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6 cyl Engine Mods

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CJM,

Thanks for checking that out for me /ubbthreads/images/graemlins/thumbsup.gif
 
I think I've got the majority of the 6 cylinder build worked out. Let me preface this with the criteria for the build: This car will be a daily driver, with some possible autox usage. My daily commute includes twisty, hilly roads as well as in-town traffic, so a well rounded engine is my goal. If anyone sees something you think I've gotten wrong, feel free to give me your input. (donning Nomex)

Here we go:
Engine bored +2mm (.080") - capacity increased to 2.64L
Head shaved to bring compression ratio to 9.5:1
Head ported and polished
TriumphTune header (6-2)
true dual exhaust system
1.55:1 roller rockers fitted
cam journals lined bored and bearings fitted
cam to be determined (suggestions?)
main bearing cap machined and extra thrust washer fitted
crank oil passages cross-drilled
rotating assembly balanced
Aluminum flywheel fitted
Triple ZS intake at first, may go to FI setup down the road
distributor recurved to Euro spec and converted to breakerless operation

Things considered and passed over:
Mazda piston conversion (2.7L)- late productions blocks(mine's a '75) more likely to have core shift problems and should be sleeved. Early production blocks should be fine.

Triple Weber intake - Great wow factor and can be tuned for high speed very well, but the general opinion is less flexible in a daily driving situation and lousy mileage in same.

6-3-1 headers - Cost vs benefits. If I were planning on racing this would be the way I'd go, but I'm not convinced it's worth the additional dinero on a street engine.

PRI 6-Pack Carb setup - Great wow factor, but cost vs benefits eliminated this

Supercharger/Turbocharger: Complexity and cost. With the right cam added to what's listed above I should get about 175bhp (est) which is more than Moss is stating for their supercharger. With an upgrade to FI I should gain additional HP.

Paeco's Stroker kit (.060" overbore and .250" stroke) I thought the TR6's stroke was already pushing it, though if I got the stroked crank and the Mazda pistons I could have almost reached 3.0L

Still being considered:
Custom front engine plate: The Spitfire one apparently doesn't fit, but I'm studying the feasability of moving the 6 cyl engine back so that #1 cyl is centered over the front axle. The object is to improve weight distribution and handling. Comments?

Transmission swap: I have an A-type O/D tranny, but what benefits can I gain if I swap to a Toyota or a T-56 type tranny?

Nissan LSD diff: Almost a no brainer, any reason I shouldn't?

OK, enough trouble stirred up for now, let the fur fly! /ubbthreads/images/graemlins/jester.gif
 
Hello Raymond,

if you don't want to go to a 6-3-1 exhaust manifold, stay with the cast iron unit Triumph fit, it is just as good.

As far as the gearbox, as I have said on this forum many times, a 4 speed plus overdrive wins hands down over any 5 speed set up. So to answer your question the benefit of a 5 speed is a negative quantity.

Alec
 
If you are doing the LSD you might as well strengthen the mounts while the diff is out.

The 5 speed is a tougher box, and the alloy versions are a lot lighter, but its an expensive conversion. I only got to drive mine a few miles, but honestly I liked the "feel" of my (non-o/d) box much better. The 4-speed just feels right to me. If the o/d works ok, stay with it imo. The sort of power you are looking for is fine for it.

What pistons are you using? Hepolite or custom? (Actually can you get Hepolite at +80?)

What valvetrain are you going with? 9/32" or stock? Also make sure you match the spring rate to the cam/rpm combo you want to run.

Same question for the guides - are you fitting seals, and if so which type?

One other thing to consider - How are the back halfshaft/hub assemblies? You start putting a lot more torque through there and the fact that they are a weak spot might show up at an unfortunate time.

Finally spend the $ to get your harmonic balancer rebuilt.
 
[ QUOTE ]
If you are doing the LSD you might as well strengthen the mounts while the diff is out.

