Prepping head for high lift cam - springs? Stem seals?

[turbodave]

Appreciate the info Jim. Just so we're on the same page - when you say "good fuel" do you mean premium or something more? Premium is all I'll be running.

Also - maybe I'm slow on the uptake here - what do you mean by "installed straight up" on the cam timing?

Finally, I left the UK many years ago; I'm not familiar with that name to be honest, but I was never really into the RV8 before I left that side of the pond, so wouldn't know anyway.

[mgb260]

Dave, On a typical aftermarket timing set there are 3 keyways. Some have 9. The 3 keyways correspond to 4 degrees advance, 0/straight up, and 4 degrees retarded. If you set up your cam at 0/straight up you are really 5 degrees advance because that is ground into the cam. So if you retard the timing 4 degrees you are still 1 degree advanced because of the 5 degrees advance ground into the cam. If you advance the cam you will lower the power curve, retard and you raise the power curve in RPM's. I figured the fuel as 91-93 Premium with added octane booster to 104. If you are just running premium limit your compression to 10.5. I figured you might be from the UK because you ordered those valves so quick. Perry frequented this site and is a Drag racer that had his MBGT into the 9's. I would not get rid of the trumpets but shorten them so the flare is flush with the bottom of the intake, it will help flow transition. Or you could use a sheetmetal intake like this for 444HP@7500RPM on my program. Similar to what Tim Lanocha uses in his TR7 race car.

[turbodave]

ahhh, my experience of cams in other engines is that the keyway is only a guide, and that only degree-ing in the cam, preferably using a vernier or 1-degree dowel adjustment is the preferred approach. I've not even looked at timing gear yet, so don't know what folks commonly use.

I got them ordered quick as I already had stuff in my cart with Rimmers...

I've had many conflicting opinions on the trumpets - the TVR guys are all over the place on opinions on them as well - but I've understood that building them back with weld  to give a flush surface (sans trumpets), and then opening up the throats, plus blending to the inlet, is pretty much a known solution that works (sure it could be optimised more), but the stock dia trumpets being a little too small for a well ported head.

[mgb260]

Dave, I still degree the cam to verify where it is, but using the keyways to put the power band where I want. You could remove the trumpets and  mill a 45 degree transition to the port. Usually use the Buick V6 timing set. Have you done the recommended oiling mods? I would use the oil pump booster plate, T/A 60lb relief spring(or adjustable relief valve), larger 5/8"Buick V6 pickup and the T/A front cam bearing also. The clearance on the rod and main bearings is best at .0015 instead of .002 like Ford and Chevy.

[turbodave]

I'm using the 94/95 "interim" front cover with the crank mounted pump, so hope to have little of the typical Rover V8 oiling issues. I will be making an adjustable pressure cap however.

I will be putting the restriction in the rocker feed (or going for full roller rockers).

Not sure what the T/A front cam bearing modification is? Can you advise? Thanks!

[mgb260]

The front cam bearing is grooved on the back side to move the oil feed hole to a better location to improve the oil wedge and reduce the load from the distributor and early oil pump. Years ago Phil Baker told me to lengthen the slots in the stock bearing from 1 to 3 o clock and 7 to 9 o clock installation for better oil distribution. There is also a front cover mod to put a squirt hole to the distributor gear.

https://www.youtube.com/watch?v=5CQx6t4SvMc

[turbodave]

ahhh, that's becuase the dizzy drive gear is also driving the oil pump?

I won't need any of that as the dizzy gear turns only the dizzy shaft.

I always like to maximize the oiling of all journal bearings by chamfering and smoothing as needed, so will take a look at the cam shells as well.

I understand that the later crank driven pumps are night and day better at moving oil than the gear driven pumps and can run higher pressures without the issues of higher pressures on the gear-driven pumps. The only downside is they are a swine to prime (i know that from experience with a 4.6 disco motor i rebuilt previously.

[kennedyrd]

Hi there, sorry for being so late to the party, but I wondered if you ever got this engine going? I was searching for data on suitable valve springs to use in my 3.9 litre Rover (sleeved 3.5) which uses a Crane F248 profile. The motor sounds very similar to what you describe, and I am experiencing valve bounce above 7000 rpm. I ran it to 7800 on the dyno to see if it would take it, but you could hear the valve thrash, and the power curve falls off a cliff over 6700 where it eventually made 357hp. I have the limiter set to 7200 rpm. It is used in a TR7 circuit car.

Other mods include custom made Wiseco pistons, as I used longer 6" SB Chev (Chinese Manley replica) steel rods that then required a rebalance as it was so heavy. I had a girdle made for the crankshaft, as I was expecting really high revs, like over 8000. Was pleased with the HP, but not the low revs. The problem is valve bounce, so I am interested if you guys got a beehive setup to work? I think my valves are heavy, as I used cut down Ferrea valves for a SBC as well. It uses  Yella Terra roller rockers with custom pushrods and custom composite head gaskets to arrive at 10.8:1 compression on flow tested self ported heads. Likewise the exhaust system was self fabricated to run forward like a TVR. This was necessitated due to insufficient room beside the engine which had been shifted rearwards as well as having some space taken from the dry sump pump.

Induction is from a modified annular booster 650 double pumper Holley on a Denco engineering single plane manifold. The heads were self ported and tested on a flow bench at the same place.

It is road legal here in NZ, but only with a special permit. It is perfectly drivable, but there is drivetrain snatch if trying to drive in traffic. I would not consider it a pleasant daily driver with the F248, but fine as a special occassion car. Idle is a lopey 900rpm once warmed up.

Is your motor similar? Does it rev higher without valve thrash, and if so what springs and retainers did you end up using? Did they require the spring seats to be cut lower, and if so by how much? I am stripping the engine and would like to address the valve spring issue while it is apart. Thanks for any info you guys may have gleaned since this post was started.

[mgb260]

Chris, Chevy Z28 springs are commonly used but good to only 6500 RPM. There are some aftermarket Beehive springs that may work. I'll try to find a link.

[mgb260]

These LS Beehive springs may work for you if you open up the spring pocket and cut down the valve guide:



https://www.alexsparts.com/ls-series-beehive-valve-spring-kit-complete-kit-137-lb-seat-625-lift/

[BlownMGB-V8]

I used a Ford beehive. Something to remember though, they work their best when near coil bind at fully open.

Jim

[kennedyrd]

Thanks so much guys! LS spring kit sounds easiest as think we used SBC retainers if they are the same?

 Also here is a picture of the motor. I must also apologise for stating it used a Denco engineering manifold. It in fact uses Harcourt manifold and rocker covers. They are NZ made, and they used to make a beautiful bearing girdle. Unfortunately it was no longer available when my motor was built.