Best Mods For An Engine

[Longboarder]

About time I chucked my hat into the ring for people to stomp on.

 

Any engine is just an air pump. It creates a partial vacuum, air is pushed in by atmospheric pressure (N/A), its compressed, expands and rushes out pushed by cylinder pressure against atmos pressure. (OK petrol gets mixed in and set on fire and helps the expansion and you can organise a better pump in than atmospheric pressure) So N/A power is all about gas flow.

 

1. Stick with the pinto.

2. Flowing the head yourself is free and 'fun' and pinto heads are cheap enough that if you make a horlicks of it you can do another.

3. Get it skimmed by about 60 thou to raise CR and get three angle valve seats cut in the head. If you are going to have seats cut you can go a size bigger with the valves at no extra cost apart from new valves. (Do it in that order so you don't lose the machining if you mess up.)

4. Take time to open up the exhaust port to match it to the manifold and a little time on matching the inlet as well.

You now have a potentialy much better pump but to get more air through you need a new cam. Piper 285 would be my choice.

Total spend so far is nearer £300 than 4. It will happily run on a DFTH or DGAV, whatever dizzy you have and the RH 4:1 exhaust and be putting out 115 at the wheels.

 

You can drive it while you decide on better carbs or injection and better ignition. Keeping it cheap I would say bike carbs and a 3D megajolt map and for £600 total you should have something like 135+ at the wheels.

 

Thats what I would do if I was starting out again and had a 2L pinto in the car and £600 to spend. If you want 170 at the wheels you are going to double or treble that budget, have a fairly lengthy rebuild on your hands and be looking for a new engine like XE, Zetec, 4AGE or Duratec.

 

Nigel

[Guest hypermick]

Peter,.

 

I'm very interested in the comment youve made. Let me see if I have grasped correctly what you are saying,.............

 

Are you actually saying that you run R1 carbs and these are the only ones suitable ? Thats the first question. The second question is : How many other bike carbs,. (choke sizes and models of bike they came off),. have you actually run on your engine ?

 

The third question is : do you own, ride and maintain a sports motorbike by any chance ?

 

I have a whole selection of carbs here, currently under test. If youve done the same tests previously as I'm currently going through there are certain points you will have picked up on. I'd therefore invite you to mention the failings, in particular, of the other carbs, since this seems to be the point you are making. (That is if I've correctly grasped what you are in fact saying ,. apologies of course if I haven't,. in which case please feel free to clarify !)

 

Also, with respect I don't need you to tell me how each type works.

 

As for the statement about Weber DCOE's,. I have a fair amount of experience with these going right back to the early 70's when I then regularly built competition FVA FVC BDA and Lotus Twin Cam engines,. and you will know that choke sizes rarely exceed 38mm (that is in the 45DCOE), smaller of course in the 40 DCOE.

 

As a matter of interest I made a point about the mounting of fuel injection throttle bodies,. I see you haven't commented on that,. may I ask if you have any input to offer ?

 

 

Tak,. if you're reading this would you like to comment on your experience of running a set of small bore Mikuni's, since I'm somewhat at a loss with Peter's comments.

 

Being a practical soul who prefers to actually engineer in real terms, on the ground, (call me old fashioned, but it works for me ) I look forward to any comments near or far.

 

 

NIGEL :

 

I would certainly agree in the main with what you've said, but for two things. (and by the way you are absolutely right when you suggest having a go, carefully mind, at doing your own engine mods. Its good fun and very pleasing when you see your hard work turn into a good result).

 

Sorry, but, no self respecting engine shop will take 60 thou off a Pinto head,. thats over twice the amount permissable. And the other point is, when you port the exhaust side of the head you don't match the head to the manifold, ( the profile stays inside the manifold flanges with some to spare so the gasses are projected pea shooter style inside the pipes) and the top of the port is the main reprofiling area. The port should look very similar to a loaf of bread, curved at the top, flattish at the bottom. Full technical explanation available if anyone wants it, but I think I've covered it already in a previous reply.

 

 

Mick.

Edited October 15, 2006 by hypermick

[Guest satman]

Just to throw tuppence worth in I had a good look around and chose Yamaha R6 carbs in the end. I looked at R1 carbs but couldnt justify the extra £70 the R6 were £50.

 

They are 38mm which is the same as my cylinder head port size, polished slightly and open up from 36mm. Boggs have made a manifold for me and the engine is now running, so the next step once the rest of the panels are on is to get it on a rolling road. Boggs say the carbs should work perfectly provided theyre set up correctly and theyre better than Webers since they stay in tune.

 

I had a months holiday so I could get on with the build. I'm knackered but happy.

 

I wont be submitting it for SVA with the bike carbs I'll be using a Weber economy carb instead.

