4.6 heads or skim early heads??

kiwicar · Post by **kiwicar** » Wed Jan 05, 2011 4:50 pm

Hi
You need to be sure the spring, cap and valve guide combination allows the cam to open the valve as far as required without anything hitting or binding, likewise the valve to piston clearance needs checking but stronger springs to overcome boost, no.
I have not used the cam myself (it won't work on an SBC) but those that have used the blower cam from RS seem to have had good results with it, and on paper it looks the right spec for a mild to medium performance blown motor.
Best regards
Mike

Post by **Coops** » Wed Jan 05, 2011 5:09 pm

sorry to hijack the post,
mike will i be ok with that crower cam of mine with the paxton?
Cam Numb: 50233

CastleMGBV8 · Post by **CastleMGBV8** » Wed Jan 05, 2011 5:30 pm

Steve,

The cam you have the RP4 is suited to an Auto gearbox and EFI system, the other hotter cams especially the 285 will not work well with EFI and an auto,the thor system is more torque optimised than the earlier hotwire or gems systems and is restrictive at high RPM so no point trying to go for a too hot cam.

Pistons look to have a large dish, what CR is stamped on ther block next to the dipstick?

Kevin

gulf blue rsr · Post by **gulf blue rsr** » Wed Jan 05, 2011 9:22 pm

Mike I'm not sure if we have slightly crossed wires here but I'm not actually intending to run this with any sort of forced induction, the only reason I was considering the Real Steel blower cam was because of the post by Alan (bigaldart) post 6 I think? He suggested that that cam is a good all rounder even without a turbo etc, at most I should think I will end up using stage one heads, going by Kevin's post perhaps this is too big a cam?

I was thinking I would check the valve to piston clearance with what I have at the moment just out of interest, good point about the rocker to guides I may have forgotten to check that!

Just looking at RPI site again they are suggesting the Torque Max or possibly the 270 Stealth would either of these be more suitable? or which supplier should I be looking at? I'm not actually that fussed about using RPI due to their attitude and price etc

Kevin,
The block does not have the CR stamped into it, after reading through the engine number sticky to the end I have worked out that the number stamped into it is a Ray Webb V8 Developments block, I find this strange as I have a build sheet and invoice from RPI saying they built it? Did RPI used to use V8 Developments blocks or to build them engines?

I'm wondering will it actually be worth while to bother with the expense of bigger cam over standard? I don't want to miss the chance if it is worthwhile

Thanks for all the help keep it coming!!

Steve

CastleMGBV8 · Post by **CastleMGBV8** » Wed Jan 05, 2011 10:28 pm

Steve,

The real steel blower cam may work with the EFI and auto box but will be similar in characteristics to the RP4 if not quite as good?

What I was saying earlier was that a bigger cam with more overlap and duration will not work with the standard EFI system unless you fit an after market ECU stage 3 heads and change the manifold and plenum to take advantage of the cams potential but it still won't be a good daily driver.

Specs for the Piper cams inc RP4

Type
Application
Power Band
Valve Timing
Duration
Valve lift
Full Lift ATDC/BTDC

Torque Max High Torque EFi and Carb 800-4500 23-61 / 61-23 264 deg. 0.415" 109 deg.
Rp 4 High Torque & 4WD Efi 1000-4800 18-62 / 62-18 260 deg. 0.432" 112 deg.
270/2 Fast Road Carb. models 1500-6000 28-64 / 64-28 272 deg. 0.445" 108 deg.
285 fast road & race all carb.
2wd or 4wd models 2000-6500 44-72 / 72-44 296 deg. 0.450" 104 deg.

RP4 is for fuel-injected engines that are auto transmission.

The biggest initial power gain can be achieved from the cylinder heads, typically Stage 1 heads add 30 + BHP prob more on a 4.6 with no loss of low down torque.

Kevin.

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gulf blue rsr · Post by **gulf blue rsr** » Wed Jan 05, 2011 11:27 pm

So then from those specs and what you are saying the rp4 is the best suited for what I'm after, I guess that the Torque Max would be better for complete low end power for an offroader or a lot of heavy towing but as an all round auto 4x4 the RP4 is the way to go?

Next problem then is ..... the RP4 cam that I have is for the early front cover driving a dizzy..... I have the serp front cover with the Thor as you know, now I know that cam I have wont work with my cover and I don't suppose it would be possible or cost effective to machine/convert it but do you know if they do the RP4 to suit the Thor timing gear?

Any ideas on those pistons? they are deep arn't they! I'm a bit bothered about the compression..... or lack of it!! The only thing is the fact that they do seem to stick up above the top off the deck slightly, there is also a felt pen marking in the valley that looks like it says -60 I was wondering do you think that possibly maybe that could meean that it has had 60 machined off the block face? how much would have to be skimed for the original block number to be machined away? how could I measure to work out the depth? is there a bench mark that I could use?

Sorry for the dumb questions...... don't want to mess this up!!

Thanks for all the help keep it coming!

Steve

CastleMGBV8 · Post by **CastleMGBV8** » Wed Jan 05, 2011 11:52 pm

Steve,

You could probably have the RP4 machined for the cam retention plate, that is the only difference I think, I could probably find out how much needs to be machined.

If you remove the cam you MUST number the lifters to the lobe they came off, if you mix them up accelerated cam wear will occur.

It is very likely that the block has been decked if the engine no. has dissapeared and that could be 40-60 thou.

As you can see the numbers on the pistons RPi should be able to tell you the bowl volume but no harm getting another opinion

With a known bowl vol, a comp ratio. can be calculated for the different heads.

