Missing power from my 1776 after putting on bigger heads

[faiz]

Hey guys,

This is probably an obvious question to some of you, I did do a search but couldn't find anything as specific as what I'm looking for.

So I have a 1776cc with a counterweight crank, Engle 110, twin 40 Weber IDFs and 1500 040 cylinder heads.

So this week I removed the cylider heads and replaced them with CB Performance 044 heads with 40x35 valves and match ported manifolds. The 1500 040 has 35x32 valves if I'm not mistaken.

So I installed them by the book and it fired up first time, tuned it up and it idled beautifully and runs really smooth.

However, it does not have as much power as before, as in it does not accelerate as fast as before!

When I reset the timing I adjusted it to what it says in the 'how to keep you vw alive' book, 20 degrees at 2500 rpm.
Have I retarded the timing? This was my initial thought.

Additionally perhaps there are other items I should install to make full use of the heads. Could anyone make any suggestions how I could get more power? I was expecting more so I'm a bit disappointed if I'm honest. I'm not sure what rockers are fitted, is there an easy way of checking?

Any help would be greatly appreciated, Especially on the timing issue, I'm sure I read somewhere that those figures in the book are wrong..

[RockCrusher]

Timing......30* at 3000 RPM is generally the acknowledged rule of thumb. You might need more or less but start there.

RC
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[midtravelmidengine]

timing sounds a bit off. try 28-32 by 3000+.

also did you cc the new heads or the olds ones? you might have also lost compression! especially with the 110 cam, it like a bit of crompression...
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[jfats808]

Head ccs on the new head more than the 040 heads? That is a classic overlook. Did you just slap the new heads on and not check your cc difference? Jetting should also change , 55/130ish range.

Had to change after Dave mentioned they were 32 vents~
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[vwracerdave]

What exhaust are you using?

40 IDF's came with 28mm venturies. With 40X35 valves I would increase them to 32mm and rejet them.
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[faiz]

I failed.
I didn't check the head cc's.
Any idea what the standard head cc's are for a 1500 040?
How do I know if the heads I removed have been fly cut to increase the compression ratio?
Heres a pic of them side by side, I'm certain that the new heads had less cc's just by looking but I should've checked. Such a retard.

Great its impossible to check now I guess unless I could ask CB what the standard head cc is on their heads.
If I have to remove them again I wont be happy.
feel bummed out cause I knew I should've done it before I put them on.

I'll try changing the timing and see if that changes anything but I really want to get to the bottom of this.
Classic moment of I knew I should've done that.

[faiz]

[midtravelmidengine]

Can you get a cloes up picture of one chamber of the 040 head? is it heart shaped?

good thing is you can still cc the old heads to see what you HAD.
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[midtravelmidengine]

What version of the 044 heads did you buy? those chambers look nice and ported look big though..
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[faiz]

[faiz]

[Howard 111]

Timing.

I run semi-hemi cut heads. It's only 6.9 CR, but it's on a turbo engine. But even off boost, it runs great because I run plenty on timing, then the MSD BTM pulls the timing down when the turbo kicks in.

Give it more timing.


.

[faiz]

I think timing is definitely retarded.
I'm going to reset it tomorrow and see.
its 11.30 at night here in england so I don't think the neighbourhood will be pleased if I start revving her up to 3000rpm as it sounds ridiculously evil!!
I think I've chilled a bit since restudying the 040s but if its still off after setting the timing then I'll get worried.

[wbrown45]

Besides setting your deck height, you may also be feeling the power loss due to the big valves in a not so big engine. I used the same exact heads from CB on my 1776. It utilized dual 40mm Dellortos, and an Engle 110 cam. The compression was about 7.2:1. I had no power until about 4,000 RPM, and then it came alive, like an old two stroke motorcycle. When I swapped to 041 heads (39x32 valves) the lower end power band woke up. When you run too big a valve in an engine you tend to lose some intake velocity. If you have ever driven a smaller engine with 4 valves per cylinder (Toyota, Nissan, Alfa, etc.) you will know what I mean. They can tend to produce their power in the upper RPM bands. I even noticed this phenomenon in larger V6's, such as the last generation Taurus. The 12V engine was 45 hp less than the DOCH 24V. But you had more torque (real world) with the 12V. If you want more power at lower revs, then keep your valve size modestly large. Just throw a stroker crank in it (I love spending other people's money!) and keep those heads. Good luck! (I would love to see England someday, I'm a serious Anglophile).
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OK Thang

[faiz]

That is what I was worried about, power coming in later.
But yes the plan is to get a 78 stroker in there when funds allow so I figured its better to get these heads than buy twice.
It does rev a lot more easily though.
I'll let you guys know how I get on tomorrow.

[miniman82]

The new heads probably have bigger chambers than the old ones, throw timing at it to see if it helps any. If not, I'd suspect your compression is now too low and you should add a turbo.
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[faiz]

[jfats808]

[faiz]

[AlteWagen]

Your old heads are deep fly cut AND semi hemi. Measure them and Im sure they will be mid 40s. The 044s usually have around 57cc chambers from the ones Ive seen. I would call to make sure what they are lately.

I think that difference in cc and chamber design made the difference.

Did you use shims to adjust compression initially? If so you can remove them to help but the correct way would be to get some machine work done. To save your case and new heads machine the base of the cylinder, a tigher deck will help A LOT!!