2.7. Head work, 'fast road' cam and twin carbs? Worth it?

[captainsmelly]

Well obviously not actually worth the time or the expense, or the constant fettling and tinkering required to keep the carbs balanced and tuned... but ..!

My car's due a timing belt. Swapping a head at the same time isn't much more work. 2nd hand head from ebay, here or breakers a few hundred quid, no need to change valves (doesn't look like you can get any bigger in there anyway) skimmed to raise compression, get it ported and gas flowed by someone sensible and a custom regrind of the cam - no more lift of course - but more sharper profile, more duration and overlap. Make up a manifold to stick a pair of 45's on, change the fuel pump and band it all on. Sell the complete original head, and all the now defunct fuel and air delivery gubbins should recoup most of the cost.

More top end and a lovely howling barking induction system for maybe £1500 net?

Is it worth it though? Is there any power to be released with a less civilized cam and intake system?

As to why I don't just buy a turbo, or more preferably an s2, it mostly comes down to insurance. With all these mods declared I will be paying 3-4 hundred pa. Standard turbo/s2 minimum £1200! Plus the pleasure of owning a one off, a real sleeper that doesn't reveal itself until WOT.

Anyone carried out similar work before? Can't find very much on google, except for americans stuffing small block chevy's into their 944's, and I'm already in the process of chucking one into a capri right now haha

Or should I just not bother?

 

[Lowtimer]

I ma not against performance modification on principle - far from it - but yes, I think it's waste of time, effort and money ditching the 944 injection system for a carb system that can only be inferior for road use.

The head and cam work, may, if you have it done by a really good and experienced person, yield some increase in top-end power at the expense of bottom end, but only if you raise the rev limit. However, your injection system is already better than twin carbs and can easily be uprated to increase top-end fuelling by changing the fuel pressure regulator and/or injectors, and giving the thing a custom remap.

If you can get an insurance quote for a considerably modified 2.7 Lux that is £900 cheaper than you can get for a standard S2, then I can see why you might think about it, but I would be genuinely amazed if that were the case. I will admit that the insurance industry has amazed me before with its decision-making, so maybe you are right.

Incidentally, if you did go to carbs, and wanted a substantial increase over the stock 165 bhp I would have thought twin 45s would be too restrictive. 48s at least, surely. Twin 45s is more a 150 hp 2.1 Pinto sort of setup.

 

[GPF]

I really can't see the point of ditching the fuel injection and going to carbs. I can't see that you would get any performance gains, and you will make a shed load of work for yourself in the process.

Headwork and cam would be interesting to do, but again not sure of the benefit. You may also need to get control of your fuel if you succed in inmproving the airflow significantly.

You can also , of course, change the induction without going to carbs.

 

[captainsmelly]

Good point on the carb sizes, yes I forgot the 2.7 is rather larger than many 2.0 engines!

Insurance did baffle me. Its on a classic policy now, for peanuts really, and try as I could (and I did!) s2/turbo are actually 10 times the cost. I've asked the merkats to find my quotes on modded policy and after a quick search there are a couple of very reasonably priced policies popping up. Restricted mileage of course, but as this is pretty much a 3rd car that does not concern me.

Regarding remaps, the previous owner fitted a piggy back style chip, apparently it ran like shit if at all so he quickly reverted back to standard. I've got it laying around somewhere.

 

[captainsmelly]

ORIGINAL: GPF

I really can't see the point of ditching the fuel injection and going to carbs. I can't see that you would get any performance gains, and you will make a shed load of work for yourself in the process.

Headwork and cam would be interesting to do, but again not sure of the benefit. You may also need to get control of your fuel if you succed in inmproving the airflow significantly.

You can also , of course, change the induction without going to carbs.

Headwork and cam would indeed be quite fun, not done it before so I am curious. Of course carbs on their own would be a backwards step, but I didn't know if they'd be less restrictive than the factory design combined with the top end work.

I have pondered throttle bodies, with a standalone management system I reckon that could be very successful but would require a pretty hefty investment.

Is there any knowledge on the state of tune of a standard cam?

 

[barks944]

I am working in an upgrade for the 944 that would give the benefits of standalone but without most of the expense or hassle. Check out my 944 DME project page. I might require some adventurous soles for the later stages of testing.

http://www.porscheclubgbforum.com/tm.asp?m=581016

 

[Lowtimer]

The standard cam is optimised for the standard rev range, obviously. If you want to move the midrange and top end up 1000 RPM you will need a wilder cam, but if combined with less restrictive inlet and exhaust, extra fuelling, and possibly a bit of head work, then you ought to get more peak BHP at higher RPM, just as with anything else tuned that way.

The Turbo cam is slightly milder, I gather.

 

[barks944]

The turbo cam has a little less lift (1mm?) and less duration on the exhaust than the late lux cam. All the 944 cams are very soft, basically no overlap.

 

[Lowtimer]

Perhaps worth bearing in mind that when the factory made its own high-rev screamer out of the 2.5 Lux, the 944S, which used a 16v head with wilder cams, and had a nominal 190 bhp, the results on the road and against the clock were generally somewhat disappointing.

 

[barks944]

I wouldn't be put off by that. The Milledge guy in the states claims 15bhp over the standard cam without requiring an increase in the rev limit. I can easily believe a chip adds 10bhp to the 944 2.5 8v and must add some decent area under the curve. Sort the intake out and remove the AFM. I'm not sure what the exhaust is like but maybe that could be improved on. You should see around 180-190 is from the 8v engines I rekon and not loose too much lower down. I think one of the chaps over in finland (Olli) was saying that they get 190bhp figures.

