Engine and Transmission Tech

Kevin was just talking about the Ford 4.6 pistons in the newbie thread. The Ford 4.6 deckheight is damn near the same as the Rover at 227mm (8.9370"). Interesting. You can also buy 94mm (3.7") pistons for the 5.0l version of this engine with stock piston height (1.210") or stroker height (1.190"). The stock stroke is 90mm (3.543") so the P76 crank (3.5") is a direct fit for the late Rover block using the stock Ford piston and the +.150 (5.85") early journal Chevy rods. Total displacement of 300cid. BITCHIN'

So on to the elusive 350 crank in a Rover block: The stock Ford 4.6 piston height is 1.210". For the stroker kits (3.75") the piston height is 1.190". That gives us some options anyway. So for the Buick 350 crank at 3.85" we'll need a +.150 SBC early journal rod (5.85") to come up to the stock 8.944" Rover deck height. I guess that would actually put the piston about 6 thou above deck. The block is probably going to need a decking though so we're looking at more like 16 thou above deck. Might be able to mitigate that by skimming only 5 thou off the block. This combo makes a 5.4L (331cid) engine that weighs around 350 lbs. Cool. Compression works out pretty good. Using my Buick 300 heads as an example (45 cc) CR is 11.6.

Another option would be to destroke the crank by, let's say, 50 thou using OS journal bearings. That leaves us with some room to deck the block more if needed; Let's say 10 thou. That puts the piston 30 thou down the hole. So we end up with 3.8" stroke and an overall displacement of 327cid. SWEET! Compression with this combo would be 10.2:1. Nice.

There are a bunch of companies that sell a 3.75" stroker kit for these engines too. Here's a source for the pistons. (just one I randomly picked):

[www.dssracing.com]

"5.0 Modular Ford Stroker 2V (3.75" stroke x 5.850" rod) Max Quench Dish, 1.190" comp hgt, -13cc, .927" floating pin, 1.5-1.5-3.0mm ring groove"

So they gotta make OS pistons for rebuild on these engines, right? Maybe not. Let's say we can get 40 over pistons though so we end up with a bore/stroke of 3.74" x 3.85". That gives us a finished displacement of almost 340 displacement.

Top this combo off with those bitchin' new heads TA is making right now and MOTORHEAD PORN! OMG somebody hold me back! aaAAAAhhhHHHH! oooOOOOHHH!! Ok Ok OK ok ok ok ok. Focus, Nic. Finish the engine you're working on now.

That was fun.

I failed to mention that the rod ratio for this combo is like Chevy 454 crap BTW at 1.52. Still bitchin' though. Just don't rev it above 5 grand! You might not have to.

Not bad Nic, not bad at all. And I can't see the engine weight being much over the 320lbs or so the standard Rover weighs either.

So what happens if we use a 300 block? (or the P76 Art is looking for)

Jim

Nick,

Rover deck height is 8.96" according to data I have and is the figure i used when building the 4.35.

Thanks for all the other info, looks like theres a few more options available to us Rover nuts!

Those pistons from that vendor i posted are very good value though and make a simple upgrade possible at minimum cost.

Kevin.

Definitely 8.96" is better than 8.944". I'm not sure where I got that number. Maybe that's my engine after decking. Well an extra 16 thou works great. I reworked the numbers and I was 25 thou off. DAMN! with the stock deck at 8.96" then the combo of the +.150 SBC rod (5.8") and the stroker piston (1.190") it's at 5 thou positive deck. Oh well. I guess we'd need the piston tops to be skimmed a bit. Destroking the block to 3.8" yields 20 thou neg deck. That may be more desirable. Thanks Kevin. That's pretty cool.

BTW, I didn't mention it above but the CR's are based on the -13cc dished pistons.

OK the 300 block. Deck height 9.5". So we need another 500 thou. so... WAIT isn't the 350 rod like 6.4" or something? I'll go look it up…

OK They are 6.35"! Promising. Wait. The bore size is wrong. I have only found references to 30 over. I don't think anybody makes off-the-shelf 50 over pistons, let alone 60 thou. They're only taking these block out to a max of 40 thou and most guys won't do it. TOo bad. I was pretty cranked up there that we'd found THE combo for the 300 deck 390 lb. Buick 350.

Keep looking. I'm still buzzing after the first round. I am really trying hard not to start working on that engine.

I didn't say anything about the P76 block. Ok. Is the P76 block deck height 9.63"? The only reference I found was that it was 17mm taller than the Rover. That works out to 9.63".

