When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
6 years ago I bought an LS7 shortblock to set off on this stupid goal lol. Really happy with the outcome. I kept joking that if it didn't make 730 I was going to leave it there, and I was hoping for 750 or more. Brule guessed 740 based on his experience with other combos so we were all around it. Unfortunately we were on their new DTS style SF-Powermark dyno instead of their SF-902 so we don't really have a barometer to compare against our old dyno sessions. I think the SF-Powermark is a heart breaker, and Westech in general is a very honest dyno shop. Lots of stories of crate motors losing 10% from advertised.
My original goal was to peak power at 7100-7300 range and carry out to 7800 in my stick shift RX7 with a short runner sniper low pro intake. The intent of the build is to be able to do things like open track day sessions and standing mile and be reliable and street friendly. I'd like to do standing mile runs with it someday and hit 200mph NA. The more I look over the data and think about the drama free day yesterday I'm extremely pleased with the outcome, especially since I piecemealed this whole combo together myself as I could afford it/found good parts on the marketplace. One of my favorite experiences was working with Billy at Comp to grind his at the time unreleased low shock solid roller lobes. I spec'ed the cam after a lot of lost hours playing with camshaft calculators and comparing dyno sheets I could track down online.
I'm extremely fortunate that my dad is a badass engine builder who made sure all this went together properly - and as drama free as the dyno session was, the build of this thing was really a frustrating nightmare at times so I owe a lot to him for the successful day.
429" LS7 build, 12.5:1 compression, wet sump conversion
LS7 block honed to 4.130"
LS7 steel crank polished and checked
Factory Ti rods and ARP bolts
Mahle PowerPak flat top pistons
1/1/2 mm gas ported total seal rings.
BES 285cc ported LS7 heads, Factory Ti intake and Ferrea stainless exhaust
Cometic 4.190x.051" head gaskets
T&D steel pedestal mount adjustable roller tip 1.8 rockers
Manley 3/8 to 5/16" tapered 7.825" long pushrods, .145" wall
PAC 1237x solid roller valve springs
Comp Cams 258/272 .774/.756" lift 113 LSA +3* - low shock solid roller
Isky Red Zone bushed solid lifters
Melling 10355 oil pump
Mains drilled for oil squirters
Improved Racing crank scraper, windage tray, and trap door baffle
Dyno'd with CID 4.5 and Holley 1050 Dominator on 100 octane - will be flex fuel EFI
Congratulations!
Outstanding Results!
I know it feels Great!
Thank you sir! Yes you certainly do know it feels great your 396 is inspiring. I originally wanted to do a short stroke build for the rx7 (still kind of do tbh) but I really wanted the power of the cubic inches lol. The decision was made to stuff a big enough cam in it to make the 4" stroke rev haha.
I thought that pac 1237x were for 700 lift and the 1238x for 800 lift
so what was your spring height with 1237x with that 775 lift cam
great job
You're correct the 1237x are only rated for 700 lift. I actually have a set of 1238x on the shelf I bought first, but I really didn't want to run that much spring pressure. Billy Godbold gave me the tip that most springs when measured can actually be run greater than rated the rated lift, you just might have to order a few couple sets. I ordered a set of the 1237x and compressed each one fully and they were all around .085-.100" from bind when using rated lift (loses some with lash). I think one I actually had to shim - the rest I was able to run with no shims.
Thank you! Nice to finally be a part of the big bore life. Are you able to get to any 1/2 or full mile events nearby, or not interested? It'd be cool to see you putting some better numbers up than some boosted cars.
Thank you! Nice to finally be a part of the big bore life. Are you able to get to any 1/2 or full mile events nearby, or not interested? It'd be cool to see you putting some better numbers up than some boosted cars.
There are 1-2 that happen near me every year. Now that the car is up and running I will try to hit 1-2 just to see. I don't doubt I should be in the upper 170s maybe even low 180s.
Well done! Did you guys have time to play with tighter lash settings at all?
Only on the one adjuster I left loose that had backed all the way out when we ran it to 7k the first time still made 720hp on break in oil and low timing hahaha.
