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Discussion Starter #1
Hi Alfa enthusiasts and pros,

I’m facing several problems since I started to rebuild and reconfigure my 2l engine in an Alfetta GTV. First, I tried the configuration Jim K. recommended in his book, but the result was disappointing: High fuel consumption and no improvement (no hp, no torque) at all. Perhaps I widened the intake ports too much and lost all the flow velocity. After a dyno run I decided to dispose of the head and start a new project with much more moderate measures. Here’s the new configuration which should work – but it doesn’t. The head I used was ok, no prior head work on it and a well-known machine shop here in Germany did the job.

a. intake valves with 46mm disc and 8mm stem and 8mm guides for an optimal air-flow design sharpened
b. outlet valve with 38mm disc and 8mm stem and 8mm guides for an optimal air-flow design sharpened
c. valve seats were changed by the machine shop and the head around intake seats adjusted. The rest of the intake ports remained original.
d. head was skimmed (0.8mm) to increase compression
e. The cams I use have 297 degree and 11.6 mm lift, perfect timing and electronic ignition by Centerline Alfa
f. pistons in Motronic design, by Rick Lovecchio
g. intake extended by 12cm, DCOE40 carbs
h. CSC exhaust stainless steel, but standard diameter

I thought these improvements and this configuration would result in a 20-25 hp gain, and so I went for a dyno run. The result was really frustrating. NO change in horse power, the curve is nearly the same as before, only torque increased substantially to 180nm. In the diagram the blue curve is the current config, the green one is for the first try according to Jim K.’s book.

Does anybody have an idea why there is no improvement only waste of money? What are my mistakes? A friend of mine recommended to chance exhaust and to buy a racing header with bigger diameter. What do you think, would it help? And what diameter and length should the header have? I would very much appreciate your help!
:helpsmilie::helpsmilie:
Ralfa
 

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Could be a multitude of reasons, your engine spec sounds ok.
You're still on 40 DCOE's what chokes have you got in there ?
Also I would think that the standard diameter exhaust wouldn't help.
I have a very similar spec engine in my GTA Rep, on 45 Dellortos, 38 mm chokes, with a Classic Alfa GTA manifold & system 52mm bore ?
This gave 136 bhp at the wheels, around 170 at the flywheel. If yours is giving 130 at the wheels, thats a good result,
Steve
 

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At the wheels, that's good. What jetting are you using. A 12mm lift cam on the intake will help use your porting.
 

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Richard Jemison
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Results

I was not going to post as it seems useless to critique other`s work, but one of the moderator`s suggested that I respond.

For the effort, and money you have spent your results are truly pathetic.

Several things suggested to you are truly wasted money and only "bling" when it comes to improving output.

The large intake valves are a detriment to flow. Only way they can work is to weld up the spark plug hole and move the spark plug in order to use larger seats. Larger seats & larger bowls & larger ports. Otherwise why bother?

I have no clue why you would reduce exhaust valve size..

Cams (from the Dyno sheet curves) appear to be typical over the counter old design lobes that only make power at high RPM.

From the dyno sheet, you seem to have ignition issues at high RPM or Fueling issues or maybe both.

I suggest you visit Ed`s Prytherche`s (Alfaparticle) thread on his street engine:
http://www.alfabb.com/bb/forums/spider-1966-up/304825-79-spider-dyno-2.html

Look at the power curve on this street motor! No peaky engine there.
This is an engine built to 10.6 to 1 CR.
Head is a race preped head with stock size (44 & 40mm) 9mm stem stainless valves and modern lobe designs on both intake cam (12mm) and the purpose designed lobe on the exhaust cam (11.7mm) And ports are quite large compared to other`s designs/shapes.
Carbs are as your`s are, small 40 DCOE Webers

If your`s was to be a race engine why use Motronic pistons?
CR should be at least 12.5 to 1, (if it`s a real race motor).

If it`s a street motor you drive to the track, and you are using the Motronic 10 to 1 pistons have the head cut a total of .060 (1.5MM) at least, to get usable compression.
While the head is off have the intake valves OD reduced as much as possible to leave only a seat contact width of .5mm (.020). Have the exhaust seat opened as much as possible to leave a seat width of 1mm (.040) The inside of the seats should be opened with a 75 degree cutter to the contact point of the valve seat. No 3 angle cuts!

If your rear wheel dyno HP was 130 then corrected flywheel Hp is 150-to 156 HP. Not the 170 range someone posted.