The 5 speed is a tougher box, and the alloy versions are a lot lighter, but its an expensive conversion. I only got to drive mine a few miles, but honestly I liked the "feel" of my (non-o/d) box much better. The 4-speed just feels right to me. If the o/d works ok, stay with it imo. The sort of power you are looking for is fine for it.

What pistons are you using? Hepolite or custom? (Actually can you get Hepolite at +80?)

What valvetrain are you going with? 9/32" or stock?
Same question for the guides - are you fitting seals, and if so which type?

One other thing to consider - How are the back halfshaft/hub assemblies? You start putting a lot more torque through there and the fact that they are a weak spot might show up at an unfortunate time.

[/ QUOTE ]

I planned to do the diff reinforcement, along with adding TSI's cradle/frame stiffener package.

I plan to get the +2mm pistons from Revington or custom order them from Paeco, whichever gives me the best price. BTW, if someone wanted to do the 2.7L upgrade Revington has the pistons - no need to modify Mazda ones. I meant to ask you where you got your pistons from.

As for valve train, I plan on the 9/32" with bronze guides and seals from PRI, along with their "super lifters".

I haven't made up my mind on what to do about the halfshafts/hubs, but I admit I love what you had made up. Once I get past the engine build, I'll be looking at getting the rear worked out.
 
My pistons are Wiseco custom, but only +020. I got them from Kai at Wishbone Classics.

He had some rather nice 9/32" valve/guide setups too.
 
I can't give you an exact # without looking at the invoice at home. ISTR just under 1k.
 
i used moss europe fast road 89 cam,comp valves,1.65roller rocks', car was quick,blasted vr6,kept up with triumph trophy, up to 110.that was with semi race exhaust.oh yes,self ported head.am now going to use tony lindsey deans cam,and flowed head.he was advised to me by kas kastner.believe he does at least two cams,worth having an e-mail swap with.can pass on e-mail address if interested.apparently he does exhaust systems,and excellant gearboxes. /ubbthreads/images/graemlins/cheers.gif
 
its a good move to enlarge sump,moss recommend adding two inch strip,personally i went for custom made.although road clearance might be an issue if made too deep.also,con rods,carrilo is one of main first choices,although polishing originals is very worthwhile. have heard there is a supra conversion for gearbox. also arp bolts, all round!/ubbthreads/images/graemlins/cheers.gif
 
Have you considered zero decking the block? Kas recommended it in his books. Chris Witor also mentions the benefits in some of his writings. One interesting point he made is the recess in the block does not take advantage of the squish area and piston quenching during compression. He said this is a way to help control "pinking" which I believe is synonymous with pinging over here. I think qenching the piston has a cooling effect that helps eliminate hot spots and pre-ignition.
I've been reading different articles on squish and quench. I don't fully understand the concept. In modern engines the squish area and the combustion chamber design cause turbulance during the compression stroke. This is supposed to provide a better mixture of air and fuel which means a more thorough burn and more power. Anyway it may be something to explore.
Take a look at this
https://www.tr6.org/cylheads/index.html
 
[ QUOTE ]

Still being considered:
Custom front engine plate: The Spitfire one apparently doesn't fit, but I'm studying the feasability of moving the 6 cyl engine back so that #1 cyl is centered over the front axle. The object is to improve weight distribution and handling. Comments?

[/ QUOTE ]

Are the engine mounts in that different of a place on the TR4 Chassis? On a TR6 the #1 cylinder is alread on if not slightly behind the front axle line. There isn't much room to move it further back without 'customizing' the bulkhead/battery tray which are IIRC pretty close to identical between TR4's and TR6's.

