Head Swap

[maddog1001]

I all. New here but not to the car. Having said that -
I have a '90 turbo with a dead head. First it turned into a sewing machine (clackety clack!) about 5 months ago (tried changing cams and followers but no good - head damaged) then HGB on new years day! I also have an '88 N/A which has passed it's sell by date. It does however have a good head and I am planning on using this head on my '90. Anyone know of any problems I'm going to encounter? - or how for that matter to reduce the compression ratio (or can I get away with it?) Thanks in advance.

[projectsupramk3]

Why would you want to reduce the compression ratio more in your turbo? You should have absolutely no problems swappin the heads, since there both almost identical. If you want you can even keep the early n/a cams in the head (these are the n/a cams some turbo owners swap in and talk about small HP gains). The only real differance in the actual head casting is the lenght of the divider between the valves for each runner. By the way the tick tick problem with the cams was most likely the shims being out of spec, replacement is pretty straight foward and it is a common annoyance with the 7m, shouldn't ever cause any problems though unless it's got a huge gap between the cam lobe and shim. The TSRM has all the different sizes and specs for the shims you'd need for any situation. How did that damage the head by the way?

[maddog1001]

Thanks for the info. I don't know what caused the head to go. The engine came out of a '91 which had a lot of bad history - largely discovered through investigation having bought the car. I fitted that engine in the '90 I have now back in the summer largely because I'd already done a full rebuild on that engine 18 months earlier and the one that was in was showing signs of BHG. I had torqued it down using BMW specs - their straight 6 is similar and as everyone else already knew Toyota's spec is too low. I can only guess that swinging it on the crane affected the head in some way.

[maddog1001]

sorry should have added - I think the casting where the followers fit was worn. Looking at the condition of the sides of the followers when I took them out several had serious signs of wear and all looked like they'd been attacked with 200 grit sand paper! Having already changed the cams etc once and with a BHG to boot I don't fancy going any further with this head - atleast not at the present time.

[projectsupramk3]

BMW specs... ohhh... so what did you torque them down to? If your doing a retorque the stock bolts should be torqued to 72ft lbs. Who knows what toyota was thinking when the said 54ft lbs.

[maddog1001]

BMW torque works out at about 75 so it fell anout right but knowing they used similar materials in similar dimentions it could never be that far off. Having read posts on the subject this build will be based on 72.