What do you think of this build

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straightlinespeed

straightlinespeed

Sometimes I pretend to be normal
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Uvita, Costa Rica
Current build in the car is as follows.

LA 360
Stock pistons Silvolite 1279 in the hole about .067
https://www.uempistons.com/index.php?main_page=product_silvolite_info&cPath=6_25_27&products_id=1654
.045 x 4.180 bore, head gaskets
XE268H cam
Stock Magnum heads
Air Gap
750cfm carb
TTI's

Using the KB calculator I figure my Static is 8.9 and Dynamic 7.4

I'll be pulling my 360 soon and correcting some issues from the prior engine builder who did not listen to what I wanted in the first place. Sadly nothing but a poor performing engine since day one and tough to get tuned. I was lucky enough to have the prior engine builder give me a new set of pistons and correct valve springs to help me out. So Im curious what you all think if I build the engine the following way.

LA 360
KB362 at zero deck
https://www.uempistons.com/index.php?main_page=product_piston_info&cPath=3_4_23&products_id=3070
.040 x 4.080, bore head gaskets
XE268H
Magnum heads if mine are not cracked. (Otherwise swap to EQ's or possibly a LA head not sure which one), wanting to keep iron heads.
Air Gap
750cfm Carb
TTI's

I figure static to be 9.5 and dynamic 7.8 with the magnum heads.

I want to keep the compression safe to use pump gas. Not sure what that is I've seen 10.5 to 9.5 SCR with iron heads. Im looking for more of good cruising engine, decent mileage, premium pump gas, but be able to have some fun with the car 90% street 10% track.

Curious what you engine experts think of this set up.
 
So, basically the same engine but with appox .6 more compression? I wouldn't expect it to run that much different than before. Going from 8.9 to 9.5 isn't going to be earth shattering. I would guess about a 10 hp gain. Should be good for high 12s in 3200 A body.
 
My current engine may have less compression. I was giving the benefit of the doubt it was that shallow, which I wont know until I pull the heads. Based off of what you say I should run, it will be a huge difference. When I had it at the track this past July the best it ran was 14.2.

But that is why I posted this, Im looking for options on this rebuild. I want it built correct this time. I was always under the impression I should keep it under 10:1 compression when running iron heads. True or not? If I could bump my compression up and still keep it within the good cruising, mileage, and pump gas. That is my main goal.
 
What you have now should be seeing very low 13s and an occasional 12.9XX, IMO. That's what forphorty's trying to tell you. It's not all in the engine.

I thought is was running pretty good now. Before I spent all of THAT money, I would iron out the combination you have now, or you may be setting yourself up for some disappointment.

It looks like as much as we have talked, you would take some of what I have told you as truth. You're talking a hair over 1/2 a compression point. Even one whole point wouldn't take you from 14.2 into the 12s. It's in the car Raime, not the motor. But do what you will and how.
 
RustyRatRod said:
What you have now should be seeing very low 13s and an occasional 12.9XX, IMO. That's what forphorty's trying to tell you. It's not all in the engine.

I thought is was running pretty good now. Before I spent all of THAT money, I would iron out the combination you have now, or you may be setting yourself up for some disappointment.

It looks like as much as we have talked, you would take some of what I have told you as truth. You're talking a hair over 1/2 a compression point. Even one whole point wouldn't take you from 14.2 into the 12s. It's in the car Raime, not the motor. But do what you will and how.
Click to expand...

I hear what your saying Rob, and what we have talked about I do get. Sadly though it has to come apart. The coolant leak decided to show back up. I need to figure out where its coming from. So in order to do that it has to come back apart. Trust me its not that I want to spend the money on machining or what not, but if it comes to that I may as well build a new engine with as much of my parts as I can. Hence why Im reusing the majority of my current build. Hell I got a free set of pistons, that I can more than likely exchange for a different set, if its determined to go a different route. Kinda, sorta, see what Im getting at?
 
Yeah. I guess if I HAD to take it apart, I would do the same, but I would not use the KB pistons. I would use the Sealed Power. No special ring requirements. I am just lazy.
 