A properly built 2 liter Nord motor will make 220-230 HP by 7000 RPM. This is being consistantly done.

Good luck getting your`s sorted.
 

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Exactly that does that mean. Flywheel figures and not rw hp. But there is an other issue with that engine rather than the configuration. The dyno sheet is from a Dynojet dyno and calculates from wheel power back to flywheel.
 

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I did a similar build like yours, also with 40 carbs and got 145 PS at the rearwheels, when I dynoed the engine, there was some fueling problems (carb mounts where leaking)
 

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Richard Jemison
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Dyno sheet

If the Dyno sheet indicates it is converting to flywheel HP then I would be praying with the head builder with a baseball bat.

However I suspect the unit is measuring RWHP and the sheet is labeled incorrectly. Or the conversion ratio inputed by the dyno operator was terribly incorrect.

A completely stock 2l Euro engine should make nearly that HP "at the flywheel" in decent tune.
 

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Discussion Starter #12
Thank you very much for your comments, it is really helpful to share thoughts with much more experienced people than I am.

The dyno sheet indeed shows hp at flywheel and not rearwheel, and unfortunately, the sheet is labeled correct. That is the frustrating conclusion of having standard hp after investing time and money!

I didn’t want to put the blame on the machine shop, I think they did well what they did, because they exactly did what I asked them to do. So ist actually my mistake and I didn’t want badmouth the shop. By the way, hunttheshunt, it was not Weinsdoerfer, it was a machine shop in Bavaria, run by the family in fourth generation and very experienced – but not with Alfa. And that could be the point, my own setup or my choice of parts is probably of poor quality.

@GTA R: I have 35mm chokes on the DCOE40. I tried the DCOE45, too, but with my setup there was no improvement, only higher fuel consumption. Do you think a manifold with bigger bore could help solving my probs?

@Alfar7: Thank you very much for your detailed answer, it opened party my mind, partly I’m confused and will try to explain what I tried to do.
The intake valve seats the machine shop inserted were about 46.5mm matching the bigger valve. The head was extended around the seats but not the whole intake, because the experience with the first head work discouraged me.
I reduced the exhaust valve according to Jim K.‘s book and the advice of some Alfa mechanics. I thought it to be an uncontested solution.
Concerning the Motronic design piston, would you replace them? I cut the head off 0.8mm, getting cr of 10.6 : 1. Should I replace them?

I didn’t want to build a 200hp track engine, I aimed at 160-170hp with plenty of torque. I more engaged in historic hillclimb and rallye with a smaller budget.

@quadrifolio: Thanks for sharing your dyno sheet, that’s I was aiming for?

OK, I think I need a new setup. Would you recommend starting with another header/exhaust manifold and which measures are recommended?

Thank you very much,
Ralfa
 

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I use a Dynojet all the time. If its a Dynojet and if it has the latest software and if the weather station was on and working Richard is right that this equates to low 150s at the flywheel. I really don't have any faith that the dyno operator was careful though as it looks like they used speed/km instead of taking a few minutes to get rpms.

Additionally while I have learned to get useful repeatable data from a DynoJet there are a lot of variables to control. For example if this car/engine was dynoed with 15 pounds in the rear tires instead of 30 and before the engine differential and gearbox were up to normal operating temp it could be more than 10hp down from where it should read.
 

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What size main jets?
Have you mapped the distributor advance using a dial back light. Run motor at 1000rpm increments and dial to tdc, read where dial is and thats your spark advance at that rpm.
This is probably something stupidly simple, your setup is not that bad.
Why not run some 0 - 60 mph runs and check the times, also a good old fashioned drag race, those will take the dyno out of the equation.
 

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But Mad North-Northwest
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From the dyno sheet, you seem to have ignition issues at high RPM or Fueling issues or maybe both.
Yeah, don't ignore this part of Richard's advice. You've had two different prepped heads on there and poor performance with both? I'd be thinking maybe there's something fubar'd with your carb setup or advance before I started playing with the heads more.
 

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Richard Jemison
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Modifications.......

@Alfar7: Thank you very much for your detailed answer, it opened party my mind, partly I’m confused and will try to explain what I tried to do.
The intake valve seats the machine shop inserted were about 46.5mm matching the bigger valve. The head was extended around the seats but not the whole intake, because the experience with the first head work discouraged me.
I reduced the exhaust valve according to Jim K.‘s book and the advice of some Alfa mechanics. I thought it to be an uncontested solution.
Concerning the Motronic design piston, would you replace them? I cut the head off 0.8mm, getting cr of 10.6 : 1. Should I replace them?

