Engine rebuild

[Rallyace 3]

I’d like to start a discussion and gain from the experience of others before rebuilding a 1900 8v for Targa Rallying. 

 

For those that don’t know, Targa Rallying is a form of Road Rallying. The events are run in daylight and have off road sections, with a 30MPH average speed, which are timed to the second. Lots of the events are multi-venue, but the road sections are essentially non-competitive, with very relaxed timing. 

 

So onto the engine. I’m certainly not looking to build a highly stressed screamer. In fact the regulations don’t allow it. I’m looking for a strong and reliable engine, with the emphasis on torque. 

 

The pistons and liners on the donor engine look to be almost new, so the bottom end will be virtually standard. New rings and bearings and a careful rebuild will be the extent of the work. I will be running a 26 tooth sprocket on the oil pump, Richard Longman baffles and a 13 row oil cooler. I also intend using a 1600 flywheel. 

 

I have modified a cylinder head following accepted guidelines. I have removed the casting marks on the ports and created a smooth radius on the “short side” radius as the port transitions into the valve guide/throat area. The valves are 3 angle and the guides are phosphor bronze and in good condition. I will have it skimmed to give a compression ratio of 10.5: 1 or 11:1 and have a Piper 270, fast road cam. I realise that this cam receives mixed reviews and probably doesn’t give anything over the standard cam. I have and it’s new so, in it goes. I also have a vernier timing wheel. I have a four branch tubular exhaust manifold and an Ashley exhaust system. I bought the manifold as the standard down pipe is close to the end of its useful life.

 

That’s the background. Now onto the areas that I would like advice with.

I may want to go with a different cam in the future - something like a 280 degree duration. I understand that the standard AFM gets a little unsettled with longer duration cams, so I’m considering a bit of future proofing. Targa rally rules restrict you to a maximum of two chokes if moving away from the standard injection. This rules out Webbers and throttle bodies. Another popular mod these days is to go to four bike carbs. I have actually bought a set of Honda Blackbird carbs. I am wondering whether a pair of these 42mm choke carbs would work well with this setup. I believe that it’s been done on Ford Pinto engines as an alternative to a single 45, or split 40’s. It would, of course, require a bespoke manifold. I don’t currently have any plans for an after market ECU, but I’m open to advice. At the moment, I’m thinking of buying an H&H rebuilt and, advance curve modified distributor.

Am I on the right lines, or are there better ways of getting a really torquey, 130BHP at the wheels engine. 

I don’t want to go 16v and a swap to an engine from another manufacturer is also out. 

I hope that I’ve given enough info on what I’m looking for to keep the discussion focussed.

Thanks in anticipation

 

 

[allanallen 528 2 Cars]

I honestly wouldn’t waste your time trying to fit two bike carbs to it, leave the standard inlet on and fit aftermarket management. I’ve seen a few older dta ecu’s with useable looms go for under £300 recently so with the mapping you’d be just over £500, worth every penny. 
 

With the increased CR and the right cam on management you’ll easily be able to make 130 bhp atw and it’ll drive nicer than a standard engine. No more messing with SADs, AFMs and all the other associated archaic s*ite. 

Someone will be able to offer some better advice but I’m not sure heavily skimming the head is the best way to get  the CR up. A swap to 1600 pistons seems to be most common budget route to 11:1. 
 

Having road rallied a 1900 8v 205 for several years the best thing you can do is build a proper gearbox with a plated diff. I ran an AB hybrid box with a 4.4fd and a tran x lsd. After running a 1600 box for a while it was a revelation! 

Edited February 19, 2022 by allanallen

[Rallyace 3]

Thanks Allan, 

I’m pleased to say that I’ve taken steps that are largely in line with your advice. I Have bought and OMEX 600 ECU and a plated diff. I already run a 4.8:1 final drive and have the option of a 4.4:1. Although there are some links to road rallying, Targa Rallying rarely has tests that will get you beyond third gear, so I don’t think that I will get the benefits that a hybrid box offers. I have given up the idea of running carbs and will stick with the standard plenum chamber and injection. I will be ditching the the AFM and will run a longer duration cam. I’m just waiting for some bits to come back from the machine shop and will then be getting on with the build. I’ve entered an event at the beginning of May, so of time, but we all know how time disappears when it comes to motorsport.

 

[joris_andriesse 8]

I currently have an MI16, but also have been driving 2x a 1.9 8v's. D6B lump, 2.08v flowed head, increased compression, lightend flywheel, bit sharper cams, 4-2-1 exchaust. Made a bit over 130hp, but with loads of torque. Drove like a dream and almost as fast as standard mi16's. Not sure what gearbox I had on them, I think S16.

[allanallen 528 2 Cars]

2 hours ago, Rallyace said:

Thanks Allan, 

I’m pleased to say that I’ve taken steps that are largely in line with your advice. I Have bought and OMEX 600 ECU and a plated diff. I already run a 4.8:1 final drive and have the option of a 4.4:1. Although there are some links to road rallying, Targa Rallying rarely has tests that will get you beyond third gear, so I don’t think that I will get the benefits that a hybrid box offers. I have given up the idea of running carbs and will stick with the standard plenum chamber and injection. I will be ditching the the AFM and will run a longer duration cam. I’m just waiting for some bits to come back from the machine shop and will then be getting on with the build. I’ve entered an event at the beginning of May, so of time, but we all know how time disappears when it comes to motorsport.

 

Great move on the omex and the slippy diff. 
 

I forget what targa rallying has become to be honest so I’m sure you’re right, I imagine a 4.8 on a standard 1900 box has a really useful 2nd and 3rd for it. 
I never really got involved with targa events, never really appealed to me, the bits I’ve seen always looked like the special tests on road rallies, dodging round tape and cones. Give me a cow s*it covered road in sideways rain at 3am any day of the week over one