Conversion of 1.7ie to a 1.7 carby with mech tappets

33gold · #1 (**permalink**) 05-04-2008, 10:13 PM

I thought I'd start a thread as when I started this project I really struggled to get info, the local Alfa specialist had never known anyone do this.

The issues so far:

I.e heads have combution chamber, 1.5/ early 1.7 do not.

Valves need to be longer than the i.e. but slightly shorter than the 1.5 twin carby / early 1.7 carbie - solution grind them back as the collets/clearance are still OK.

compression is lower on i.e (9.0) versus 9.5 on carby (so you assume as there is a dished piston that you can reface head by a fair deal?

I found out that with 300 degree cams the valve hits the piston (I was testing with some clay on the pistons) as the duration means that at TDC on the exhaust/inlet phase is quite large - solution make a recess in the piston for the valves; I have gone as large as I safetly can before I get to the first ring groove. Now need to cc the head and piston to work out compression and calculate how much to take off the head - I have about 3mm clearance.

Does anyone know how much rod stretch/piston expansion you are likely to get so I can take this into account?

roban · #2 (**permalink**) 05-04-2008, 10:31 PM

If you check the valve to piston clearance without the head gasket, head directly to the block, this will give you a big enough clearance when the engine is assembled. Gaskets are approximately 1.2mm thick when torqued down. With boxer engines it is normal to have the block decked, not remove material from the head. You may find that you will need larger diameter cam belt tensioner to compensate for the material that has been removed from the head or block, depending on which way you deal with this situation.

Good luck with the project.
Bob

33gold · #3 (**permalink**) 05-05-2008, 05:29 AM

Thanks m8, the piston at tdc is inline with the top of the block, I have checked squareness of the block but not had it decked at right angles to pistons (I think that's what you mean) due to cost. I had no gasket in to allow for more tolerance when assembling. This car is a low cost club racer destined for hillclimb and sprints (less than 3 minute races timed against the clock) so small budget stuff. I will work out what compression ratio I can get without domed pistons (again limited budget). I just assumed that as the i.e.'s pistons didn't top out at tdc as the compression is lower than carbies. I'll use the gasket thickness as the rod stretch/piston expansion.

roban · #4 (**permalink**) 05-05-2008, 04:59 PM

If you are looking for an alternate piston than an Alfa you can use Nissan L28+1mm oversize pistons. They have small dish in the top and depending on the valve diameter on the inlet side, you may not have to releive the piston. these pistons are also lighter and less expensive than Alfa pistons. Pistons fit an 87mm dia. bore. Gudgeon pin is the same dia. and lighter than the Alfa pin. When i mentioned decking the block, which is just machining it, I think this is preferred because if you take 3mm off the head you could be getting really close to the water jacket at certain places on the head. The 1.5 heads seem to have enough material around the combustion chamber area to allow for 3.5mm of material to be machined out. The attached photo is of a 1.5 head of which I have done a couple without a problem. Just keep experimenting, there are lots of gains to be had from these icrediable little engines. Bob

PSk · #5 (**permalink**) 05-05-2008, 06:37 PM

Yes you do not want to take meat of the head as that defeats the considerable advantage of running the later "combustion chamber in the heads" heads.

Take it off the block and run flatter pistons (thus lighter). You can only take so much off the block also so be careful.
Pete

33gold · #6 (**permalink**) 05-05-2008, 10:18 PM

Bearing this in mind I may run a lower compression and consider this as a mod down the track (just bought Alfa piston rings). Thanks for the info.

Spooty22 · #7 (**permalink**) 05-06-2008, 06:33 AM

Hi,

If you are ditching the i.e. gear, would you be willing to sell your old lambda sensor, with the harness and plug? I really need one.

Thanks

33gold · #8 (**permalink**) 05-06-2008, 09:49 PM

I only bought the engine, so I only have injection parts attached to that. No manifolds etc. Sorry.

tukilevu · #9 (**permalink**) 05-16-2008, 02:49 AM

Just out of interest, what is the difference in the heads between a carburettored model and an IE? My son recently bought a 33 which was sold as an early model 1.7ti but turned out to have a 1.5 motor. We have a 1.7IE motor and gearbox which we could put in and were considering a few options, one of which was to put carbies on it. The other option is to just drop the 1.7 IE motor in as it is but of course that will mean some mods to the wiring harness to incorporate the injection. Any thoughts on the best way to go?

Don't mean to hi-jack the thread, but this is the only thread that I could find that was even remotely close to what we were considering.

