Jump to content

Manta c30se conversion (Cornwall)


Recommended Posts

Hello boys and girls, can anyone help me with basic steps to fit a c30se into my manta b gte coupe?? Old engine and box gone so need info on converting the straight 6 auto to manual (flywheels? spigot bearings? starters?) Will i need to modify, the sump, engine mounts, bulk head, rad mounts etc? Can anyone enlighten me? Anyone local done the job? Anyone know anything I've not thought of or can you help with parts?

Many thanks guys!!!! :thumbup

Link to comment
Share on other sites

All related to 12 V so if your talking 24 obviously from the block upwards this is different... oh and front casing too.

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.


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 [:D] New shorter posts to minimise global warming by conserving ones and zeros [:D] The uncivilized end of the North West [:(]

I was looking for a sketch of the plans n stuff, scanned in years ago, looks like it got binned.

One nice benefit is as the mounts are farther forward the gearbox will swing down enought to easily change it complete with lever.

Don't be tempted to put plates on the block to move the mounts 1 cyl back to avoid modifying the crossmember as there is then enough engine (over half) in front of the pivot point.

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.id="size5">

Still had hard copy



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

Large: http://www.atcy66.dsl.pipex.com/misc/emount.jpg



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.

Large: http://www.atcy66.dsl.pipex.com/misc/plans.jpg

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 £600id="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 [:D]

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 [:D] New shorter posts to minimise global warming by conserving ones and zeros [:D] The uncivilized end of the North West [:(]

If you've got a GTE ahh it's a cav, well if your cav is a 4 speed that will fit, as will the flywheel etc. Standard GTE clutch lasts 10k miles or two good standing starts, that is a subsequent expense not included in the £200.

I would convert to 5 speed first first as having the box securely mounted in the right place is key to keeping the back face of the block lined up with the gearbox in the original place, if you want to put it together with standard parts. Either that or get it bolted in on your existing box sort the mounts etc, then change the box if your using something that requires custom prop or box mounts.

If you go for an Auto all Manta throttle pedals (AFAIK) have the mount for the kickdown on, but not the tube in the bulkhead next to the throttle cable hole.

You may need a needle roller bearing if converting an auto engine to take manual box, at least one I've come across already had the roller behind the plug.

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

Have a look when you have them both out, or maybe someone else on here knows? Most of that kind of stuff seems to have generic type numbers.

I've swapped flywheels across models over the years so pretty sure the end of all cranks is the same, which would mean that if they fit any flywheel they will fit any CIH drive plate. I would hope the 3.0 drive plate is tougher, and if the box was the same externally i.e mounts and fits your prop I would use the 3.0 stuff.

And yep, the back face of the 6cyl CIH block is the same as the 4cyl CIH, gearboxes will fit.

As your cav won't have EFI you will have some plumbing and wiring to do unless you found something with carbs. Bright side if you are using the older L or LE Jetronic engines it plumbs in the same as the Manta GTE stuff. Just watch out for the external ballast resistors on the older type and the odd EGR valve which adds to the complexity of vacuum pipes.

Don't let the above paragraph bother you. Ideally you are looking for an engine where all the EFI stuff looks like Manta GTE just with two extra injectors and a slightly different auxiliary air bypass valve.

Found a pic of sump


The engine above was for the second car..... it went to Ireland too


No warranty implied or given [:D] New shorter posts to minimise global warming by conserving ones and zeros [:D] 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.





Link to comment
Share on other sites

Erm yeah. Is it worth it?!!!! Nah seriously I figure that he sound of a big six, and the fact that the 24v is a good 50 brake more than the XE (which was the other option), its gotta be the way to go! Gonna be fun. Done a few conversions in the past but still a novice! Can't wait for the lighter evenings!!! :thumbup

Link to comment
Share on other sites

Hello mate

I found it quite simple to fit the engine, i use the 2.0 litre c.i.h gearbox and flywheel (this needs to be modified to have 8 bolts instead of 6 to mount to engine). I bought a helix clutch kit for a manta 400 from demon tweeks which is strong enough to cope ( flywheel needs 6 holes for this to mount on to).

