I am afraid

johnboy914 · 09-30-2001, 05:59 PM

I got my motor back from the shop after a rebuild. (2.0, 9.3-1 compression rat., scat cam, 40 IDAs, 11lb fywhl) It runs hot in my opinion. When I get on it for a while it hovers just below 250, when I get off of it the temp drops some. Oil pressure is good up til about 230. Then the 10lb/1000rpm rule starts to bend a little. I am running 20/50 oil. My mechanic is much less concerned about the temp than I am. He says shut it down at 270. I am reaching 250 on a 65 degree day. If it were 90 out, I think I would be hurting. Any thoughts?

John Rogers · 09-30-2001, 06:13 PM

Do you just have the stock oil cooler? If so you are courting disaster due to the high temps as you are seeing. The stock cooling system, meaning oil cooling and air cooling are going to be slightly inadaquate for a hot rod. Try to find a pyrometer and do a good hard run and hop out and measure the case temp at the bottom and the head temps and see how much higher than stock they are? Good luck.

johnboy914 · 09-30-2001, 06:24 PM

Yep, stock cooler and cooling tin. One thing that I don't have are the air flaps on the bottom of the pan. Are those crucial? I have checked the oil temp gauge with a pyrometer, the gauge is dead on.

SteveStromberg · 09-30-2001, 08:15 PM

Did you install the flap over the oilcooler? Steve

johnboy914 · 09-30-2001, 08:19 PM

The thermostat flaps are held in the open position.

Jake Raby · 09-30-2001, 08:27 PM

270 IS HOT!

Anything over 240, and dino oil starts to lose its properties..

The high CR you have does a good job of heating up the pistons, did you do any Conn Rod mods to aid of the cooling of the pistons?

An external cooler is definately needed, or you may spin/scorch a bearing!!

Keep a VERY close eye on that Scat cam, when you drain the oil, hold a magnet in the stream to see hom much Iron comes out...Also watch the valve adjjustments, to see if they loosen repeatedly...

All I have to say is WEB CAM (I have bought 35,000 Bucks worth of them with out a single failure yet!!

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The flaps on the bottom of the floor pan are a good idea. I'm not sure if you could exactly call them "crucial", but it sounds like you need all the cooling help you can get. And those do help.

I also suggest pulling the rear valance off and seeing what effect that has on temps. I have heard from a couple of sources that it should help lower them, but I don't have direct experience.

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

Rot 911 · 10-01-2001, 06:18 AM

Hope you don't mind if a 911 guy jumps in here, but 250, while becoming borderline hot, is not yet in the critical stage. Especially on a new engine that is not yet broken in. You have much more friction than you would on an engine with some miles on it. If you don't see a drop in temps after 500 miles, then I would worry. One other thing you might check is to see if your sending unit is accurate. You never know if it got knocked around in the rebuild. Wouldn't be the first time something quit working that was working just fine before you rebuilt an engine.

Kurt V
72 911E

johnboy914 · 10-01-2001, 09:21 AM

I just put the valence on. It didn't change the temp. I will put the flaps on tonight. What temp should this thing run at? I had an old bus and it ran at 180-90, 200 on the hottest of days on the steepest of hills. If I do need to put a remote cooler on, where should it go? Does it need an aux electric fan?

mejulihn · mejulihn's Garage

For adding an external oil cooler you may want to check out Pete Dubler's tech article on the PP site.

campbellcj · 10-01-2001, 01:29 PM

Your car is cooking...I think you'll need to add an external cooler, and you should also consider switching to synthetic oil (e.g., Mobil 1).

My stock 2.0 has gotten up in the 270 territory, but that is after 10-15 minutes on the track (i.e. full throttle) in 100+ degree heat. On the street, especially since I added a cooler, it stays under 230 and usually more like 190-210.

I wouldn't run it at 250 or higher for more than a couple minutes if I were you, until you pin down the problem.

Good luck,

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Chris C.
73 914 2.0
70 911E Targa
campbell.chris@gte.net

campbellcj · 10-01-2001, 06:33 PM

Quote:

Originally posted by Dave_Darling:

I also suggest pulling the rear valance off and seeing what effect that has on temps. I have heard from a couple of sources that it should help lower them, but I don't have direct experience.