33gold · #10 (**permalink**) 05-16-2008, 06:57 PM

The i.e. heads have a combustion chamber as well as dished pistons, early carby motors have no combustion chamber in them, just dished pistons
If you just want to get a running car then just swap over all the inlet manifolds and carbies etc. it won't perform as well as a carby 1.7 as the i.e. cams have much less duration, and the static compression ratio is less on the i.e. but it should be a bit up on the std 1.5. You will need to rejet the carbies.

tukilevu · #11 (**permalink**) 05-17-2008, 02:43 PM

I think if we put the 1.7 motor in, we were thinking that we will probably put a set of 40 mm carbies in it rather than the standard 1.5 ones. Not exactly sure on this one, the 36 mm carbies would probably give better response if they were re-jetted, but may tend to run out of breath a bit at the top end.

Do the carbies bolt straight in to the heads where the injection manifolds come off? And are all the carby linkages/cross-shafts the same as what is on the 1.5 motor?

Spooty22 · #12 (**permalink**) 05-17-2008, 03:48 PM

The IE heads are the same as far as bolting up the carbies is concerned. The only difference is the IE inlet manifolds have injector bosses cast in. This shouldn't be an issue though.

I am in the process of a conversion which is the exact opposite. I am converting the 1.7 carby motor in my Sud to IE.

With a few modifications of course. I am keeping my carby heads and cams, as well as the dizzy. The carby motors have higher compression, wilder cams (more duration and lift) and a different dizzy curve. I am just adding the IE induction system, effectively. There is no reason why this motor shouldn't make just as much power as the carbs. The IE system is very well designed, and should make adding a turbo later on, if I want to go down that path, much easier. I am going to mod the L-JET airflow meter to provide a richer mixture, which should work well with the carby cams. New injectors aren't expensive either, same as a Hyundai Excel!

With the sale of the 40IDFs on eBay too, I am sure I will well cover the cost of the IE gear. I may even make a profit

33gold · #13 (**permalink**) 05-19-2008, 07:32 AM

Injection with an aftermarket ECU controlling ignition too will give more power than carbies any day. I am running limited budget and love the old style stuff as that's what I worked on as a mechanic back in the day. If you look at the actual valve seat diameter on early 1.7's and 1.5's its actually 32mm which is the choke size on 36idf so IMO 40's won't do much even at high revs, in fact they may even cause a pulse back up the carby when the flow hits the valve seat; of course if you increase valve size the 40's are viable. Plus with race cams the 36's should get me a bit of lowere end torque. I am getting the injector cutouts welded out of my 1.7 i.e. heads before finishing the polishing

33gold · #14 (**permalink**) 05-19-2008, 07:48 AM

not sure is anyone has cc's an i.e head and piston dishes but.....

bore is 8.7mm so bore area is 8.7 x 8.7 x 3.14159 / 4 = 59.45 cm2
Volume of 1 cyl is bore area x stroke so; 59.45 x 7.2 = 428.04cc
Multiply this by 4 =1712cc which is ok

Now to calculate compression = (vol of cyl + comp chamber vol) / comp chamber vol so;
428.04 + 49.5 (from manual) / 49.5 = 9.64:1 compression

This is the same for carby and i.e. engine yet according to the manual i.e. is 9:1 and carby is 9.5:1

Does anyone know if the manual listed compression is dynamic rather than static as the chambers are the same for i.e. and carby?

To make matters worse I cc'd my heads and piston dishes (I have removed matarial as valves hit piston) and made these only 47.5cc = 2 cc less than std!

The issue is that just by reducing my head cc by 6cc I could hit 10.8 to one so a small amount gets a lot more compression. Do I play it safe with the manuals figures? Has anyone else cc'd and found such a big difference - I am sure that the heads have not been refaced.

tukilevu · #15 (**permalink**) 05-20-2008, 10:56 PM

I think you blokes are talking a bit higher end than what we are considering doing but it is all good - this is more relevant information than I've been able to find in weeks of searching.

You say the ti's had wilder cams - and this would account for some of the power increase between the carbed motor and the injected motor. Does anyone know if there are any other cams available for a standard IE motor, something about a fast road car standard and not so lumpy that you couldn't sit in it?

I think your arguments about keeping the 36 mm carbs are probably pretty sound, especially as we don't have autobahns in this country where you can really open the taps up. Does anyone have any info on possible jetting changes to go from a 1.5 set-up to a 1.7?