Ae111 Blacktop 20v

[Gunner]

thats what i recon

[DAMO46]

Yeah I might get the valve train kit off you gunner.
Sam a 7ag with a black top head, rods, stock bt pistons, and skimming the block what would you say it would rev to and still make power?

[Sam-Q]

that all depends on your cams, is your question related to the 288's?

[ae86hachiroku]

It really depends on your cam timing and how you suit it to the cams, 288 will/can deliver a hard hit in mid range as well as top end. It's only bottom end that suffers with such a high degree camshaft.

Damo go check out Satoru works, I'm pretty sure they pushed 7AG's fairly hard in D1 awhile ago and have build logs on the website.

[DAMO46]

yes thats correct sam.

okay ken thanks for that!

[Sam-Q]

blacktop head + blacktop + 7A bottom = 12.1:1 compression, you up for that? this is why I suggested the silvertop pistons.

how such a combo will act with 288s is unknown to me.

[Gunner]

dont forget to factor in thicker headgaskets, I know it not optimal, but its an option

[Sam-Q]

an option yes but a very poor option, it would be a very bad thing and downright strange thing to do. Not only is it far less than optimal but it is easly solved by fitted some easy to source pistons. Thicker gaskets screw up the combustion chamber dynamics and should be avoided in every situation.

[Gunner]

I would agree, if you were arguing that it increase the risk of gasket failures, and in turn greater damage to the head or block.

But the fact is it is a common practice, amongst a hell of alot of engine builders, and if made such a catastrophic change in cumbustion chamber dynamics it would not be.

Say for example, I have damaged my head and block in a gasket failure, I need to machine the block and the head, I recieve the head back from the machinist, I have lost a total of 0.3mm. I was running 12:1 comp previous to the machining. I dont want the comp to go any higher due to the risk of detonation at this level on pump fuel. I would fit a gasket to suit, rather than scrap the head Ive just spent thousands on getting work done.

I do see where you are coming from, and I do understand that, there is a chance that a thicker gasket can actually increase the chance of detonation, due to the effect it has on the overall cumbustion chamber design, but the chance of it is not that great.

Anyway that what i was taught, your thoughts are obviously different on the matter. I would like to hear your thoughts on it, whether here or in another thread.

[Frak]

For the guys that have built a few 20v's have you guys noticed that the exhaust seats cop a hammering?

Every 20v I have taken apart/built has really badly pitted exhaust seats, the intakes are always fine. Nothing a quick valve cut won't fix, but I have seen some really low km engines over the years and the exhaust seats are always the same.