K1500 engine build update

[Supercharged111]

You could run 10:1 all day on cheap gas and a stock tune. The timing is so retarded you have a significant margin not to mention a knock sensor for when you get a **** batch of gas.

 

[Schurkey]

Too much quench area will also mean more combustion chamber volume, lowering your compression ratio and making you less knock prone.

Lower compression ratio can mean less tendency to detonate.

Often, going from a tight-quench engine with marginally higher compression, then adding a thicker head gasket to lower the compression ratio makes the engine MORE prone to detonation due to the lazy, inefficient, low-turbulence burn.

 

[Erik the Awful]

I did say less knock prone.

But I am curious, are you saying that less quench causes a lower amount of turbulence resulting in less mixing of the air/fuel mixture, and the resulting pockets of rich and lean mixtures lead to detonation?

 

[Supercharged111]

I did say less knock prone.

But I am curious, are you saying that less quench causes a lower amount of turbulence resulting in less mixing of the air/fuel mixture, and the resulting pockets of rich and lean mixtures lead to detonation?

Yes, he articulated the details that I'd forgotten.

 

[badco]

.032 is minimum piston to head you want to run. Quench isnt as important on your average engine but flame travel and such is. if your trying to make any kind of power throw away the tbi heads, idc if you make 12.5;1 compression a open chamber 882 head will make more tq and horsepower just from intake flow. That swirl hurts everything above .300 lift very badly. On dyno at 3500 the graph drops like a rock. The tpi head made 60# more tq and 46hp just swapping them. Stock engine. The vortec engine with a knock off performer and adapter to tbi makes better power than both and goes right in tbi trucks

 

[Schurkey]

are you saying that less quench causes a lower amount of turbulence resulting in less mixing of the air/fuel mixture, and the resulting pockets of rich and lean mixtures lead to detonation?

Sort of.

More quench distance = less in-cylinder turbulence. It may be that turbulence homogenizes the air-fuel mix; but it also dramatically speeds the flame-front making for a faster burn. In the process, it pushes the majority of air-fuel out of the furthest reaches of the combustion chamber, so that these end-gasses are exposed to the flame front. By reducing the pocket of heated end-gasses to a minimum, those same end gasses can't spontaneously ignite creating detonation. Tight quench distance also reduces HC emissions.

Because a turbulent burn consumes the fuel more quickly, less spark advance is needed. The flame burns more intensely, but for a shorter period of time--which means the boundary gasses in the chamber do a better job of insulating the piston, cylinder walls, and combustion chamber in the head--leading to less heat rejected to the coolant, and more force moving the piston down the hole.

There are some indications that there can be "too much" quench area, and that notion gets into the "Somender Singh" grooves, and that leads to a hundred posts about whether Singh is a genius or a goofball.

When the quench distance becomes great enough, it's not only totally non-effective, but at least the flame front can reach the end-gasses. This is no longer a "quench" combustion chamber, now it's an "open" chamber. You end up with a slow, lazy burn but less chance of detonation.

The danger is a quench distance between about .050--.120. Too tight for flame travel, too loose to be effective in reducing end-gasses and boosting turbulence. Higher HC emissions from the non-burned end gasses. And this is exactly how the Big Four built engines for years and years.

Don't get me started on the damned "rebuilder" pistons that have been "destroked" by .010--.020; making the quench situation even worse.

 

[L31MaxExpress]

.032 is minimum piston to head you want to run. Quench isnt as important on your average engine but flame travel and such is. if your trying to make any kind of power throw away the tbi heads, idc if you make 12.5;1 compression a open chamber 882 head will make more tq and horsepower just from intake flow. That swirl hurts everything above .300 lift very badly. On dyno at 3500 the graph drops like a rock. The tpi head made 60# more tq and 46hp just swapping them. Stock engine. The vortec engine with a knock off performer and adapter to tbi makes better power than both and goes right in tbi trucks

