Clearanced my block at the intake valves

Mike T

Well-Known Member
Well after going back and forth I finally decided to clearance the block where the intake air sees a little ledge at the top of the bore. Not sure how much it may help but it's done.



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Something worth mentioning.......since we all learn from our mistakes....I did have a little issue that's not apparent in the photos.

If anyone does this at home don't be temped to radius the trailing edges of the relief beyond the scribe lines!

I did and found that the gasket is already on the edge of the bore in this area so I'll need to clean the gasket up a few thousandths (steel gaskets) to make sure that it's not a potential hot spot hanging into the bore. Using stock type gaskets would not have allowed me to do this.

I'll add a illustration of the area that I'm talking about.
 
Great idea!:cool:

Why?

It looks like it introduces other potential problems like weakening the sealing force of the h/g in that area as well as altering the quench and compression ratio of the cylinder.

Also I'd like to know how far away the top ring from the base of the bevel?

Is this really a benefit in a boosted motor??
I know it's an old school band-aid for oversize valves in a small bore but is there proof that it's beneficial in our motors??
 
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Is this a street or race motor?

Probably will drive it 5-10k a year and will be running it at the track as well.



Why?

It looks like it introduces other potential problems like weakening the sealing force of the h/g in that area as well as altering the quench and compression ratio of the cylinder.

Also I'd like to know how far away the top ring from the base of the bevel?

Is this really a benefit in a boosted motor??
I know it's an old school band-aid for oversize valves in a small bore but is there proof that it's beneficial in our motors??



Rob I'll try to explain my thought process.

An engine builder that I really admire recently critiqued a set of heads that I ported for this motor. He said that modifying the block in this manner would be beneficial.

Most HG's that I've blown have been at the 12 or 6 O'clock position (looking from the side of the motor) so I really don't see this as weakening the HG seal.

CC's ?? Maybe 2 CC's.

I've made other changes to the heads that were far more radical to the quench area than this and that didn't seem to hurt performance or detonation resistance.

The top ring is about .195 from the notch at TDC so there is plenty of room.



Performance gains??? I don't know but how could a 90 degree protrusion be good for airflow?
 
Thought so.
Almost looks like an AL block with sleeves from 2K miles away. Good luck!


LOL.... I just noticed what your talking about. With the rings in the block it does look like sleeves at first glance. Didn't notice the John Deere in the bottom of the cylinder either.
 
I have also done it on the exhaust side as well.....not as much interference there but it does open up the shroud area a smidge.
What did you find out on the rings Mike?
 
What did you find out on the rings Mike?


I cut all but 1 of the rings from a "new" but older set that was in my tool box for a while. I got complacent when cutting the last ring and didn't check it in the bore (apparently was a little short already) so that's when I ordered the new set thinking I'd rob 1 ring from the new set. Well as you know they where a little different. Decided to use the newer style and recut them all again.
 
Rob I'll try to explain my thought process.

An engine builder that I really admire recently critiqued a set of heads that I ported for this motor. He said that modifying the block in this manner would be beneficial.

Most HG's that I've blown have been at the 12 or 6 O'clock position (looking from the side of the motor) so I really don't see this as weakening the HG seal.

CC's ?? Maybe 2 CC's.

I've made other changes to the heads that were far more radical to the quench area than this and that didn't seem to hurt performance or detonation resistance.

The top ring is about .195 from the notch at TDC so there is plenty of room.



Performance gains??? I don't know but how could a 90 degree protrusion be good for airflow?[/QUOTE]

Did he recommend this because the valve was to close to the cylinder ? If you were around 30 thou or more from the cylinder wall there isn't really any benefit to doing this in a turbo application because the boost forces the air in versus an NA application where the piston itself fills the cylinder where this was popular in the 60's and 70's.

It would be more beneficial to hold the valve open longer with a higher ratio rocker than what you gain by doing what you did. The reason that it became popular in the first place was when over sized valves were stuffed in a factory head before aftermarket heads became popular. I know that GM [pontiac ] used this method back in the day as well as chrysler on the hemi head.

That was before forced induction, except in the case of top fuel and funny cars of the day.

I'm not saying it will hurt performance in your case just that it may not have been needed in the first place. I haven't seen your heads so I guess I could be way off base.

My machinist has done this (notched the cylinders) on many race motors and has confirmed that little to no performance gains are seen on the dyno and in some cases it has even hurt some. It is done more out of necessity so the valve/s have the clearance needed to avoid the wall not for any straightening or anti swirl effect of the incoming air.

I'm always looking for an advantage myself and that's why I question what you have done, to see if you or some one you know can verify any performance advantage in yours or a similar application versus not notching because it is valve specific or because there is a gain in some other area.
 