[Longboarder]

Hypermick, my local machine shops, I use two, will do whatever I ask of them if possible and if I pay them. I do my research which generaly means reading the words of wisdom of serious old timers, decide what I want to achieve and how to do it and then go and thrash it out with my engineers. I discuss mods with them and they do warn me when they think I'm doing something daft. The above mods were exactly what I did to my old pinto engine and it was solidly reliable and fairly powerful.

 

60 thou off a 2L pinto head raises the compression ratio from the standard 9.2 to 10.2. You should not have any problems with the head. If you are going to be modifying the chamber shape significantly, unshrouding valves etc then 80 thou will be needed to get a 10.5 CR but then you would need to be checking for plug or valve to piston contact depending on cam profile and possibly having clearance pockets machined in the piston tops for said items.

 

The RH 4:1 exhaust has headers a little on the small size at the manifold face. The normal practice would be to take out the exhaust ports in the head to standard gasket size avoiding taking much off the floor of the port but this will leave them bigger than the manifold. Thus I suggest matching them to the manifold.

 

Simon wants more power, is on a tight budget and reluctant to do it himself. Much the same as I was a few years back. I would expect him to do a lot more reading before doing it himself. My suggestions are sound and would be hard to beat on price.

 

Nigel

[Guest hypermick]

Nigel:

 

I can't help feeling that you've forgotten that the cross section of readers on here are of mixed technical abilities, mechanical understanding and engineering experience. When I say this I do so in order to guard the projects they are working on and not in any way to undermine their capabilities.

That said, it would be fool hardy to suggest as you have done that 60thou can be swiped off a head without other considerations being made before raising the compression thus.

 

You are aware, aren't you that one other primary and fundamental aspect of the engine (and nothing to do with the head itself)which is equally important before taking anything off the head ? (Considered in the absence of the rest of the engine (sitting on your garage floor as is usually the case) whilst your head is sitting alone in the machine shop ready for machining ).

 

So that the rest may benefit, and in the light you partially missed this out from your last posting, perhaps you'd like to mention the other "bit" which needs taking into account, since it might just save some poor blighters engine, who otherwise might just be tempted to go off having his head skimmed in the first instance.

 

Mick

[Guest chris brown]

60 thou off a 2L pinto head raises the compression ratio from the standard 9.2 to 10.2

I agree Nigel 60 thou is the max advisable to be removed and is what most if not all of the BriSCA F1 boys used. Mine runs with a 40 thou skim leaving 20 thou for further skim. BTW 40 thou puts the cambelt exactly ½ a tooth out so a veneer pulley is advisable

 

Just had a read of Des Hammill book (Chapter 6) and he says 80 thou but indents may be required in the pistons for plug electrodes. this gives a CR of 11.3

[Longboarder]

Hypermick, this isn't a quiz or some sort of test. We don't agree on head skimming. Plain and simple. That doesn't make me or you a bad person or justify you hopping on a high horse like Ivanhoe and suggesting I'm the big bad baron. I don't post on rhocar with any intention of messing up anyone elses projects or putting them, their cars or anything else at risk. I do expect intelligent comment and or criticism and am quite prepared to accept it if I'm wrong and take the flack.

 

My posts are not intended as a complete guide which an engine modifier experienced or novice can cut out, take into the garage and follow like a comprehensive manual. You have obviously noticed an error or have additional information you wish to post to help other members. Excellent. Thats what this board is mostly about. Can I suggest you simply get on and post it without making us beg and plead.

 

Nigel

[Guest hypermick]

Good point that Chris makes about the 40 thou, and the significance of 1/2 tooth difference which brings me straight back to one of the reasons for not taking the skim beyond 30 thou max towards the easy mods to increase performance economically without taking risks.

 

I'm just wondering how long it will be before someone replies to my last posting regarding the other engine "bit".

 

 

 

 

Mick.

[Longboarder]

Mick, it's not a quiz or test. Examine your motives for witholding this information. If you have something to say just say it.

 

Nigel

[Guest jetskijase]

Like many others probably reading this thread, I also like keeping my eye out for little things people have done on the cheap to give our engines a little more pep.

 

So thank you longboarder for your down to earth info, and everyone else for that matter,

 

Execpt mr perfect mick whoever you are

 

Over several threads on this site i have read and you are such A stuck up know it all ,that to be honest i couldn't give a flying f&ck what you've worked on or wheter you've been to the f%&king moon and back on a pinto,

 

WIND IT IN AND STOP CRITISING EVERYONE !!

 

GET TO THE POINT AND STOP QUESTIONING EVERYONE'S REPLYS, WRITE OR WRONG I DON'T CARE.