I didn’t want to build a 200hp track engine, I aimed at 160-170hp with plenty of torque. I more engaged in historic hillclimb and rallye with a smaller budget.

@quadrifolio: Thanks for sharing your dyno sheet, that’s I was aiming for?

OK, I think I need a new setup. Would you recommend starting with another header/exhaust manifold and which measures are recommended?

Thank you very much,
You didn`t describe the Distributor and ignition system being used. What is it?
If it is a points type toss it, and get a 123 triggering a MSD (or Crane ) Capacitive discharge ignition system. That will give stability and voltage needed even in high compression ratio motors.

What are the Specific 40 DCOE Webers you are running and all their jetting?

I suggest at any point you remove the 40s and go back to 45mm DCOEs with the manifold properly ported for them. If you post the specific series of 45 DCOE webers you have we can contribute jetting advice. They will provide far better results when correctly fitted and jetted.

What exactly are the cams? Maker etc. Same cam intake and exhaust?? (big error) With more info on the builder and cam #s I suspect Lobe Centers/ Lobe separation angles (LSAs) are all wrong. Correcting that might save buying other cams. However I am concerned with the small exhaust valves and guides. Cam design on the exhaust is the way to manage combustion events, not sticking in an obstruction.

The more detail you give the more we might be able to correct the screwup without disasembling the engine.
 

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Discussion Starter #17 (Edited)
Yes, gigem75 and Gubi you’re both right. There is really some concern with the advance, it doesn’t really match 100%. With standard fuel I have some pitting at high rev, as dyno sheet shows. But now I use 100/105 octane fuel and it works. But I’m not sure whether advance cure is perfect for me. Carb jetting is now standard, main jet (if I remember right) is 140 or 145.

Alfar7, I use Centerline's ID405 Electronic Distributor (https://www.centerlinealfa.com/ignition-system/1297) with a Bosch red coil. I'm not sure which Weber are installed now, I changed them too often. But I can check it on Weekend. If you advice to go back to DCOE 45, I still have them in the garage.

But I'm not sure how to port the intake. The first head I destroyed was ported too much, air velocity under 5000rpm was too slow. Ok, the cams are distributed by a German dealer, now labeled as C&B cams, but on my cams there is their own Name and numer (OKP). Here's the link: I don't have any sheet on the cams. And yes, intake and exhaust cams are the same. Do you advice regrounding or replacing? And exhaust valve, should I replace it by the standard 40mm? The airflow diagram in Jim K.'s book convinced me to go for 38mm.

But obviously everything I made had no real effect on the engine. That's disappointing, but I don't give up, your comments and advices are encouraging me to go one more step ahead

Greetings
Ralfa
 

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What I think Richard is trying to know is if you have an EmCon (Emision Control) carb wich are no good for performance engines, so you need to tell us if your 45 carbs are DCOE or DCOM, I forgot to say that my pistons-liners are Spruells 11,5:1 JE pistons
 

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Discussion Starter #19
What I think Richard is trying to know is if you have an EmCon (Emision Control) carb wich are no good for performance engines, so you need to tell us if your 45 carbs are DCOE or DCOM, I forgot to say that my pistons-liners are Spruells 11,5:1 JE pistons
Oh, my fault, thank you for clarification. The carbs are old DCOE for European market, no emision control. Are you happy with the Spruell pistons? Is CR 11,5 : 1 not too much for street use? That could be a possible solution, changing pistons. I'm not sure how dome's design affects my setup, but the Motronic dome seems to be very unfavorable.
Greetings
Ralfa
 

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Oh, my fault, thank you for clarification. The carbs are old DCOE for European market, no emision control. Are you happy with the Spruell pistons? Is CR 11,5 : 1 not too much for street use? That could be a possible solution, changing pistons. I'm not sure how dome's design affects my setup, but the Motronic dome seems to be very unfavorable.
Greetings
Ralfa
My engine has a 10,4:1 CR, I´m happy with the pistons aldo I know that CP pistons are also very good, that choice always depends on what you´re after. Working on the head, knowing what you have on the bottom end, is what is going to give you or not, porting a head is kind of a black art, you MUST know what are you doing, otherwise, like in your case, you get poor performance, listen to Richard and follow his instructions, you will notice the diference. Perhaps a set of his cams would help?
 
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