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Topics - Dunc the Funk

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Matt Shaff's Engine Shop / Gear drive runout?
« on: June 07, 2020, 03:53:49 AM »
Hiya, just checking some stuff before re-assembly. Last year we had the cam dowel come out & I found that the hole in the gear drive cam hub was oversize. I removed the cam, drilled the cam hole larger then reamed it & the hub larger, fitted a bigger dowel & it ran ok. I thought I really ought to look at gear backlash & runout while I have time & the motor is fully apart. Rotating the crank & cam with the gear drive bolted down shows no tight spots but the backlash does change a bit during rotation. I removed the cover again to check runout on the cam gear. It's a maximum of 4 thou (or +2 to -2). Anyone know if this is ok?

Matt Shaff's Engine Shop / Rod bearing clearance
« on: May 23, 2020, 02:39:46 AM »
My local machine shop checked our crank & gave it a very light polish. The guy said the rod journals are at standard. The bearings used by last year's rebuilder were standard (Clevite CB-743HND) and the previous year's builder were one thou thinner (CB-743HXND). The rod manufacturer (MGP) says we need 3 to 3.5 thou clearance. I assumed that when we first got the engine it had been set up loose for traditional thick oil so that seemed ok. Anyway I used fully synth 10w50 the first year & 15w50 last year with no major issues.

This year I ordered King CR 808HPND in standard but before fitting I thought it would be a good idea to check clearances with last year's bearings. I only have Plastigage. Everything was dry & clean & correctly torqued. I was surprised to find clearances were between 1.5 and 2 thou. Now I could use Clevite thinner bearings as above or King equivalent (STDX type) but firstly availability is not so good and secondly 4 of the bearings will still be a little tight at around 2.5 to 2.75. My question is would it be better to have a thou or two taken off the rod journals now then I can use the bearings I bought & not have the same issue next rebuild? I'm planning on using 10w50 oil as the crank is already set for 3 thou.

Matt Shaff's Engine Shop / BBC Main Stud Life?
« on: May 16, 2020, 09:18:40 AM »
On a blown methanol 517ci BBC with 4 bolt steel main caps on an iron Gen IV truck block with aluminum rods, probably around 1000hp and operating at 7000-8000 rpm max, what sort of life expectancy would you give the main studs e.g. in terms of rebuilds, seasons, runs?

Matt Shaff's Engine Shop / Cause of fretting on main caps?
« on: February 07, 2020, 01:11:46 PM »
We only put 13 passes on our blown methanol BBC last season. I was surprised to find serious fretting had occurred on caps 2,3 & 4. 4 was loose in it's register.
As far as I know this did not happen last season when we probably did 20 odd passes. Is there anything I should think about with the tune that may have caused this?

Matt Shaff's Engine Shop / Removing crank hub spacer
« on: November 18, 2019, 05:14:33 AM »
My BBC has a steel crank hub with a large-flanged bolt. In front of that there is an aluminum spacer for the blower pulley to sit on. The bolt will not go through the outer part of the spacer bore where it steps down. So in order to remove the hub I need to remove the spacer which seems to be a press or interference fit on the hub. I've been thinking of applying heat with an electric heat gun to expand the aluminum and also fabricating some kind of 2 legged puller that will fit. Anyone got some tips on removing the spacer?

Altereds / Wheelie bar length?
« on: November 03, 2019, 07:10:30 AM »
I will be replacing our wheelie bars over the winter. The ones we have currently are 52" (4' 4") and their main problem is that being quite short the tolerance on the setting is too small. I'm thinking of moving up to 72" (6'). Any longer & they will not fit in the current support vehicle & I'd have to fab some way of fixing them on our open trailer. I think it's sufficient length anyway, but what do you folks run on your cars?

Altereds / Ran our first seven!
« on: September 17, 2019, 01:58:21 PM »
Team Thundergod just had a crazy weekend. On Friday the car wouild not start at all (see previous threads re poor starting). Eventually we realised it could only be the fuel pump so we borrowed one & it fired up right away. Ran it but it was so fat because the pump was delivering way more fuel that we only did a couple of 9 second passes. I finally got the tune more or less back on track & we went 7.98 @ 169. Still way rich! We were hoping for a better final pass as I had leaned it a bit more but I made a mistake by filling the tank to the brim with the system still full of fuel, then leaving it in the hot sun for half an hour. Fuel must have pushed into the cylinders, it would barely turn over let alone fire & we missed our chance.

Video from Santa Pod Raceway:

Spud Miller's Cave / Hat nozzle type and starting issue
« on: August 09, 2019, 01:32:33 PM »
Our motor has been difficult to start, it always fires after priming but will often die either immediately or while you are feeding it on the bottle. Once on the pump it runs fine.
Inspecting it recently I noticed that the hat nozzles are the non-ported type. Would having the single hole ported type help with starting?

Altereds / First full pass on current combo at last!
« on: July 19, 2019, 11:54:39 AM »
Exactly a year on from our first meeting with our 'new' combo we finally, after a weekend of frustration, got her down the track under power all the way. The driver pedalled slightly off the line to a 1.33 60', 5.67 @ 137 at the 1/8th but it really charged after half track to 8.40 @ 184mph! We were hoping for 7.7 / 7.8 @ 170 ish but what the hey, looks like we could run 7.3s sometime soon! This was with only 30 degrees of timing! I think it leaned out at the big end, plug plating was burnt just up to 1st thread. Check out this video, we're on at 22 mins, LH lane, you can see me start the motor & on the line.

Dan Dishon's Transmission Den / Can you ID our converter?
« on: July 06, 2019, 08:39:05 AM »
We got our converter second hand with the motor & I'm trying to find some info on it. I don't know the manufacturer but it has this stamped on it:
829 B14XLS +1/4 A1014135. It's about 10.5" diameter. Obviously the +1/4 is the extra lug thickness for the motor plate but that's all I can say.
When the car launches, rpm goes to about 5k immediately. I've searched mainly with the B14XLS part but drawn a blank. Any idea on the manufacturer to start with?

Altereds / Helmet filters?
« on: May 20, 2019, 02:12:22 PM »
We have a blown methanol altered running FC headers (see pic). The driver has a helmet with built in filters which he bought when he thought he was going to get a FC drive. Is it necessary to have filters in a car like ours?

Matt Shaff's Engine Shop / Lost cam dowel - what to do?
« on: May 14, 2019, 12:42:13 PM »
We had our blown methanol BBC freshened up for the season by a fairly well known hot rodder/race car builder here in the UK. There was not much wrong with it from last season, basically he just replaced the bearing shells. We test ran it for the first time last week, it fired up and ran well. After draining the oil we found some small non-magnetic particles in the oil filter. Not enough to really worry about but a bit puzzling. Some of them seemed to be aluminum & some looked like phosphor-bronze. When we checked the lash before running again, it developed a tight spot that got worse the more we looked for it, until it was pretty much locked up. We took off the blower & inlet & I noticed I could move the crank about 5 degrees without moving the cam. We took off the fuel pump & front distributor drive & found that the cam dowel was missing & the bolts loose which hold the drive & cam hub to the cam. It seems the builder did not torque them up enough. He agreed on that & stated that there definitely was a dowel in the cam. We have not been able to find the dowel. it was not in the sump. A more experienced builder & racer told me they do sometimes come out & the gear drive is so hard it can actually munch them up. We tightened the bolts, replaced the rockers one at a time, turned it over by hand & it seemed ok. We didn't run it because I could not get a dowel & also we were worried about where the bits had gone. So after that long story, my question is should we have it completely stripped, inspected & cleaned or just replace the dowel?

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