Current engine, vs power it would pick up if I mill the heads. Think it's worth the labor & $300 at the machine shop ?

 

Tough call. How long has motor been together? Could it be due for a refresh on valve job, resurfacing and springs/seals? Do you think the predictions are accurate. How much is milled? Usually gains from compression increase when you are in the 10:1 area or close to that are very small. Mill head may gain what? Half point at most? Maybe less? .030” is typical mill and usually 5-6 cc. Not a huge gain usually but every bit helps depending what you want out of it. I would think looking at cam specs maybe better than just a mill job, or more intensive porting job to the heads to gain airflow. Hard to say

 

The short block has been together since about 2012, but it only has maybe 250 mi on it.

The heads are from 2015, probably about a hundred miles on the heads. (Afr 210)

I would be taking .060" off, which would increase the compression from 9.3:1 to 10.3:1.

So I guess what I'm trying to figure out is, is it worth doing to pick up a little more low end torque where it's a four-speed car with 3.54 rear end, or is it not worth taking the heads off having the milled putting them back on redoing all the valve adjustments and everything lol.

This motor is going in my c3.

-- Joe

 

.060 seems like alot. Intake may need cut too

can you just advance cam a bit?

 

Sure, or I could just leave the combo alone lol.

I spoke with AFR, they said the difference between the 75cc and 65cc AFR210's is they flat mill .060". Absolutely no other changes.

-- Joe

 

Wow didnt know that. So its already flat milled .060, and if a guy wants to go to 58-60cc another .030-.040”...thats a ton off the head surprised intakes still fit well

 

Oh no sorry, I have 75cc AFR210s, I want to take them to 65cc.

Turning a older blower motor into a naturally aspirated motor.

-- Joe

 

Funny I had my LS6 head chambers on my TT C5Z opened up to 72 or 77ccs (forget now) by West Coast Cylinder Heads to lower my CR (had a -2 cc dish also) to around 9.2:1. Worked really well and I always figured if for some reason I wanted to go back to NA, I could swap the heads back out with some stock LS6 243 casting heads. Ends up I never did go back to NA on that car.

 

You will probably need shorter pushrods also.
My , how was your intake port alignment when you put the engine together?
If it was spot on, then I would leave it alone. So many other things change with that big of a cut.

Keep this in mind: the new powers-that-be will soon have the gas prices at $5.00/gal. Do you really want to have to pay for premium fuel?

 

Lol, true but all I do is drive to car shows.

-- Joe

 

Is this theoretical gain?

First of all - you won't feel it. Not enough of a difference. 10 HP.... no one can feel that. Even if the difference was between 100 and 110 it would be tough to notice. At that power level you are talking about 2%. Trust me no one could feel this.

Second - If that's a theoretical number - you might get less because you might find that the increased compression won't tolerate the same timing on the pump gas you run on. If you run leaded C16 then that's likely not to be an issue. IDK what you are running for fuel.....

IMO it's absolutely NOT worth the money or the time it would take and the inevitable potential to introduce leaks, etc.

For reference I dropped my compression from 9.8 to 8.5 and didn't lose enough to actually tell the difference in the real world driving experience, but it got a LOT easier to tune - it's effectively impossible to make it detonate no matter how much timing I have thrown at it. I did this for adding a ProCharger, but still - the difference NA in power on pump gas wasn't worth the trouble the higher compression gave in terms of ease of detonation.

Just my view on it.

GD

 

It's some simulations using EE Pro. The engine was previously used as a blower motor, but it's going in naturally aspirated in my C3, 4 speed car, so I was looking for a little more torque in the lower RPM's for in-town driving, not peak HP.

I could sell my AFR 210's and buy some smaller chamber 195's I suppose, or just leave it alone. Maybe with the right spark curve it will still be stout in the lower RPM's. Car has a 3.54 rear to keep the RPM's reasonable on the highway (not for fuel economy but rather noise lol).

This is kind of the opposite of every one elses build these days. It seems like everyone wants turbo cars that are a stone under 2500 RPM and don't start coming alive until 3500-4000. I'm trying to make something that makes a ton of torque where you actually drive it around town, which is really 1500-3000 rpm.

-- Joe

 

Big inch motors even with low comp usually have plenty of low end driving torque tho

 

True.

I'm getting the sense that you'all agree with my initial thoughts, it's not worth the time and effort to get 15-20 foot pounds, which is why I posted looking for opinions.

I guess I'll just leave the long block alone.

I'm gonna sell the miniram though. Besides the fact that it looks a little too "modern" , I'm not impressed with how different the plug readings are on the front vs rear cyls. I think the force induction probably makes it worse, but it's not very even air distribution.

Probably gonna do Holley sniper. I've played with a few now and the Holley software is a little nicer than Tunerstudio (megasquirt), and while it doesn't have all the functionality of a MS, for this project it's not lacking anything I need. (Dizzy, fuel pump control, electric fans, AC)

-- Joe