|
|
|
Mar 29, 2007 10:14:57 GMT
|
|
I'm going to be preparing some new heads for my ghia, they will be mildly ported and get high lift rockers.
The cars turbo'd so should make good use of better breathing.
Are 3 angle valves worth doing? What sort of price would a decent machine shop charge?
Also, should i polish the ports? I seem to remember its worth leaving them rough to mix the fuel/air up better.
And lastly, what about matching the inlet/exhaust manifolds to the ports. Ive got vauge memories of reading that its not always a good idea.
Any advise from more experienced people would be great.
|
| |
|
|
|
|
|
|
|
Mar 29, 2007 11:49:58 GMT
|
|
If it's turbo'd I don't think a 3 angle valve job is going to be worth the extra spondooly when you can crank up the boost a bit and it will have the same effect for free.
Polished inlets is a bad idea if it's on a carburettor because the fuel sticks to the ports. Smooth ground finish is best.
Most definitely match up the inlet/exhaust to the ports, it's the cheapest way to maximise power potential. Again, not 100% as necessary as it is with a normally aspirated engine but every little helps and a little grinding time is free.
|
| |
|
|
bstardchild
Club Retro Rides Member
Posts: 14,965
Club RR Member Number: 71
|
|
Mar 29, 2007 12:18:33 GMT
|
|
Both are worthwhile and relatively in-expensive - all about negative boost (or maximising what boost you have)
|
| |
|
|
tigran
Club Retro Rides Member
In rust we trust. Amen.
Posts: 6,444
Club RR Member Number: 142
|
|
Mar 29, 2007 13:15:16 GMT
|
|
They are only about 4 pounds per seat, but then you have to get matching valves which i got quoted at £8 per valve. Seems cheap but it all adds up even with only an 8v head.
|
| |
1964 Rover P5 i6
1987 BMW 525e - The Rusty Streak
1992 Micra K10
2001 BMW E46 316i
2002 BMW E46 330Ci
2013 BMW F31 320d
2018 BMW G31 530d
|
|
Alain
Part of things
Dance monkey boy, dance!
Posts: 372
|
|
Mar 29, 2007 13:19:25 GMT
|
|
Are you still in Sheffield dude?
There's a very good machine shop in Halifax, but the name escapes me...
|
| |
 '74 Type 181 - Undergoing 'resto' (albeit friggin' slowly! 2 years and counting...) Wedge Panel Van GTi (Still needs finishing) '85 Passat GL5 Estate (Now Breaking) '87 Passat GLS5 Estate (Daily Hack) |
|
street
Posted a lot
6.2 ft/lbs of talk
Posts: 4,662
|
|
Mar 29, 2007 13:57:40 GMT
|
Heres a good article on gas flowing heads: www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/velocity.htmlGets a bit in-depth but it's well worth a read. Incidentally- I always read that you should not polish the ports, because in the inlet side the fuel doesn't mix with the air properly etc etc and with the exhaust side you just wont see any benifits. In fact the article I linked above it says that a shiny finish is worth at best 2%..... I don't neccesarily agree with that. Fair enough about the inlet side of things, but on the exhaust side surely it will stop exhaust soot sticking to the port walls which will eventually inhibit flow? I'm sure it looks like there are next to no gains from polishing on a flow bench, but after a few thousand miles I reckon shiney exhaust ports are gonna look a lot cleaner and flow better than rough finished exhaust ports surely? |
| |
|
|
|
|
|
Mar 29, 2007 13:58:37 GMT
|
|
Yeah, still in sheff.
Ive been down to sheffield engine services and they seem nice.
Maybe ill forget the 3 angle and just concentrate on port matching and shaping.
Why are special valves needed for 3 angle seats?
£4 a seat and £8 a valve is nearly £100 for an 8 valver, thats too much. That money could make more power spent elsewhere.
|
| |
|
|
|
|
|
Mar 29, 2007 14:00:15 GMT
|
|
thanks for the link, ill have a read.
I think ill leaver them smooth ground, better safe than sorry.
I get your point about the exhaust ports though.
|
| |
|
|
bstardchild
Club Retro Rides Member
Posts: 14,965
Club RR Member Number: 71
|
|
Mar 29, 2007 15:33:12 GMT
|
They are only about 4 pounds per seat, but then you have to get matching valves which I got quoted at £8 per valve. Seems cheap but it all adds up even with only an 8v head. That seems bloody expensive to me I'll post some prices later Remember you need to get the seats and valves cut anyway normally so what you really need to look at is the "extra" charged for 3 angles Best bit about a decent valve and seat cutting is no lapping required |
| |
|
|
|
|
|
Mar 29, 2007 16:58:30 GMT
|
|
A proper and worthwhile 3 angle valve seat job takes quite a bit longer than just refacing the 45degree seat.
