I'm putting together a LQ9 and trying to come up with a game plan... I have a set of 862 heads sitting on the shelf, obviously there are better heads out there but would these work with the flat top lq9 or will compression be too high?
the car is a daily so I'm limited on how big of a cam I can throw in there.

What maintenance stuff should I absolutely do while I have the engine on the stand?

 

With those heads and the LQ9 flat tops, figuring about .005 out of the hole with a stock .052 head gasket, you will have 11.56:1 compression, which might be more than you want.

 

That's what I was thinking too, thanks, not tons of lq9 info out there from what I can find, everything seems to be lq4 or ly6

 

If you need engine specs, Summit has a full database on their site, in their info section called "On All Cylinders".
Plus they have a page of different calculators for cam timing, compression, etc. within the main Summit site.

 

Powernation did a 408 stroker build using an LQ9. I would been referencing that, there are some great rotating assembly combos from Summit that are budget friendly and you might get more of what you want out of the motor that way. I'm picking up an LQ4 this week from a friend and starting my build.

 

Just keep in mind, an LQ9 is just an LQ4 with flat top pistons. No other changes. The LQ4 even got the better LQ9 cam once it was introduced.

 

OP,

You've received some good advice from the community.

You could run the 862 heads on your LQ9 as long as you're willing to run 93 octane with a good custom tune. Another option could be taking your 317 heads and having them worked over from a company such as Total Engine Airflow (TEA). Have them milled, bowl blended, and a valve job. This will increase power/torque across the range and make the heads more efficient. Milling .020" off will still align with the intake and should get you around 68cc. With the factory .051" head gasket that would bump you up to around 10.5:1. Put some .040" head gaskets in and you could bump that up to around 10.8:1. The bonus of the .040" head gasket is reducing the quench distance. Reducing quench helps promote a more efficient combustion cycle and reduce the chance of knock. In the 10.5-11:1 range, you could run 87 octane but you might need to be conservative on the timing. You would get better performance and reduce the chance of knock running 91 or better.

For a well-mannered daily-driver cam check out our SUM-8715R1 known as the Ghost cam. Specs on it are .600/.575, 222/234, 115+3 with -2* of overlap. It will have a smooth idle to noticeable lope depending on the idle speed. With its good manners, it will make respectable power near that of stage 2 cams. You can use the stock converter with the Ghost cam. A 2,500+ converter is recommended but not required. With some .600" lift beehives the Ghost cam will be happy out to 6,800+. As an upgrade we offer Trickflow TFS-2500286P .660" lift duals.

You'll want some upgraded pushrods. With the Ghost cam, we typically see a 7.400" or 7.425" pushrod used. Things can vary especially when milling heads so we always recommend measuring for pushrod length before purchasing pushrods. If you don't already have a pushrod length checker we offer the Trickflow TFS-9501 . For pushrods, we recommend a minimum of a 5/16" Chromoly pushrod with a .080" wall. You can typically find a set of 16 for around $100. From there you can get into a thicker wall or larger diameter pushrod. For excellent stability and strength check out our 11/32" HDR pushrods with a .120" wall. These have 25% less stress and 28% less deflection than a typical 5/16" x .080" wall Chromoly pushrod.

Some upgraded lifters and trays would be recommended. We have a couple of options to choose from. The LS7 lifters are very popular for a wide variety of daily-driver/mild builds. You can get the SUM-HTLSKIT2 combo that comes with the trays. As an upgrade check out the Morel 7717 lifter and tray kit SUM-HTLSKIT3.

Let us know if we can be of any further assistance. We'll be happy to help!

 

Nice post Summit!

 

Thanks for the detailed info!

I was worried about the compression ratio since the flat tops put it higher than the lq4 and ly6, I can run 93 though if that's all it takes.

Are there any cams you'd recommend that use stock pushrods? Is the added lift worth the extra cost in a daily driver?

 

OP,

As long as this is going in the 1970 Tempest in your signature and you use 93 with a good custom tune you'll be just fine at 11.5:1.