I am going to try running without the rear valence for a while, and see what effect that has. I noticed last weekend at the track (Streets of Willow - Calif desert) that the stock exhuast really bakes the back of the car. The entire trunk area turns into a "heat sink" upon which you could literally grill meat I bet. After a 15 minute practice session, the trunk floor was hot enough that I couldn't touch it. (It was 100 degrees out that day, which certainly contributed.)

Sooner or later I am going to yank the whole stock exhaust system and go to a coated header/collector and race muffler setup, which should help dramatically. The idea is to get a lot more heat out the exhaust pipe, and a lot less 'stored' in the heater box, muffler and body/trunk sheet metal.

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Chris C.
73 914 2.0
70 911E Targa
campbell.chris@gte.net

mtndew342 · 10-02-2001, 09:05 PM

I own a 74 1.8 litre and was having the same problem for quite a while. My car has no flaps (same as in the up position) from the past owner and as far as I understand this should make it run cooler! In my case it turned out to be the timing, if your timing is off at all it can really reak havoc on engine temps! Not to mention power! Just my two cents.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Different flaps. The flaps we were talking about are underneath the front of the engine bay.

Not having the cooling flaps under the engine tin is not the same as having them in the "open" position. The flaps help direct the air flow, and make sure that air actually does go through your oil cooler. They should be there.

This isn't quite as bad as leaving the flaps out on a Type I engine (where it is a Really Super Bad Thing), but the flaps are a fairly important part of the cooling system. They should be in place.

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

norustscott · norustscott's Garage

The problem of cooling your engine is suspect to the 9.3 to 1 CR...Stock numbers are 7.6 to 1...combine that with a poorly operating cooling system and possibly mis- proportion intake and exhaust valve sizes and you may have your answer...Lowering the CR will have minimal affect on your power...hope this provides insight...scott

Pinseekers · Pinseekers's Garage

My 2 cents worth.
I had a similar problem on my newly rebuilt engine. Eventually dropped a valve (ugly & $$$). Anyway the mechanic for the state (AUtomotive repair) came to the conclusion that it was improper deck height too much compresion. He said he had seen it before in his racing days said it was not uncommon.
When they corrected the problem it ran MUCH cooler; but with a significant drop in power.

iustasail · iustasail's Garage

9.3 is high with stock 2L heads! If you did not have significant head work done including port/polish, unmasking with the whole thing being flow tested at the end. Your new engine is starting to approach hand grenade status especially with those oil temps! Unfortunately just an external oil cooler will not alone do the trick. 912's could get away with 9.3-1 CR by angling the exhaust valve 57 deg thus making something approaching a hemispherical combustion chamber. With the side by side valve arrangement in the VW derived 2L head safe CR is about 8.6-1 also 9.3-1 CR is in the realm of forged pistons, if you are not running forged pistons that CR will kill your top end fast! You might get a solid 30K out of it if you get the oil temps down; that's why most go for stroking and 96mm pistons with 8-8.5 to one CR to get close to 130 hp!

You may want to look at your carb jetting, you could be set up to lean thus causing you to run hotter.

E

Jim T · 10-04-2001, 03:56 PM

I agree, stock heads, 9.3 compression and 250+ oil temps, you have a grenade on your hands, no doubt.

Jake Raby · 10-05-2001, 06:49 AM

If you want to keep the CR @ 9.3:1 you do need to let the engine breathe better, thus actually dropping the dynamic CR at different RPM to a safe level.

The biggest number of mistakes I see, and get questioned about come from engines that are mis-configured. The combinations of cam, heads, CR, valve sizes, combustion chamber voluume and induction are a must for any engine to live a long powerful lifee, and to be able to be tuned easily.

I'm a fan of higher CR, but only if some coefficient changes are madse to the rest of the engine.

johnboy914 · 10-05-2001, 07:01 AM

I checked the timing again after it came back from the shop, it was retarded by quite a bit. I set it at 31 total advance. I can fudge a little cuz I live at 7500ft. The temp has dropped. I was feeling frisky and got it up to 115mph the temp didn't go above 190. Climbing long (15-20 mile) hills, floored, it will creep into the 210 zone. I am hoping that the timing was the source of the higher temps. I am still going to put a external cooler on it. I can't see how that could be a bad thing. Does that octane boosting stuff help with a higher CR?