Author Topic: heat shields on a tunned engine?  (Read 17566 times)

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nrg19uk

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Re: heat shields on a tunned engine?
« Reply #60 on: October 25, 2011, 12:24:14 PM »
Did you have the head skimmed last time?
Neil gargaro

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Re: heat shields on a tunned engine?
« Reply #61 on: October 25, 2011, 01:03:48 PM »
Disgusting view  :- Sounds like overheating  :$

It's interesting what is the compression ratio. You say that's 2 or 3mm lowered...  Swiatek #385 (288*, yours is 290* so the same) camshaft requires 1.8-2.5mm lowered head. Measured by me -1.8mm (old type combustion chamber, not 650E or Panda 30) with standard gasket 1.1mm (if I remember well) gives 9.4:1 CR. In my opinion -2.5mm will be about 10.5:1, and maybe is a bit too much for everyday use. (Abarth 595 has 10:1 and the "berlina" type 695 8.5:1; 695SS 10.5:1).

Check the volume of yours like this.



What gasoline do you use? This setup needs 98 or 100.

Spark plugs? You will probably need (if you run standard ones) colder heat range: NGK 8, Champion 6, Bosch 4, Denso 24. The most suitable number you will find out testing it, but start from colder to hotter! Also take modern plugs.

The static ignition advance according to Swiatek must be about 15*. For 126 there are the old type of distributor 18* +/-2* over 3000rpm and the new type 21* +/-2* over 3900rpm and both 10* static advance. For Abarth is 4* static and 34* automatic, but maybe with special type of distributor. Anyway it comes to about 35* final advance.

Do not over tight the head! If it's more than needed, when overheats, aluminum expands and smashes the gasket.

And not on last place, make sure that it is not running on bad mixture! Lean causes overheating.

If you need a new head, look for a 650E one! To be 9.4:1 needs -1.4mm lowering.

Polish the chamber to prevent carbon deposit and the bad effects that gives.

Make sure that the contact surface is flat!

I hope it was helpful ;)

Have fun! :)

Rusty's Uncle

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Re: heat shields on a tunned engine?
« Reply #62 on: October 25, 2011, 02:52:25 PM »
Ouch , that looks messy again. One thing is for sure , you are going to have to use a solid copper head gasket next time. If you can find the right people you should be able to have the head repaired by specialist welding but I am guessing that you do not want to increase the compression ratio any more so minimum of skimming. You are not alone with engine disasters as my "special" engine only ran for 100 miles or so before I hit problems but that was due to hidden sandblast grit in the rocker box cover which has ruined the engine. But when I put it together I upped the torque on the cylinder head nuts a little knowing that I was running a higher compression head, good luck  :)

smallcox

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Re: heat shields on a tunned engine?
« Reply #63 on: October 25, 2011, 03:19:57 PM »
That's not to good,

As for your compression ratio, I do not beleive this to be the problem as from the pictures I run a simular head with a standard cam no problem and looking at how much is removed from the picture on standard pistons would be about 8.8:1. there is an underlying problem but you could get the head skimmed a bit to remove the damage from the face and then insert a couple off copper rings under the barrels to lift the cyclinders up. This is not good practise but would be this cheapest option. Is the exhust blocked because you shoud not have that amount off heat build up locally in the exhaust port
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alapimba

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Re: heat shields on a tunned engine?
« Reply #64 on: October 25, 2011, 03:23:36 PM »
Did you have the head skimmed last time?

just the enought to have it flat again when the gasket reached the head

alapimba

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Re: heat shields on a tunned engine?
« Reply #65 on: October 25, 2011, 03:33:25 PM »
Disgusting view  :- Sounds like overheating  :$

It's interesting what is the compression ratio. You say that's 2 or 3mm lowered...  Swiatek #385 (288*, yours is 290* so the same) camshaft requires 1.8-2.5mm lowered head. Measured by me -1.8mm (old type combustion chamber, not 650E or Panda 30) with standard gasket 1.1mm (if I remember well) gives 9.4:1 CR. In my opinion -2.5mm will be about 10.5:1, and maybe is a bit too much for everyday use. (Abarth 595 has 10:1 and the "berlina" type 695 8.5:1; 695SS 10.5:1).

Check the volume of yours like this.



What gasoline do you use? This setup needs 98 or 100.

Spark plugs? You will probably need (if you run standard ones) colder heat range: NGK 8, Champion 6, Bosch 4, Denso 24. The most suitable number you will find out testing it, but start from colder to hotter! Also take modern plugs.

The static ignition advance according to Swiatek must be about 15*. For 126 there are the old type of distributor 18* +/-2* over 3000rpm and the new type 21* +/-2* over 3900rpm and both 10* static advance. For Abarth is 4* static and 34* automatic, but maybe with special type of distributor. Anyway it comes to about 35* final advance.

Do not over tight the head! If it's more than needed, when overheats, aluminum expands and smashes the gasket.

And not on last place, make sure that it is not running on bad mixture! Lean causes overheating.

If you need a new head, look for a 650E one! To be 9.4:1 needs -1.4mm lowering.

Polish the chamber to prevent carbon deposit and the bad effects that gives.

Make sure that the contact surface is flat!

