Re: 521 cid broken camshaft dowel for timing gear . bent valves

lance flake May 20th 2023, 12:01 pm

Radial clearance on any moving part in an engine I like .050 plus. I have tan .040 on a valve pocket and was fine. I’ve seen .030 radial on a valve pocket hang a valve

Lem Evans May 20th 2023, 12:52 pm

maverick172 wrote:
supervel45 wrote:The articles were pushing 1.72" valves on the small bores when they came out, if I recall correctly.
no way they would of worked.
what your thoughts on timing chain it the roller bearing on the back vs the brass bushing ?

I use and sell the bronze [not brass] retainer. No place for that cast iron plate i.m.o. A guy can run the roller stuff but, it's not needed with the bronze plate.

supervel45 May 20th 2023, 11:37 pm

Maybe it's just me, the fewer needle bearings in an engine the better.

https://www.429-460.com/t9439-cam-thrust-plate-options

I would double check before rushing off plugging main mearing feeds like in the above link.

I ran a gear drive on a small block years ago without problems with a cast solid mechanical roller cam when Comp offered them.

I'd skip it today just because. I doubt it will snap a billet roller cam and mine was a cast street roller, but they say if you get a backfire or kick back it puts a lot of stress on parts. Also it may soak up some HP.

maverick172 May 21st 2023, 7:59 am

Lem Evans wrote:
maverick172 wrote:
supervel45 wrote:The articles were pushing 1.72" valves on the small bores when they came out, if I recall correctly.
no way they would of worked.
what your thoughts on timing chain it the roller bearing on the back vs the brass bushing ?

I use and sell the bronze [not brass] retainer. No place for that cast iron plate i.m.o. A guy can run the roller stuff but, it's not needed with the bronze plate.

so just so we are on the same page .. you do not need a thrust bearing at all on the cam gear as long as there is a bronze thurst plate in the engine?

Lem Evans May 21st 2023, 11:03 am

Unless you have something that's designed to take a thicker roller housing .

maverick172 May 21st 2023, 11:44 am

Lem Evans wrote:Unless you have something that's designed to take a thicker roller housing .

ok.
so in your opinion , what is the best timing chain to use on a 700to 1000hp engine . cast iron cam gear or steel? and if i use steel cam gear without a thrust bearing on back can i usea fatory thrust plate (if case hardened ?) or do i have to use a special bronze one or a aftermarket "steel" thrust plate ?

Dave De May 21st 2023, 1:15 pm

Best gear and chain set that I've used is a Roll Master. The IWIS chain doesnt stretch.

https://www.buyracingparts.com/rollmaster-billet-timing-sets/rollmaster-timing-set-429-460-ford.html
Lem probably stocks these.

Lem Evans May 21st 2023, 1:40 pm

Dave De wrote:Best gear and chain set that I've used is a Roll Master. The IWIS chain doesnt stretch.

https://www.buyracingparts.com/rollmaster-billet-timing-sets/rollmaster-timing-set-429-460-ford.html
Lem probably stocks these.

I do have some. Including ones that I've had double pin drilled.

Paul Kane May 22nd 2023, 2:50 pm

Lem Evans wrote:So, long story short.....1.70" exh. valve does not work in a 4.390" bore?

The story ain't over yet. Maverick needs to take those heads and install them onto a couple of other 4.39" bore blocks and see if the exhaust valve clearance issue persists on those blocks too, or, if it's just the mass produced block in particular that he happened to use. The manufacturer does say the SR-71's are supposed to clear 4.39" bores with the 1.70" valve, and that many heads have been sold that way and installed without issue.

Purely by coincidence I eyebrowed a 4.39" bore block just last week even though my "extrapolated mock-up" suggested the 1.70" SR-71 valves would indeed clear. Even though the calculations added up for me, I wanted to be prudent so I notched the deck anyway out to a 4.50" bore gasket ring, and I also red dykem'd the cylinder bore and scribed a horizontal line 0.300" below deck (piston's top ring land is 0.350" down for this build).

Back to Maverick's Situation: if the exhaust valve clearance issue persists with Maverick's particular heads even on other 4.39" blocks, then my recommendation would be to utilize a 1.80" cutter for the 1.70" valve which will net 0.050" radial clearance. Start with a few head gaskets stacked so as to raise the head up then check the depth of the cut down in the bore, then remove a gasket at a time until the cut is 0.250" down (in his case).

supervel45 May 22nd 2023, 3:50 pm

^ That's an excellent post Paul, as usual.

Were your SR71's shaved .030"?

supervel45 May 22nd 2023, 5:22 pm

maverick172 wrote:
supervel45 wrote:The articles were pushing 1.72" valves on the small bores when they came out, if I recall correctly.
no way they would of worked.
what your thoughts on timing chain it the roller bearing on the back vs the brass bushing ?

I would go with Lem's Bronze retainer plate.

It kills at least 2 or 3 birds with one stone.

I'd likely get that double pin compatible Timing set Too that he has in Stock, even if I only ran 1 pin for now, in case I went bigger cam/springs down the road. I don't usually push parts around here but, that sounds like a pretty good Combo Deal.

1. It is compatible with any camshaft metal, that contacts the back side.

2. It is compatible with any timing gear metal.

3. It takes dimension checking out of the picture when using stock dimension gears.

4. It has no needles to potentially fall out and lock up your oil pump.

5. On tear down inspection, if it shows wear on one side only it can be flipped over or resurfaced if the wear is minimal.

I have built a lot of transmissions with thrust washers with likely 100's of thousands of miles, and as long as they were oiling properly showed minimal wear on the thrust washers.

I have run them on occasion behind timing gears, and did not notice much wear either.

In Pro Mod or Top Fuel or other mechanical area's that are very high load the roller stuff makes some sense.

Even some of the Pro Engine builders are in debate if Roller Cam bearings are worth it or if they show any real HP gains.

Did I forget to say screw Chine Rollers also, and I really don't like them where ever they come from as quality control is on the decline everywhere, metals are foreign sourced, ect. and If It Is More Likely to Fail IT WILL. "KISS" Principle! KEEP IT SIMPLE STUPID whenever possible helps Keep Murphy at Bay. Wink

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