Thread: BBC 402 looking for advice on head work, cam and stall

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I was going to recommend the Super Scrapers too. They are very nice. Just be careful as they are pretty sharp.

Went over too Harbor Freight brick and mortar store today and bought a 7.99 bubble pack set of wood chisels. There's a 1" and 3 other's of various smaller sizes.

I'll go to town on the block deck this weekend. Maybe even get a measurement on that piston dome!

-unix

I took those dome dininsions right out of the Speed pro catoloque

Originally Posted by jerry clayton

I took those dome dininsions right out of the Speed pro catoloque

That Speed Pro part number was pulled straight from a google image search where I was trying to find a piston that "looked" similar to what I have. Not the best thing to do I admit, but... was desperate to get some info to you guys, even if it was totally inaccurate. I'll have to measure it to be sure.

After cleaning a bit I see .090 or maybe .060 stamped on top of each piston. 60 over maybe or would that be something else?

-unix

that would probably be the oversize and you may even find the piston part number---------

Looks like the late model LT + 8 speed is still available:

https://dallas.craigslist.org/dal/pt...430874209.html

I've found at least one resource that claims swapping this absolutely requires the ECM and TCM from the donor. Programming a "new" one with the VIN associated with the donor will be difficult and potentially expensive.

-unix

Posted on wrong thread.
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Life sort of beat me over the head about mid January so I've been really not paying much attention to this build. I'm gaining interest again now and getting ready to put it all back together again!

Went with COMP XR-270-HR/11-422-8 ( 1600-5400rpm, 110LSA, 270/276adv-dur, 218/224 @.050" ) roller kit with all components from COMP including cam and lifters. Will be installing roller rockers and molly pushrods.

The #063 heads were kept stock except for SS valves and the upgraded dual springs/retainers/keepers/seals, etc. as per the specs on the roller cam.

Hopefully I'll have this thing assembled and running in no time eh!

My current worries are...

o need to figure a way to either make one "set" of my lifters solid or purchase a single pair of solid roller lifters for pushrod length checking. I figure the pushrods I'll need will be an inch minimum shorter than stock so my check procedure needs to be spot on. What do you guys do in this situation to determine proper pushrod length

o without proper pushrods, which you really can't get without torquing down at least one head, how then will I be able to accurately do piston to valve clearance checking prior to getting accurately sized pushrods?

chicken => egg

Anyways,

Thanks,

-unix

Originally Posted by unixoracle

What do you guys do in this situation to determine proper pushrod length

https://www.youtube.com/watch?v=o5is9BsH5OU&t=16s

Originally Posted by unixoracle

Without proper pushrods, which you really can't get without torquing down at least one head, how then will I be able to accurately do piston to valve clearance checking prior to getting accurately sized pushrods?

Pushrod length will not vary valve lift. We try to get the proper pushrod length in order to center the shoe or roller of the rocker arm on the valve stem tip. Drop two oiled solid lifters into the block. Clay the pistons and sit the heads in place without head gaskets, just snugging them down with a few bolts. Install pushrods and rockers. Snug rocker bolts down to zero play. Install the head with a couple of bolts and just snug them down. Roll the crank over two full revolutions and remove the head to cut and measure the thickness of the compressed clay. Add the thickness of the compressed head gasket to your findings. DO NOT USE PLAY DOH, IT WILL NOT RETAIN ITS SHAPE AFTER THE VALVE HAS MADE AN INDENT. Use only oil-based (gray) clay from a craft or hobby shop. Oil the valve faces so that the valve will not stick to the clay.
https://www.youtube.com/watch?v=tjs61-TCZYw
https://www.youtube.com/watch?v=Dz7Fqo_oufU
https://www.youtube.com/watch?v=Y66lvdHbm60&t=285s

WATCH THESE VIDEOS SO YOU CAN ASK QUESTIONS BEFORE YOU DO THE PROCEDURE.

Some pictures...

Here ya go... cam stab, pvc press and..... the button!!

With my front cover, which appears stock, and the longest nylon cam thrust button I could buy at Summit, I still needed a longer button. There was a good quarter inch of movement fore/aft of the cam between cover and rear stop. After finally deciding against a new cover I simply dimpled the existing steel cover with my BFH and an impact socket to take up the space. It took a while but after several iterations of measure, remove, bang, replace, measure..., I managed to get the thrust clearance to .006 on the dial. Oh and oddly enough, the lobes are just about centered there in the lifter bores.

-unix

IMO, hardened seats are not needed in situations like yours. 3.73 gears. 3600 pounds. That engine will make 400 HP fallin outta bed. Hardened seats from the factory were a joke anyway and penetrated only about .010" IF you were lucky. Induction hardening is not the best by far, so to say the factory really used honest to goodness hardened seats is a stretch at best.

IMO, unless you plan on towing, or a heavy duty truck application, hardened seats are not needed. Especially in a car with good power and a decent gearset. You will not be straining that engine at all. THAT is where the need for hardened seats comes into play.

I like those heads. They are the same as what I am using on my 402 dirt road build. They can flow like gangbusters for what they are by simply blending the bowls and smoothing out the transition from under the valves into the ports......NO port work at all and you will pick up over 50% of what an entire full port job will offer. Most people don't realize that most of the benefits from porting is in the valve bowl area, but it is and it is VERY simple to do yourself.

Run the Mr Gasket .021 steel shim gasket and that will bump compression up to close to 9.5. Perfect for an iron headed engine on pump gas. With proper camshaft timing and a really good hot ignition curve, with BIG tube headers, I bet 450 or more HP is not out of the question, as we all know these engines were under rated from the factory anyway.

The head work did not include hardened seats. It was, I think another 150 bucks but even the machinist shook his head against it and it was his shop. The bill to get my heads pressure tested, valve jobed and assembled with all new parts to my cam spec was 1200.

These heads have had some mild work previously. I'm certainly no judge at all but the surfaces of the metal are really smooth running from the intake ports all around and down into the bowl area on both the inside and outside of the curve. This is just my feeling around down in there with my fingers. I can't really tell whether any unshrowding has been done as I think what's there are factory marks.

Exhaust ports seem to have been smoothed a bit. Both intake and exhaust ports appear to have been matched to the intake.

I did notice the new valves have a recess in them where the old valves did not, this will reduce compression! So I'm thinking now I'll swap out my Fel Pro .044 compressed gaskets for your suggested Mr. Gasket .021 or maybe even go thinner if I can depending on the results of my upcoming PtoV clearance testing!

-weq

You could always CC a combustion chamber with a pair of the original valves and then with the new valves to find out for sure, but I suspect you will find the difference in volume will be so negligible that it won't make any real difference.



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