NEW 2512cc race motor build

[Vagos]

hello to everyone on the foroum.I decided to leave the 2.7 stroker for the time now and go for a 2512cc motor again in favour of a better revving motor than the stroker 2,7.My last 2512 even though it was short lived was a very strong motor but i decided that i want a bit more than that.So major part for big HP numbers is the cylinder head offcourse.I sent a 2.4 cylinder head with 1.940/1.600 valves to a specialist in uk called the cylinder head shop and ask him to prepare the head upon rallybob specs.Porting,5 angle cuts,harden seats e.t.c.The head came back and it was perfect!A good start defenetly this time.Next i change the risse camshaft with dbilas one.The new camshaft has 330duration,105 lobe center and 14mm!!!!valve lift.Since each cam takes up to 4degrees advance or retard i might reduce the lobe to 101 in favour of bigger top end.New 97mm wossner pistons offcourse plus H-beam rods which are about 100g lighter than stock!!!saving up to 400g in the total assembly line!the crank is still the one from BAMOTEC and i replace the my cast iron flywheel with one from risse motorsport.the new flywheel weights about 5,5kilos!Sachs racing clutch and plate and special ARP bolts for the 2,4 crank.I will be using the dual 50 DCO/SP webers again with their divine sound.Offcourse MSD6A and MSDblaster coil for the spark and finaly my Grp.A 63.5mm exhaust from again from risse.I plan to do a very careful built this time as i have big expectations from this engine.It sure has the potential to make lots of power.But still there are a few things i must clear them out before closing it.First i must decide what the compresion will be the cylinder head shop musure my combastion chambers to be near 57cc.The wossner pistons cames about 0,15mm of the top of the block ,so with 1mm compresed head gasket i must have near 11.2:1 compresion.Offcourse this compresion is not good for such a big camshaft i believe im must be in the region of near 12 or at least 11:5 to make it work ok.can please someone verify my above speculations?Head was not skimmed yet and i mesured it to be near 102.71mm.So i will give her a 0.2mm skim musure the c.chamber again to achieve the desireble compresion.there are still some things left which i would like to know and i want the help from the members of the foroum.One what is the mod to the Opel distributor?Hiro asked me last time if i have the centrifuge advance mechanism still functional.What do you mean hiro by that??My distributor is full stock.I just run it (last time)with no connection of the vacum to the carbs.So i guess the advance stays as it is from the setting.
And most crucial part.I saw on hiro web page what i think it might be cam timming but i cannot quite figure it out.what i know about cam timming is.When the 1st inlet valve is at full lift we plave the dial gauge on the retainer.Begin one circle of the engine up to 0.50 on the dial gauge and take a note on the degree wheel then we contine past the 0.50 to zero and 0.50 and take a note again ad the two numbers together and divided by two to find true centerline.Some cams are musured by 0.25 and some at 0.50 can anyone please explain this difreence to me.what is the correct way to degree the cam on the cih engine.I used the search engine and didnt find a post to answer my questions.Here are the pics of the cylinder head and the parts.

[Vagos]

more pics of the parts

[Vagos]

and some more

[michaedo]

Look forward to following the buildup on this one.

[markandson]

If you don't want to go to EFI then I would at least put a AFR gauge in the car and an O2 sensor on so that you monitor the mixture then you will have a better chance of not melting this beautiful thing you are building.

[Vagos]

Originally Posted by markandson If you don't want to go to EFI then I would at least put a AFR gauge in the car and an O2 sensor on so that you monitor the mixture then you will have a better chance of not melting this beautiful thing you are building.

it is in my plans as with the msd combo the sprark is very powerfull and leaves room for much improvment.

[Hiro]