Kevin.

gulf blue rsr · Post by **gulf blue rsr** » Thu Jan 06, 2011 7:50 am

CastleMGBV8 wrote:Steve,

You could probably have the RP4 machined for the cam retention plate, that is the only difference I think, I could probably find out how much needs to be machined.
Yes please if not too much trouble that would be a good help
If you remove the cam you MUST number the lifters to the lobe they came off, if you mix them up accelerated cam wear will occur.
Yes I will do that anyway.

It is very likely that the block has been decked if the engine no. has dissapeared and that could be 40-60 thou.

As you can see the numbers on the pistons RPi should be able to tell you the bowl volume but no harm getting another opinion

With a known bowl vol, a comp ratio. can be calculated for the different heads.

I will give RPI a call today and V8DEV. for a second opinion to see what I can find out. I guess RPI will tell me I need to scrap the whole lot and buy a nice new complete buily engine from them at huge £££££££
Kevin.

CastleMGBV8 · Post by **CastleMGBV8** » Thu Jan 06, 2011 10:18 am

Kevin,

Sorry I called you steve, got mixed up with another thread.

Just a thought, the RP4 could already be machined for the cam retainer, worth checking.

Yes ask V8 Dev you'll get a more reliable answer.

Your right with the last comment.

Kevin.

kiwicar · Post by **kiwicar** » Thu Jan 06, 2011 10:20 am

I would think the blower cam would work well N/A, the extra exhaust timing tends to enable the engine to make power for longer past peak power, the timing is moderate and the 114 LSA gives you a good idel and part throttle responce, you may get a little less peak power than the with a cam with a tighter LSA but the price you pay for those extra BHP is more gear changing and an engine that is a little more prone to bog when you hit the throttle at low revs. The cam I have in my chevy engine is basically the same idea as the blower cam (wide LSA and extra exhaust duration, but with 40 degrees more timing. That will be NA to start with and was originally only intended to be on a NA engine.
Best regards
Mike

spend · Post by **spend** » Thu Jan 06, 2011 12:50 pm

They just look like std 4.6 pistons to me from your picture.. 4.0s maybe 1/4" bowl & 4.6's nearer 1/2" nominally IYSWIM, it's kind of obvious when you've seen a few, but someone will give you exact measurements if you need to check. It's something like 22.3cc bowl IIRC.

DEVONMAN · Post by **DEVONMAN** » Thu Jan 06, 2011 1:17 pm

I've just measured a 4.0 piston and the dish is approx 4.0mm deep and it is stamped G12 where yours are stamped D27.

I agree with 'spend', from your pictures yours look like 4.6 pistons.

Regards Denis

gulf blue rsr · Post by **gulf blue rsr** » Thu Jan 06, 2011 9:34 pm

So here we go then more info and hopefully getting sorted with my plan of attack!!

I spoke to Shaun at V8 Developments....and what a very helpful man he is!!!
1st I described what I have, gave him the engine number and he agreed yes it was almost definitely one of their engines, built for and then finally supplied by RPI to the customer.

I told him the block has -60 marked in the valley with felt pen and the fact that the piston sticks slightly proud of the block, he agreed that yes it was probably decked 60thou and that the original would have had the pistons shy by 40 thou of the top hence now sticking proud by about 20 thou.

Then he worked out the CR based on the heads and pistons being 35 and 34 cc each the outcome was that he recommends that I should stick with composite gaskets as the piston would meet with the head otherwise!! he also reckons that the CR is border line high for the Range Rover weight and what I tow and the way I like to use the loud pedal..... he asked if I drove gentle, I told him my other car is a 911 turbo

he guessed I drive quite hard

but because it is Thor injection the knock sensors would pick up on the possible pinking due to the high CR.

We then moved onto cam, because he reckoned that with the early stage 1 heads and the fact that the piston will be quite high into the head giving good squish the engine should perform quite well above standard, because of the risk of pinking and the knock sensors upsetting the ecu his advice was stick with a mild or even stock cam.

In the middle of our discussions after getting all the info he was talking to his colleagues at the same time, he said we need to do some sums on this to get the right solution so went away and rang me back 10 Min's later with all the above.

Not at any time was he trying any big sales talk with me, just kept giving me sound helpful advice, it was only at the end I told him I wanted to buy a cam and timing gear which is when he finally committed to if it were his engine he would for safety stick with the standard cam etc, he even said that it would be the cheaper option so an added bonus:)

So this is the way I will be going and I will buy the cam etc from them.

Now why is it that every time you ring RPI you come off the phone thinking they are just out to rubbish everyone else and get every penny out of you? It just proves that it does not have to be this way!! I know where my money and phone time will be going in the future

Oh and Kevin, its not a problem that you called me Steve...... it is my name

Thanks for all the help with this I will keep you posted on how I get on and will no doubt be along soon with more questions for you all !!

Steve

CastleMGBV8 · Post by **CastleMGBV8** » Thu Jan 06, 2011 10:59 pm

Steve,

Good to hear you got the right sort of service and advice from V8 Dev. nothing like that to inspire confidence and make you want to take advantage of their products and services.

The bowl figure for the 4.6 piston I have is also 22.3cc but that could be incorrect as I can't remember the source and would have given a cr with tins of 10.24/1 and approx 9,75/1 with comp gaskets, but with 60.thou of the decks that may be about right, 9.75 should be fine on normal fuel with the knock sensors taking care of any detonation.

Kevin.