10.2 Compression Iron Head Setup

[brian6pac]

I haven't heard anybody ask what was your bearing clearance, how much oil pressure were you running.
.0015 clearance on the mains with 35-40 PSI oil pressure OR
.003 clearance with 60 PSI oil pressure ?

 

[Scody21]

All,

How safe is it really to run a 367 LA with 10.2 static compression? Engine has Indy X Iron Heads w/2.02 valves and CP116's slightly in the hole. A .042 HG for quench was used on the original build and 93 Sunoco was used always and 34/35 degrees of timing. In the 3 years of use the car did not audibly ping. The engine is in for rebuild, due to vibration and some mains/rod bearing that were making some copper in my oil filter. The engine is being rebuilt/rebalanced with new forged rods. The builder is trying to sway me to running a thicker Cometic gasket to bring down the comresssion. This is a street car primarily. Other details include going to a mechanical solid roller lifter setup, the cam selection has not been made yet. We deliberately built the engine that way in 2017.

I know people run 10.2 motors on pump gas but I want to be sure. My concern is that a thicker gasket (.060 + ?)will open up the quench dimention and it will ping or be less effective in detonation prevention.

What are your thoughts?

Thanks,
Marion

Sorry to see the issues your having with the bottom end. This is a really good thread about fuels for future reference...

compression ratio vs octane

 

[mario03srt]

I haven't heard anybody ask what was your bearing clearance, how much oil pressure were you running.
.0015 clearance on the mains with 35-40 PSI oil pressure OR
.003 clearance with 60 PSI oil pressure ?

The car oil pressure was new 70psi cold and 45/50 hot. Before removal it was 60/25. Not sure of the original clearances, most likely per spec.

 

[mario03srt]

The crank is shot and the bearings are toast. All that material has traveled throughout the engine. You're walking on thin ice there!

The crank has been remachined and balanced.

 

[TT5.9mag]

@mario03srt will you answer the cam question please.

 

[mario03srt]

I missed the .042" on the head gaskets. My bad. I just used .039" as a guess.

I'm getting the report from the builder the .025 does not sound correct. I was given that figure over the phone. I'm thinking it was .005 originally. But I will make sure today I'm going up to go over cam selection.

 

[mario03srt]

@mario03srt What cam is in this thing?

Comp XE 274/286 230/236

 

[mario03srt]

The engine is at Kammer Racing in Dayton Oh. They know their stuff x10.

 

[mario03srt]

Comp XE 274/286 230/236

It and the lifters looked perfect.

 

[mario03srt]

I was doing some rough calculations and I don't think he's anywhere near 10.2 with that combination. I'm coming up with something in the 9.5 range assuming about 9 cc pistons, a 62 cc head, and a 0.045 gasket.

5cc valve reliefs.

 

[TT5.9mag]

Block was 4.030?

 

[mario03srt]

Block was 4.030?

.040 bore

 

[mario03srt]

Block was 4.030?

.040

 

[TT5.9mag]

Inputting some basic numbers, without knowing gasket bore diameter, (I used 4.180) I get your compression ratio coming out at 9.93:1.
@AJ/FormS can use the cam info to calculate dynamic compression and my guess is that engine should have run on 89 octane or so.
Edited to add:
I used 65cc for chamber size.
Changed it to 62cc and I get 10.27:1

 

[6PakBee]

5cc valve reliefs.

That's better, now I'm coming up with 10.18 which is close enough to 10.2 in my book.

 

[mario03srt]

Inputting some basic numbers, without knowing gasket bore diameter, (I used 4.180) I get your compression ratio coming out at 9.93:1.
@AJ/FormS can use the cam info to calculate dynamic compression and my guess is that engine should have run on 89 octane or so.
Edited to add:
I used 65cc for chamber size.
Changed it to 62cc and I get 10.27:1

10.27 is the number they are giving currently.

With the vac advance and cruise it would not ping when gassed, was quiet for hard driving, although I must say I have 3" exhaust w/ flowmasters so... I have used the same Sunoco 93/94 for 25 years in all my performance vehicles w/o issues. The issue is what about other fuels at "other" gas stations. I get it. This car is really has been treated very easily. I have a big champion radiator, milodon hi flow pump, dual Spal Fans and shrouds.

 

[rumblefish360]

At 10.27-1 & the use of 93/94 octane w/the given timing specs, I highly doubt this engine was pinging.

 

[RustyRatRod]

I'm getting the report from the builder the .025 does not sound correct. I was given that figure over the phone. I'm thinking it was .005 originally. But I will make sure today I'm going up to go over cam selection.

If it was .005" then the block has been decked. The .025" figure is correct for a stock deck block.....well give or take. Chrysler's decks were always tall......and crooked. lol

 

[TT5.9mag]

The engine detonating has so many variables that it’s hard to say if it was or not. Weight of vehicle, gear ratio, RATE of advance, quench volume, AFR, etc etc. looking at the plugs and the pistons, and rod bearings in this case is the only way to know.