If that is the case then in order to use the Ford 4.6 pistons (3.552") we need to find a 6.5" rod. WOW! The rod ratio would be 1.68. Not bad. Do you think the valve shrouding would bad with the big stroke? 3.552" bore x 3.85" stroke would yield: 305cid

I have no idea where we're going to find a 6.5" rod though.

Is that what you were asking?

Yeah, pretty much. Still looks like the 300 based 350 is the one to concentrate on though.

Jim

Nick,

With a P76 block you would have problems from stopping it splitting down the middle and a 52 thou overbore would be pushing your luck a bit.

Real Steel in the UK are doing a 5.0 stroker kit with forged pistons for £1500 so with out the VAT =£1300 = $2150 probably too much for you guys.

I was also looking at that Ford Modular 4 cam engine, the 5.0 version with a decent induction and exhaust would make an easy 350+ BHP but again it's money!

Kevin.

I'm with you there. I gotta admit it was sorta like uncovering the Holy Grail when it all fell into place though. A 350 crank in a Rover block with off-the-shelf parts is insane! I swear I momentarily achieved immortality. LOL

I love that Monster engine idea that Dan built but my only beef with it is the rod length. It'd be nice to have a little better ratio to work with. I realize the trade off is the piston stability but Ford's making it work.

I found a Buick 3.3 V6 piston 1.310 comp height. 60 over might work if they sell them. Looks like they only go 40 over though.

Can the 300 block be taken out to 3.8"? Then maybe we could consider those Supercharged Buick 3.8 pistons. 1.09" height. But then we're back to those elusive 6.5" connecting rods. The next two need 6.25" rods. Dodge 3.8 V6 piston 1.369. Ford 2.3L piston 1.33

For the P76 I found a 1.170 piston Chevy used in their 2.2L 4. They supercharged that one, right? So we're looking for a 6.53" rod then. LOL! Magic rods!

Maybe we should start with the rod. Buick 350: 6.35" and find a piston with 1.22" compression height.

Nick,

You've gone full circle, the oversize Ford is 3.7" and 1.220 comp height. LOL

I think in retrospect you could always have done something differently but you have to have worked with whatever was available at the time.

If I was to build an engine again it would be a different spec but on thinking about it I quite like what i've got, it's a bit different having 300 heads and with the big valves and bowl mods it give the flow i needed for the potential of the crower 50232 cam and thats whats important.

I also quite like the relatively short stroke of the 4.2 77mm. crank as it makes for a sweet free revving engine but still has plenty of torque, the longer stroke engines don't seem to want to rev much over 5200 RPM and there was one UK Rover V8 specialist who experimented with strokes in excess of 92mm and the engine ran rough and wouldn't rev.

For additional capacity on Rover blocks the 96mm. top hat liner is the way to go, your pretty much into having wet liners but if the liners are left 2 thou proud at the deck you get the O ring effect so sealing is not a problem..

It's all down to what you want the engine to do, big bore, shortish stroke for all out performance long stroke any bore for a torque monster 4 x 4 type engine.

Kevin.

I'll say one thing, it's a whole lot better to have the engine actually in the car and running than having it on the stand waiting for custom parts to be made like mine is! Kevin, you don't know how I envy you right now.

I think the 350 rods are the way to go. The late model ones are the best and they are quite strong, and reasonably light. The BuickV8 guys have been going towards Hersche rods and Diamond pistons over the last year or two and it seems Diamond is quite flexible in making what you want. I used Venolia but after all the costs added up I think the Diamonds would cost less. All in I bet I was close to double the original quote of $75 a piston, whereas I've heard of $400 forged sets. So finding an off the shelf piston can sure make a difference, but sometimes the extra cost of getting exactly the right part can be worth it.

What it seems to come down to is either special rods, special pistons, or both. Luckily there is nothing exotic about what is needed so there are more choices. There are some NASCAR SBC rods available and sometimes you can find 6.4" rods, maybe even 6.5". But they are not production parts so either take-outs or expensive. Nic, I think you are on the right track though, with the 350 rod. It's long enough to give a favorable rod ratio so the engine can wind up. That's where the extra deck height of the 300 is a real advantage.

As far as having the piston protrude above the deck, that isn't a real problem unless it's more than about .020" because you can have thick head gaskets made. I have learned that the only significant difference between 340(300) head gaskets and 350 is that the 350 gaskets have the pushrod section solid and punched with clearance holes whereas it's all open in the earlier gaskets, but the holes are large enough to work on the earlier engines. So 350 gaskets can be used and 350 MLS gaskets are available in any thickness. (BOPR gaskets don't work because of coolant ports but these may work on BOPR) So if you're .010" proud of the deck a .050" gasket is just the ticket. Any more than about .020" though and you'll start seeing gasket issues at the intake.

