Sweet Singing Straight Six

[monkeynuts]

I was offered a senator 24v this afternoon by a neighbour. i know that these have been fitted into mantas before so this evening i searched this forum for any information on the subject. after reading through it twice i'm still trying to digest mantadocs comprehensive 12v conversion notes! I would be lying if I said I wasn't tempted by the sound of a six purring away under the bonnet and 200bhp is just about enough to keep me satisfied with my daily whip.

My concerns are;

The injection system - motronic/jetronic set up - wiring?

The extra weight over the front of the car - suspension?

Stopping power - brakes?

There is a lot of helpful info on here regarding fitting a straight six but very little info on how it effects the cars characteristics. i would be very interested in talking to some of you that may have fitted one or owned a manta with either a 12v or 24v in it. on a different note, It's my birthday on monday so my mrs is buying me a years membership to the club which will give me access to the wealth of knowledge in the members area (i hope!!). All i have to decide is what to treat myself too. . . . . . a 24v six or some new power tools!!

Any comments or advice will be gratefully recieved.

Thank you,

Jason

[mantasrme]

I’ve just about finished off a 24v installation in a manta for someone so can answer some of your questions.

The injection wiring is as simple to do as a c20xe system so there are only 5 wires to connect from the inj loom to the car loom. (I have the colours written down somewhere)

I can’t comment on the handling as I won’t get to drive it, its going back to the owner to fit a 400 kit and paint it before final build and getting it on the road.

However whilst working on it I can tell you that with uprated front springs that sit the crossmember at a good height, the extra weight out front of the crossmember has lifted the rear of the car!

We can get the ride height back level again but all that weight at the front end is certainly going to change the handling, its not going to handle like a race car without a lot of trick suspension setup, but for a daily driver you may not notice.

For stopping power we have gone for 284mm front discs and calibra turbo callipers, along with sierra callipers on a disc braked axle.

Currently there is only a brake bias valve in the system to balance the braking. This may need to change to a bias pedalbox but we will have to see when its on the road.

As to fitting the 24v there are a couple of options of how to do it.

Starting with gearboxes and assuming you want a manual box you can use the manta GT/e gearbox and this makes the job easier and far cheaper.

If you use the carlton/senator gearbox its physically much larger and requires the transmission tunnel top to be lifted 1” to get clearance (you apparently can fit the gearbox at an angle downwards, but this messes up your bonnet clearance and propshaft angle!)

Also you need a custom propshaft making. The rear of the carlton box has a 3 bolt flange that bolts to the prop with a large rubber bush/damper.

As the manta prop slides in/out of the manta box as the axle goes up and down we need to replace that with a sliding section of the propshaft.

Dunning and Fairbanks are a well known propshaft specialist and luckily only 15miles from me so I took the manta shaft and the carlton shaft along to them and explained what I needed to do.

The solution was a custom slip joint and machined adaptor that would be joined to the rear half of the manta prop, the adaptor would bolt to the output of the gearbox and their slip joint bolts to that, total cost was £150

You also need to re-do the gear lever linkage as it needs moving forward around 2” to come through the centre of the original hole in the tunnel top (assuming you put the engine as far back as possible)

The engine itself needs the mounts on the crossmember moving forward the same as the 12v does. I used manta GT/e mounts bolted to the block as the 24v ones are alloy and reach down a long way.

I tried the carlton rubbers first but the engine sat far too high for the bonnet to clear. I changed to 35mm thick V8 landrover mounts and shimmed under them a little to get the engine sat where I wanted it.

You need to get it low enough for the bonnet to clear but high enough that you can squeeze a sump between the crank and crossmember.

The sump is a huge alloy affair and needs a load chopping out of it and re-welding to clear the crossmember. Also the sump is very deep at the front and would sit 2” lower than the crossmember if we left it there.

So we also chopped the bottom off and put a wing out on the NS to regain capacity. Obviously this also meant we had to modify the oil pick up pipe to be shorter.

It was going to need modifying anyway as the chopping of the sump around the crossmember was in the way of where it originally ran.

I chopped the sump myself and made up a cardboard template then had the fabrication and welding done at a local machine shop, cost £145

The carlton alternator bracket also houses the power steering pump and is a huge alloy affair on the OS of the engine. This would sit in the chassis rail and clutter up the OS even more than it is.

So we moved it to the NS lower of the engine.

After being led the wrong way and hunting for a 12v bracket from a 6cyl, which turned out wouldn’t work at all

I made an adaptor bracket up and used a GT/e bracket and alternator with the carlton polly-v pulley (thanks to Steve for the pics of his)

For cooling I used a sierra radiator and cossie twin fans mounted under the nosecone between the chassis rail ends, with a pipe joiner mounted thermo switch to control them.

