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Old 02-23-2019, 04:50 PM   #26
vintagewrench
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Cameron's right about the rods. A 4:56 is a good compromise depending on the track, I've found from experience and doing the calculations (don't trust the tach) that 7000 rpm will get you up to 115 mph.
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Old 02-25-2019, 12:21 PM   #27
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I am not 100% sure on what rods they are, but I learned more this weekend about the car.

Spent most of the day Saturday wrenching on it and cleaning things up. Got rid of the homebrew plenum box and parts store filter, running open trumpets now (I'll get some proper filters for them soon). Rebuilt the front hubs as the wheel bearings were not correctly installed. Fixed the fuel pump mounting so it doesn't rub on the trunk floor anymore. 'Fixed' the front suspension to where the shocks are actually attached, need to come up with a long term plan for getting that sorted out though.

After going through it more I decided it was solid enough and took it to an autocross Sunday instead of the other car. The site isn't the grippiest and the forecast was for cool and overcast so I figured I couldn't get enough heat into the R7s to matter, so I ran the 13 year old Proxes RA1s that came on the other set of wheels. Short story is the car is a blast to drive and way quicker than it has any right to be.

Long story, the car behaved well. The coolant issue is still present though but at least now it seems I have pinpointed it to the radiator cap (non-pressurizing one that then feeds to the pressurized reservoir) and I think I'm going to just get another radiator that fits right and forgo the pressurized reservoir setup soon. The car is quite balanced, easy to steer with your right foot and really likes to be driven with the ass hanging out a bit. I think it may be a tad dodgy for big track stuff, especially under braking but I'm also used to a much 'tighter' car so maybe I can just learn to love it. The car spent a little while on the limiter each lap, probably 2 seconds bouncing it in 2nd gear (not worth the up down shift required) and it didn't seem to care a bit. It would give a poof of smoke right as a lifted at the end of a big left hand sweeper but other than that it seems great.

Questions that I still have...

Does this thing really need race fuel? It has VP110 in it as it came to me that way, but it seems excessive. Anyone with anecdotal evidence for what is necessary in a B20? I'd be curious if there are some accepted timing limits, compression limits, or power limits that people have found on pump gas so I have something to base the decision off of once it sees some dyno time.

The brakes seem solid (no pun intended) but I may look into something a bit more robust in the future. Is there a straightforward swap or an easy way to add proportioning to these cars? It has the dual line front calipers with the single line with the accumulator thingies for the rears. Under braking it seemed to want to swap ends pretty easily, made for quick trail braking at autocross but not sure I want to feel that at 90mph on track.

What would the board say is good oil pressure on a race motor? It's seeing 35psi at idle, and 90-100psi at full chat. Judging from the oil bottles that came with it, they were putting 20w50 in it, which seems excessive...
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Old 02-25-2019, 04:32 PM   #28
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Any pics of the car in action? Great update!
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Old 02-25-2019, 05:15 PM   #29
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No photos from the event yet, but here’s the running clip I promised!

https://youtu.be/bRG-JMDT1J8
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Old 02-25-2019, 11:47 PM   #30
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Quote:
Originally Posted by roflcopter View Post
Questions that I still have...

Does this thing really need race fuel? It has VP110 in it as it came to me that way, but it seems excessive. Anyone with anecdotal evidence for what is necessary in a B20? I'd be curious if there are some accepted timing limits, compression limits, or power limits that people have found on pump gas so I have something to base the decision off of once it sees some dyno time.

The brakes seem solid (no pun intended) but I may look into something a bit more robust in the future. Is there a straightforward swap or an easy way to add proportioning to these cars? It has the dual line front calipers with the single line with the accumulator thingies for the rears. Under braking it seemed to want to swap ends pretty easily, made for quick trail braking at autocross but not sure I want to feel that at 90mph on track.

What would the board say is good oil pressure on a race motor? It's seeing 35psi at idle, and 90-100psi at full chat. Judging from the oil bottles that came with it, they were putting 20w50 in it, which seems excessive...
Do you know what the compression ratio is? If it's under 10.5:1 you can probably get away with 93 octane. What's the total ignition timing set to?

164E front ventilated rotors and calipers are a direct swap for the 140 solid rotors.

The accumulator thingies you refer to are actually proportioning valves. You should be able to hear them make a thunk sound when you step on the brake pedal hard if they're working.

Brake hoses are a known issue on these cars. What does it have and what shape are they in?

The oil pressure is actually a little high. ~10psi/1000rpm is the norm. Is the gauge accurate?
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Old 02-26-2019, 09:16 AM   #31
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Do you know what the compression ratio is? If it's under 10.5:1 you can probably get away with 93 octane. What's the total ignition timing set to?

164E front ventilated rotors and calipers are a direct swap for the 140 solid rotors.

The accumulator thingies you refer to are actually proportioning valves. You should be able to hear them make a thunk sound when you step on the brake pedal hard if they're working.

Brake hoses are a known issue on these cars. What does it have and what shape are they in?

The oil pressure is actually a little high. ~10psi/1000rpm is the norm. Is the gauge accurate?
If the documentation I have for the motor is correct it is 11.0:1. These just have mechanical advance right? So the base timing at idle should indicate how much if any they have changed it for the whole rev range? I'm borrowing a timing light tonight, I seem to have misplaced mine.

Good to know about the brakes. I will check the prop valves and make sure they are functioning correctly, is there a way to adjust them if they are working?

The car has stainless brake lines for all the soft hose.
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Old 02-26-2019, 01:23 PM   #32
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Quote:
Originally Posted by roflcopter View Post
If the documentation I have for the motor is correct it is 11.0:1. These just have mechanical advance right? So the base timing at idle should indicate how much if any they have changed it for the whole rev range? I'm borrowing a timing light tonight, I seem to have misplaced mine.

Good to know about the brakes. I will check the prop valves and make sure they are functioning correctly, is there a way to adjust them if they are working?

The car has stainless brake lines for all the soft hose.
if its just mech advance distributor, engine off, measure the BTDC marks and add a few at the same intervals with a paint pen at like 20-25-30-35-40 different colors helps. start the engine and hold the revs at 3-3500 rpm and check. racers used to swap springs on the mech advance to move the point of total timing around to suit the cam used.

not sure on the brake valves... but I think so.

good.
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Old 02-26-2019, 01:39 PM   #33
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Some distributors have just mechanical and some have both mechanical and vacuum. I don't see a hose connected to your distributor but that doesn't mean it doesn't have it. Use a "dial back to zero" timing light to find total advance.

There is an adjusting screw on the proportioning valves but I'd make sure the front brakes are working properly before trying to adjust them.
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Old 02-27-2019, 01:26 AM   #34
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Looks fast.
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Old 02-27-2019, 01:50 PM   #35
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Looks nice.
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