MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - Block Huggers Vs. RV8 Headers

Has anyone found that V8 installation (Rover 3.5) using block hugger headers leads to an unsolvable heat problem? I have tried Water Wetter, 40 Below, and oil additives with little to no benefit. I have a three row high capacity radiator, with two stock electric fans and one waterpump mounted 14" flex fan. I even tried header tape, which did nothing but crack my 2 month old stainless steel headers. I am considering going to the RV8 headers, but am not sure I like the idea of cutting up my fender wells. Anyone have a better option, or is the blockhugger method just proned to this problem?

Thanks

Mike
Michael Akin

Testing 1.2.3
Michael Hartwig

Stupid BBS. After all that typing, it didn't post my message. Here it goes again:

Can you give us more info about the heat problem. Does the engine overheat while driving fast, slow, or all the time. Here are a few things I can think of:

1. Are you sure the engine is overheating? Senders can give wrong readings.
2. Make sure all the air is out of the system. Especially with the MG where the radiator is lower than the engine.
3. Is the thermostat working properly. I usually heat water in a pot to 180 degs then drop the stat in to make sure it opens.
4. Check you mixture. Are you running too lean?

I would doubt it's your headers. You rarely see temps in the 90's?? More like 70 degrees??

Mike
Michael Hartwig

I have, in an RB car, block-huggers that are Jet Hot coated. Seems to have licked the problem. I have the same fan config. as you do, with a bigger motor.
Harry

Mike

Same configeration, standard V8 rad, 1 flex fan, 2 electrics, on a manual switch just in case of an emergency plus block headers. Problem, too much heat and too few escape routes. I have a 1979 body shell, I replaced the good shock with an old one, just in case I beat to much and damaged a good shock, then beat the inner fender down to within 1/4" of the old shock, this moved the fender approx 4" away from the headers. I then replaced the good shock. I also dressed the area of the firewall just beneath the heater box. Overall both have increased the escape route for hot air. Here in Atlanta this summer I have regularly been in jams in temps. of over 90 degrees, with absolutly no trouble.
Is the top hose on your conversion level or is there a high spot that is above the top of the rad.? if it is high then the water may not be able to get over the "Hump" and get back into the rad for cooling.
Good luck Mike.
Mike Cook

Thanks for all of the great advice. The temperatures in Colorado will be in the 90's regularly in the summer. We had 87 days of 90+ this year! The overheating problem only occurs when it is mid 80's and higher. It occurs more while sitting still as opposed to at highway speeds. To verify that it is overheating, I loose significant coolant through the overflow, and can hear it boiling over. While on the highway, the heat gauge (stock MG) runs about 90 percent of the way to the red. I have not put a temperature gauge on it other than that.

The thermostat is working (have replaced three times with varying temperatures, but now working with 160Deg). The car also passes emissions testing without all of the emissions gear hooked up (air pump, cat, etc..), so it is not lean. If anything, it is slightly rich.

Two things I didn't do:
1) How do you "Burp" the radiator to expel air pockets? My Rad has a plug on the top, and utilizes the stock overflow, although this is a new, three row rad.

2) My upper Rad hose actually leaves the intake manifold at about 45Deg. So, the bottom of the hose is acually higher than the top of the hose at one point between the Rad and the intake manifold. Is there another alternative, and where do I get it?
Mike Akin

Harry in VA, the Jet Hot option is a certainty. I have talked to many folks who have used the Jet Hot option on other applications, and they speak very highly of it.

I also have pushed the fender wells out to increase air flow, but not as far at Mike in GA. Will try this as well.

Thanks guys for all your advice.
Mike Akin


DOES ANYONE THIS SIDE OF THE POND DO JET COATING ?

Thanks in hopeful anticipation

Roger

Roger

Mike.
I do not think that your problem is one concerning headers, from what you say about "water boiling" makes me think that it a case of the water not completing a full circuit of the system. This I think is confirmed when you say you loose water out of the overflow, that is more than likely radiator water rather than returning water through the top hose. When the engine is hot check to see if the top hose is hot all along it's length, if not it could be an air lock.
Mike
Mike Cook

There are header coatings you can apply yourself that claim to signifcantly reduce radiated heat.

You might try looking on Tech Line Coatings site which is www.techlinecoatings.com.

I've purchased some of their do it yourself products for an airplane exhaust, but have not used it yet. Their tech rep told me it is best cured in an oven at 750F but can be cured in-situ on the motor after heating in an oven a 450F to get an initial cure.

Can't endorse it yet, but you might want to check it out.

They also have a list of commercial applicators on their web site if your not inclined to try it yourself, and some of them were outside the US.
Phil Dooley