There are some pictures of the project on My Website and i have more to upload which i will try to do later on.

I’m sure there were some other challenges to fitting it but those were the main ones from memory.

To be honest I’m not keen on the engine in the manta, its just too heavy for the amount of power it gives. According to a website I found with engine weights the 6cyl engine weighs almost twice what the c20xe does

But then I’m after performance and handling from my cars

[monkeynuts]

thanks for that, it has given me more to think about. i've checked out shaun's 24v 400 and i must say cracking job on modifying that sump, and good bit of welding too. i Know these engines are heavy i've found info saying the xe is about 240lb and the six pot is 395lb so i know i'll be adding. brakes are going to be uprated anyway and i've already got uprated suspension on the back (fronts in progress!). this is never going to be a race car, just something i can drive to work and occasionally have a bit of fun with from time to time. i'm imagining more of muscle car type characteristics!!

i still want to know what they drive like?

[monzta]

Well i have driven both A and B series Manta´s with 12V straight 6´s (180hp goldtops) and they do tend to get nose heavy.

One trick is to put in 20mm longer front springs. That mean if you have a 40mm lowering kit on your car, front springs should be original. If you have the car 60mm lowered you should have 30 or 40mm springs in the front.

But more importantly there are things you can do that will put back some good balance to the car.

1. move the battery to the trunk.

2. mount lightweight front arches and hood (fibreglass).

3. remove all sheet metal parts under the front bumber (front panel etc).

Now you wont get the same balance as before, but it wil be drivable with no problems at all. I have done this to both the A series and the B series i have owned with 6 cyl conversion.

If you dont do the above the car will still be drivable. It will be very hard to drive. The most important thing is to make sure the front suspension can handle the extra weight (schocks and springs"!!!!=) Once drowe a Manta B 400 replika with a 3,0E and it flattened out, locking the front wheels and all i could do was pray... Luckely nothing happened, and the owner imidiatly made improvements to the front end..

[Kevin Abbott]

Last person i knew who had a six in their manta without pushing it back by doing major body mods as Ian Packer had done . Stuffed it into a motorway barrier.

I'll probably get hung out to dry by my comments but it makes the manta even more understeer than they normally do

[monkeynuts]

Last person i knew who had a six in their manta without pushing it back by doing major body mods as Ian Packer had done . Stuffed it into a motorway barrier.

I'll probably get hung out to dry by my comments but it makes the manta even more understeer than they normally do

all advice, wether encouraging or not, is still advice and i appreciate it.

[maher the hermit]

moved mine back a couple of inches just enough for the gearbox (which is a standard GTE box) to clear the tunnel with no mods and it drives ok. suspension is hard as a rock tho and no antiroll bar fitted either ive had it to 120 gets a bit larey on the bends so wouldnt push my luck. I use it or did as its sorned at the mo just for the 6 pot noise and shear acceleration. Its fittted with wilwood 4 pot calipers and to be honest there crap so will have to invest in a bigger brake setup as and when funds decide....

[monkeynuts]

moved mine back a couple of inches just enough for the gearbox (which is a standard GTE box) to clear the tunnel with no mods and it drives ok. suspension is hard as a rock tho and no antiroll bar fitted either ive had it to 120 gets a bit larey on the bends so wouldnt push my luck. I use it or did as its sorned at the mo just for the 6 pot noise and shear acceleration. Its fittted with wilwood 4 pot calipers and to be honest there crap so will have to invest in a bigger brake setup as and when funds decide....

Thanks for the reply,

but now i have more questions!

where abouts did you fit the engine mounts on the cross member, original holes or modified?

did you shorten the prop and/or move the gearstick back?

what suspension were you running?

does the 4 pot calipers fit over the standard discs?

I had planned a vauxhall set up calibra calipers/284mm vented discs on the front and possibly a mk4 astra rear disc conversion as suggested by other members on here. but would like to see how the drums work out first.

[mantadoc]

Last person i knew who had a six in their manta without pushing it back by doing major body mods as Ian Packer had done . Stuffed it into a motorway barrier.

I'll probably get hung out to dry by my comments but it makes the manta even more understeer than they normally do

We've always fitted 400lb front coils and not had any problems if you set it up to be rear out.

Some of my old ramblings for 12V will answer some questions and probably confuse others

Basically dead easy, same as Manta. Use gearbox and prop that you would in a Manta.