RustyRatRod said:
Yeah. I guess if I HAD to take it apart, I would do the same, but I would not use the KB pistons. I would use the Sealed Power. No special ring requirements. I am just lazy.
Click to expand...

I dont mind having to file the rings. But do you have a particular piston # in mind? Anything else you would change?
 
Re-check your calculations for the Silvolites; the .067 below deck look incorrect. The Silvolites you ID have .099" lower compression height than the KB's, and I get a deck height of -.110", not -.067. You would have to deck the block quite a bit to get a -.067 deck height. I am computing 8.22 static CR for the Silvolites, with standard deck height of 9.599" and a 63 cc combustion chamber. My KB numbers are coming up about 9.25 SCR, so that is not too far off from yours. (I am using the Pat Kelly CR program.)

I'd go with the KB's simply for the quench effect to help combat detonation, and deck the block .010" to get the .040" max piston to head clearance. You would still need to deck the block a small bit (about .010") to get them flush, unless that was already done.

I personally would not worry about the hypers and the rings; just one more step to get the ring gaps to the KB specs. I've raced hypers (rallying) on a turbo car making about 1.6-1.7 HP per c.i. on around 14-15 psi max boost and they survived fine (despite my initial concerns). Oddly, we used pretty standard rings gaps with them opened up just a bit above stock, so I am curious why KB says to use such larger top ring gaps on their hypers.
 
nm9stheham said:
Re-check your calculations for the Silvolites; the .067 below deck look incorrect. The Silvolites you ID have .099" lower compression height than the KB's, and I get a deck height of -.110", not -.067. You would have to deck the block quite a bit to get a -.067 deck height. I am computing 8.22 static CR for the Silvolites, with standard deck height of 9.599" and a 63 cc combustion chamber. My KB numbers are coming up about 9.25 SCR, so that is not too far off from yours. (I am using the Pat Kelly CR program.)

I'd go with the KB's simply for the quench effect to help combat detonation, and deck the block .010" to get the .040" max piston to head clearance. You would still need to deck the block a small bit (about .010") to get them flush, unless that was already done.

I personally would not worry about the hypers and the rings; just one more step to get the ring gaps to the KB specs. I've raced hypers (rallying) on a turbo car making about 1.6-1.7 HP per c.i. on around 14-15 psi max boost and they survived fine (despite my initial concerns). Oddly, we used pretty standard rings gaps with them opened up just a bit above stock, so I am curious why KB says to use such larger top ring gaps on their hypers.
Click to expand...

That is right! Thank you!! I forgot about the compression height difference.. I was thinking that the 8.9 SCR was to much for those pistons, but just couldnt figure out why.

8.2 SCR and 6.8 DCR is where my engine is sitting currently.

Ok, with that getting straightened out now. Do you believe a piston such as the KB362's is a good option or should I look at another piston with less head volume to bump up my compression a little more? What is a safe SCR with iron heads to run? I've seen anywhere from 10.5 to 9.5 is safe with pump gas.
 
The really low cost Speed Pro's are still down in the hole almost .050" with a compression height of 1.637". Better (not great) CR but no quench.

The Speed Pros that RRR listed are .015" further down than the KB232/362's (.015" lower compression height) and it will take a fair amount of block decking to get a quench height of .040" or so, AND if you do that to get the quench height right, you will have a a static CR of 10.7. So, if you do quench with the Speed Pro's for regular, runnin' around street use, you're pushing well past the conventional wisdom of staying at 9.5 or less for iron heads. So then you don't deck the block to keep CR in bounds and give up the quench effect.

I like to go for the quench effect since first doing one many moons ago and not having detonation with a 10+ SCR iron headed 351C, and the KBs look to have been purposely designed so that you can get the quench distance right with a couple of different ranges of CR, one of which is a pump gas CR range.