On a .100 overbore: I doubt it'd work real well. I'm down to just a hair over .100" wall thickness in a couple of places on my 340 block with a .050" overbore (stock 350 bore size). That's a side wall and we were able to stay above .150" on the thrust faces, but for a street motor you'd really prefer to be close to 3/16". Dropping that down to 1/8" or below is getting a little risky. So while it might work out OK, you'd want a sonic check and might have to go through several blocks to find one that gave you enough thickness evenly distributed on the thrust faces. Still, if that was the only piston available...
You might ask the piston manufacturer what they would charge to make them undersized. Just a thought, you never know when there might be some scrap parts laying around that could be saved that way.

But wait, isn't the 300/340 a 3.750" bore? 3.800 for the 350? Yes. I just looked and that's correct. You can use the V6 pistons with no problem.

Jim

Ok peep this:

[www.flatlanderracing.com]

They sell "Honda" rods for the Chevy. There are some at 6.25" so that with the Ford 2.3 "truck" piston (3.78") at 1.33" ends up at 5 thou above deck. 9.505". They also sell Small Journal 6.2" rods. That paired with the Dodge 3.8 V6 piston (3.777") at 1.369" puts the piston top at 9.494", a mere 6 thou below deck. A little block decking and we're golden. No need to cut the journal.

Those Dodge pistons have a 16cc dish in them. So with these and my 45cc Buick 300 heads compression is 11:1. Nice. With the stock 54cc heads it's at 9.9:1.

What's the final cc on those TA heads? This is doable, guys.


I forgot to include the displacement: 345cid (5.66l) with the stock Dodge bore. The rod ratio isn't terrible at 1.61. AND you've got a shorter lighter "350". COOL!



Edited 1 time(s). Last edit at 10/29/2009 01:20PM by NixVegaGT.

I suppose you could go all the way and use the "Honda" journal size to monster up the stroke to 3.96". Using the 6.2" "Honda" rod and the Ford "truck" 2.3 piston 20 over you'd get 3.8" bore x 3.96" stroke:

A 400 lb. 360cid (5.9l) Buick 300 with a very Chevy like 1.58 rod ratio.

Wicked. I wonder how long that would last. LOL.

Nic, I looked at Honda rods recently to see if the 340/350 crank could be de-stroked to clear the cam, rails, etc in an aluminum block. If I recall correctly, the journal sizes were something like 1.89" or thereabouts. That would enable a de-stroker crank of 3.75" or so. I seem to recall hearing that a tuner had welded a crank up to 3.75" to fit the aluminum block

Custom rods are an enabler for certain combinations like this and often turn out to be not that much more than well-worked stock rods.

That's true, you could use the "Honda" 6.3" rod with the Ford Truck piston at stock bore and you're at 336cid (5.5l). with a rod ratio of 1.68. The Buick 350 ratio. That's only 30 over on the block too. Good conservative idea.

In the Rover it's a bit tougher. Lets see… If we can use the Acura B18a rod, I'm pretty sure that's still 1.89" journal, we can get some that are 5.967". We use the full .110 thou destroke to 3.74". Using the stock Ford 4.6 piston (1.120) for a more favorable rod ratio of almost 1.6. Nice.

[www.importperformanceparts.net]



Edited 1 time(s). Last edit at 10/29/2009 04:31PM by NixVegaGT.

Ok, so I'm, on-page, 350 sbb has same head bolt pattern as 300/340? Thanks, roverman.

Oop's, fergot, on "those" 350"sbb's, reportedly making 1,000 hp., stock/reworked cranks? Should we need, doubt-it, there's the sbf., raw forgings. Scat claiming 120 ksi on tensile. Thanks, roverman.

I've heard the SBF mentioned a couple times as a source for a crank. Does the SBF and SBB have same main spacing or something?

I think after the current engine is done I might take on the Rover "350". The math is just way too intriguing for me. I wonder how far out the bottom the pistons will go...

Hmmm, there's only 1.6 inches left over after the stroke is drawn on the Westwood flanged liners. That leaves the pins just bearly in the cylinder by about 100 thou. That would explain the rattly issues that Kevin was talking about. (That's with the 3.74" stroke and the 1.12" Ford piston) The piston lands are probably popping out the bottom and exposing the smaller diameter of the forged pistons till it comes up to temp.

That might be the caveat right there. I wonder how much room there is for longer liners. Is that why you were looking for them, Art?

Nick,

In case it wasn't a typo, the Ford 4.6 comp ht. is stated as being 1.220" for those forged 3.7" ones.

Kevin.