E85 swapping, some CR ?'s
E85 swapping, some CR ?'s Hey guys, I want to switch to E85 because: I have the fuel system to, Its more readily available locally now, and the car is down for the summer heat, so i figured it was the perfect time to. I just had some questions before upgrading..
Current setup:
stock block/crank
Mahle 16cc dish
Patriot Stage 2 heads w/ GM mls gaskets
Patriot Xtreme Springs
CamMotion custom cam (223/218 @.50" 577/565" 116lsa+4)
GTK1000
made 630/680 on 91 octane @ 15-16 psi
The current setup should net a 8.8:1 CR but I want higher for E85 like closer to 10:1. I was thinking I can keep my current heads and just have them milled to 59cc ish chambers and switch to a cometic mls .040 which should net 9.7:1. @ the same time I had contemplated doing a bit bigger cam but am now unsure of my PTV clearance with losing .030 off the heads then possibly having more lift or duration...
Any ideas?
Current setup:
stock block/crank
Mahle 16cc dish
Patriot Stage 2 heads w/ GM mls gaskets
Patriot Xtreme Springs
CamMotion custom cam (223/218 @.50" 577/565" 116lsa+4)
GTK1000
made 630/680 on 91 octane @ 15-16 psi
The current setup should net a 8.8:1 CR but I want higher for E85 like closer to 10:1. I was thinking I can keep my current heads and just have them milled to 59cc ish chambers and switch to a cometic mls .040 which should net 9.7:1. @ the same time I had contemplated doing a bit bigger cam but am now unsure of my PTV clearance with losing .030 off the heads then possibly having more lift or duration...
Any ideas?
I would just mill the heads a bit and run more timing with E85, or maybe even just put more timing into it for starters and see where that gets you with E85 before pulling the heads and milling. I would probably leave the cam as is for now too.
Thanks for the reply guys,
I was hoping to keep the cam in so I'm ok with that..
I wonder how much effect taking .030" off will have on lifting heads..?
If we assume the heads are .5" thick that's only like 6%, Have any experience with that?
I was hoping to keep the cam in so I'm ok with that..
I wonder how much effect taking .030" off will have on lifting heads..?
If we assume the heads are .5" thick that's only like 6%, Have any experience with that?
I would just run it as is.
There is a bit more power to be gained by bumping the CR, but the same cane be done by bumping the boost up another pound or two.
The throttle response will be better off boost with a higher CR, but I built my setup at almost the exact same CR as you just incase I need to go back to pump 93 someday.
There is a bit more power to be gained by bumping the CR, but the same cane be done by bumping the boost up another pound or two.
The throttle response will be better off boost with a higher CR, but I built my setup at almost the exact same CR as you just incase I need to go back to pump 93 someday.
Thanks for all the input guys, I'm going to keep the engine as is for now and just switch to e85.. but I suppose since it's apart and I dont need to spend on my engine I can buy the GTM78 I've had my eye on! Score! 
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Verdad Gallardo I think that's a good idea. It's going to be much easier to just add timing and boost with E85 and from what I remember you didn't have a whole lot of timing in it from way back when so there are definite gains to be had by just switching to E85. Hell I'm around 8.5:1 because I built mine for 91 oct as well and switched to E85 a year ago and haven't looked back and just threw more timing and boost at mine.
Nice, Thats good to hear I didn't realize you ever switched over.. I've been holding off merely because the inconvenience factor, but finally gave in.. I just recalcd my compression and it is 8.66:1 so a lil lower than I thought. yea when we last tuned (actually both times) it was hot and i think you had kept the timing pretty conservative b/c 91 octane + heat + beating the **** out of it=no bueno. Are you still on a .96 AR hotside?
Yeah, I'm still on a .96 only because I can't get something bigger. Since switching to E85 my back pressure has gone up a bit for sure and I sure could use a larger exhaust housing.