 

[AJ/FormS]

For a streeter,
the only compression ratio the engine cares about is the
Effective Compression Ratio.
Static Compression Ratio is a tool we use to get the Dcr to where we think it needs to be. But if you build an engine to operate at a specific elevation, or a specific air density or with a specific carb, then you can throw both of those out, cuz you need to compensate for the lack of oxygen molecules.
Yes you can run 10.2 Scr, with a matched intake valve closing angle, to achieve a correct Dcr, for the intended octane rating. But if you run it up at 5000ft it will be a dog.
It is possible to far exceed the Dcr for the intended gas, simply by limiting the amount of air inducted, or lightening the load, or even running a somewhat specialized chamber shape.
It's all about the peak running pressure in the chamber, and the resistance that the load presents to the crank, when that pressure peaks.
As for me
Would I run 10.2 with a XE274/286/110,@876 ft elevation with iron?
Sure/No problem. I might even run it up to 10.5 with a very tight quench, or a double-Q head like the LA-X . But for a streeter, I wouldn't run a 230/236/110 hydro again. It gets lousy fuel mileage no matter what you do, cuz the extraction period is just too darn short.
I'd go one size smaller, tighten up the split, and the LSA for my close-ratio Manual-Trans, and make it a solid.
But don't you do that, cuz that's when your problems would start, cuz 10.2 will likely result in too much pressure.

The 230/236/110 is a powerhouse cam, but it sacrifices too much bottom-end for me, and like said, it sucks gas pretty bad. I've been running my 230FTH Hughes since 2004, and in all those years I have been waiting for it to puke so I can replace it.... but it just keeps on going...
If you have an automatic, then the 230* will be fine with a higher stall, to get you past the soft-zone. At a true 10.2Scr, with iron heads, I would install that cam at 108 to 110, and put enough valve spring on it to go to at least 6200, (I'd spring mine to go 7000 but Ima sticking to a FT lifter.)

Try to get your Q to .040 or less, and not more than .050. My Q has been as low as .028 with great results; I highly recommend it. Currently it is at .032 to .034, since about 2004.
If you cannot get under .050, then 10.2 MAY be too much to run full-timing with a 750carb, and best pumpgas.
10.2 with alloy heads is too LOW to justify the cost to performance . They will want about 11.2..... with that XE274cam

 

[yellow rose]

10.27 is the number they are giving currently.

With the vac advance and cruise it would not ping when gassed, was quiet for hard driving, although I must say I have 3" exhaust w/ flowmasters so... I have used the same Sunoco 93/94 for 25 years in all my performance vehicles w/o issues. The issue is what about other fuels at "other" gas stations. I get it. This car is really has been treated very easily. I have a big champion radiator, milodon hi flow pump, dual Spal Fans and shrouds.

What coolant temp do you run?

 

[rumblefish360]

Hopefully not 180*.

 

[Bewy]

10.2:1 is borderline for detonation on pump fuel. You may get way with it with some careful planning. Heat is the problem with det. If you can reduce engine heat & use cold air induction, that will help. So a good free flowing coolant system. Blocking off some of the exh xover heat will probably help to keep the A/F mixture cooler. A friend had an engine that pinged & he installed an engine oil cooler. No other changes, it stopped the pinging.

 

[mario03srt]

What coolant temp do you run?

Hi,
The fans are set for on 185 & off 180 and stays 183 cruising.

 

[mario03srt]

For a streeter,
the only compression ratio the engine cares about is the
Effective Compression Ratio.
Static Compression Ratio is a tool we use to get the Dcr to where we think it needs to be. But if you build an engine to operate at a specific elevation, or a specific air density or with a specific carb, then you can throw both of those out, cuz you need to compensate for the lack of oxygen molecules.
Yes you can run 10.2 Scr, with a matched intake valve closing angle, to achieve a correct Dcr, for the intended octane rating. But if you run it up at 5000ft it will be a dog.
It is possible to far exceed the Dcr for the intended gas, simply by limiting the amount of air inducted, or lightening the load, or even running a somewhat specialized chamber shape.
It's all about the peak running pressure in the chamber, and the resistance that the load presents to the crank, when that pressure peaks.
As for me
Would I run 10.2 with a XE274/286/110,@876 ft elevation with iron?
Sure/No problem. I might even run it up to 10.5 with a very tight quench, or a double-Q head like the LA-X . But for a streeter, I wouldn't run a 230/236/110 hydro again. It gets lousy fuel mileage no matter what you do, cuz the extraction period is just too darn short.
I'd go one size smaller, tighten up the split, and the LSA for my close-ratio Manual-Trans, and make it a solid.
But don't you do that, cuz that's when your problems would start, cuz 10.2 will likely result in too much pressure.

The 230/236/110 is a powerhouse cam, but it sacrifices too much bottom-end for me, and like said, it sucks gas pretty bad. I've been running my 230FTH Hughes since 2004, and in all those years I have been waiting for it to puke so I can replace it.... but it just keeps on going...
If you have an automatic, then the 230* will be fine with a higher stall, to get you past the soft-zone. At a true 10.2Scr, with iron heads, I would install that cam at 108 to 110, and put enough valve spring on it to go to at least 6200, (I'd spring mine to go 7000 but Ima sticking to a FT lifter.)

Try to get your Q to .040 or less, and not more than .050. My Q has been as low as .028 with great results; I highly recommend it. Currently it is at .032 to .034, since about 2004.
If you cannot get under .050, then 10.2 MAY be too much to run full-timing with a 750carb, and best pumpgas.
10.2 with alloy heads is too LOW to justify the cost to performance . They will want about 11.2..... with that XE274cam

The car has a B&M 3000 Holeshot with 3.55's also an airgap dp intake which are pretty good down low. Torque has not been an issue to me. Also I'm running a FiTech system. Cam selection is on the table. The builder wants to go solid roller cam and has mentioned going to Bullet or Comp. He says about 1 out of 9 hyd lifters are failing. BTW my cam and lifters looked great at teardown @ 1k miles! Yeah! Any suggestions? They are kinda dead set against a hyd flat tappet, but that another $1000 with rollers, cam, push rods.