Originally Posted by Vagos hello to everyone on the foroum.I decided to leave the 2.7 stroker for the time now and go for a 2512cc motor again in favour of a better revving motor than the stroker 2,7.My last 2512 even though it was short lived was a very strong motor but i decided that i want a bit more than that.So major part for big HP numbers is the cylinder head offcourse.I sent a 2.4 cylinder head with 1.940/1.600 valves to a specialist in uk called the cylinder head shop and ask him to prepare the head upon rallybob specs.Porting,5 angle cuts,harden seats e.t.c.The head came back and it was perfect!A good start defenetly this time.Next i change the risse camshaft with dbilas one.The new camshaft has 330duration,105 lobe center and 14mm!!!!valve lift.Since each cam takes up to 4degrees advance or retard i might reduce the lobe to 101 in favour of bigger top end.New 97mm wossner pistons offcourse plus H-beam rods which are about 100g lighter than stock!!!saving up to 400g in the total assembly line!the crank is still the one from BAMOTEC and i replace the my cast iron flywheel with one from risse motorsport.the new flywheel weights about 5,5kilos!Sachs racing clutch and plate and special ARP bolts for the 2,4 crank.I will be using the dual 50 DCO/SP webers again with their divine sound.Offcourse MSD6A and MSDblaster coil for the spark and finaly my Grp.A 63.5mm exhaust from again from risse.I plan to do a very careful built this time as i have big expectations from this engine.It sure has the potential to make lots of power.But still there are a few things i must clear them out before closing it.First i must decide what the compresion will be the cylinder head shop musure my combastion chambers to be near 57cc.The wossner pistons cames about 0,15mm of the top of the block ,so with 1mm compresed head gasket i must have near 11.2:1 compresion.Offcourse this compresion is not good for such a big camshaft i believe im must be in the region of near 12 or at least 11:5 to make it work ok.can please someone verify my above speculations?Head was not skimmed yet and i mesured it to be near 102.71mm.So i will give her a 0.2mm skim musure the c.chamber again to achieve the desireble compresion.there are still some things left which i would like to know and i want the help from the members of the foroum.One what is the mod to the Opel distributor?Hiro asked me last time if i have the centrifuge advance mechanism still functional.What do you mean hiro by that??My distributor is full stock.I just run it (last time)with no connection of the vacum to the carbs.So i guess the advance stays as it is from the setting. And most crucial part.I saw on hiro web page what i think it might be cam timming but i cannot quite figure it out.what i know about cam timming is.When the 1st inlet valve is at full lift we plave the dial gauge on the retainer.Begin one circle of the engine up to 0.50 on the dial gauge and take a note on the degree wheel then we contine past the 0.50 to zero and 0.50 and take a note again ad the two numbers together and divided by two to find true centerline.Some cams are musured by 0.25 and some at 0.50 can anyone please explain this difreence to me.what is the correct way to degree the cam on the cih engine.I used the search engine and didnt find a post to answer my questions.Here are the pics of the cylinder head and the parts.

Hi Vagos,
Nice setup!
We are following parallel routes as I will probably also stepback from my current 2.7 to a better revving 2.5

Some more comments/suggestions:
Your CR is now 11.6 with a 57cc chamber volume & 1mm thick headgasket,
Maybe this is already enough depending upon your ignition & cam settings?
I think your camshaft has a too tight lobe separation angle relative with displacement,
The peak hp rpm will be quite low therefore your 2.5 will not be able to produce more power above about 6800-7000rpm,
This is a pity because your setup is better than mine & I already rev upto 8200rpm with a 310° camshaft (DB32C).
Another side effect of your tight angle/high duration camshaft is that the valve crossover lift @ TDC will be quite high (I guess upto 5.5mm please recheck),
This might be an issue with a skimmed head & very big valves,
Remember with the 2.4 Wossner pistons you can not recarve much the valve notches because metal is quite thin there...
With a wider lobe separation angle (ie 110-112°) you could keep the same duration & lift,
And in the same time reduce valve overlap therefore no problem with valve notches & no need for a very high CR,
And as I said gain on the power curve in the 6500-7500rpm range.

About the distributor mod:
Find a way to secure (bolt/rivet etc) the vacuum advance mecanism inside the distributor,
If this mecanism starts wandering around with vibrations then it can add a full 5° of advance in your original ignition setup...
Nice detonation or hole in your Wossner piston might result from this!
As a starting indication I'm using only 22° of total ignition advance @ 4000rpm with my DB32C camshaft & CR11.4

About camshaft setting:
My method is the easy beguinner's way as all the camshafts I use are fully measured for comparing lift/duration/crossover,
This way I know for each camshaft where is the cam crossover point @ TDC,
I just position this crossover point relative to TDC usually with 2-3° retardation depending upon the camshaft.
This method is easy but crude because it doesn't take into account the lobe separation angle,
Therefore it is just a startpoint from where I tune the camsetting to get the powercurve I want.

About your FW:
Is this a custom steel FW or a std cast iron FW extensively reworked?
Becarefull as this one might blow in pieces @ high rpm...
Better for safety would be a full billet steel or alu FW.
Hiro

[Vagos]

HI hiro and thanks for the info.as far as the camshaft goes i too had take the 105 lobe separation as a bad thing on buying it but since i can drop it 4 degrees ending up to 101 centeline it might make a difreence.Unless the original base of 105(in my case) is always a factor i cannot skip.I was thinking of going to 342@ 100 lobe 13,9mm valve lift cam again for Dbilas.But step back to 330 for a more civilized motor.Anyway this cam TDC lift is 5.2mm.I think i wont have any problems with my valve pockets since i have already see a set up here in greece with 97mm wossners and 48/43 valves running the above 342@ cam with no problems and the 342 cam has 6.0 valve lift at TDC!!!I still have my risse cam with 324@,104 lobe and 6.0/5.2TDC and 13mm valve lift.Do you think it might be better to step back to this cam or go after the 342???The flywheel is brand new Billet steel.Risse gives it to the High revving CIH 16v motor also.11:6 compresion is good!!!how much do you think the combastion chamber increased after i removed meterial like you for the wossner dome not to hit the head??/
cheers