I am not speaking for Mike and only sharing my perspective:

Few of us have the equipment time or money to provide conclusive and numerical evidence of the little things we believe make sense. In this case, the change (eyebrow) makes sense . . to me. Will it hurt? Not sure. Will it help? Not sure, but it makes sense.

I have obsessed ove a few things that may have hurt performance but it made sense and I felt good about it, and could care less to *measure* the improvement. It all adds up. ☺

Rob, what you are saying makes sense as well so please don't misunderstand my post.

Never met or talked to Mike but from following his threads on the DP, head porting etc., his enjoyment appears to be in creating and trying things. Luckily for us, he chooses to share those publicly fully understanding he may get ridiculed.

There is a lot to be said for that.
 
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I am not speaking for Mike and only sharing my perspective:

Few of us have the equipment time or money to provide conclusive and numerical evidence of the little things we believe make sense. In this case, the change (eyebrow) makes sense . . to me. Will it hurt? Not sure. Will it help? Not sure, but it makes sense.

I have obsessed ove a few things that may have hurt performance but it made sense and I felt good about it, and could care less to *measure* the improvement. It all adds up. ☺

Rob, what you are saying makes sense as well so please don't misunderstand my post.

Never met or talked to Mike but from following his threads on the DP, head porting etc., his enjoyment appears to be in creating and trying things. Luckily for us, he chooses to share those publicly fully understanding he may get ridiculed.

There is a lot to be said for that.

I'm not here to ridicule him or what he has done. I'm glad he is willing to do things that may or may not help. We all have done something at some point that we think no one else has done or has been recommended by someone in the pursuit of power or reliability.

It's a good thing that people share what they have done or plan to do. In the case of doing what he has done it's been proven that as long as he hasn't gone outside of the parameters it's more than likely there won't be any ill affects. Every engine has it's own characteristics though, and what might be beneficial on one could be negative or neutral on another. That is why I ask the questions when I see something done out of the ordinary on our engines.
Notching the block is nothing new, it has been done for over forty years. The thing that makes me ask these questions is that the 3.8 only has four head bolts per cylinder and is notoriously weak in the head sealing department and want to know if this will increase the chances of gasket failure in this case.

When considering any modification it should be noted will this mod be beneficial on my intended use? That's why I ask questions like is this a street/strip motor or a race motor. Will it be a high boost application?

The more info that you have on something the better decision you can make on whether you want to follow someones lead or stay in the safe zone so to speak.

There is no doubt that in the notch area you are putting more stress on the fire ring. This may or may not be an issue on our motors but if there is evidence of it I would like to know. I also know that how it's performed { oringed } to prevent the fire ring from being pushed out due to the shape of the cylinder bore, the boost levels and a host of many other factors will determine the outcome of this or any other modification and if the OP doesn't know what they are then maybe someone else with the same mod will chime in after reading and share their experience.

You said you could care less to measure any improvement and that's fine for you, but others may want to know what if any improvement was gained and also what if any detrimental effect any said modification may have had so they can decide if that mod is worth doing in their situation.
 
Rob I think your questions are all reasonable and quite honestly I can't give a definitive answer on some of them. I understand your point that the heads and block as cast from the factory can make huge power by changing valve events, adding boost and so on. This is a proven fact but I've chosen a little different path with this motor. I've said in other post that this one is my personal "lab rat" and I'm having fun with it.

To sum this motor up it will have a CR in the lower 8-1 area, middle of the road roller profile that's been around for a while and heads that are somewhat unique in chamber design. The basic idea has been to straighten out any irregularities that may impede flow.......preliminary flow testing of the heads has been both promising and rewarding.




Jerryl has pinpointed the motivation for most of my post. I like to post photos of small projects that I'm working on with the hopes that it may spark a worthwhile conversation or give someone a visual of something that they may not have seen before or fully understand.
 
Rob I think your questions are all reasonable and quite honestly I can't give a definitive answer on some of them. I understand your point that the heads and block as cast from the factory can make huge power by changing valve events, adding boost and so on. This is a proven fact but I've chosen a little different path with this motor. I've said in other post that this one is my personal "lab rat" and I'm having fun with it.

To sum this motor up it will have a CR in the lower 8-1 area, middle of the road roller profile that's been around for a while and heads that are somewhat unique in chamber design. The basic idea has been to straighten out any irregularities that may impede flow.......preliminary flow testing of the heads has been both promising and rewarding.




Jerryl has pinpointed the motivation for most of my post. I like to post photos of small projects that I'm working on with the hopes that it may spark a worthwhile conversation or give someone a visual of something that they may not have seen before or fully understand.

That's all well and good. Just make sure you post the results if possible as you go.

Just be honest and share it all, The good the bad and the ugly, so others can either use or stay away from certain modifications.
 
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