408 Build Thread (New numbers)
This is a completely seperate matter. I just realized my compression ratio was actually 10.3:1 which for an NA motor i think leaves a lot on the table. I think im gonna have my machinist mill the heads and get it up closer to 11.5:1 and have it retuned.
TECH Addict
Joined: Sep 2009
Posts: 2,481
Likes: 5
From: PA/MD
It was checked, but not line honed.
This is a completely seperate matter. I just realized my compression ratio was actually 10.3:1 which for an NA motor i think leaves a lot on the table. I think im gonna have my machinist mill the heads and get it up closer to 11.5:1 and have it retuned.
This is a completely seperate matter. I just realized my compression ratio was actually 10.3:1 which for an NA motor i think leaves a lot on the table. I think im gonna have my machinist mill the heads and get it up closer to 11.5:1 and have it retuned.
cam specs are 236/242.8 .629/.629 114+2 LSA. Im thinking this could be the reason for my lower power outputs, how do i figure out my DC?
Something else to think about, OP, did you have any oil in the intake tract of your heads? Did you check to see if the rocker bolts maybe with the portwork he took off some of the area at the bottom of the rocker bolt holes and maybe they are open to the intake port? Not that it would cause a major horsepower loss, but it still not desireable if they are exposed and unsealed with a thread sealant if so.
Well it appears my clearances were tight last time, i went to install the new standard bearings with the polished crank and my clearances are a little on the tight side with plastigauge. (.002) I borrowed my machinists dial bore and i got like .003 at the best. I went and got new plastigauge since the stuff i was using was old and im gonna recheck, if i get anything like .0025-.003 im gonna run it, if it comes up tight again ill probably have to get undersized bearings.
Used new plastigauge and it came up with .001 again, so now im ordering undersized bearings. I posted the standard bearings in the parts classified section. Never been ran, so if you need a set im selling them for 170 shipped.
I thought you said you got .002? Now you are getting .001.
Stock LS1/2 is 0.0008-0.0021 in.
If you buy undersize bearings .001 that will tighten the clearance up. The under size means the crank is .001 undersize or turned. My mains were at .0025 so I bought .001 undersize bearings and only used one half this tighten them up to .0021. Using one half would tighten them up .0004-.0005.
Stock LS1/2 is 0.0008-0.0021 in.
If you buy undersize bearings .001 that will tighten the clearance up. The under size means the crank is .001 undersize or turned. My mains were at .0025 so I bought .001 undersize bearings and only used one half this tighten them up to .0021. Using one half would tighten them up .0004-.0005.
I thought you said you got .002? Now you are getting .001.
Stock LS1/2 is 0.0008-0.0021 in.
If you buy undersize bearings .001 that will tighten the clearance up. The under size means the crank is .001 undersize or turned. My mains were at .0025 so I bought .001 undersize bearings and only used one half this tighten them up to .0021. Using one half would tighten them up .0004-.0005.
Stock LS1/2 is 0.0008-0.0021 in.
If you buy undersize bearings .001 that will tighten the clearance up. The under size means the crank is .001 undersize or turned. My mains were at .0025 so I bought .001 undersize bearings and only used one half this tighten them up to .0021. Using one half would tighten them up .0004-.0005.
my machinst says that most new cranks with standard bearings usually have .001-.0015 clearance so he usually gets under sized bearings. So thats what ill do, then recheck and see what i get.
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Verdad Gallardo Found out that #4 journal is out of round by about .0025" which explains my inaccurate clearance readings. I took it to my machinist and he said its very weird. He says its not like its been worn egg shaped, but more like it may not have been cut properly from the factory. He said he should be able to just polish the high side and get it back round over the weekend. so we will see.
In regards to You're pistons hitting the crank, what some poeple don't realize is just because there is clearance while rotating by hand, does'nt necessarily mean it will clear running. Say You have .030" clearance rotating by hand, it's a whole different thing at 6500rpms given the expansion due to heat and the stretch at those kinds of rpm's , it may stretch .030" or so. The pro engine builders will know more
In regards to You're pistons hitting the crank, what some poeple don't realize is just because there is clearance while rotating by hand, does'nt necessarily mean it will clear running. Say You have .030" clearance rotating by hand, it's a whole different thing at 6500rpms given the expansion due to heat and the stretch at those kinds of rpm's , it may stretch .030" or so. The pro engine builders will know more
I havent posted in a while as i have been busy rebuilding, but ill fill everyone in. I have roughly .003" clearance on all the bearings. I clearanced my oil pickup from practically on the bottom of the pan to .3"
On the performance side of things, i bumped compression to 11.5:1 and i added a FAST 102 mm intake that has had some porting to the runners, and a SSRA intake.
Car runs relatively well, definitely needs a new tune which i will be getting on the 23rd.
Cold oil pressure is 57, and hot is about 40psi, using 5w-30 break in oil.
On the performance side of things, i bumped compression to 11.5:1 and i added a FAST 102 mm intake that has had some porting to the runners, and a SSRA intake.
Car runs relatively well, definitely needs a new tune which i will be getting on the 23rd.
Cold oil pressure is 57, and hot is about 40psi, using 5w-30 break in oil.
TECH Addict
Joined: Sep 2009
Posts: 2,481
Likes: 5
From: PA/MD
Looking at your numbers and your cam specs, I think you need more cam in that thing. That cam sounds small for a 408. You at least need to be in the 24X/25X range. Especially with as much compression as you are running. If you are interested I am thinking about going bigger on my cam. My specs now are 242/250 .621/.595 113-109.
Looking at your numbers and your cam specs, I think you need more cam in that thing. That cam sounds small for a 408. You at least need to be in the 24X/25X range. Especially with as much compression as you are running. If you are interested I am thinking about going bigger on my cam. My specs now are 242/250 .621/.595 113-109.
Staging Lane
Joined: Jul 2013
Posts: 63
Likes: 0
From: NewHampshire
I have a fully forged 408 lq9 iron block 11.47/1 compression. My cam is 247/251 624 lift with a old fast 90/90 and tfs 215 heads. And my car made 482 hp 483 tq at the wheels. That's with a m6 430 gear and 325 50 15 drag radials the cam is a little radical but I drive it every day. And just spanked a terminator mustang. That said I prob would not go any bigger with the cam its good where it is. Just thought you might like to hear from someone who has a 408.