But no, because the dyno is always pumping cold water in we couldn’t do a true hot lash. Recommended hot lash is .014/.016 intake exhaust so we just reset them cold to .006 and .008” after break-in and ran it. Looking up top there’s definitely a chance it’d like to be .002-.004” tighter. Will have to get it in a car and get it nice and hot to check it for real.
Also the valve covers were a pain in the *** the smoke on the pull is the gasket not being sealed up and spraying oil out the side.
Only on the one adjuster I left loose that had backed all the way out when we ran it to 7k the first time still made 720hp on break in oil and low timing hahaha.
But no, because the dyno is always pumping cold water in we couldn’t do a true hot lash. Recommended hot lash is .014/.016 intake exhaust so we just reset them cold to .006 and .008” after break-in and ran it. Looking up top there’s definitely a chance it’d like to be .002-.004” tighter. Will have to get it in a car and get it nice and hot to check it for real.
Also the valve covers were a pain in the *** the smoke on the pull is the gasket not being sealed up and spraying oil out the side.
Understandable! I was just surprised to see power taper off before 7500 with that intake setup, figure it wants more duration or the exhaust was holding it back. Small stuff though and won't make a huge difference.. gonna be a riot in your car
The holley cast valvecovers, but the tall version. I have the short ones on my other engines and they're great. Overall they're not bad if you don't have to take the valvecovers off but as we all know the gaskets stretch with heat and are hard to keep in place, especially when there isn't anything pinching the gasket in the groove.
I was surprised to see the power roll off above 7400 that is really the only thing I wished had been different, but I think it'll carry when it has the sniper low pro on it even if it makes less power overall. Powerband wise it is 97% of peak from 6500 to 7700 so I don't think it is rolling off early - I think that is just really what you get. I might've been a little delulu thinking I'd achieve a 7200rpm peak and flat to 7800.
Some tweaks that might've helped it that we didn't do was getting the AFR into the 12's up top, and more timing above peak. It was richening up at the top end to 11.6:1, but torque peak was 12.9. We didn't have any adjustment left to make on the carb to lean it only up top. I do think it might've taken a little more timing above 7500. It made best power at 27.5* and the gains were meaningful but small from 26* so we didn't put any more in it. 29-30* might flatten the curve out up top. BTW these spark values are just for reference - Westech thinks their new spark controller is off by maybe ~3-4* they've seen a lot of LS engines taking 32* for best power on this dyno which is higher than normal.
I did do some simulated shift points with t56 magnum ratios. Pretty healthy looking haha.
The holley cast valvecovers, but the tall version. I have the short ones on my other engines and they're great. Overall they're not bad if you don't have to take the valvecovers off but as we all know the gaskets stretch with heat and are hard to keep in place, especially when there isn't anything pinching the gasket in the groove.
I was surprised to see the power roll off above 7400 that is really the only thing I wished had been different, but I think it'll carry when it has the sniper low pro on it even if it makes less power overall. Powerband wise it is 97% of peak from 6500 to 7700 so I don't think it is rolling off early - I think that is just really what you get. I might've been a little delulu thinking I'd achieve a 7200rpm peak and flat to 7800.
Some tweaks that might've helped it that we didn't do was getting the AFR into the 12's up top, and more timing above peak. It was richening up at the top end to 11.6:1, but torque peak was 12.9. We didn't have any adjustment left to make on the carb to lean it only up top. I do think it might've taken a little more timing above 7500. It made best power at 27.5* and the gains were meaningful but small from 26* so we didn't put any more in it. 29-30* might flatten the curve out up top. BTW these spark values are just for reference - Westech thinks their new spark controller is off by maybe ~3-4* they've seen a lot of LS engines taking 32* for best power on this dyno which is higher than normal.
I did do some simulated shift points with t56 magnum ratios. Pretty healthy looking haha.
I'm rolling with stock valve covers and thicker gaskets. Too many compromises on the aftermarket stuff, and tbh i was feeling a bit cheap when it came to spending on them lol.
But you are definitely right, there is some power and curve movement left in it when it gets the AFR and timing dialed in in the vehicle. Not game chaning power but it's there. Time to go enjoy it!
03-07-2024, 05:29 PM
Solid roller LS7 engine dyno results 
still made 720hp on break in oil and low timing hahaha.