With the magnum heads, I think you need to be going for the KB232's, not the KB362's. For the 362's, look at the pix and see the raised pad near the valve eyebrows? I think those are supposed to be for the open chamber heads, to fill up the flat open area in the combustion chamber and form the quench in that area. Your magnum heads are flat there and I believe the smaller raised pad of the 232's makes quench with the flat area on the magnum heads, with a specific head gasket thickness. BUT, I am just surmising on those details; you ought to call KB and do your homework and not listen to me 100% on that aspect; I am just entering 360-land for the 1st time (planning a 360 build with magnum heads too).....I need to find out myself how tall those KB232 quench pads are and how they work for sure with the compression height and gasket thickness with the magnums. (If they are too tall, I just have them milled down.)

It looks to me that the KB232's will make an SCR of around 9.3 with a .04" thick head gasket and 63 cc combustion chambers. Looks like a good place to be.
 
nm9stheham said:
The really low cost Speed Pro's are still down in the hole almost .050" with a compression height of 1.637". Better (not great) CR but no quench.

The Speed Pros that RRR listed are .015" further down than the KB232/362's (.015" lower compression height) and it will take a fair amount of block decking to get a quench height of .040" or so, AND if you do that to get the quench height right, you will have a a static CR of 10.7. So, if you do quench with the Speed Pro's for regular, runnin' around street use, you're pushing well past the conventional wisdom of staying at 9.5 or less for iron heads. So then you don't deck the block to keep CR in bounds and give up the quench effect.

I like to go for the quench effect since first doing one many moons ago and not having detonation with a 10+ SCR iron headed 351C, and the KBs look to have been purposely designed so that you can get the quench distance right with a couple of different ranges of CR, one of which is a pump gas CR range.

With the magnum heads, I think you need to be going for the KB232's, not the KB362's. For the 362's, look at the pix and see the raised pad near the valve eyebrows? I think those are supposed to be for the open chamber heads, to fill up the flat open area in the combustion chamber and form the quench in that area. Your magnum heads are flat there and I believe the smaller raised pad of the 232's makes quench with the flat area on the magnum heads, with a specific head gasket thickness. BUT, I am just surmising on those details; you ought to call KB and do your homework and not listen to me 100% on that aspect; I am just entering 360-land for the 1st time (planning a 360 build with magnum heads too).....I need to find out myself how tall those KB232 quench pads are and how they work for sure with the compression height and gasket thickness with the magnums. (If they are too tall, I just have them milled down.)

It looks to me that the KB232's will make an SCR of around 9.3 with a .04" thick head gasket and 63 cc combustion chambers. Looks like a good place to be.
Click to expand...

The 232's are the quench head and according to KB site has a .050 raised pad and 18cc volume
https://www.uempistons.com/index.php?main_page=product_piston_info&cPath=3_4_23&products_id=3024

The 362's are a step dish with no quench pad and a 19.4cc volume. I think I see what your talking about with the small pad above the eyebrows, but wasnt sure if that was and accurate portrayal of it.
https://www.uempistons.com/index.php?main_page=product_piston_info&cPath=3_4_23&products_id=3070

I dont understand the whole quench theory honestly. I've read thru the sticky post here on the site numerous times, but it hasnt sunk in yet. I've been playing more and more with the calculators and have come to figure out that everything is based off of zero decking the pistons. Then changing the head gasket thickness and bore also effects the compression ratios.

So those that recommend the Speed Pro's with 5cc volume, to keep the SCR down do you leave them down in the hole to get to that, or a larger CC head design? Which if you do sounds like you lose the quench. So how important is the quench? Or am I way off on this?
 
BTW found a note that the KB232 pad is .050" tall, so it looks like it will have to be milled with standard dimensions to get the right quench height. Ooops. I see you found that!

BTW, the quench effect is to squirt the air out of a very small gap at TDC in the combustion process to swirl it around and improve the combustion process. I suppose it was so-called as it 'quenches' any tendency to detonate....? The term has been around and the effect known and used since at least the 60's. My first time using it was 40 years ago with some TRW forged quench dome pistons in that 351C that I referenced; it must have worked as I never had detonation issues with over 10:1 true SCR and a low duration, high lift cam with low gearing and a stock TC, which is a good combo for detonation. It would ping on regular gas occasionally; I even towed with it with no detonation. Made me a believer.... But I would like to hear others chime in on that too.
 
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