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your project is very interesting.
what more modern lifters are you going to use? something else in 38mm or a different size? stock 928/944 DOHC use a 35mm which is also the size used in Subaru and VW amongst others, huge availability.
do you think the valve spacing on an early 928 head is "close enough" that a 944 cam would be able to actuate the lifters without much problem due to off-center misalignment?
since you're doing welding stuff to the chamber what are your thoughts on a proposed experiment i came up with once upon a time?
I found it interesting that very early US 4.5/4.7 928 heads had a similar sort of "heart shape" that later went away.
Spencer, if you do not want to go the Greg way with radiused lifters which require a very special cam profile, the largest bucket lifters I have found are 42mm and from a European Ford. The hydraulic lifters can be modified to mechanical. Large oversize lifters will be needed when high lift cams come into use
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Åke
Last edited by Strosek Ultra; 02-19-2018 at 06:34 AM.
I would reconsider going with titanium, it is a very soft metal and wears very quickly in an engine. I would look into chrome moly steel parts as they can be made almost as light as Ti but last a lot longer.
Lindsey Racing sells beehive springs with chrome moly retainers if you don't want to custom make it yourself.
For different applications I have used titanium retainers for at least forty years and never had an issue. I make them myself, I use Titanium Grade 5.
Åke
For different applications I have used titanium retainers for at least forty years and never had an issue. I make them myself, I use Titanium Grade 5.
Åke
The problems come when you treat them like standard steel parts and don't replace them at the required intervals, which are much shorter.
That's why they're great in race engines that get inspected often, but not so great in street engines that go 50,000+ miles between full tear downs.
A bit more progress, just an experiment at this stage, I polished one runner where I welded the tube together. The would be how to integrate the plenum and the runners, the plenum could be made to be a satin finish. After the bellmouths are soldered in I can’t properly polish the plenum. So a decision will need to be made soon. Thoughts?
Do you have a picture of the bellmouths outside of the intake?
im guessing you’re dropping them in?
It is possible to machine the entire side off the intake and weld them to a plate first, then weld that plate to the stock plenum.
Do you have a picture of the bellmouths outside of the intake?
im guessing you’re dropping them in?
It is possible to machine the entire side off the intake and weld them to a plate first, then weld that plate to the stock plenum.
Basically you are correct but what happen when I grit blast the plenum? Grit will get stuck inside the plenum and make its way into the engine. This is the reason I did it in that order.
If you are sand blasting and the part is clean and free of oil it doesn’t trap as much. Even without you should be blasting it with a pressure washer, and numerous cleaning cycles.
If you are sand blasting and the part is clean and free of oil it doesn’t trap as much. Even without you should be blasting it with a pressure washer, and numerous cleaning cycles.
I should add some details, I was on the road and gave quick answers. So to explain my intent, when I started the plenum and manifold project I thought a stock looking but performance adequate system. The appearance and aesthetics are also important. To get the stock appearance you need to replicate the casting finish. To do this after the welding is finished being ground back, the aluminium needs to be shot blasted in one form or another to achieve this finish. The bellmouths are curled at the back and would trap grit as they are pushed up against the side plates. How can you be sure that all the grit has been washed away when you can’t open up the plenum?
So I fitted the bellmouths inside the plenum but loose, this allows the washing out and visual inspection of the plenum. I was very cautious about the grit issue given how many 928 engines have been damaged by blasted intake manifolds. As I previously mentioned I didn’t want a welded look for this engine, so soldering around the bells allows the best for this.
Do you have a picture of the bellmouths outside of the intake?
im guessing you’re dropping them in?
It is possible to machine the entire side off the intake and weld them to a plate first, then weld that plate to the stock plenum.
Maybe I didn’t answer this properly, the bellmouths cannot be fitted after the plenum was welded together, they needed to fitted inside the plenum before the welding.
There is a thread on Rennlist in the 944 forum that did detail this, it wasn’t a lot more than the smaller valved head. However it has a lot more potential due to its size and shape. A 928 head cannot be ported to be big enough to support a 7.0 litre engine, the casting will get too thin. With a big valve and big bore 108 mm/4.25” and 16 mm lift I’m hoping for 350 cfm. This is not unreasonable as I have achieved 305 cfm at 12.7mm/0.500” on a 104 mm bore. Sorry I can’t directly answer your question.
There is a thread on Rennlist in the 944 forum that did detail this, it wasn’t a lot more than the smaller valved head. However it has a lot more potential due to its size and shape. A 928 head cannot be ported to be big enough to support a 7.0 litre engine, the casting will get too thin. With a big valve and big bore 108 mm/4.25” and 16 mm lift I’m hoping for 350 cfm. This is not unreasonable as I have achieved 305 cfm at 12.7mm/0.500” on a 104 mm bore. Sorry I can’t directly answer your question.
Thanks, that is a nice flow number, comparing to stock.
02-19-2018, 06:14 AM
