Head mods

[SeriesVtime]

Hi Jim,

I'm curious why you've 'cooled' on the 'Vizard modified cumbustion chamber'? Improvement not worth the hassle?

Jeff

 

[RootesRacer]

Hi Jim,

I'm curious why you've 'cooled' on the 'Vizard modified cumbustion chamber'? Improvement not worth the hassle?

Jeff

I dont want to answer for Jim, I'll give you the answer were it asked of me.
With the Vizard mod, or Holbay for that matter, just doing the mod results in a GAIN if chamber volume, so unless you go with flat top pistons, you are at best going to loose some low end torque, and at worst horsepower too.

Most folks that build or rebuild their rootes engine dont have the resources or likely the knowledge to have custom pistons made that round out the compression needed due to the chamber mods.

 

[Jim E]

I pretty much agree with Jarrid

 

[RootesRooter]

Shave the head 50 thou and you'll lose most if not all of the extra chamber cc's created by the Vizard mod.

Combine it with a "KB" grind cam from Delta Cam in Tacoma, WA and you'll LOVE it. More torque and hp throughout. The normal acceleration 'gap' in my Series V tranny between 2nd and 3rd disappeared entirely!

 

[puff4]

Not trying to gang up, but I'm kind of with Jim and Jarrid, too.

As to shaving the head, yes, that would probably work, but these heads are getting rarer and rarer to find with enough meat on them to rebuild - I kind of hate to see someone whack off 50 thou all at once... just makes it that much closer to being unusable down the road.

 

[Bill Blue]

Kevin, sounds like they are pre-skimmed and perfect for the conversion!
Bill

 

[Tom H]

My calculations (confirmed with actual results on my 1725 head) shows the following:

1) Vizard mod adds about 2.2 to maybe 3.0 cc to chamber volume, depending on how agressive you get in removing the metal. The drawings I used show the side walls of the modified chambers as having a straight (not curved)slope, which minimizes the actual volume increase.

2) A valve grind also increases the volume, by 1-1.5 cc as the valves set deeper into the seats

3) You decrease the chamber volume by about 1 cc for each 11 thou you mill the head.

So as Bill indicates, if your head is already skimmed 30 thou or so you are all set for a Vizard mod. It will just bring the CR back to stock, if you use stock pistons.

In my case I ended up with a volume gain of about 4.3 cc due to Vizard mod, valve job, some repaired damage on the chambers, and a 6 thou skim. But I compensated for that by a 3 cc reduction in dish volume on custom pistons, which were required since I also used Chevy rods and added 0.10" stroke. The increased stroke combined with the net increase of 1 cc volume kept the CR close to stock at 9.3.

I'm not sure what all accounts for the improvement, but the combination of Vizard, KB Grind, 0.10 more stroke, 0.037" increase in bore, and a Weber 32/38 makes my old Alpine a great runner. I can best notice it when I step on the gas at 70 MPH in 4th gear OD and feel the acceleration.

Tom

 

[Jim E]

Maybe I should peal this discussion off and move it.

Typically when I was doing the V mod the chambers would be around 41-42 cc when it was all said and done. I measure using a plastic plate and 50 cc syringe so my acuracy could have a plus or minus a half cc pretty easy but I am more concerned with doing the measure the same and the number being equal chamber to chamber even if I am not dead on the cc.

The other thing that the V mod would help with is these motors usually need to have the block decked due to the corrsion on the deck surface. Have seen them where 8 thousands would not clean them up completely. So that is another compression increase to think about. Then too any over bore will rasie the compression.

So I am thinking the full V mod on a dish piston motor with the block decked and a over bore will put you in the low 9 to 1ish range. Which is more or less the same motor I had in my SV at one point along with the KB grind cam and a lightened flywheel with a set of 150s. nice mover at speed and would run on the cheap gas. When I added a set of 40 DCOEs it really woke it up at speed, the 70 on the freeway hit the gas and it moved deal.

But.... this combination makes for a different driving car in my opinion basically you spin the snot out of them the motor is rev happy and anyone with this type of combination really needs a rev limiter because they will easy spin until bad things happen.

I also think the V mod is wonderful on the chevy rod destroke motor which is really rev happy, but again it is a different creature not to mention it has a bottom end that can take a beating.

Now on a non V mod motor, more or less stock bottom end and the KB cam the low and mid range power just seems to be a lot better. Of course we are somewhere in the low 10 to 1 range and you will have to run premium and tinker with the timing to find the spot it likes. By the way I like the small exhaust valve head on this engine.

So guess I now lean more toward the higher compression less spin happy motors I just like the low and mid range grunt. Guess I need a test mule... have thoughts of one set up for gas or E85 and try some builds I have in mind. My thoughts are if you are going to order custom pistons then go big bore maybe 70 to 90 over with chevy rods and then talk to Delta about a low and mid range cam [which I am thinking to do for the stock rotating assembly motors too] then tinker around with different head configurations and see what happens. I think a big bore 11 to 1 grunt motor on E85 would be interesting. I also think the racers might want to think about a more spin happy version of the big bore chevy rod motor on E85.

Anyway I maybe full of bologna but those are my thoughts on the whole deal.

 

[Chuck Ingram]

Anyway I maybe full of bologna but those are my thoughts on the whole deal.

Hey Jim
Balogna is good.

 

[Tom H]

Jim, I used the same technique to mesure chamber volume. I measured 39.2cc on the original head. That was a virgin head (even at 40+ years old). After I did the Vizard mod it was about 41.5cc. But that was before I had the head repaired. There was damage in #4 from corrosion and a busted ring. They welded up some of the damaged area, had to shave 6 thou and did a valve job. That ended up making the #4 chamber 43.5 cc. The others were about 42.2 cc - increase due to valve job less decrease due to shave. So I had to carefully increase the other 3 by another 1.3 cc - not easy, had to grind a depression in some of the flat area in the V's between the valve seats.

