Shaving head and block--affect on timing??

[crafty]

I bought the car with a BHG. Timing at 10 degrees and it ran and idled good. Put in a 2MM MHG and had 5 thousands taken off the head to true it up. Nothing off the block. I timed it at 10 and it still ran and idled good.

Now I had another 6 thou. off the head and 9 thou. off the block. (.20 over JE Pistons) When I time it at 10 there is a small hiccup out the exhaust at idle. When it's set at 6-8 degrees there is no hiccup and it seems stronger and spools the turbo faster.... I put a new 2MM MHG in with this rebuild. I have also checked the shim clearances and they are all within specs.

Has anyone else had to retard the timing as they shaved the head and block? I realize the distance from the crank pulley and the cam shafts is a little closer, but I didn't think it would affect the timing by 2-3 degrees.

Dennis

 

[PIONEER]

I ran a 2.0MM head gasket on my setup some time ago. It would made my car skip a beat around 25-2700 RPM under hard driving. My head/block was 15tho taken off overall. I'm back to 1.2MM Now and it doesn't have any problems.

Get an adjustable Cam gear and see if it helps.

 

[crafty]

How would I know where to adjust the cam gears to? It sounds like a possible answer to get it back to original timing. Right now it seems to pull great and idles well at 6-8 degrees. I'm going to the dyno tomorrow, so i guess we'll see. Before the rebuild I had 350 RWHP and 400 RWTQ. I'm hoping to see close to 370 hp with a fresh motor.

Dennis

 

[PIONEER]

How about you breakin that motor a little before you BREAK IT on the dyno :icon_redf

You don't think it might be too early to dyno a new rebuilt motor? I usually take it easy for atleast the first 1000miles.

 

[IJ.]

How about you breakin that motor a little before you BREAK IT on the dyno :icon_redf

You don't think it might be too early to dyno a new rebuilt motor? I usually take it east for atleast the first 1000miles.

Ditto!

 

[crafty]

Yeah, I have 550 miles on it already. Got it running five days ago. Should have almost 600 by tomorrow after work. So far I have only pushed 10 psi. but have already ran it up to 6000 rpm's.

I assembled this motor myself, so I feel pretty confident. (Famous last words) So far it has performed great. Only one little tranny leak(Stupid factory clamp).

I guess there are two trains of thought on break-in. Baby it or beat it. I have no patience-- so beat I shall.

I will try advancing the timing while on the dyno (if there is time) and see if there is a difference. At 150-175 a hour I don't want to be on there all day.

Dennis

 

[IJ.]

Dennis: It's not just the Ign timing that's affected it's the Cam timing as well.

 

[PIONEER]

Crafty:- I see you are not from canada, but it wasn't too long ago when a Guy from canada hit me up about getting some engine parts to build his engine. I helped him through the process, got him some parts from my dealer connection for cheap, he built it, 1st week he started off easy, the next week the gloves came off and he did a few 5K pulls. By the end of that week he had a rod knock.

Take it easy, it'll last a long time
Drive it hard, it'll cost a lot more.

 

[crafty]

Poineer: Yes, your right, I'm from Wisconsin. Green bay area. I will also be going to the track on friday to beat it some more!!!!!! I ran mid 12's before. Now I hoping for low 12's---High 11. We'll see.

IJ: I know it's affected, but the question is, "How is it affected?" And how to compensate for it.

Dennis

 

[IJ.]

Dennis: I think it would be negligable for the amount of material removed and well within the range of adjustment on a set of aftermarket gears (You'd really only have to use one adjustable pully to get it back to stock)

You need someone with a stock motor and a degree wheel to check the timing @ 50 thou lift so you can baseline it!