Cylinder head query

Sunbmw · Post by **Sunbmw** » Thu May 12, 2011 8:25 am

Hi again chaps, sorry for the post bombardment, but I have amassed loads of parts recently, and I am now getting to the stage where I need some questions answering...........

I recently bought an engine, it had roller rockers, and I was pleasantly surprised that the heads had been very nicely ported, so I am going to utilise them, however, when I placed the heads on my block for the first time yesterday, I noticed that the heads have an extra set of bolt holes, and the block is devoid of tappings to take said bolts. The block is a 3.5 item, that is x-bolted (the reason I bought it in the first place), but only has 8 boltholes per head.

Question is, will I still be able to use the heads, and would it be worth drilling and inserting the block to utilise the extra fastenings?

Opinions please.......................Thanks.

SuperV8 · Post by **SuperV8** » Thu May 12, 2011 9:06 am

No you don't need the outer bolts which are missing on you're block. Your heads maybe the older type which includes the extra row of bolts and also a larger combustion chamber, 36cc. The later heads have a 28cc chamber.
May be worth measuring your combustion chamber to confirm?

Tom.

Sunbmw · Post by **Sunbmw** » Thu May 12, 2011 9:10 am

Thanks Tom, I'll get measuring.

I wasn't aware that the heads had any difference in chamber size, that will make a difference when I order my pistons, as I intend to use very high compression "Intruder" pistons.

SuperV8 · Post by **SuperV8** » Thu May 12, 2011 11:02 am

The change was made when they went from tin to composite gaskets to keep the same compression ratio as the composits are obviously thicker.

What compression ratio are you intending to run?

Tom.

ChrisJC · Post by **ChrisJC** » Thu May 12, 2011 8:18 pm

Definitely DO NOT use the outer row of bolts. The extra row cause the head to tilt over slightly, relieving pressure on the valley side of the head, and causing leakage into the valley area. This is the reason that all old Rover V8's are sludged up, it's combustion products getting into the valley and into the oil. When the P38 Range Rover was introduced, they went to composite gaskets, and a symmetrical clamping regime to eliminate this problem. You won't find a sludgy P38 engine.

Most engine builders just omit the outer row of bolts if the holes are present.

Chris.

Sunbmw · Post by **Sunbmw** » Thu May 12, 2011 11:13 pm

Thanks again everybody, every day is a school day.

As for CR, not sure yet as I am learning every day, but I have a very wild cam, and intend to use quad 45's or throttles..........

kiwicar · Post by **kiwicar** » Fri May 13, 2011 5:31 am

Hi
post up your cam specs and we can give you an idea of Cr you need.
Best regards
Mike

DaveEFI · Post by **DaveEFI** » Fri May 13, 2011 8:07 am

ChrisJC wrote:Definitely DO NOT use the outer row of bolts. The extra row cause the head to tilt over slightly, relieving pressure on the valley side of the head, and causing leakage into the valley area. This is the reason that all old Rover V8's are sludged up, it's combustion products getting into the valley and into the oil. When the P38 Range Rover was introduced, they went to composite gaskets, and a symmetrical clamping regime to eliminate this problem. You won't find a sludgy P38 engine.

Most engine builders just omit the outer row of bolts if the holes are present.

Chris.

Interesting theory - but if there were combustion gasses leaking into the valley, wouldn't the head gaskets blow in short order?

IMHO, old engines are sludged up because the breathers and other servicing has been lax. Although no engine stays clean inside forever.

Sunbmw · Post by **Sunbmw** » Fri May 13, 2011 8:45 am

Rather embarrasingly, I don't know the exact cam spec, it is a Crower item that I have bought off HairbearTE off here, and if I am honest, I haven't picked it up from my mate who kindly collected it for me!

I am led to believe though that it is pretty wild, Marcus may be able to shed more light?

kiwicar · Post by **kiwicar** » Fri May 13, 2011 8:58 am

Hi
From what I remember he did have a pretty wild mechanical cam up on here a while ago, is it that one? If you can get the grind nomber off the cam we can google it and see what you have. Unfortunatly I don't think there are many alternative engines that can "donate" pistons for the 3.5 rover bore (like you can with the 3.9/4.6 bore) but again it may be worth a hunt around.
Best regards
Mike

Sunbmw · Post by **Sunbmw** » Fri May 13, 2011 9:12 am

kiwicar wrote:Hi
From what I remember he did have a pretty wild mechanical cam up on here a while ago, is it that one? If you can get the grind nomber off the cam we can google it and see what you have. Unfortunatly I don't think there are many alternative engines that can "donate" pistons for the 3.5 rover bore (like you can with the 3.9/4.6 bore) but again it may be worth a hunt around.
Best regards
Mike

I would say that is the one Mike, like I say, I haven't got it in me hands yet, gonna go collect it maybe this weekend, then we can see.

I am under no illusion that I may have to have some pistons made or be very lucky. I hear that Ross pistons in the states are the ones to go for?

ChrisJC · Post by **ChrisJC** » Fri May 13, 2011 11:08 am

DaveEFI wrote: Interesting theory - but if there were combustion gasses leaking into the valley, wouldn't the head gaskets blow in short order?

No. If you take the tin gaskets off a well used 14-bolt engine, you will see that they are stained on the valley side, and clean on the outer side. I've seen it many times on knackered old engines. If you change your oil regularly, it's not a problem, but as soon as you start stretching service intervals, the oil gets sludgy and deposits it everywhere.

It's a marginal leak, but over time it is significant.

Look at the head gaskets on this page.
http://www.v8engines.com/engine-4.htm

Chris.

Sunbmw · Post by **Sunbmw** » Mon May 30, 2011 4:33 pm

Hi all, I have lierally just collected my cam, from my mate that was off Marcus (HairbearTE), and the grind number is 50305. I hope that you can give me some indication now as to what C/R will be optimum.

Cheers in advance guys.

Sunbmw · Post by **Sunbmw** » Mon May 30, 2011 4:38 pm

Just had a look myself, seems exactly what I am after..............

http://www.crower.com/products/camshaft ... appet.html

Pardon my ignorance, but what is meant by "Flat tappet"?

kiwicar · Post by **kiwicar** » Mon May 30, 2011 5:28 pm

Hi
that is alot of cam!

especially on a 3.5, I have about the same timing on the cam in my chevy, but that is 6.3 litres and I have it on a wider LSA, and I won't be running it on the road!
Flat tappet is just that, it runs with the tappet having a flat contact surface with the cam lobe, as opposed to a roller tappet cam that has a roller on the end of the tappet that contacts the cam.
Best regards
Mike