60 hp gain from TPI heads is not going to happen. It was about 15-20 and only at about 5,000+ rpm. Vortecs won't even gain 40 hp. Stock engine, stock cam, just changing heads. Been there and done it. TBI heads WILL make more torque than the smogger 882s or 624s. Higher compression and much quicker burn meaning less timing and less negative work on the crank. Put TBI heads on a G30 based RV with those 76cc smog junk heads on it along with the TBI system. Ditched both smog pumps. RV ran like it had 2 stock Q-Jet 350s under the hood. Built a TBI head 406 with a comp HE260 cam and slipped it into a TBI G30 van based RV with a 46mm bored Edelbrock TBI intake and 46mm TBI. Towing a large boat it had zero problems running the speed limit uphill.

 

[brian c lindsey]

It'd be better to start a new thread, and to tell us WHAT ENGINE THIS IS.

you are right , but as he has his engine already out where he can look at it and answer my question , why not

 

[badco]

60 hp gain from TPI heads is not going to happen. It was about 15-20 and only at about 5,000+ rpm. Vortecs won't even gain 40 hp. Stock engine, stock cam, just changing heads. Been there and done it. TBI heads WILL make more torque than the smogger 882s or 624s. Higher compression and much quicker burn meaning less timing and less negative work on the crank. Put TBI heads on a G30 based RV with those 76cc smog junk heads on it along with the TBI system. Ditched both smog pumps. RV ran like it had 2 stock Q-Jet 350s under the hood. Built a TBI head 406 with a comp HE260 cam and slipped it into a TBI G30 van based RV with a 46mm bored Edelbrock TBI intake and 46mm TBI. Towing a large boat it had zero problems running the speed limit uphill.

Not gonna argue it but i do have dyno sheets from the test and I have flow sheets on almost every sbc head you can think of. If its compression your after just use a 416 head and it flows more than humps and matches vortecs. If you make any power above 3500-4000 with tbi heads you must really have them opened up. Compression is useless without flow, quench and turbulence play minimal roll in a stock engine. Put .035 piston to head with stock rods and first time past 5k they going to touch. A stock rod with the heavy tbi piston will stretch over .038 at rpm.

 

[L31MaxExpress]

Not gonna argue it but i do have dyno sheets from the test and I have flow sheets on almost every sbc head you can think of. If its compression your after just use a 416 head and it flows more than humps and matches vortecs. If you make any power above 3500-4000 with tbi heads you must really have them opened up. Compression is useless without flow, quench and turbulence play minimal roll in a stock engine. Put .035 piston to head with stock rods and first time past 5k they going to touch. A stock rod with the heavy tbi piston will stretch over .038 at rpm.

I have gotten over 300 out of them multiple times with small cams at 10:1 compression. No head work on them at all. I got 250 at the wheels out of a stock 8.75:1 1-ton 350 TBI long block that had 18cc dished pistons and 810 heads with a factory 96 LT4 cam in it. With the stock cam that engine had a near flat HP curve from 4,000-5,000.

Another guy just ran one that made 330 hp at the crank with stock TBI heads on a 10.2:1 350 with a 214/218 roller cam. Peak HP was about 5,300 rpm. Stock iron high rise marine q-jet intake and headers. Ran 26° total timing. Made 20 hp more at 26° than 30°. Engine also made ~400 ft/lbs at 3,000.

If I wanted more compression and excellent flow out of a stock small block casting it would be 520s or 059s. Raised port Vortec 305 head. With some cleanup work and 1.94/1.60 valves had a set at 248 cfm.

GM did not even get 60 hp out of the complete Vortec treatment on the 350, including the roller cam, SFI, and improved exhaust setup.. They gained 45 hp. 210 to 255. Don't care what flawed test you claim to have run, 60 hp out of TPI heads is not happening unless the TBI heads had massive valve float.

I have personally watched a 350 Vortec on the dyno with both stock TBI heads and Vortec heads. With the stock vortec cam, performer intake on both, Q-Jet and timing properly adjusted. Went from 290 hp on the TBI heads to 310 on the Vortecs. TBI heads had more low-end torque.