Gonna tune him up! (Will it stay together)

[Kevin frazier]

No and i wont ever know as i will never try that settup again. When i put that head on and got it going i did not check static compression, and i didn’t check before tune, Neville said with that combo it was probably around 250psi and thats way to much. I will never skip that step again. I would have never been happy with 160 160 so now i get new cams and more hp and tq. Win win just gotta do clean up on aisle 3 today at Konrads and open him up ( widowmaker not Konrad, tripps )and make sure everything looks good in there.

 

[wjb]

So you are going to use the same pistons and shaved head? Are you thinking that the new cam profile will lower the dynamic compression ratio to an acceptable level?

 

[Kevin frazier]

So you are going to use the same pistons and shaved head? Are you thinking that the new cam profile will lower the dynamic compression ratio to an acceptable level?

im taking the head to a cylinder head shop and gonna have them check it and do a valve seat job. If the pistons are still good im gonna ask the man in the tin shed if i should strip it to check crank and pistons or install new cams and rock on after getting cylinder head back.

 

[Kevin frazier]

So you are going to use the same pistons and shaved head? Are you thinking that the new cam profile will lower the dynamic compression ratio to an acceptable level?

Nevilles 10:1pistons will lower the dynamic (static) compression, previous #s were around 205 210 iirc with those cams

 

[wjb]

So, lowering the static compression ratio by 4 tenths with pistons, (10.5 to 10.1) got it. Then replacing stock cams with performance cams that have presumably more duration and lift and most likely a more narrow lobe separation angle which would lower dynamic compression due to longer intake event while increasing power in upper rpms.
Sounds like a plan to me! (try to not blow it up this time)

 

[Claviger]

160/160, I guessed before scrolling yay. Shame about the gasket, on a positive note, they're $77, and if nothing else is damaged a fairly inexpensive fix. Good luck with it!

I would recommend buying studs if you don't already have them, can save a head in these moments(+they're cheap compared to multiple purchases of stretch to yields).

Regarding CR...
My head is decked 23.6 thou. I have proud valves that aren't dished, further raising CR, and I ended up at ~13:1 using 11:1 pistons.

As I recall your pistons come out to 10.5 with 15 thou decked, so you're likely closer to 11:1 now with 25 off it. I would recommend CCing the chambers and pistons so you know. Probably around ...64-65cc chambers, it'll help in the future. Nev will know this all already so can pick the right #s for you.

Stock cams are nominally 220/232 @8.3mm lift with only 23° overlap @1mm lift and a LSA of 101.5°. Nevilles cams are.... substantially larger, so lower the DCR a good bit.

Quick calc says ~265 cranking PSI with 11:1 using stock cams. Anything over 230 on the compression tester is, IMHO, not safe on R3s. At 235 I experienced some knock on hot days when running 93 octane, even with MMT added to the fuel. After swapping cams to fix the undersize cam issue and using the correct event timing it never knocked, ever, even on crap New Mexico "premium" 89 octane.

 

[wjb]

Stock cams are nominally 220/232 @8.3mm lift with only 23° overlap @1mm lift and a LSA of 101.5°. Nevilles cams are.... substantially larger, so lower the DCR a good bit.

Coming from an automotive background those cam specs are CRAZY! Automotive cam duration is measured at .050 inch lift (just 1.27 mm not 8.3!) and a nice street performance cam would be in the 220 to 230 degree duration range. LSA for street performance cams are in the 110 to 114 degree range. I don't think I've ever seen a street cam with LSA under 108 degrees!

 

[Claviger]

Coming from an automotive background those cam specs are CRAZY! Automotive cam duration is measured at .050 inch lift (just 1.27 mm not 8.3!) and a nice street performance cam would be in the 220 to 230 degree duration range. LSA for street performance cams are in the 110 to 114 degree range. I don't think I've ever seen a street cam with LSA under 108 degrees!

Yep. The rocket can happily take on some very wild cams compared to cars.

My 265 kit carp cams were, I think 258/248 @ 1mm.

My Nev specials are a good bit longer, with notably longer control ramps so they're gentler. Duration is longer at 1mm than most sport compact "race" cams are at advertised duration

He has larger grinds even lol. If I could download 1/2 of what that man knows...

 

[wjb]

Think about what he could do if the Rocket had a roller profile instead of a flat tappet!

 

[Kevin frazier]

The tail pipe had a clue in it, yup, i feel kinda proud, i broke my first piston, seems i did a proper job just by looking at the exhaust cutout on this piece of piston. Its pretty melted