/ubbthreads/images/graemlins/cheers.gif
 
[ QUOTE ]
i used moss europe fast road 89 cam,comp valves,1.65roller rocks', car was quick,blasted vr6,kept up with triumph trophy, up to 110.that was with semi race exhaust.oh yes,self ported head.am now going to use tony lindsey deans cam,and flowed head.he was advised to me by kas kastner.believe he does at least two cams,worth having an e-mail swap with.can pass on e-mail address if interested.apparently he does exhaust systems,and excellant gearboxes. /ubbthreads/images/graemlins/cheers.gif

[/ QUOTE ]

If you don't mind, I'd love to get his email. I'm still on the learning curve when it comes to cams, and talking to someone who actually makes them would be very helpful. Thanks for all the good advice /ubbthreads/images/graemlins/cheers.gif
 
[ QUOTE ]
Have you considered zero decking the block? Kas recommended it in his books. Chris Witor also mentions the benefits in some of his writings. One interesting point he made is the recess in the block does not take advantage of the squish area and piston quenching during compression. He said this is a way to help control "pinking" which I believe is synonymous with pinging over here. I think qenching the piston has a cooling effect that helps eliminate hot spots and pre-ignition.
I've been reading different articles on squish and quench. I don't fully understand the concept. In modern engines the squish area and the combustion chamber design cause turbulance during the compression stroke. This is supposed to provide a better mixture of air and fuel which means a more thorough burn and more power. Anyway it may be something to explore.
Take a look at this
https://www.tr6.org/cylheads/index.html

[/ QUOTE ]

Zero decking - glad you mentioned it because I had forgot! Does anyone know why the factory put the recess in the later blocks?

Very interesting article, though I admit I have a hard time understanding some of the physics involving sqhish area, qhenching, flow dynamics, etc - to misquote a popular movie "They're a lot of big words in there and I'm naught but a humble car nut" /ubbthreads/images/graemlins/jester.gif
 
[ QUOTE ]
Are the engine mounts in that different of a place on the TR4 Chassis? On a TR6 the #1 cylinder is alread on if not slightly behind the front axle line. There isn't much room to move it further back without 'customizing' the bulkhead/battery tray which are IIRC pretty close to identical between TR4's and TR6's.

[/ QUOTE ]

The frames of the TR4A IRS and the TR6 are virtually identical - the engine mount points being one of the differences. On the TR4A, the front engine plate has mounting tabs wich attach between the front suspension uprights - the holes for which you can see on the TR6 frame. The TR6 engine has the motor mounts on the side of the block which attach to special tabs on the rear of the uprights.

One thing that was told to me time and again when I started pursuing this engine conversion was "the first two cylinders are in front of the axle on 6 cylinder cars and ruins the handling" I did think it was a bit overstated, but I thought it might be worthwhile to see how feasible it would be to move the engine back a bit more to improve the weight distribution. I do realize it will most likely mean doing some alterations to the firewall, but it might be worth it if it improves the handling.

If I were to move the front of the engine back far enough to use the TR4A mount points, would it make any real difference in handling, or am I better off investing in springs and sway bars?
 
My opinion would be that changing weight distribution and changing springs and sway bars do different things to improve handling, although there is also some overlap.

Bringing the mass of the car as close as possible to a point half way along the wheelbase is an important objective; NOT just a 50/50 weight distribution. The point here is to reduce the polar moment and make the car change directions more quickly. Imagine carrying a barbell on your shoulders and trying to turn quickly, the more weight on the ends of the bar, or the longer the bar, the more difficult it is to turn, even though the weight is distributed evenly. Bring the weights in closer to your shoulders and you can turn quickly without "overshooting" from the pendulum effect.
While the engine and transmission are the most massive items in the car you can also get cumulative results from a number of smaller changes, like relocating the battery, removing bumpers etc.

The use of different suspension components can also control weight transfer under either braking or cornering and so has similar benefits, but the main objective here is to keep the contact patch as flat as possible on the road so as to get the most possible grip. This is more important after the car has taken a "set" in the corner and is in a steady state cornering mode, while reducing polar moment is most helpful in transitions, i.e. turning into a corner or a series of esses, weight distribution helps both types of behaviour.

Finally, reducing unsprung weight and rotational mass helps a bit too.
All the above just my opinions, please discuss, differ, refute, contradict or otherwise!
Simon.
 
Very good points Simon, and a subject I could use a lot of input on as well! /ubbthreads/images/graemlins/thumbsup.gif
 
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