First make a choice are you going to lower the Anti-roll bar and shorten the drop links, thus making a car you can't drive hard without ripping the ARB mounts out of the rails. Not enough length in the links to allow for the track change so as it rolls it works the ARB mounts laft and right.

Or....

Make a sump and pickup pipe?

Measure from back of block to engine mount bolt hole on a 4 cyl, next do it for a 6 cyl. That's the dimension you need to bring the bolt holes on the crossmember that far forward. Then you can use Manta CIH mounts on the engine, 3.0 monza mounts on modified crossmember.

Use the monza mounts that look like the 4 cyl ones but longer.

If you have the later round LH mount lose it and use the solid type (like right hand)

Hint standard engine mount plates on crossmember have an edge on top that sticks up, bend it onto the crossmember and weld it too it. Otherwise the standard steel mounts on the crossmember will shift with the weight.

Then make 4mm plate extensions that are bolted to original mount hole on crossmember and gusseted to the crossmember and welsed too. Must be rigid and strong but not too high. or bonnet probs later.

it's a 12V yes?

Dump the front pulley for a Manta one, single V instead of triple gains space.

Dump water pump for early one so it has 4 bolt flange so gain space and either use fixed fan (slim and cheap) or electric.

Volume out sump and design tank hint nearer sump is to crank over crossmember area lower you can sling it. I did this by putting sunp on a flat surface upside down work out lowest height over back big end journal. Cut a block of wood to that height. Hold a scribe flay on the wood and slide the block around the sump scratching the line of what to remove.

Bored now

Blah blah move rad crossmember

Do exhaust as either close 2 into 1 Y

Or get some joints out of scrap exhausts and 1pipe goes from manifold to a 2 into 1 under engine (space between crossmember and bellhousing is ideal) other pipe runs other side of steering column, but because of joints easy to dismantle.

First time I did this we pulled 2.0 Fri PM and he drove it to work Sunday.

No warranty implied or given [] New shorter posts to minimise global warming by conserving ones and zeros [] The uncivilized end of the North West []

<font size="5">No warranty of any kind implied or given etc, this is just how I've done it a couple of times and not a recomendation of any kind.</font id="size5">

Still had hard copy

Small

Triangle, sticky out edge on right and edge on bottom fold over and welded up corners to add rigidity. That slight slope on the edge of the right sticky out bit is not an accident.

Remember what I said earlier about the tag on the engine mount piece that is welded to the crossmember being tapped over to touch the crossmember where it comes up..... don't forget that.

The template is turned over to make the L/H mount.

Another smaller hole is required near the mount hole to allow the tang of the mount to engage.

This bracket was bolted to the crossmember through the rubber mount fixing hole and welded too. The actual steel may have evolved since the template but only in the area of the triangle.

The crossmember is the same regardless of L/H mount design, the L/H engine mount rubber and mount on engine are what changes. This brackett was designed to be used with the solid Monza mounts (they will fit standard Manta R/H side and L/H for older cars that don't have the round mount. However, as the Crossmember bit is the same it may well work for the round mount too, although I wouldn't advise letting a mount for the 2.0 with the weight of the 3.0

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Small

Circle nearest bottom left represents anti-roll bar, circle to the right of it represents steering rack.

Top left of pic shows original sump cut to 9 1/2 cm, this was on Ant's car. I think on John's we took it down to 7 cm or 7.5 cm or something but should have cut it a little higher maybe as it made more work cutting and shutting the pickup pipe. You want it close to the big ends without the possibility of touching. This allows you to tilt engine down more to change box really easy.

Baffle sump tank, just flat pieces of steel running from front to back about an inch os so above the bottom to stop it sloshing side to side. work out where the pickup pipe strainer is before ou weld the ones nearer the middle in.

This tank design avoids moving the ARB and the issues that brings.

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<font size="4">Back when I did this for Ant he got an engine for £100 and all the rest of the stuff cost under £100, so for less than £200 he got about 170BHP back when PMCs 145BHP kit was over £600</font id="size4">

Spot the extra scoop, on this one the water way in the throttle body rubbed the bonnet so a hole was cut and the scoop added, anyone guess what it was off?

The bonnet internals were cut away in the required area. We didn't need a scoop on the second one and as far as I remember the mount design was the same.

Note where the fixed fan sits, I cut a slot in the mesh in the bonnet centre triangle, as per the one in Hooten park to aid in lifting the bonnet, of course with the 3.0 running it was finger tickling good as I soon found out.