The bulkhead doesnt need cutting, i cut the lip off of the front chassis crossmember as the engine sits quite close. I used the 24v radiator and a kenlowe blow thru fan which is mounted under the nosecone. I removed the nosecone and bolted it back on, this makes fitting the engine much easier. The front valance needs removing as this gets in the way of the rad (also loses weight off the front).

I havnt modified the sump or the subframe although it does sit close. I put the c.i.h engine mounts on the engine and welded 3mm plate both sides of the subframe which is supported with gussets. The center support frame in the bonnet needs removing as this fouls the inlet manifold. I bought a fibreglass bonnet with a sheet of carbonfibre bonded underneath to reinforce it and only have the outer frame. Again, this bonnet along with fibreglass wings has lost alot of weight off the front.

The suspension needs uprating, i use bilstein shocks with 400lb springs which works well. Its worth uprating the brakes also. I lowered the anti roll bar although i might remove it as its not adviseable.

The exhaust pipe was the fun part, i gave the car to janspeed as they new what they were doing and done a better job than i could ever do. It cost me £650 but its got a lifetime guarantee, its 2.5 inch with 2 silencers.

These are the basics of fitting the engine, it just leaves the wiring(which is easy when you know how ), fuel lines and the coolant hoses.

Hope this has helped mate

Oh, and it it is worth it, best car ive driven

Link to comment
Share on other sites

  • 4 years later...

If you become a full member you'll find a wealth of info on here that you can't currently access. However in this case if you were to look one comment above you will find your answer. :)

Those of us with 6cyl conversions tend toward 400lb/in on the fronts as a decent starting point. Obviously you then work out what free length you need for your particular setup and personal ride height preference.

Got any more info on your project? Always interested in other people's 6pot conversions.

Link to comment
Share on other sites

^ what're the photos in aid of cop?

Don't like to be critical, but seeing stubs of wire in a weld on a fairly critical bit like an engine mount (along with some holes where it isn't welded) does flag a slight concern.

Those engine mounts also look to be pretty far forward, have you cut the sump in that picture?

Did you need to cut the front crossmember to fit the rad in like that?

Sorry for so many questions, just interested, as I have done it in the way I reckon works well which retains the front crossmember and fits a decent rad and twin electric fan setup. (the mk1 cav does not have a nice flat fronted bumper with a lower section to hide a tall senator rad like that.)

Link to comment
Share on other sites

Hi Jason photos are for the chap who is asking about the mods involved .some members choose to do there mods differently. questions for welding box section completely welded in before gussets fitted as photo shows before. .The mig welder played up on fitting the plate so I left it. I believe 1 inch off weld hold a ton. on regards to mods I choose to fit the engine the old way as Ive done in the past 1990s . Front cross member is removed and a box section is welded across the front chassis rails .no mods to the sump as the front bowl meets up to the steering rack. Radiators used in the past is a gte astra mk 2 or 1600 astra mk2 hard to get these . II found springs a problem as the front sags with 400ib , bigger peter loydd rallying.groupfotosbmwmanta050.jpg

  • Like 1
Link to comment
Share on other sites

Lovely looking manta, and I wasn't having a dig. Just interested to see :) - I reckon the further back you can get the engine the better, I had to do a fair bit of chopping to get the 12v sump nicer fitment to the crossmember. I chose to make a big wing sump in the end for two reasons a) I could get the engine a little further back and B) the sump was no longer the lowest point of the car (it was very low and vulnerable before). Also, you aren't wrong in that the rule of thumb is that 1 inch of weld will hold a ton, however that is statically, a cantilever exposed to dynamic forces is a very different system indeed.


Link to comment
Share on other sites

I've removed it and compensated with appropriate springs and dampers. I much prefer to avoid anti-roll bars on the front of cars if I can anyway, usually manufacturers fit them so that the car rides comfortably over bumpy stuff with a relatively softer spring and yet still feels planted in the corners because it doesn't roll as much... I'd rather just set it up to handle as best it can without too much concern for ride comfort in the first instance. If I find that I yearn for an anti-roll bar to tune the suspension further then I will build my own setup with some actual calculation involved rather than simply chucking the standard one on. (When I first bought the car someone had shimmed the ARB front mounts - I'd have bet it would only need a week or so of use before it sheared a drop link)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...