[Guest salty_monk]

As long as you don't get valves & Piston's meeting & you can find high enough octane fuel you can skim off as much as you like, I think that's Nigel's point..... His engine was a "good-un" as it Chris's.

 

Before you skim the head though, make sure it hasn't been licked before in case you do go too much. Burton do a "thick" gasket for anyone who has gone a little over the top...

 

Dan

[Guest hypermick]

Jetskijase,. there isn't really a lot to say about your comment other than that it definitely doesn't come from the mouth of anyone professional.

 

An uninvited remark like yours does nothing more than make an attempt to provoke an equally versed reply which from me you won't get, so don't bother having a second try, unless of course you have an urge to provide the rest of the forum with entertainment at your expense.

 

Instead of sitting there trying to read my previous threads, why not learn a little more about engines? I can suggest a few good books which aren't all pictures, Could you cope with that ?

 

Nigel, it always pays to check the piston crown to block face difference measurement with the pistons at TDC before skimming any head. The production pistons have varying crown thicknesses, which makes a difference to the final compression. This is one of the reasons why I certainly wouldn't go beyond 30 thou max for safety and for the cheap end tune up (which is of course the point of this thread),. unless of course the engine is being built to close tolerances, in which case then more serious factors come closely into play.

 

I really cannot see why, after thirty plus years of practical engineering experience, that experience, which by the way is all first hand, shouldn't be shared around. Its what this forum is actually for. If you chose to ignore it fine,. sit back and do so, quietly.

 

 

Sorry if you feel like the big bad barron Nigel, there again, I'm not wearing your cap am I ?

 

Suits you mind, lovely fit !

 

Happy Days

 

 

Mick

[Guest chris brown]

Jetskijase,. there isn't really a lot to say about your comment other than that it definitely doesn't come from the mouth of anyone professional.

 

An uninvited remark like yours does nothing more than make an attempt to provoke an equally versed reply which from me you won't get, so don't bother having a second try, unless of course you have an urge to provide the rest of the forum with entertainment at your expense.

 

Instead of sitting there trying to read my previous threads, why not learn a little more about engines? I can suggest a few good books which aren't all pictures, Could you cope with that ?

 

Nigel, it always pays to check the piston crown to block face difference measurement with the pistons at TDC before skimming any head. The production pistons have varying crown thicknesses, which makes a difference to the final compression. This is one of the reasons why I certainly wouldn't go beyond 30 thou max for safety and for the cheap end tune up (which is of course the point of this thread),. unless of course the engine is being built to close tolerances, in which case then more serious factors come closely into play.

 

I really cannot see why, after thirty plus years of practical engineering experience, that experience, which by the way is all first hand, shouldn't be shared around. Its what this forum is actually for. If you chose to ignore it fine,. sit back and do so, quietly.

Sorry if you feel like the big bad barron Nigel, there again, I'm not wearing your cap am I ?

 

Suits you mind, lovely fit !

 

Happy Days

Mick

You stuck up big headed prat

[Guest hypermick]

Is that your attempt at northern humour Chris ? Stick to the context of the thread otherwise you'll have the moderators telling you off.

 

Sorry I forgot,. you live by the "I like what I say & I say what I like rule " silly me forgetting an obvious thing like that. Just watch you don't fall down the pit at work while you're rehearsing your next line.

 

If Jetskijase can't ruffle me you certainly won't.

[Peter Bell]

Mick sorry you got a bit excited about my answer but it was my reply to your original statement that by using R1 carbs the engine had to be running at 6500/7000 rpm and would be intractable. It was this I disputed, I was just saying that due to the type of carburettor they are the butterfly size not too important as the choke slide controls the air speed., which is kept constant to create good fuel atomisation, but then you know that.

 

I did not say that R1 carbs were the only one to go for, I had a set. Possibly 36mm could be best, it will of course depend on many things, airflow through the head, cam selection cr. exhaust manifold and ignition system will make a great deal of difference.

 

Not sure why you wanted to know about my motorcycling days, most of it was many years ago (apart from spell with a superdream ) And they were with monobloc Amals apart from one with GP Amals which was an interesting carburettor.

 

The original question posed was trying to get more power out of a pinto for presumably reasonable costs, I would suggest that a pair of sidedraughts would be a similar cost to bike carbs, a bit more fiddly to keep in tune and more thirsty, due to the compromises of a fixed choke design.

 

As for the injection bodies, they would be the ultimate way to go of course but the costs involved get higher by the time you have added a high pressure pump, swirl pot, timing disc, emerald or megasquirt systems etc. surely it might be better to fit that to a more modern engine design than one getting on for 40 years old?

 

Hopefully you will post the results of your experimenting with different carbs etc. to a pinto it would be very helpful to many of us on here.

 

Regards Peter