4.2 Block

Wilts289 · Post by **Wilts289** » Mon Nov 26, 2007 11:36 am

Hi to all,
yet another new member who having reached retirement thought it time to play. I've been running a Hawk 289 with a standard 3.5l and like everyone else "feel the need"! I have aquired a 4.2l engine and have followed the advice to have it pressure tested before anything else and it's passed with flying colours, so usual bearings/ARP studs rings etc.
Not after vast amounts of power as mainly used for touring, and also reactions not quite what they were! Questions are; what camshaft? and am I better off using new 28cc heads (off which I have aquired a pair which are marked TVR 390). or using my existing Vitesse heads. If new heads better bet, can I use tin head gaskets and get the increase in CR without valve clearance problems?
p.s. spent hours reading forum the other night and wife now convinced I'm up to no good on the internet!

chodjinn · Post by **chodjinn** » Mon Nov 26, 2007 11:49 am

I believe the Vitesse heads are 36cc, so by changing to 28cc heads you will see a slight increase in compression ratio (but not a massive change). Same applies for using tin gaskets instead of composite (think that's worth 0.5 to 0.7 increase in C.R.). Shouldn't be any clearance issues as long as the block/heads haven't had the decks skimmed etc. I'm sure someone will correct me if i'm wrong!

As for cams, I'm not good with that sorry!

seight · Post by **seight** » Mon Nov 26, 2007 2:33 pm

I'm using a 4.2 and the only advice I would give is - if at all possible avoid a +.020 rebore. You can't get oversize pistons for the 4.2! In mine I had to have a set of low comp 3.9 +.020 pistons and get them shortened. It was a bit of a nightmare really but I have ended up with 10:1 CR using 34cc heads and composite gaskets.

Mike

Wilts289 · Post by **Wilts289** » Mon Nov 26, 2007 3:06 pm

Fortunately bores only required honing so still using original pistons/rods, and was hoping that using later 28cc heads with tinplate gaskets would be enough to take CR up a bit without risking valves having a chat with the pistons!

ChrisJC · Post by **ChrisJC** » Mon Nov 26, 2007 3:43 pm

Pretty unlikely for valves to meet pistons. But you do need to check lifter preload when putting the valve gear back together if you've got a non standard head thickness / head gasket combination.

Chris.

Post by **katanaman** » Mon Nov 26, 2007 5:59 pm

Valves hitting the pistons will also depend on what cam you fit. If you go for a high lift/long duration cam then I can only recommend you check the clearances carefully. This would rule out cams like the Piper 285 and the Typhoon if you don't want to go to the bother as the Typhoon could be pretty close. If you have it all apart anyway then why not just pocket the pistons and your good to go whatever you do? I probably wouldn't go for a high rev cam in that engine anyway as they can snap the crank at revs without work, so why not be different and forget ultimate horse power and go for ultimate torque instead.

Wilts289 · Post by **Wilts289** » Mon Nov 26, 2007 8:10 pm

Certainly prefer the torque route Marki, what cam would you recommend,
bearing in mind car only weighs in a 990Kg.

Post by **katanaman** » Mon Nov 26, 2007 8:55 pm

Not sure to be honest as I have never looked at the torque camshafts. I know there is a piper one but cant remember the name and there is one Real Steel does called a stump puller. I would give Paul @ V8 Tuner a call and see what he has to say or V8 Developments both of which are reliable and both offer member discounts

Post by **Coops** » Mon Nov 26, 2007 9:01 pm

Oh you mean here Marki

http://www.v-8.org.uk/forum/viewforum.php?f=4

Post by **katanaman** » Mon Nov 26, 2007 9:05 pm

Yup that's the one

Wilts289 · Post by **Wilts289** » Tue Nov 27, 2007 5:52 pm

Hi again Marki,
had a chat with Paul at V8 Tuner, very obliging and helpful chap, and he recommended the Crower 50229 for the 4.2. Thanks for guidance.
and may I say what a great forum this is.

Post by **Coops** » Tue Nov 27, 2007 7:26 pm

glad the forum has another satisfied member.

Post by **katanaman** » Tue Nov 27, 2007 8:11 pm

Your welcome M8.