The engine bas wasn't pretty before we started, anything not tidy I didn't touch []

For this car we used a Carlton rad, some 2" by 4mm strip was used to fold a U shape, the sides of which touched / were welded to the inner edges of the chassis rails. It was a sloped nose carlton. Boxes were welded to the bottom of the U to hold the Carlton rad bottom mounts. Can't remember the top.

The rad crossmember was removed after some box section was welded between the front of the chassis rails to maintain structural integrity.

The second car had a fibreglass 4 slot, so with this removed we mounted a Sierra 1.6 rad between the rails after notching them, mounting was done by 4 mini exhaust bobbin mounts. Rad crossmember was again removed but this time replaced by box section that sat behind the rad.

No warranty implied or given [] New shorter posts to minimise global warming by conserving ones and zeros [] The uncivilized end of the North West []

This is a mates car about 10 years ago.

As it arrived, bumper bent from muppet towing it. Apparently it broke down on its way to be sprayed and the owner couldn't get the bonnet open so sold it.

Easily opened with the old "push the bracket back" trick.

I did open it before it was bought.

Worth the £200 for the wheels and lights I think. Compomotive 3 piece.

Fibreglass nose. Not a preference but ok.

Stripped front and raiator crossmember roughed out.

Rad cross member to chassis rails tidied.

Anti-roll bar left in standard position.

Engine in, big wing sump behind anti-roll bar.

Chassis rail repaired where rusty and notched to fit a 1.6 Sierra rad that way lying around.

Mini bobbin exhaust mounts from the original mini x4 for the rad mounts.

Rad in place. There is a box section welded in between the chassis rails between it. Very important to tie the rails together after removing the original.

You can fit a rad in this position with a steel nose, you just have to cut out the support bit.

[maher the hermit]

I think my front coil springs are 400 pounders as well?? the wilwood 4pots are fitted with vented carlton discs but like i say there crap!!! dont forget the 24v engine is lighter than the 12v due to having an alloy head

And yes had to shorten the prop, move the gearstick linkage forward and alter the front engine mounts. I used a volvo 740 rad on mine that was the best one i found when searching my local scrappy with tape measure in hand and works a treat.....

[monzta]

Lots of good info here as well

http://www.manta-b.de/

I know this guy and met him at Blitz hitz some years back. His manta ran a 4,0 litre Mantzel powerhouse with 272bhp and that car ran smooth. It could have been factory build.

As i said, it is a question of doing it the right way, making sure the car can´t flat-out is a matter of life and death.!!!

But if this build is done right its a cheap, and very nice conversion and you wont be dissapointed. Yes it will oversteer, but you can as i also said re-adjust the weight by moving some things into the rear, and removing some sheet metal parts from the front and replacing it with fibreglass parts.

[mantadoc]

Yes it will oversteer, but you can as i also said re-adjust the weight by moving some things into the rear, and removing some sheet metal parts from the front and replacing it with fibreglass parts.

Mantas can understeer on any given day. The black one was used as a daily drive in all weathers for about 3 years before it was sold on.

The difference you are talking about by going to fibreglass panels, moving the battery etc is less of a change in balance than filling the petrol tank, lot of money for little benefit.

For example the weight variation between a full and empty petrol tank is 79lbs, more than two average car batteries.

Of course a full tank of gas slows the car down, and fitting the battery further back in the boot would give a marginal advantage over the equivalent weight where the tank is because of the extra distance from the front axle which would be the effective fulcrum for balancing the nose.

The point is, these things only pay off in a serious performance or competition car and if building one of those a straight 6 cast iron lump is unlikely to be a choice.

The straight 6 is an opportunistic or relaxed high speed cruiser choice where a car can still be surprisingly nimble for it's weight but "bang for the buck" is probably the biggest factor. In many cases, especially if buying fibre panels new you would then be in the price range of a C20XE.

[manta3000]

shit,now u have got me wondering,at moment in middle of taking apart my gte,400 kit is just about off,1 arch left, a b***ard to remove

it also has a 24 v installed,not by me,did drive briefly very heavy steering,no p/steering fitted?,when i bought it,but i had previously owned it for 8 yrs and just wanted it back,

450mls round trip to get back home. car is getting stripped back to bare +new kit fitted,going to do hopefully everything as it"ll be summer only car.

thing is do i stick with 24v setup,or go 16 v. i run a 24v gsi carlton and have owned for 8yrs,brilliant motor

bits like original rad hangers have been removed,but not in a hurry,but want to make right choice,your thoughts?

i remember even in standard my manta being an excellent car,dont want wife,or me to be dissapointed when it goes back on road.