My spread sheet shows that with a 60 thou overbore, stock stroke, stock piston dish of 7.2cc, deck shaved by 8 thou (leaves 10 thou) and a chamber volume of 42.1 (stock 39.2 plus 2.2 from Vizard plus 1.2 from valve job, less .5from 6 thou mil) gives you a CR of 9.11- just about matches your thoughts.

Now I can do the math and measures very well. What I don't have much feel for is the effect. You describe an engine like this as "spin happy" . Not sure I understand.

And yes, I think you should move these last 9 or so posts to a new thread on the Modified section . Maybe call it Head mods.

And while you're at it can you tell us about the valve stem seals you are now using. I don't think I heard about such until I saw this "head for sale" post.

Tom

 

[Bill Blue]

Jim, I don't know what your are full of, but you have been thinking and assessing and that is good. It drives me nuts when guys do something simply because that's the way it has always been done.

Bill

 

[RootesRacer]

This is all good info, when I did my last head, I had the benefit of a flow bench to determine if my efforts were paying off.

Based on what I found, I came to the conclusion I didnt care 100% for either the vizard, nor the holbay specified modification, as neither went far enough so as to reach my flow goals.

The vizard was closer to what I liked, but I found that the improvement it made didnt flatten off until much more material was removed than could be tolerated.

I ended up with my own set of mods that looked much like the vizard mods, but only in the flow critical areas of the head so as to maximize flow rates without adding too much extra volume.

My head "before" volumes were 38cc and my "after" volumes were 43cc or a net change of 5cc. This after having new seats and new stainless valves so as to raise the effective compression by eliminating extra recession volumes.
I would estimate I actually removed 7+cc of material per chamber.

My end flow numbers went (IIRC) from 110CFM intakes to 155CFM intakes.
The exhaust was a better yet % improvement, though I dont recall those numbers. This was with very large valves, and it also showed the ridiculous
valve lifts specified from Holbay ETC, were totally unnecessary since flow started to taper at around 350 lift, and little extra was to be had from 400 to 450 lift.

Bottom line is in the end, to get my net 10.5/1 CR, I had to raise the pistons compression height to above the deck, obviously they were flat tops ETC.
Had I done these mods with stock pistons, I surely would have lost power and torque.

 

[Jim E]

"You describe an engine like this as "spin happy" . Not sure I understand."

Spin happy or rev happy, the motors like to spin up into higher RPM ranges than the stock units, as in they spin up easy not labored and that seems to be where they make power and like it, run smoother the higher in RPMs they go. Which is why I say this sort of build needs a rev limiter because I think they spin so easy they will turn until the guts come out.

 

[RootesRacer]

"You describe an engine like this as "spin happy" . Not sure I understand."

Spin happy or rev happy, the motors like to spin up into higher RPM ranges than the stock units, as in they spin up easy not labored and that seems to be where they make power and like it, run smoother the higher in RPMs they go. Which is why I say this sort of build needs a rev limiter because I think they spin so easy they will turn until the guts come out.

Yeah, just about anything you do to these motors regarding porting and
camming results in much more power in the upper RPM band it is actually
worthwhile revving into the danger zone.

My warmed over 1725 with a cam and DCOE webers is still climbing the HP
curve at 6500 RPM when the stock valves and springs start to float.

It makes a wonderful (albeit self destructive) noise at the point of float.

 

[Tom H]

Jim, Thanks for the explanation. I guess I really need to try a couple different Alpines at a time to realy get an understanding, but your description helps. After modifying mine it's not too easy to remember how it drove 3 years earlier! I'll have to bring mine to an Invasion or some other group event.


And could you explain what you are doing with valve stem seals on these heads? I think this is something new.

Tom

 

[Jim E]

The stem seals are a quality umbrella piece, you machine the top of the guide so it fits on it. Do not have the part number in front of me but they look about like the below picture.

 

[old grumpy]

High lift, long duration camshafts are nice in theory (and on the track) but can be a pain in regular driving. The challenge is to be able to make more power from the standard camshaft and that power is to be found in the head....more or less.

I hope some clever one will do this time consuming work (another 15-20 hp from the Alpine camshaft) and the the rest of us can copy the ideas

Holbay did some good work on the head with the small ports and the carburetion. The Holbay engine is not high rev. engine. It's a tractor!!

 

[RootesRacer]

I hope some clever one will do this time consuming work (another 15-20 hp from the Alpine camshaft) and the the rest of us can copy the ideas

Sure, no problem.

Though I wouldnt consider myself that "clever", about 10 years ago, I produced 15 or so HP extra power with a stock cam, unmodified ports, with standard compression pistons.

The power adder was fuel injection and "good" ignition power and timing.

Want 10 extra HP over stock?
Add twin DCOE webers to the mix.

 

[old grumpy]

Was I too conservative? Ok, modified head, port and combustion, flat top piston, DCOE
Result: about 20 HP between 3500 and 4500??

 

[RootesRacer]

Was I too conservative? Ok, modified head, port and combustion, flat top piston, DCOE
Result: about 20 HP between 3500 and 4500??

No matter how you put the mods, the stock cam (SV) doenst have much overlap and will yield peak torque at around 3800 RPM.

The added compression and carb flow will give more torque across the board, but the cam itself will be the limiting factor in making HP.

Not sure why you would want to keep the stock cam for any reason with any other mods. Its short duration and lack of overlap would only make it good for a "turbo" application, and I dont see any of you doing that.