[RallyBob]

Originally Posted by Vagos One what is the mod to the Opel distributor?Hiro asked me last time if i have the centrifuge advance mechanism still functional.What do you mean hiro by that??My distributor is full stock.I just run it (last time)with no connection of the vacum to the carbs.So i guess the advance stays as it is from the setting.

As Hiro says, it is really important to modify the distributor with locked vacuum advance. And probably the curve needs to be changed as well. Otherwise performance will be restricted, and engine damage can result.

Some info here:

http://www.opelgt.com/forums/27331-post148.html
http://www.opelgt.com/forums/27332-post149.html
http://www.opelgt.com/forums/27333-post150.html
http://www.opelgt.com/forums/27335-post151.html
http://www.opelgt.com/forums/27338-post152.html
http://www.opelgt.com/forums/27341-post153.html

HTH,
Bob

[Vagos]

Thanks rallybob!!i have seen the pictures in your site but was not sure what to look for as i thought it was a special mod for the turbo motor.I got it now.
think i made a terrible understood about lobe seperation.Hiro please dont bother to answer my previous post as i have figure it out now correct i think.I dont know where i learned that the tighter the lobe seperation is the more high you go in the rpm range where in fact it is the exact opposite.So actually i need to increase my cam to 109 degrees from 105 if i want the engine to rev higher.so i dont know how much rpm can this give me 100-200prm?

[GTJIM]

Originally Posted by Vagos So actually i need to increase my cam to 109 degrees from 105 if i want the engine to rev higher.so i dont know how much rpm can this give me 100-200prm?

The lobe separation is not 'adjustable' after the cam is ground - it is set by the person who grinds the cam. Less lobe separation increases the overlap between the Exhaust and Intake cycles which can lower the dynamic compression ratio at lower revs and 'tune' the cam for higher revs - more lobe separation increases low rev torque. This must be done when the cam is actually being ground.

This is quite different from advance or retard of the entire cam - which can be altered with an adjustable cam gear or the other usual methods.

[Vagos]

Thanks Jim i suspect it will be something like that.Something to make clear.The engine is for dragracing style of use.No need for a flexibile or smooth motor and bottom end.Absoloute power only!!!It seems there might be an option for a smaller cam to make more power due to high rev.Hiro any camshaft from Dbilas or risse to suggest??I think these two look promising.316@/107/12,6 lift and the assymetrical 316/300/108/12,6/12,0.

[Hiro]

Originally Posted by Vagos Thanks Jim i suspect it will be something like that.Something to make clear.The engine is for dragracing style of use.No need for a flexibile or smooth motor and bottom end.Absoloute power only!!!It seems there might be an option for a smaller cam to make more power due to high rev.Hiro any camshaft from Dbilas or risse to suggest??I think these two look promising.316@/107/12,6 lift and the assymetrical 316/300/108/12,6/12,0.

I could not find wide separation angle camshafts from the usual CIH race shops,
for this reason I have them custom made by Cam Techniques in Florida,
they do nice work at a very reasonable price,
but you have to tell them exactely the specs you want.
Hiro

[Hiro]

Originally Posted by Vagos how much do you think the combastion chamber increased after i removed meterial like you for the wossner dome not to hit the head??/ cheers

depends how you will carve the side of the chamber,
usually it's about 2cc but I always recheck the exact chamber volume after carving & milling.
Hiro

[Vagos]

Thanks!!i could give a try to cam tech but to be honest i cannot quite tell what would an optimal camshaft for dragracing.What might be the optimal camshaft for dragracing application upon my set up????

Does anyone knows any good online compresion calculator???Upon paper and a book i have i just cannot make it clear.

[opelnut10]

Originally Posted by Vagos Thanks!!i could give a try to cam tech but to be honest i cannot quite tell what would an optimal camshaft for dragracing.What might be the optimal camshaft for dragracing application upon my set up???? Does anyone knows any good online compresion calculator???Upon paper and a book i have i just cannot make it clear.