I hope it was helpful ;)

Have fun! :)

Hello

THank you a lot for your post.

Regarding the CR, we measured it because since the last blown gasket i always thought about that issue so acording to my counts, using the gasket that i used of 1.8mm the CR was at less then 9,5:1 i guess it was 9,1 if i remember correctly. My mechanic measured as you show in your picture.

I did about 1600km this time until this happend and around 600 was on the highway, 300km one day and 300 in other with only stoping one time and driving at around 100km/h.

I allways use 98 fuel with adictive.

You mentioned overheating and bad mixture and indeed my car was running too rich. [youtube]http://www.youtube.com/watch?v=jOIQrdgL0lc[/youtube]...

Do you think this was the cause? in the day that the problem occured i was driving slowly, the day was a hot but not too much.

One doubt that i have now is.. this head will still be of good used? if i go with a cooper gasket this time it will have i guess 1,2 or 1mm it means it will be a stronger gasket but even more compression due to the lower combustion chamber, right?

What should i do? i really didn't wanted to put a std head and loose power (the car was really nice before the problems) but i'm really sick of problems...

I saw that 650E heads on ebay.. should i go with this route?

Regards

alapimba

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Re: heat shields on a tunned engine?
« Reply #66 on: October 25, 2011, 03:42:25 PM »
That's not to good,

As for your compression ratio, I do not beleive this to be the problem as from the pictures I run a simular head with a standard cam no problem and looking at how much is removed from the picture on standard pistons would be about 8.8:1. there is an underlying problem but you could get the head skimmed a bit to remove the damage from the face and then insert a couple off copper rings under the barrels to lift the cyclinders up. This is not good practise but would be this cheapest option. Is the exhust blocked because you shoud not have that amount off heat build up locally in the exhaust port

the last time i already did that and used 2 copper rings on each barrel to try to don't have such a high compression...

the question with the head at the moment according to my mechanic is... the reason from the problem can't be the weakness on the head? as you see on the picture it bends easily due to be so skim and can cause the head to lift or the gasket or something like that and allow it to lift and then the gasket blow?


smallcox

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Re: heat shields on a tunned engine?
« Reply #67 on: October 26, 2011, 05:16:25 PM »

((((Do you think this was the cause? in the day that the problem occured i was driving slowly, the day was a hot but not too much.))))
If you get bad backfire when engine is switched off from idle this is a glue off a weak mixture, Thi sin it's self destoyes engines.
The original head gasket is more than capable off handling the extra power


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alapimba

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Re: heat shields on a tunned engine?
« Reply #68 on: October 26, 2011, 05:28:31 PM »
Whats your opinion about my cylinder head? should skim it and try to use it one more time or this was his dead?

Regards


smallcox

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Re: heat shields on a tunned engine?
« Reply #69 on: October 26, 2011, 05:48:38 PM »
Without seeing the cylinder head first hand makes that a hard one, but if you can get it skimmed and cleaned up then I don’t see any reason why not. The compression can be altered by removing material from the combustion camber or/and fitting a spacer under the cylinders to get the desired c/r. don’t get over fixed on the c/r as this I don’t believe to be you main problem. With a longer duration cam you can run higher c/r’s.
Use a good quality original gasket not the cooper type as the copper type will cause more damaged should something go wrong.

Once completed gat the engine check the fuel/air ratio as a rich mixture will not cause the damage you show but a weak mixture will. Also at idle feul ratio will be different than when at engine speed. did you have the carb rejetted after the mods again if not this will defently cause a weak mixture.

Good luck
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Rusty's Uncle

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Re: heat shields on a tunned engine?
« Reply #70 on: October 26, 2011, 06:11:47 PM »
 :D smallonegurubloke you are the Man,  ;D
You may have just solved my problem as well. When I put the tuned head on my 499ccs and the other bits all was well but I got that backfire when you turn off the engine.
My shortlived 652ccs engine with all the goodies would also backfire. I am running an oversize carb on the 499 and tried standard on the 652 to see how things went and I am a bit of a hammer chewer in this tuning department  :P
So I reckon that a little bit of "messin' with the jettin' " is in order  :)

alapimba

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Re: heat shields on a tunned engine?
« Reply #71 on: October 28, 2011, 04:28:05 PM »
Hello

I have been inspecting this head and comparing with a friend cylinder head that has a race engine with 10,2:1 compression and we realised that my head were probably run with a even bigger compression ratio so it's better forget about it.
Now i have to start again from 0, so i'll buy a new head.

I'm thinking in a 650 "E" head and use the valves from the old head.
What do you guys think? for this i'll spend around 250€ i guess in the new head, shipping and machine it to fit the bigger valves.

With this budget i should go with another route?
THanks

thepuddlejumper

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Re: heat shields on a tunned engine?
« Reply #72 on: October 28, 2011, 10:29:52 PM »

alapimba

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Re: heat shields on a tunned engine?
« Reply #73 on: October 28, 2011, 11:38:32 PM »

alapimba

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Re: heat shields on a tunned engine?
« Reply #74 on: November 09, 2011, 12:33:24 PM »
Got my new head today.
now i have one doubt... what is the job of this holes in the head?
Should i bolt something here? i didn't had this on the other head... or at least were filled



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