Road Race Engine Build

[ericjon262]

Something to note. If you use the LZ timing chain tensioner with a pre-99 timing chain you'll have to message the tensioner a little. Otherwise the back of the timing chain pins rub on the tensioner backing plate. A couple of light taps should do it.

This is good to know, thank you!

[neophile_17]

I measured the stock pushrods in the LZ and then the LA1 pushrods I had just as a second data point. The LZ pushrods are longer than all the spec sheets that I have seen for the LZ. The spec sheet states 5.750" and 6.000"

[neophile_17]

What where you spinning it to? And what springs did you use?

Maybe 6500, I try to keep it in the power band not just make noise. I can't remember exactly but they're probably Comp 26986s.

Something to note. If you use the LZ timing chain tensioner with a pre-99 timing chain you'll have to message the tensioner a little. Otherwise the back of the timing chain pins rub on the tensioner backing plate. A couple of light taps should do it.

[1QUICKHATCH]

My low mileage LX9 with stock timing chain, mild springs, and 0.504" lift had slight valve impressions on the pistons so more than that and you are very likely to have clearance problems on an LX9. I think guys with high mileage stock motors were having the same witness marks too. Hate to be the bearer of bad news but it's easier on the schedule to know you might have to cut valve pockets early that be surprised in my mind.

What where you spinning it to? And what springs did you use?

[neophile_17]

Interesting... I won't deny that my motor experienced a coolant failure which might of contributed but I had stock LX9 heads- not Gen 2 heads. I also re-used the 60k mile timing chain if that makes a difference. If you measure it you'll know otherwise I guess it's just internet hearsay.

My 1615 grind supposedly had .565 on the intake valve and left no impressions in the pistons. Lx9 bottom end with gen 2 heads

[neophile_17]

My low mileage LX9 with stock timing chain, mild springs, and 0.504" lift had slight valve impressions on the pistons so more than that and you are very likely to have clearance problems on an LX9. I think guys with high mileage stock motors were having the same witness marks too. Hate to be the bearer of bad news but it's easier on the schedule to know you might have to cut valve pockets early that be surprised in my mind.

[ericjon262]

I've never measured them, the new 3500 I'm about to be working on will be carefully measured though. that being said, if you took careful measurements, and more than one came up longer, I wouldn't worry about it. I am worried about piston to valve clearance in mine, my cam runs about .576" lift, so I need to be careful for sure...

[neophile_17]

Got all the cam bearings/spacers in and the cam spins nice and free like it should.

Piston to valve clearance is more than adequate for 0.533". Someone on that Fiero forum said these engines were safe up to 0.545" valve lift and that seems to be in right ballpark. I should have gotten an exact number for clearance but I was more than safe and moved on.

I did a little playing with push-rod length and it looks like I need an extra 0.075" on the intake and 0.085" on the exhaust. Anyone else find that the exhaust push-rod needed more length than the intake? I wouldn't have expected this but maybe this is to compensate for extra heat.

[neophile_17]

I was going to do that but I learned how to use a new toy at work and the bearing spacers aren't going to be very rebuild friendly. Also, I redid the math and I'll be at 0.533" lift with a lot to too much valve spring. So I shaved 0.055" off of one side of Teflon coated SBC bearings and will sink those in the spacers tomorrow. Then I can check piston to valve clearance and get the crank off to be balanced. I was hoping the piston weights were or could be made close but the LZ pistons are 100g heavier than the LX9 pistons. I have the Federal Mogul version with the thinner ring package. The Mahle pistons are different.

[ericjon262]

alot of the "sloppy mechanics" (the guys who by a 4.8/5.3/6.0 and a big ebay turbo, and, well,, send it) say not to even look at cab bearings, ever. but you're also building an engine that you hope to run all our for 24 hrs. I will say, that short of roller cam bearings, there is no reason to get fancy ones. just make sure you get a quality brand.

[neophile_17]

I decided to order the SBC coated bearings and I'll trim them down before installing them in the bearing spacers.

Since I'm going to aftermarket gauges the standard GM oil pressure sensor wasn't going to work and it's not NPT. Fortunately it looks to be the same as the LS sensor for which there are tons of swap parts. Will post back as soon as I get my adapter can confirm.

[neophile_17]

I went to order my cam bearings from WOT-Tech and I find out that the standard width coated bearings don't seem to be available any more. Can they be special ordered or are they discontinued? If no longer available what is my next best option for a standard width bearing. My cam spacers don't work with the wide bearings. It looks like my options are standard Durabond, Mahle/Clevite, and Sealed Power but I'm open to others.

[neophile_17]

Any idea what the balance factor of these engines should be? V8s seem to all be 50% but 60 degree V6s seem to be different with numbers between 35% and 50% depending on crank design.

According to the 60 Degree V6 Chevrolet Power Service Manual the Balance Factor is 50%. HTH

I practiced adding Time-Serts to a couple LX9 heads that will go on the "Stock" LA1 bottom end or what I'll probably end up calling the little engine from here on out. When I went to Time-Serts the LZ* heads there was a pretty significant difference in the cutting and tapping feel. The LX9 heads are softer. I probably wouldn't Time-Sert them again if using a milder valve spring and cam. I did end up cutting one of the holes a little too deep (shaft collar slid) but I only lost one thread on the rocker bolt so more than enough engagement.

Piston rings for both engines should arrive tonight along with the filing tool. Hoping to get the little engine buttoned up in the next 10 days.

[neophile_17]

Tax return money came in so I made a couple of parts orders. Purchased the rods and a Pre-99 crank timing gear from GM. Microsquirt, TimeSert 1812CORE, and gauges are also on the way. I had already bought 10mm rockers from the JY but they are a straight design not offset like the LZ* so I'll just TimeSert the heads to handle my valve springs. I figured it was time for a full set of gauges once I realized nothing in the old Fiero gauge pod actually works and good data should help us keep this thing together. More updates once I get the stock LA1 buttoned up and off the engine stand.