Mike

do you have the proper stock MGBV8 top hose and thermostat housing/elbow? There are many different types to suit the various vehicle installations.Most of the Range Rover applications have the engine mounted very low in relation to the top rad outlet-these use an elbow with at least 45 deg angle. The MGBV8 outlet has a much flatter angle with an extra spigot which takes a steam vent pipe from the centre of the stock manifold water jacket. The stock set up also routes neatly around the distributor.
The elbow is availible over here in the UK as a nice quality repro ally casting-I think that I paid about 13-14 £ for mine about four years ago-from Dave Vale at the V8 Conversion Co. I believe that Brown and Gammons also do them as well-possibly also Clive Wheatley.
I think that if is an air lock problem that this will cetainly help.I havent noticed any special problems when filling the system -I just fill it up through the plug on the top of the rad with the heater valve open and burp the system by squeezing the bottom hose hard when it is nearly full(measure the volume so that you know what it should take).When it is nearly full squeezing the bottom hose should get the jiggle pin in the thermostat(which you will have placed at the 'top' like it says- rattling). Run the motor for about five minutes with the plug removed and squeeze the hoses to help the bleeding process.
I can't really compare notes as it probabaly doesn't get really hot here compared to your temps. I only run a totally std MGBV8 rad with a mildly modified motor. This has no difficulty keeping cool-I only just managed to get the needle the wrong side of centre when climbing the Voseges on the V8 register tour in Sept.I use 'block hugger' manifolds wrapped to reduce radiant heat. They have recently cracked though-and I would now consider the RV8 type as the longer primaries allow more movement and better air movement.The wheel arch is a low pressure area-so air should flow out around the manifold .
I also put the good behaviour down to careful ducting of the lower valance inlets to the lower part of the radiator-you have got to force the air through the rad-and that goes for the fans as well.These need ducting at the top edge of the slam panel as well.


Regards

John Bourke
John Bourke

John

Thanks for the advice in ducting and burping. I thought I should tell you that I used header wrap on my blockhuggers after trying everything else. This is when my frustration started, as my headers cracked as well. Then I found out that wrapping the headers voids the warranty on them. At $500 a set, I don't want to do that again, and though you wouldn't either.
Mike Akin

CERAMIC COATING IN THE UK

Camcoat.
127 Hoyle St. Bewsey Ind. Estate.
Warrington Lancashire WA5 5LR
Tel 01925 445003 Fax 01925 444988

Phil in Phoenix - excellant website - thank you

Roger - Factory Fuel injected 3.9
Roger

The problem with exhausting thru the inner wing is that this part of the car is a structural member, triangulating the top of the A post to the X member pick up onto the front chassis rail.
Have you ever driven an RV8? They have terminal SCUTTLE - SHAKE!
The problem of high running temperatures appears to be that there is nowhere for the hot underbonnet air to go. ts all very well having a super efficient rad and fans, and water wetter etc, but if there is nowhere for the air to get out, then the engine will get hotter.
Louvres in the bonnet are no help because of the insufficent pressure differences, causing no flow.
All this get no nearer to making them run cooler!
Doug
Doug Smith

I can't say that I agree with Dougs summary of the RV8. I have driven only about a half dozen examples but I have not experienced the same degee of problems. However I do agree that the inner wing is a structural area and here I can say with some experience that the method of providing reinforcement to the inner wing of the RV8 is a simple steel ring that is only lightly spot welded. Where I have followed the RV8 inner wing route I have seam welded a home created ring. Being as there is a direct compaison between these cars before and after conversion I again can't agree with the scuttle shake issue. It may well be that Doug has experienced just bad cars, or I have been lucky with good cars.

The advantage of hot air removal is a sound one with these inner wing holes, also the positioning of any bonnet vents is critical, otherwise air flow can be into rrather than out of the engine bay

Rog
Roger Parker

What’s causing the headers to crack? Excess heat or banging the steering? There is only about 1/8” between the header and pinion shaft on my MGB V8. Have the headers cracked on the steering side?
George Champion

Re: RV8 Headers and chassis rigidity:

I've never driven an RV8 but been driven in one few times. My own conversion is based upn a GT and I have found that the roadster shell always seems to have some degree of scuttle shake.I think that the whole issue is also bound up with the suspension specification-and which I have pointed out in the thread on wide wheels and tyres. I believe that the chassis rails of a B are relatively flexible -especially in front of the cross member. Doug is right in that they are only braced by the inner wings(fenders)which in turn are braced by the inner wing reinforcing sections in the wheel arch. Cutting the hole for the RV8 headers without adequate reinforcement-AND also bolting on any thing stiffer than a 3/4 dia anti rollbar in conjunction with wide wheels/stiffer springs is a recipe for the chassis legs to flex especially in a roadster body shell.
I suspect that Doug is no doubt thinking of what MG did when they needed to brace up the MGC engine bay to handle the extra weight of the cast iron straight six-with box sections connecting the chassis rails to the inner wing reinforcers.
If and when I get around to changing to RV8 headers- I shall make a box section to emulate that that of the MGC as I am slightly sceptical that just an extra thickness of spot welded sheet metal ring around the aperture is enough to compensate for the removal of the basic metal shape and it's stiffening effect.

George:

I was most careful to open out all the holes in my headers so that the bolts were not binding-I knew then that the manifolds change shape and needed sloppy holes to expand and contract.I also know that wrapped manifolds can over heat which in turn causes cracking and crystallisation of the MS seam welded tubing that most manifolds are made from.(This happened to the highly stressed centre branch of my well tuned 1950cc manifold).What I was not prepared for- was the extent to which the manifolds can move.When I removed the exhaust side manifold for repair I found that the holes which had previously been a generous fit were now at least half one diameter of bolt out which made removal difficult without stripping the threads in the cylinder head.I think that studs are the only answer.I also think that if the primaries were longer they would be able to flex more and not cause cracking at the collector.BTW I dont think that it is the steering shaft-mine show no signs of contact-but I have fabricated a steady bar which runs across the back of the engine and which seem to successfully limit movement.(I have about 10mm max clearance to the shaft.)


Regards

John Bourke
John Bourke

This thread was discussed between 25/10/2000 and 30/10/2000

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now