BritishV8 Forum

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!

QuoteThe 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?

QuoteIf 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!

Nick,

Pin size of 4/0/4.6 piston is .966" so no good for chevy rods @ .927" I'm afraid.

The 4.2 crank Curtis is talking about is the smaller bearing size also.

kevin.

Opening up the SBC small end by over 30 thou is probably a bad idea...

OK I got another idea from looking up piston availability for Tamas. Wisco sells a VW flat-4 piston that's 94mm bore, pin dia.: .866", with a compression height of 22mm (1.378") that might work. Hmmmm.

Wait, here's another possibility. Forged Mahle VW flat 4 piston: 94mm bore, .866 pin, comp height: 34mm (1.56"). Could use that with your 5.85" rod that puts the slug 35 thou down the hole. That's a little closer. Here's some linx:

http://www.geneberg.com/product_info.php?cPath=31&products_id=534
http://www.importperformanceparts.net/imports/wisecopistons_vw.html

Lastly a link to the 6" small journal chevy rods:

http://www.flatlanderracing.com/eagle-chevysb.html

Another option with the 6.0" rods is either the KB-186 or KB-834 Chevy 305 bore piston.  My engine spec is very similar to Kevin's, but I'm using the KB-834 (10cc dish) pistons with the 6.0" SBC small journal rods, a 3.9 block and 4.2 crank, and the 3.9 heads for a static compression ration of about 10.9:1 (8.2 DCR with Isky 282 cam).  That's with the block decked about .020 and the composite head gasket.  Quench distance of around 0.048".  According to Kevin (if I remember correctly), the 4.2L stroke can vary from 3.000 to 3.020, so I've assumed middle ground of 3.010 for the above.

Nic and clan, We should be cautios about using "air cooled" pistons in out motors. Many mfg's use different "cam" profile on skirts, specifically for air cooled motors,(ie. pistons run hotter) and different running clearances. I'm not saying, no, but ask mfg'r?roverman.

Art, I got a similar response from a well known UK specialist. He felt that pistons from air cooled engines run different clearances / are designed with different expansion characteristics compared to wet engines. Having said that, big forged Mahle pistons are used locally in e.g Ford 4-banger race engines and seem to cope well. Again, Fords are iron blocks so who knows. But the Mahle pistons look tempting being forged and having coating on the skirts.

Could be. I was thinking the same thing at first but I got the info from some guys using them in the BMW M10 engines. THanks guys.

Just curious. I know the argument about "it came with one" but if you are changing the engine to that extent, why not consider an LS2? 368lbs dry (without the stock manifolds), 400hp, 400ft/lbs, under $6k delivered with a 2 year warranty. It's about the same size as a 215, so size isn't an issue...

Totally. When I started my project the LS engines were really expensive so I stuck with my initial plan. The main reason to modify the Rover engines is because it's fun.

I think the LS block is actually an inch shorter in length. If I remember right, the LS block is 22", and I think the Rover is 23" or so. Very light and tons of potential. Good engine.

On the weight, not that I'm arguing against the LS here but just saying: My engine ended up just under 300 lbs. dry. So that's a bit of a perk. If I went with the LS I would need to modify the firewall to get better chassis balance for the track. As it is with my 300 lbs engine I'm at 53/47. Another 70 lbs would put me in bad shape. That's just me in my Chevy Vega though. GM built them to be a little front heavy by putting the engine right over the front "axle". I was able to move the engine back 2.5" to put the center of the engine just behind the center line of the front suspension. This isn't as big an issue with the MG cars since the engine is place a little farther back.

I thought the dry weight of the LS was like 345lbs. ?

http://cgi.ebay.co.uk/Rover-V8-Wildcat-Heads-Throttle-bodies-TVR-Racecar_W0QQitemZ290376968468QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item439bd0e914

Thought this might be the best place to drop this teaser in.
Be sure to show the spousal units and drop a big hint about Christmas.
; )
B

Bernard, I'm hopin Mike Perkins,(wedgewoks), wound-up with that set-up for his 4.02" bore, Rover monster.Mike? roverman.