Onto lift and pushrods. Added lift is power/torque throughout the powerband. If you're on a tight budget we understand wanting a no springs/pushrods cam. However, we think the benefit of added lift is well worth the $200-$300 cost of springs and pushrods. To get a cam that wouldn't require springs or pushrods would be one of our drop-in truck cams like the SUM-8712R1. Specs on it are .500/.500, 210/218, 112+1 with -10* of overlap. It would provide around a 25 hp gain to the wheels but you're leaving another 50+whp on the table to save $300. If that cost isn't worth the reward then go with a drop-in truck cam. Otherwise, we wouldn't hesitate to go with the Ghost cam, our .600" lift beehives, and some 5/16 Chromoly pushrods with a .080" wall.

As an FYI we have a special going on with our Pro LS cams. With the purchase of a Pro LS cam, you'll receive $50 summit bucks that you could use on a future purchase.

Let us know if we can be of any further assistance.

 

Thanks, once again, great info. I could swing the pushrods, especially since I won't be buying different heads. Springs were in the plan, I'll just need slightly better ones.... What head gasket would you recommend with the 862 heads on the lq9?

Just to double check, will the power curve of the low/mid range power from the smaller heads play nice with the higher rev power band cam? I'm all for extra power, just want to make sure it's in a useable range

 

We would go with a .045" Cometic MLS head gasket. That will bump compression up .1-.2 of a point. More importantly, it will reduce the quench distance. Reducing quench promotes a more efficient combustion cycle and helps reduce the chance of knock.

Regarding the combo with the SUM-8715R1 "Ghost" cam. Yes, the Ghost cam is a great match for your combo and goals. While it shows a powerband of 2,800-6,800 it's going to be making power/torque before that 2,800 number. A cam isn't an on/off switch where it won't start making power until 2,800 or stop at 6,800. It's all in the combo. You have cubic inches and compression going for you here. That is going to help power/torque throughout the range. This will be a fun combo that will be easy to get along with. Get a good custom tune for 93 octane and you'll have smiles for miles

To give you an idea of the range and good manners of the Ghost cam check out the video below of fellow member @Mavn LS3 Vette.

Here is an idle clip from Mavn of the same combo. With the right tuning, you can make just about any cam lope.

 

@Summitracing that makes sense. I was thinking low rpm because that's where I cruise but your right, when i mash the pedal it's going to be in the higher rpms anyway.

Would this head gasket be ok? https://www.summitracing.com/parts/f...make/chevrolet It's .048 thickness so slightly thicker but saves me about $100 in head gaskets and still thinner than stock .05 gasket.

I read up on quench a little, thank you
https://help.summitracing.com/app/an...0Clearance.%22

 

Yes, that Fel-Pro .048" head gasket would work just fine and save you some money at the same time. The tech section of our Help Center is full of good reading material. Quench is something often overlooked, but an important step in putting an engine combo together.

 

Hey odd question about this setup. With that kind of compression in an LQ9 the Ghost cam would put the dynamic compression ratio way over 9:1. I ran into a similar problem with my LQ9 with 243 heads (10.9:1 static compression) and the Summit stage 2 cam. My dynamic compression was 9.2:1 because of the 43 deg ABDC. In my combo I had to run E85 or I got lots of detonation.

 

How are you getting your values? The DCR is calculated using advertised. And if I use your 10.9:1 value I get:

 

I used this calculator https://www.uempistons.com/p-27-comp...tio-calculator

It says to use .050 + 15 deg.

I got the exact same numbers from this one https://www.gofastmath.com/compressi...tio-calculator

It also uses .050 numbers.

I would love it if I was doing something wrong to calculate this. That would mean I just need to figure out what in my tune is causing detonation. But every calculator I use tells me the same thing.

 

DCR can really only be calculated using advertised, not 0.050" values. They are trying to estimate advertised by adding to the .050" however if it's only adding 15* to closing then it's approximating the advertised is only 30* more than .050" value. Most aftermarket cams are more like 50 to 55* increase duration @ .006" which means you really need to add 25 to 27.5 to approximate.

Wallace Racing allows you to input the advertised directly IVC, which is provided on Summit's Cam Cards. http://www.wallaceracing.com/dynamic-cr.php

 

Thank you so much for this. This helped me out a lot. I had no idea. I have been looking at DCR using the .050 numbers for a long time now.

 

thanks for brining up that question about dynamic compression, mine is coming out to 8.98:1 if I plugged everything in correctly.

The 8715r1 cam actually bleeds off more compression than the smaller cam I was originally leaning towards.

How high in dynamic compression can you go on 93 octane? When does it start getting to high?

BTW, here's a good article from MT: https://www.motortrend.com/how-to/hr...p-compression/