Jkeating904

Ive got a LQ4 motor im building and a buddy of mine gave me a really good deal on an MS4 cam he decided not to use. Also ive got a set of 862 (same as 706) that ive been cleaning up over the last month or so. And everything ive read says that the MS4 cam loves compression, so i figured maybe heads off a 5.3 would bump it up (kinda like a old school 350 with 305 heads maybe) Then i was worried about PTV clearance. I remember reading that i need atleast .080 i think, and the stock LQ4 has .100 that might be off, but im pretty sure thats it. So i guess what my question is does the 862 heads give me any less PTV, from 317s, and can i mill them at all without valve reliefs? thanks for any advice you guys can give me. also the motor is gunna be carb'd in an FC RX7 if that changes any answers.

Gunslinger09

Since you are going to have the heads off the motor anyway the best thing to do is check the PTV after you mill the heads. Should be and ought to be are guesses measure and know for sure.

Jkeating904

I was planning on claying the pistons before i mill them. i was just wondering if anyone has ever done this, and if they had an easy answer for me.

Gunslinger09

Do it after you mill the heads and be sure.

Jkeating904

ok thanks, appreciateate it!

bww3588

iTrader: (49)

Check ptv before you mill the heads...then decide how much to mill. Once they are milled, there is no going back if there is not enough clearance.

ghettocruiser

iTrader: (17)

OP... did you come up with any figures for PTV?

Im going to be running an LQ4 with MTI Stage 2e heads (862's PP'd with bigger valves). Just curious if you got any measurements. My block is out getting some work done and it'll be a bit before I can check my own stuff.

J.

AGearHead4Life

iTrader: (5)

OP - I'd like to get an update on what you found out as well. I'm about to slap a pair of ported 862's on my LQ4 and am trying to decided how much I can safely mill them with a 231/237 .598 cam. I was hoping for .030 to get a 57 cc chamber and aim for 10.9-1 ratio.

ghettocruiser

iTrader: (17)

Do you already have that cam? If so...doing a clay test will reveal what you can take off. My problem is I dont have a cam yet...so Im still trying to figure out my combo.

Tho...a lot of guys have been telling me to just order the cam that will match what Im doing, and then check. If I have to fly-cut...so be it.

But Im still curious what the OP figured out!!!

J.

Grr

iTrader: (2)

just flycut and get it over with, you will thank yourself later

AGearHead4Life

iTrader: (5)

Any updates? Did you try it out Jkeating904? I'd like to hear your results. track times or dyno would be even better

Jkeating904

Wow sorry guys i havent been on the site in awhile. But I do have the cam, I am waiting on my springs once i get them i am going to put the heads together and clay the pistons to see where I am and what I can get away with. I got those numbers from an article I read (form hot rod TVs website I think). I just googled what the PTV clearance that LQ4 motors need. I should have some answers within 2 weeks or so. I will take some pics. and let everyone know when i come up with.

Jkeating904

has anyone ever heard of someone flycutting pistons by hand while they are in the motor?

AGearHead4Life

iTrader: (5)

The way people make comments, it seems like you can. I havent researched it yet. Maybe somebody who knows will chime in.


I've built a LQ4 that I'm currently porting a set of 862's for. I plan to clay soon to see how far I'll be able to mill them down. I'd like to get a 11:1 if I can. I'd really like to get a little over 11, but expect to only reach about 10.7:1.

Gunslinger09

Yes it is done all the time there are tools for flycutting the pistons while the engine is still in the car.