 

[zcacogp]

Interesting sounding project, but bear in mind that Porsche knew a thing or two about building engines when they made your 2.7, and it wasn't designed on the back of a fag packet. What are the odds that some guy with a dreml and possibly a flowbench would be able to do a significantly much better job? On more mass-market cars there is the argument that improvements are easy to come by as the heads were made for the lowest possible price and a small amount of re-work (removing casting defects etc) would produce good improvement, but that doesn't really apply to Porsche engines.

OK, I'm playing devils' advocate, but I have heard a number of stores about disappointed customers who have shelled out quite a lot for a cylinder head flow job. Don't become one of them.


Oli.

 

[barks944]

I'm having my head worked on atm and the guy just looked at it and said that he could smooth it out a bit here and there and open it up about around the valve seat but there wasn't a great deal to do but there are some improvements. As you say Porsche know how to design an engine, but also bear in mind they have a marketing plan so the specification they design an engine too is for a specific torque curve which is not necessarily the best possible they could achieve. I'm sure for marketing reasons they deliberately kept the performance of the 944 models away from the 911's of the time.

 

[djaychela]

On the head work front, although it is a Porsche, it was a mass-produced engine, and the tooling of the time couldn't produce heads as accurately and well finished as today's mass market engines nor one that has been fettled well by someone who knows what they're doing.

As for carbs, I really think that's a backwards step - if you're having that sort of work done, get a proper mapped injection/ignition setup and you'll get the maximum power potential out of the engine everywhere. Carbs will always be a compromise, and involve a lot more messing about once it's complete as well.

 

[Lizard]

I would drop the finnish fella a mail ref what they do to the 8vs as they have got good gains. I'd potentaily be interested in cam & headwork also.

I've def got good gains out on VWs over the years, head mods alone have gained real calibrated engine dyno 12-15bhp gains, that is 16v heads tho where rpm is higher & flow is important.

I have chatted to EMC ref power gains on 2.58v, they never mentioned cam swaps tho, but even tho they have hit 190 on 2.5s its a lot of work & money to achive & terrible mpg.

How about an engine transplant tho? I have classic insurance on one of my track toys & as long as the engine was from another model in the range it was fine, provided the brakes were also used, im 200cc bigger & 30-40bhp & I still pay peanuts. Hence might just be easiest to shove complete s2 set up in there, v cheap full engine/box set up on ebay now.

 

[djaychela]

ORIGINAL: barks944

I am working in an upgrade for the 944 that would give the benefits of standalone but without most of the expense or hassle. Check out my 944 DME project page. I might require some adventurous soles for the later stages of testing.

I'd be game for that if I still have my 944 (looks dicey at the moment due to work issues), I've mapped my rally car engine and also had a couple of Megasquirt setups in the past.

 

[barks944]

Would batch injection mean that with an overlapped cam you might loose a lot of fuel down the exhaust? I wonder if this could be why it gets low MPG in a tuned state.

 

[GPF]

ORIGINAL: barks944

Would batch injection mean that with an overlapped cam you might loose a lot of fuel down the exhaust?

Good question! But that late NA cam has a little overlap doesn't it?

By the way, your inbox is full so I can't reply to your pm.....[]

 

[barks944]

I've got a graph of the cam profiles for the models at home. I'll dig it out and post a link.

Theres some space in my inbox now .

 

[captainsmelly]

I have pondered engine swaps - reckon an alfa v6 lifted straight out of a 75 would do a nice job. It's already intended for a transaxle layout and although it's a fair bit wider than the 4 pot it looks like it could drop in without rearranging the engine bay too much. It's a little bit more powerful than the porsche lump but it's mostly about the noise.
But I don't want to take out a perfectly good motor just to replace it with a slightly better motor, and really want to keep the car as original as possible, just rework the character slightly more to my tastes.

@ barks944 your chip sounds very interesting. Fascinating project you've taken on, however the details have gone right over my head! That's very clever stuff you're doing, far beyond me to even comprehend! When's it likely to be useable?

I have looked at the insides of 2.7 heads from online pictures, they do seem very well engineered indeed with only a small scope for improvement that I can see. The main purpose of the head job would be to raise compression, keeping it on the safe side as this is a road car not a race car, but still a good bit higher than the conservative factory level. After all this car covers low mileage mostly for fun.

With the camshaft, I'd like to see how the profiles stack up. Sounds like there's no overlap at all? Would make sense with batch injection. So maybe a megasquirt fuelling setup, retaining standard afm and intake (maybe clean up the insides) custom cam ground for overlap would be cheaper and better solution?

The manifold looks very well set up to my (untrained) eye. How well does the rest of the exhaust system flow? It's rather quiet and I really don't want to go down the 4" backbox route again (I was young ok) but maybe replace the center box with plain tubing would help?

To clarify then, carbs are a no no. Throttle bodies are cheaper than I thought though, I'm seeing full kits for 1600 - 2000 quid, including ecu, injectors, fuel rail and sensors. The largest I can find in catalogues are 45mm but I'm sure they can swap to larger sizes with ease, jenvey build them up to 50mm.

 

[JamesO]

If you go to the trouble of megasquirt, ditch the AFM its not needed. I modded an airbox so it had a nice round pipe straight to the rubber boot, it looked pretty much stock.
Megasquirt can be made to work with the rest of the sensors (i have done it on a 2.7), the only tricky bits are the crank sensors and idle valve. I have the (rough) write up of the project somewhere.