budget. So, my questions are:

1) "What tips can you give me about evaluating the condition of a 4.2 of unknown history?"

2) "How do you feel about the 4.2 block/crank (3.70" bore, 3.03" stroke, and 5.66" rods - right?) in combination with 4.0 (small combustion chamber) heads?

3) Robert, which machine/engine shop have you been working with?

Curtis,

Sounds like the 4.2 may have potential, it's the same block as the 3.9 with the 77mm./3.03 stroke, 3.9 rods and unique pistons for the 4.2 engine..with a different compression height. The capacity is actually 4.276cc. so more a 4.3 than 4.2.

The comp ratio with 36cc. chambers and tin gaskets was only 8.94/1 so a usefull increase in compression can be had using your later 28cc. chamber heads.

The 3.9/4.2 suffered much less than the later 4.0/4.6 engines so you will probably find the bottom end only need a light rebuild and upgrades as desired.

If your heads are standard then if your looking for a bit more power an upgrade to stage 1, seats and throats opened up and blended into the bowls at least will find another 30+ BHP a fast road cam will probably yield another 20 BHP.

The standard seats in the heads can be recut to take the normal big valve sizes of 1.63" Inlet and 1.4" Exhaust

You may know this but if your getting the hotwire EFI with it they are very sensitive to cams with much overlap and a LCA of less than 112deg. Carbs are easier to tune round this problem unless you convert to a megasuirt ECU for the EFI.

Hope thats a help, and thanks for all the great work you do for the Forum.

Kevin Jackson.

Thanks Kevin!

Quote:

The comp ratio with 36cc. chambers and tin gaskets was only 8.94/1 so a usefull increase in compression can be had using your later 28cc. chamber heads.

Are there good piston options for the 4.2? Even with 28cc chambers (and a little extra boost since the heads were skimmed 0.010"), I'm still looking at significantly less than 10:1 compression. I think I'd probably prefer to end up close to 10.5:1, with composite head gaskets.

I think I still have a set of used Rover 4.0 connecting rods squirreled away that might be salvageable. I believe they're 6.11" (vs. 5.66") long, which would seem to be quite a big technical advantage... but is it feasible to find a piston that would let me use them?

Quote:

If your heads are standard then if your looking for a bit more power an upgrade to stage 1, seats and throats opened up and blended into the bowls at least will find another 30+ BHP

I'd love to see (or better yet, publish!) a detailed write-up with photos of how to properly open up the Rover ports. Abacus did a real nice valve job for me, but I didn't pay for any porting work at all. (There would've been more to gain if I'd been in a position to upgrade either my intake manifold or especially my headers.

Curtis,

In the uk the availability of pistons for the 4.2 engines is limited, and as far as I know there are no oversizes available, I have heard of people machining (topping and tailing) low compression 3.9 pistons as a replacements although I don't think this is suitable for a performance based engine as the top ring land may weakened significantly, I think D&D may offer similar pistons.

Rods, the 4.2 is a small bearing engine so the 4.0 rods can't be used.

My engine used the 3.03" crank, narrowed chevy style 5.85" rods and KB flat top hypreutectic pistons (for the |Buick 300 chamber size) but it does require quite a bit of machining to get the pistons close to the top of the bores, from memory I think we had to take 40thou. off the decks.

With the smaller chamber heads and comp gaskets you need a piston with a bowl size in the region of 15cc to achieve a comp ration of 10.5/1 but I do not know off hand of one available but they may be out there.

Clearly if you can use the rover rods that a big saving but the rover 4.2 pin sixe is .874" and not many after market pistons come with that size unless custom made and expensive.

Perhaps a call to D&D may give some suggestions.

As for the heads, as Dan Jones has often contributed some excellent virtual articles on heads mods for the Rover and Buick 300 heads I would have though he could put it together with his picture library for a specific article.

To my mind engine spec is dependent on what you want the car to do, if you want a car that will be used 80% on the road then you do not want an engine that is over cammed with excessively large valves and ports as this will ruin the drivability.

With my 4.35 engine I modified the heads with the standard big waisted stem valves sizes of 1.63" In. and 1.4" Ex, the seats were opened to seat size and the area below opened up to match that radius and then blended into the bowl areas, the guides were shortened but I purposely left the larger Buick 300 port runners as cast to maintain good fuel suspension at lower RPMs, this in combination with the Crower 50232 cam has produced an engine with excellent characteristics and drivability, it will pull top gear (4th) down to 1500 RPM 35 MPH and pull smoothly away, however drop it down to second and it will take off like the proverbial scalded cat, ask Pete Mantell for a second opinion, it was wet when Pete and I went for a drive so had to be a little gentle with the loud pedal.

I haven't taken the new engine over 5000 RPM yet as it has only just had it's first oil change but there every indication that it will rev freely round to my self imposed red line of 5800 RPM, the Crower 50232 peaks at 5500 RPM but will apparently run strong to 6500 RPM if required.

Regards

Kevin.

Kevin, Are you talking about using Keith Black Chevy 305 pistons with the 5.85" connecting rods? It looks like that leaves about 55 thou to deck the block to get 0. Pretty good plan.

I think you could use the 4.0/4.6 piston if you use Chevy 6" rods. That puts the piston 35 thou down the hole. That could be easily decked. Nice rod ratio for quick revs: 1.98:1. WOW!