cheers colin

[monzta]

shit,now u have got me wondering,at moment in middle of taking apart my gte,400 kit is just about off,1 arch left, a b***ard to remove

it also has a 24 v installed,not by me,did drive briefly very heavy steering,no p/steering fitted?,when i bought it,but i had previously owned it for 8 yrs and just wanted it back,

450mls round trip to get back home. car is getting stripped back to bare +new kit fitted,going to do hopefully everything as it"ll be summer only car.

thing is do i stick with 24v setup,or go 16 v. i run a 24v gsi carlton and have owned for 8yrs,brilliant motor

bits like original rad hangers have been removed,but not in a hurry,but want to make right choice,your thoughts?

i remember even in standard my manta being an excellent car,dont want wife,or me to be dissapointed when it goes back on road.

cheers colin

I would definatly go for the 24v as this is in the car allready. It will set you back some considerable amount of dough to install a good 16V and then tune it untill it reaches 200bhp as the 24V has standard!

As i said there are still things that can be done about the weight distribution. And i dont care what anyone says, it DOES matter. Yes yes moving 8kg of battery might not be that much (but you dont remove it you relocate it and there is a big difference. Moving 8kg of battery from the nose and placing it in the trunk gives you a 16kg lighter nose!!!!) and alot of small stuff all adds up, and i shit you not, there is a reason that the TE2800 A series had this done and that car actually competed in rally racing! They actually managed to put the cars weight distribution very close to the original GT/E 4 cyl again by making a fibre glass nose and relocate the battery and other small stuff to the trunk. The TE2800 engine was not moved backwards.

I am not saying that you can get a perfect weight distribution when using a straight 6. But you can do something about it and get a car that actually runs pretty nice after all. And yes a Manta B with a straight 6 is better in a straight line

If you want to use the car for trackdays, go with a 16V, if you want a cruise that can roar and go pretty fast i´d stick with the 24v but hey its all up to you

[monkeynuts]

definately leaning towards the 24v choice. i'm still looking for a coupe in order to do a 400r which will be running a calibra turbo lump (c20let). i dont want to do nearly the same thing twice as i've only got enough of the usual bits for one 16v conversion. so, as long as the the price is right i'll be getting the 24v for my daily runner. if the weights all off i'll throw a couple of paving slabs in the back and add some nos to compensate!!!!

[manta3000]

as for straight line speed,before manta 24v was taken off road,it just walked away from my gsi 24v,and that doesnt happen very often

basically car will be used in summer,but i aint going to track it ,cause

1)wife wont let me

2)if i pranged it,we wont go into that

so i think i"ll stick with 24v,most of metal will be cut away under h/light area anyway,well whats left,as i dont think need any of it?

colin

[mantadoc]

Yes yes moving 8kg of battery might not be that much (but you dont remove it you relocate it and there is a big difference. Moving 8kg of battery from the nose and placing it in the trunk gives you a 16kg lighter nose

Not quite but the -8 and +8 gives a variance of 16KG so will affect the centre of gravity like moving that much, but 11 gallons @ 7.2lbs per gal. = 79.2lbs or 36KG variation from tanking up. That's high enough up to raise the centre of gravity too. A few people notice the differnce in acceleration, very very few notice it in handling.

there is a reason that the TE2800 A series had this done and that car actually competed in rally racing! They actually managed to put the cars weight distribution very close to the original GT/E 4 cyl again by making a fibre glass nose and relocate the battery and other small stuff to the trunk.

Yes there is a reason......... to make it a serious competition car, and probably fitted to the road car for homologation purposes, so backing up my point.

The straight 6 makes a fantastic grand tourer that can really pick up it's heels in a Manta B or a great opportunistic choice for bang per buck but spending large amounts of time or money to try and make it handle like a GTE is a great technical exercise but not really economical or at least would very likely not add up on a spread sheet.

Feel free to disagree it it only an opinion based on experience and value for money. At this point I will play the "I dont care what anyone says" card.

Ultimately it is for the original poster to weigh opinions as it's his money to spend

[monkeynuts]

well, theres alot of info here to absorb and i have plenty of time to weigh up the pros and cons.

The car with the 24v in it has been layed up for some time and isn't going anywhere. strangely enough i bumped into a former colleague of mine (this weekend) from the local vauxhall dealership we used to work in and, when mentioned, he remembered the blue senator immediately. he was charged with maintaining the vehicle for many years and commented on how good the engine was and how few miles it had covered over its life. both, good points to consider.

The manta is set to one side for now as its time to start work on my vw camper. after being laid up over the winter it needs a good going over for the Mot and at least one patch of welding that i know of. I've only just gutted the interior ready for a refit as well so thats another task to add to the list.

thank you to those that have left comments