rebuild recipe..help judging this.

[casual]

Alright heres what I've got going. I'm rebuilding my Renix motor and upgrading at the same time its got 250k+, odometer stopped working in late 09. Shes probably over 300k now lol..Goal: more efficient, more MPG and more power! Its a daily driver & camping rig, that gets driven hard.
I will be posting 4 variance of my build and need help on deciding which would be best! I want to run on 87oct and will not go higher! So heres the basics, only changes will be pistons dish & the cam!!
3.935 bore
3.413 stroke
58cc combustion chambers (I'm sure this will change, once the heads built it'll be CC'ed to be more accurate!)
.008 deck clearance
.038 head gasket thickness (mopar headgasket)
4.00 gasket bore
17cc piston dish (SP 677CP)
6.123 connection rod length
stock renix cam (75 intake closing valve angle)

With specs listed above, "renix cam & SP677's(17cc dish)"- Static comp- 9.2:1, Dynamic comp- 6.7:1

With specs listed above, "renix cam & SPH802s(15cc dish)"- Static comp ratio- 9.4:1, Dynamic comp- 6.84:1

With specs listed above, "Comp 68-201 & SP677s(17cc dish)"- Static comp ratio- 9.2:1, Dynamic comp- 7.79:1

With specs listed above, "Comp 68-201 & SPH802s(15cc dish)"- Static comp ratio- 9.4:1, Dynamic comp- 7.96:1.

I don't know what my combustion chamber CC will be yet, so these are just ball park figures! I want a slightly higher compression ratio than stock but still run on low grade 87oct gas.! So which option do you guys think is the best? Will the higher Dynamic comp cause me issues or no? I was always told if you can raise the dynamic comp without raising the static comp then its a good thing! But I'd rather ask you guys!
I live in California and its always hot here 80+ almost year round and summer we see 100+, I'm about 1000 feet above sea level, incase it matter! The motors going into a Renix era rig, so I do have a knock sensor, and I will be adjusting the AirFuelRatio with a adjustable map sensor. Monitoring AFR with my AEM wideband!
Help me decide on a recipe for my motor guys!

[SilverXJ]

.038 head gasket thickness (mopar headgasket)

Its .043-.044" thick, not .038"

17cc piston dish (SP 677CP)

using a dish that small with that tight of a quench will guarantee pinging on regular and midgrade.

6.123 connection rod length

You can't use the above pistons with this rod. Using the 6,123" rod with that piston, the piston will actually stick out of the block about .2"

[casual]

The headgakset thickness is .043..but compressed we get .038...So I put in .038.
Any reason why it'll ping with a small dish and tight quench? As long the compression ratio is in spec it shouldn't do it right?

And from what I was seeing now my pistons won't stick out of the head but I might be wrong..I'm not doing a stroker! I'm doing a rebuild thats .60 over!
Stock pin height 1.601, Sealed power pin height 1.585...That would make it .016 lower wouldn't it?

[SilverXJ]

No, the mopar head gasket and its variants are .043-.044" compressed, not .038".

And didn't see the part about not being a stroker. This is a stroker site so I assumed it was a stroker.

[casual]

No, the mopar head gasket and its variants are .043-.044" compressed, not .038".

And didn't see the part about not being a stroker. This is a stroker site so I assumed it was a stroker.

No I understand completely. I hunker down here because theres great info and great people to help you when you need it! Hmm, I know we ran a "mopar .043" headgasket in a jeepspeed style rig..when the motor popped we had it all apart, and measured the thickness..We got .038-.037, maybe it was a fluke..
Anyway, I know theres no set compression ratio for 87, 98, or 91oct fuel...but I need help in that department!
I was always told if you can get a higher dynamic compression ratio without changing the static then its a good thing..Not sure how true this is though! Also any reason why a small dish and close quench isn't a good idea?
Reading Dino's sight, he dropped in a Mopar .043 head gasket with stock dish pistons which is 13cc..I'd be running the same and a bigger CC.

Also any advice or info on running a Static compr of 9.2-9.4:1 & a Dynamic comp of 7.79-7.96:1? I'd love to run a cam for some more power, and since my static comp is staying the same, I should be ok right? Again I'm not 100% so I'm asking for help and advice! Maybe Dino will pop in here and give me some advice!

[casual]

I've also found the Crower 44915.

With previous specs listed above, "Crower 44915 & SP677s(17cc dish)"- Static comp ratio- 9.2:1, Dynamic comp- 7.13:1

With previous specs listed above, "Crower 44915 & SPH802s(15cc dish)"- Static comp ratio- 9.4:1, Dynamic comp- 7.28:1.

Seems like a safer option than the Comp, since it doesn't raise the DCR as much..except its close to the limits of the stock springs..Lift is .448" on intake & exhaust both!

[Cheromaniac]

Reading Dino's sight, he dropped in a Mopar .043 head gasket with stock dish pistons which is 13cc..I'd be running the same and a bigger CC.

I did that back in 2003 on my old 4.0 after I ported the head and had it milled 0.010". The static CR ended up being ~9.1:1. At the time I was still living in Saudi and the only fuel grade available was 91 octane (95 RON).

Also any advice or info on running a Static compr of 9.2-9.4:1 & a Dynamic comp of 7.79-7.96:1? I'd love to run a cam for some more power, and since my static comp is staying the same, I should be ok right? Again I'm not 100% so I'm asking for help and advice! Maybe Dino will pop in here and give me some advice!

Whichever aftermarket piston you use for a stock 4.0 rebuild, the deck clearance will increase 'cause they're all slightly shorter than the stock pistons (1.601" pin height). Here's what I suggest:

1. Use the tallest aftermarket pistons available i.e. Speed Pro H802CP (15cc dish, 1.592" pin height). Deck clearance will be 0.030".
2. Mopar 0.043" head gasket.
3. Polish combustion chambers and aim for 60cc. You could also port the head while it's off.
4. Mill 0.030" from the block deck to reduce deck clearance to zero (with a quench height of 0.043").
5. Add 0.030" shims under the rocker arm bridges to correct the lifter preload for the block decking.

The resultant SCR will be 9.1:1 but with the tight quench and stock renix cam, the engine should be ping free running 87 octane. Raising the DCR with an aftermarket cam might reduce the ping threshold enough for you to have to run a higher grade of fuel.

[SilverXJ]

I don't see a problem running 9:1:1 and regular gas. However, I can't guarantee it won't need a higher grade. I know that my 2000 w/ an FIPK and 62mm throttle body pinged lightly under a constant low load. However, that was the only 4.0L I had that did that. I consider it a fluke.

Also, you probably measured the head gasket in the wrong spot, i.e. just the metal area. The best way to do it is to measure it while it is compressed.

[casual]

Thank you both so much!!
I'm currently looking into tuliped valves..the kinds that are dished on the underside. Like LS1 valves!
Looking into them because they'll add a few CC's to the chamber. I don't want bigger valves, I just want swirl polished and undercut valves!
I plan to build the head first, that way I can judge what I'll need to do for the bottom end. Once the heads built, I'll find out how many CC's the chambers are and go from there! I don't mind running 89-91 in the summer if its a last resort, I just want to aim for 87oct. I'd be mucher happier if I can get 87 all around.

I need help finding valves actually, I perfer them to be tuliped on the underside, but if not no biggy! Anyone got any help. Links would be useful!