If you are going to drag race this engine the cam specs I found worked the best was a split duration with the long side being on the exhaust side. I ran a .510 lift 108 lobe center with 288 on the intakes and 296 on the exhaust side for duration with a 1 3/4" tubes on the header and I turned it 7200 with stock stamped rocker arms and a 620 CFM Holley two barrel. The engine would rev 7500-7600 but did not make power above 7200 (just more noise)The ignition was an Accel super coil with the distributor locked and weights and spring worked to have it all in at 36 degrees at 2800. I ran 1.84 intakes and 1.5 exhaust with true compression at 12.2-1. You have to have at least 104 octane gasoline to run this setup.

[Vagos]

Looks good.Something i dont understand is that in US we are talking in difreent mesurement of duration??288/296???What times did you manage to do in the 1/4 mile with your combo???

[Hiro]

Originally Posted by Vagos Looks good.Something i dont understand is that in US we are talking in difreent mesurement of duration??288/296???

US cam specs are measured @ 1.27mm valve lift,
this is the only correct way of determining duration for a race cam.
EEC cam specs are usually measured @ 0.3-0.4mm valve lift,
therefore they are very misleading above ca. 310° duration.
for this reason I've made the complete opening diagram of all my cams,
this way I can compare US spec cams & EEC spec cams.
Hiro

[opelnut10]

Originally Posted by Vagos Looks good.Something i dont understand is that in US we are talking in difreent mesurement of duration??288/296???What times did you manage to do in the 1/4 mile with your combo???

This was an IHRA Super Stock Class car, limited to modifications (no porting or polishing, no engine set back, .060 overbore, stock stroke, etc.) the car had to weigh 18 pounds per cubic inch (118 cubic inches) with the driver. I set 9 IHRA world records (et and MPH) from 1975 to 1980 the best pass I made was a Suffolk Virginia in November 1979 it went 14.28 at 95 MPH in a quarter mile. Check my gallery there are some pictures of the car in action.

[Vagos]

In my class we must have engine from the manufacture full street apearance,carpets,heater e.t.c and must be N/A.we allowed the use of semi-slick tyres.my friends Kadett C coupe with ported head 47/40 valves,dbilas cam of 332@/104/12,8 lift.50's throttle bodies and 97mm piston to make 2512cc with 75%Locked diff and 9:33 on getrag240 run an awesome 12,7.Im hopping to be near his time.Something tells me my engine will probably make more due to better cylinder head.

Still anyone here to say anything about the cam timming i mentioned above???

[davegt27]

http://www.opelgt.com/forums/attachm...-build-037.jpg

looks like a Toyota 4AG head off to the side


David

[Vagos]

Yes it might be i dont remeber i post this pics from the mechinery shop.Come on people any link to a page or post to expain in detail how to correct degree a camshaft on a CIH engine???Is it the same as a SOHC engine???

[davegt27]

Edit: 4AG stuff removed--sorry to confuse you

HTH
Davegt27

[Vagos]

Hi dave and thanks for the pics.I dont want cam timming for a DOHC head.The head isnt even mine!!!I dont care.I need info for camshaft timming our CIH engines!!!What i know for cam timming is that after you find TDC.you have the 1st intlet valve at full lift and set the dial gauge on the valve ratainer and reset to zero.Then rotate the crank to normal engine rotation and as soon as the needle pass 0.25mm or 0.50mm(dont know which of the two is correct??it depends on the camshaft or the engine type?)You take a note on your degree wheel.Continue to rotate the crank to nornal rotation of the engine pass the 0.25mm(or 0.50mm) to 0 and 0.25mm(0.50) again.Take a note on the degree wheel again.Ad this numbers together and divided by 2 to find true centerline and advance or retard the camshaft to achive the desire number.Is this correct???

[Kadett-o-Maniac]

Originally Posted by Vagos my friends Kadett C coupe with ported head 47/40 valves,dbilas cam of 332@/104/12,8 lift.50's throttle bodies and 97mm piston to make 2512cc

Many of my friends uses this combination too, most of them on legal street use and it works very good, so my new engine will follow them in near every part, but i will use only the 45mm Weber carbs, better for set up on legal street use, i must or will also use the middle speed range and with the 48 or 50 Webers this is not possible, the only thing they know, is throttle valve open or shut...

My flywheel is also made of good iron steel made after e pattern of Bamotec with the same weight like 5,5kg, with BMW E30 325i pressure plate and a Rekord E 2,2i Caravan entrainer disk!

I have the same chinese h-beam rods like yours, but worked off by Bamotec, the measures of the eye below are not correct, please be careful here on this part, did you measured it Vagos?

Mine would be between +0,02 and +0,05mm, now they are 55,00mm!

Pistons are from Omega in 97mm with dome to get a compression ratio 12:1, but i let rounded every edge from the dome, better for the flow in the cc!

Rocker arms are the original made of steel, but fully polished like mirror, as good, as i can made it myself!

Next time, i will show you more of my "special parts" with pics, reworked by myself!

Best regards