There is little point cutting 3 angles if the 45degree seats arent cut to the full diameter of the valve and the throat cut isnt enlarged to match. most normal engine reconditioners miss this point.
Paul
|
| |
|
|
|
|
slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
|
|
Mar 29, 2007 17:20:10 GMT
|
|
It shouldnt cost any extra to have 3 angle seats. Basicly all you have to do is put in a 3 angle cutter insted of a 45deg one. Also why would you need to enlarge the throat to do them?? if you enlarge the throat you will loose your bottom cut! been there myself
Whats way more important is that you have a 30deg back cut on your valves! this shouldnt cost too much. I would'nt charge much more than £20-25 for a set of 8 as it only takes about 5mins to do a set. If you re-use your old valves and want the 45deg re-surfacing aswell it will cost a bit more maybe £30-35 as it takes about double the time. A monkey could do it with the right machine tho tbh!
don't bother 'polishing' ports it relly is a waste of time.
don't 'match' the ports just make sure the 'hole' in the inlet manifold is smaller than in the head and vise versa for the exhaust. Its much easyer that way and alot of people say its better as it stops the gasses from traveling the wrong way down the outside of your ports.
Lapping is allways required too even with a serdi, less maybe but you still need to do it even if your only checking they are right tbh!!
|
| |
|
|
|
|
|
Mar 29, 2007 17:39:53 GMT
|
thanks, some good info here. Good news about the manifold matching as i'd have to have the engine out for longer to do that. As it is i can get the heads all ready to swap then do the whole head swap in a day. Ill see what my local machine shop want to 3 angle and if its cheap enough i might as well  |
| |
|
|
|
|
|
Mar 29, 2007 18:26:27 GMT
|
|
Not worth it imho if the car is blown, wont make the slightest bit of difference to output (thats noticeable) compared say to an intercooler or timing set up or even the fuel you use.
|
| |
Resident Toyota Geek Current Fleet: HDJ81 Landcruiser, GZ20 Soarer, JZX81 Cresta
|
|
John
Part of things
Posts: 347
|
|
Mar 29, 2007 18:30:38 GMT
|
|
Listen to what Slater says, as I would write the same.
I will add that the only porting I would do is to remove any really rough flash in the casting and smooth the short side radius. You can do this with a round file.
Do a search for David Vizard and read his articles. He knows his stuff.
|
| |
|
|
street
Posted a lot
6.2 ft/lbs of talk
Posts: 4,662
|
|
Mar 29, 2007 18:52:01 GMT
|
|
Could someone explain what lapping is pleeeeease?
|
| |
|
|
tigran
Club Retro Rides Member
In rust we trust. Amen.
Posts: 6,444
Club RR Member Number: 142
|
|
Mar 29, 2007 18:53:56 GMT
|
|
Using a stick with a suction cup on the end of it to grind the valves with some lapping paste against the valve seat. So that you get a perfek' fit.
|
| |
1964 Rover P5 i6
1987 BMW 525e - The Rusty Streak
1992 Micra K10
2001 BMW E46 316i
2002 BMW E46 330Ci
2013 BMW F31 320d
2018 BMW G31 530d
|
|
street
Posted a lot
6.2 ft/lbs of talk
Posts: 4,662
|
|
Mar 29, 2007 18:59:07 GMT
|
Aaaah I see, seen someone doing that. Cheers me owd!  |
| |
|
|
|
|
|
Mar 29, 2007 19:33:02 GMT
|
Listen to what Slater says, as I would write the same. I will add that the only porting I would do is to remove any really rough flash in the casting and smooth the short side radius. You can do this with a round file. Do a search for David Vizard and read his articles. He knows his stuff. Thats my plan, not going to go mad |
| |
|
|
Alain
Part of things
Dance monkey boy, dance!
Posts: 372
|
|
Mar 29, 2007 20:28:48 GMT
|
|
Taylor Machine Services ;D
Unit 35
Phoebe Lane Industrial Estate
Halifax
HX3 9EX(Road Map)
West Yorkshire
Tel: 01422 382993
|
| |
'74 Type 181 - Undergoing 'resto' (albeit friggin' slowly! 2 years and counting...) Wedge Panel Van GTi (Still needs finishing) '85 Passat GL5 Estate (Now Breaking) '87 Passat GLS5 Estate (Daily Hack)
|
|
bstardchild
Club Retro Rides Member
Posts: 14,965
Club RR Member Number: 71
|
|
Mar 29, 2007 22:30:00 GMT
|
Lapping is allways required too even with a serdi, less maybe but you still need to do it even if your only checking they are right tbh!! Disagree with that but then i am running 0.5mm seat contacts ;D |
| |
|
|
|
|
