My Supercharged V8 Capri Conversion

v8 jago · Post by **v8 jago** » Sat Nov 29, 2008 9:27 pm

Good luck in getting it back up and running soon.

She`ll be a beast. Looking forward to seeing it going.

Post by **Coops** » Sat Nov 29, 2008 11:06 pm

i dont mind if it aint a beast, as long as i can get her mobile for next year, and get some miles done driving her,
will think about building the spare 3.9 i have here into something else, may look at a stroked set up, or even forceinducted,
but thats another thing that can wait with the other list of jobs

Post by **Coops** » Thu Dec 11, 2008 6:07 pm

right honest replies here:

still looking at these stg3 heads,
do i go ahead and buy the double springs, caps collets and get the machining done and possibly a bit more porting,

or sell them on and buy a set all ready done?

Post by **katanaman** » Thu Dec 11, 2008 7:06 pm

Honest reply, depends on the ££££ diff. I guess an honest evaluation of how good or bad the porting already is on your heads would be handy too. I think they are V8 dev heads so they should be pretty good mind you.

Post by **Coops** » Thu Dec 11, 2008 7:23 pm

yeah i know mate,
mailed rob and co to see what they recomend, they may even exchange them as they are there own heads,

just trying to make the money stretch further

,

CastleMGBV8 · Post by **CastleMGBV8** » Fri Dec 12, 2008 11:25 am

Tony,

Did you find the cause of your missfire after the rolling road session?

My thoughts FWIW are that for the current spec of your engine you were definite down on power for some reason, which could possibly be on the ignition side.

As you are now going wasted spark with full control of your timing, this potential problem should be sorted.

If I were you I would have a good look at the stage 3 heads, have at least a couple of valves out and check the work below the valve seats and bowl areas and see how well this has been done, I consider this the most important area of head modification and on an engine of 3.9 capacity see no reason to go to stage 4 with the ports opened out to max dimensions unless it was for full race purposes and you were going to be using in excess of 7500 RPM.

Port matching, heads to manifold will give gains in the upper rev range if you haven't done it already.

Some people get very excited about flow figures and that fine, but what is more important, is the quality of the mixed gas that is arriving in the cylinder, which is why on my Buick 300 heads I left the port walls relatively rough as this assists with the fuel staying in suspension as does the casting area that supports the valve guide which is designed to promote swirl, this can be cleaned up a bit but should not be removed as in some heads I've seen, again unless for a very high RPM full race engine.

Looking at what you have, a twin plenum EFI which we know will support in excess of 300BHP, a Crower 50233 cam again good for 250+ BHP and heads which if well modified should be able to flow well enough for the the sort of power you are looking for, and still retaining reasonable on road drivability.

Can you post up some pics of the heads with the valves removed so we can see the bowl area as that will show how well they were done.

As to mods well i think it would be worth replacing the Rover valve spring retainers for reliability reasons, whether it's woth going to double valve spring depends on your rev limit, the singles are said to be good for 6500RPM and are ok except for extensive high RPM race use.

I think if it's all put togther and the ignition dialed in to give 10 deg. at 1000RPM and a max of 32 deg all in by 3400RPM you may well be surprised at the difference, and you may only have to spend £200 to address the valve spring and retainer issue. If using gas you will need to set up some retard and Perry would be your best advisor, look at what he is getting out of a fairly standard 4.6 engine and his rolling road figures were well down as he was over retarded on ignition timing.

One other point, have you set up the valve gear geometry properly, as although not directly a power maker it will ensure correct operation of the valve gear and increase reliability, in my opinion shims are a definite no no and whilst you can obtain the correct preload, they will only make the geometry worse and accerate wear of the valve gear.

Hope that helps to clarify things.

Kevin.

Post by **Coops** » Fri Dec 12, 2008 2:48 pm

Im awaiting some prices from Rossco for the parts,
as soon as i hear back, i can start ordering the bits from who ever is cheapest to try and get the car ready and built for March,

once rebuilt i'll see if it was an ignition fault, maybe a coil breaking down, but its given me the kick to go wasted spark now so may as well do it all while off the road,

CastleMGBV8 · Post by **CastleMGBV8** » Fri Dec 12, 2008 4:03 pm

Tony,

Still like to see the headwork behind the valves, when you get a chance can you post a couple of pics.

Kevin.

Post by **Coops** » Fri Dec 12, 2008 4:54 pm

Gona have to wait a while mate,
the heads are still on the engine in the car, which i think is still round the garage, as not been to see it since begining of september

not sure if i took any pics earlier on in this post of the chambers etc.

CastleMGBV8 · Post by **CastleMGBV8** » Fri Dec 12, 2008 6:21 pm

Tony,

Saw from your other post that you are still thinking of selling the stage 3 heads, it may be that you have missed the point of what I said in my earlier long post.

If you go to stage 4 heads the gas speed will be lower, and performance will suffer in the lower and mid ranges, and the car would be not very pleasant to drive on the road, although it would be less affected on a 5.0 + engine.

Don't forget peak power is only a figure that is achieved once you have accelerated through the rev range to get there, if you are down on power everywhere else but the last 1000RPM the car will be slower!

looking at it logically if you can achieve 250+ BHP from you current set up and when racing, add a 150 shot of gas to poss give another 120BHP you will have approx 370 peak BHP and good torque from about 2000RPM onwards, it will be quick.

Kevin.

Post by **Coops** » Fri Dec 12, 2008 7:29 pm

wernt going to stg4 mate,
was staying stg3 but with double springs etc,

Post by **katanaman** » Fri Dec 12, 2008 7:34 pm

thev8kid wrote:wernt going to stg4 mate,
was staying stg3 but with double springs etc,

And there was me trying to start a deal for you with Seight-V8

Post by **Coops** » Sat Dec 13, 2008 9:55 am

well could be tempted marki

the reason for my heads Kev was this misfire,
the cam spec stated doubles, but i am running uprated less one coil singles. and a few guys have said ah i would change them to doubles as thats the problem, all though had no probs up till now, which as we said earlier maybe electrical, (still think it is)
so was going to upgrade the heads to doubles or find a set with them allready done if it worked out cheaper and sell my single uprated coil stg3 heads on.

as soon as i have a price on a cam and lifters and other parts etc (have mailed 6 companys inc v8d, v8tuner and are man rossco) i will start ordering the main engine parts, going to pop new shells and rings in while the engine is out also may as well.

CastleMGBV8 · Post by **CastleMGBV8** » Sat Dec 13, 2008 10:55 am

Tony,

What cam and lifters are you thinking of getting.

Re the bottom end, unless you had oil pressure problems i would leave well alone, same for the rings, I would do a pressure or leakdown test to see what is happening, if pressures are good then leave it, otherwise to fit new rings will need the cylinders honing or the new rings will not bed in correctly, and you could be in a worse position than before.

If it were my engine I would just get the new ignition system installed, the cam dialled in and then get the ignition and fuelling mapped properly, this is where you are going to find real performance and do not see any reason to fit a wilder cam, the 50233 should give you what you are looking for.

You can then use the gas to give you the extra power you want at the track.

Kevin.

Post by **Coops** » Sat Dec 13, 2008 11:13 am

the engine bottom end i built about 3-4 yrs ago, so im going to check it to be sure,
i know about the bore honing mate thats why i have a honing tool

, thanks for the reminder,
Im using the same cam 50233 reason for a new one if you check back you will see a few of the lifters and 2 of the lobes are worn, thus going to renew it.

i cant afford for the engine to be put back together to test it with the possible risk of taking apart to renew anything, so going to go through the whole engine while its out of the car,