Good plan Fett, but I'd be wary of pushing the compression that high 'cos IMO it's a bit too high, I could do without having to run Vpower/tesco99 Plus an additive. I could always retard it a bit more, but the power drops off a cliff and the economy goes down. I've picked up some 3.5 efi rangie heads for a tenner (woo) and going to port em myself (did it on an A series head, how hard can it be?)

While I'm in the combustion chambers I'm going to try and take the comp down a bit so I can run a bit more advance without the extra cost of the additive.
 
Reckon that will go too far, comp gaskets on a tin gasket head will take it down a bit low, can't remember the numbers but was around 8.6 ish (could have worked that out totally wrong though!!) Worked it out for potential supercharging.

I'll get it by making the combustion chambers a bit larger than standard and not skimming the heads, if I can get away with it. If they've got to be skimmed I'll fit comp gaskets then skim to get around 10:1.

that's the plan anyway, unless the 10 pound heads are scrap!
 
about 10:1 was what I was thinking , daily running on lpg and then v power for chasing people :D
 
3.9 is basically a 3.5 cam with 2 degrees of advance not worth while fitting.

if you want to do the head work yourself check out this thread

The V8 Owners Forum - :: View topic - DIY head porting



fett said:
using a 3,5 efi as a base my plan is to fit it with a 3.9 cam , prst and polish it my self and mybe fit 10.5:1 p6 pistons- depending on whay I decide its final use is.

I know the 3.5 efi heads are way better then the carb ones and been told they are the same as 3.9 heads

Just gonna keep it cheap using second hadn bits
Click to expand...
 
V8Safari said:
Also thought of the weber 500 carbs - expensive but nice - maybe with the econotune heads. Just too exspensive......looking for most cost efficient way of getting extra power but maintaining reliability
Click to expand...

Yeah Edelbrock 500 is the better carb over the Holley. Mine had a Holley, got rid, fitted a 500, sorted!!
 
500 too big for the 3.5 really - will loose low down in expense for high up. not good for a big heavy brick lol
 
My 80 inch has an afterarket cam thinking of junking the whole engine. Not even run it yet. I can gurantee forsure its had a bigger cam that needed driver ALWAYS fits a bigger cam that the engine wants. I'm sure it will make my 3.9 on carbs run like a bag o ****e. Time to build a new engine that is matched. Hell I might even go 3.5!
 
POAH said:
3.9 is basically a 3.5 cam with 2 degrees of advance not worth while fitting.

if you want to do the head work yourself check out this thread

The V8 Owners Forum - :: View topic - DIY head porting
Click to expand...

I had heard differnt, if your right what cam would you fit for a rrc 3.5 hi comp on su carbs- and before you start I may well need the su carbs as it goes off road and webber and elderbrock no good for that. no silly numbers please, just a straight swap cam the same price as an oem 3.9 cam??
 
Most the common carbs like Edlerbrock etc suffer from dumping **** loads of fuel in when you go over a bump a few guys bolted new carbs onto their V8's and came racing. Everytime they got up to any speed or hit a bad bit the engine bogged down!! Needless to say next event they bolted back on SU's!

My bro explained to me that building an engine is like baking a cake if the recepie isn't match it'll just be another variant of a sponge!

His main point was Yea you can add extra bits Cams and so on to an engine it may even increase its BHP. But its still an old engine with a go faster bits. Match the recepie build it all with parts that work together you get a cracking engine. I will dig out the specs of the 3.5 he built and got rolling roaded. Twas about as far as you can go on SU's! I personally drove the 90 it was in and twas ideal trialler would drop to 650RPM and still pull hard right the way up the rev range.

Some of the trials guys bolt in a highlift cam and the engine doesn't pull a skin off a rice pudding until 2000RPM then it takes off. They end up revving the tits off it and sliping the clutch to get up a slight incline. Add to that they use rhodes lifters and then run a high pressure oil pump!!!!! So you get bugger all bleed down!!! Tis funny to stand back and watch!!!

Thats why I'm nervous about my hybrid engine thats been messed with!!! Need to save some money and get down to real steel order me some bits.
 
Last edited:
I agree , I would like to do better than 8.25:1 comp though , although I was surprised to see thats what my mates mkII 3.8 jag was running lol.

I also agree that I need a cam with low down tourque for my RRC but heard the 3.5 was a poor cam, maybe that was just the carb one though- did they change it for efi?
 
No idea Ring Real steel they won't chat crap they will tell it like it is. Funny when somone says fit a Piper or any other aftermarket Cam. Whatever cam its all bollix until you find out exactly what the cam is exactly.

My offroader has "An aftermarket Cam" so it'll be one of those silly race ones most likley so bugger all good until 4000Rpm! Great exactly what I want for trials Errrr Not! Maybe in a westfield or 400Kg race car not on a ton+ offroader.
 
jai_landrover said:
My 80 inch has an afterarket cam thinking of junking the whole engine. Not even run it yet. I can gurantee forsure its had a bigger cam that needed driver ALWAYS fits a bigger cam that the engine wants. I'm sure it will make my 3.9 on carbs run like a bag o ****e. Time to build a new engine that is matched. Hell I might even go 3.5!
Click to expand...

why junk it if you've not run it? might be a peach and only need cam swapping
 
I'll get it running but I have a 3.5 here waiting to be sorted funds and time. 3.5 drops me into a lower class and I know it can be a 3.9 beater if dome right. No doubt I'll run it for a couple of times but I just know It'll be a bastid to drive. You may be right. I hope you are! It may be ok. Think I'll be following a known recepie and seeing real steel that way I know it'll drop down to 650RPM without fear of stalling. Pull 3rd gear or even 4th gear low range for hill climbs and be a sorted engine opposeed to another stab in the dark with a few parts.
 
jai_landrover said:
so it'll be one of those silly race ones most likley so bugger all good until 4000Rpm! Great exactly what I want for trials Errrr Not! Maybe in a westfield or 400Kg race car not on a ton+
Click to expand...

or even a 1.2 ton P6....

Internet is full of fit this fit that do this for hundreds of horsepowers, I don't want that, I want a torque monster. Which makes it a little more complex.

Got the K series Midget for zipping about at 7K rpm, want the V8 for grunty monstering.
 
I noticed those 9.75:1 vitess piston sets on there , that might be a good way to go for me and still be able to run it on normal unleaded?
 
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